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S0965997815000058 | In this paper a new mathematical geometric model of spiral one or two-layered oval wire strands are proposed and an accurate computational two-layered oval strand 3D solid model, which is used for a finite element analysis, is presented. The three dimensional curve geometry of wires axes in the individual layers of the oval strand consists of straight linear and helical segments. The present geometric model fully considers the spatial configuration of individual wires in the right and left hand lay strand. Derived geometric equations were used for the generation of accurate 3D geometric and computational models for different types of strands. This study develops 3D finite element models of two-layer spiral round, triangular and oval strands subjected to axial loads using ABAQUS/Explicit software. Accurate modelling and understanding of their mechanical behaviour is complicated due to the complex contact interactions and conditions that exist between individual spirally wound wires. Comparisons of predicted responses for the strands with different shapes and constructions are presented. Resultant stress and/or deformation behaviours are discussed. | Finite element analysis of spiral strands with different shapes subjected to axial loads |
S0965997815000083 | This paper focuses on the new version of a recently developed meta-heuristic algorithm, Colliding Bodies Optimization (CBO), and its utility for optimization of truss structures. The idea of the standard CBO is derived from one-dimensional collisions between bodies, which does not use the internal parameter and memory in its formulation. However, the exploitation phase of the CBO is weak due to not using a memory for saving the best-so-far solution in its formulation. Here, in the two dimensional version of CBO, denoted by 2D-CBO, a memory is added to the standard CBO formulation to improve the performance of the latter algorithm. This addition increases the exploitation ability and convergence rate of the CBO. Comparative studies illustrate the superiority of the 2D-CBO algorithm compared to those previously reported in the literature. | Two-dimensional colliding bodies algorithm for optimal design of truss structures |
S0965997815000095 | Understanding how fuel sloshes in a fuel cell, as a vehicle races around a circuit, is an important but mostly unexplored factor when designing fuel containment systems. Cell designs are based on knowledge of how liquids slosh in other containers, with the design and placement of structures, such as weirs, based on engineering judgement. This work aims to provide better understanding for this difficult problem with a view to improve future designs. A Graphics Processing Unit (GPU) based Smoothed Particle Hydrodynamics (SPH) model is presented to simulate the fuel sloshing problem, with results from a simplified and real fuel cell geometry shown and compared against real data recorded in a vehicle. The vehicle motion and accelerations are included in the SPH simulations using a body force within the momentum equation. Results show good agreement between the simulation and the real fuel movement, with bulk motion captured well for accelerations up to 5 times gravity. Focus is placed on the practicality of the method for use as part of an industrial design process, therefore the amount of time needed to compute results is considered throughout. Computational performance is found to be within acceptable limits, while numerical accuracy is actively considered through the use of Kahan compensated summation. It is concluded that the model is successful in capturing the necessary fluid dynamics for it to be useful in fuel cell design. It is expected that the method will provide insight into current cell designs and highlight where improvements can be made. | Automotive fuel cell sloshing under temporally and spatially varying high acceleration using GPU-based Smoothed Particle Hydrodynamics (SPH) |
S0965997815000101 | With the accuracy limitation of some transfer methods in the self-parallel fluid–structure interfaces, a data transfer method is proposed by an ISOMAP (Isometric Mapping) nonlinear dimensionality reduction. Through this new method, the data transfer problem of the self-parallel interfaces is solved. Example of a 3D turbine blade shows that the proposed method can improve the transfer accuracy in the non-matching meshes. | An enhanced 3D data transfer method for fluid–structure interface by ISOMAP nonlinear space dimension reduction |
S0965997815000113 | This paper proposes a novel nature-inspired algorithm called Ant Lion Optimizer (ALO). The ALO algorithm mimics the hunting mechanism of antlions in nature. Five main steps of hunting prey such as the random walk of ants, building traps, entrapment of ants in traps, catching preys, and re-building traps are implemented. The proposed algorithm is benchmarked in three phases. Firstly, a set of 19 mathematical functions is employed to test different characteristics of ALO. Secondly, three classical engineering problems (three-bar truss design, cantilever beam design, and gear train design) are solved by ALO. Finally, the shapes of two ship propellers are optimized by ALO as challenging constrained real problems. In the first two test phases, the ALO algorithm is compared with a variety of algorithms in the literature. The results of the test functions prove that the proposed algorithm is able to provide very competitive results in terms of improved exploration, local optima avoidance, exploitation, and convergence. The ALO algorithm also finds superior optimal designs for the majority of classical engineering problems employed, showing that this algorithm has merits in solving constrained problems with diverse search spaces. The optimal shapes obtained for the ship propellers demonstrate the applicability of the proposed algorithm in solving real problems with unknown search spaces as well. Note that the source codes of the proposed ALO algorithm are publicly available at http://www.alimirjalili.com/ALO.html. | The Ant Lion Optimizer |
S0965997815000125 | As a method for surface severe plastic deformation (S2PD), ultrasonic nanocrystal surface modification (UNSM) enhances metal surface properties through striker peening, a metal dimpling process driven by ultrasonic vibration energy. UNSM treatment introduces residual stress, surface hardening, and nano-crystalline structures into metal surfaces which are beneficial for reducing wear, fatigue, and corrosion properties. In this paper, the process of UNSM is described and a simplified physical model created using the equivalent static loading method is presented. Along with the simplified physical model, a finite elements simulation model was developed. Effective plastic strain was considered as a parameter for evaluating the level of work hardening produced in the simulation. The dynamic processes and energy dissipation were also examined, and it was found that different kinds of energy dissipation occur during UNSM treatment. Comparisons between the processing parameters (processing velocity, static load, and feed rate) were performed using a simulated example of UNSM linear processing. The results show that the linear processing produces a uniform region containing identical distributions of residual stress and effective plastic strain. The effects of the parameters on the processing results (residual stress, plastic deformation and work hardening) were likewise studied using UNSM linear processing. Compared to processing velocity, a high static load produced more work hardening and higher compressive residual stress. Surface deformation and residual stress results were also more sensitive to static load than processing velocity. Feed rate was found to be an important parameter as well, greatly influencing both surface deformation and work hardening. | An investigation of ultrasonic nanocrystal surface modification machining process by numerical simulation |
S0965997815000198 | This article discusses on the detection of fault occurred during friction stir welding using discrete wavelet transform on force and torque signals. The work pieces used were AA1100 aluminum alloys of thickness 2.5mm. The plates were 200mm in length and 80mm in width. Presence of defect in welding causes sudden change in force signals (Z-load), thus it is easier to detect such abrupt changes in a signal using discrete wavelet transform. Statistical features like variance and square of errors of detail coefficients are implemented to localize the defective zone properly as it shows better variations (in defective area) than the detail coefficient itself. | Defect identification in friction stir welding using discrete wavelet analysis |
S0965997815000228 | The paper presents a novel visualization technique for cracks propagating in mono-dispersed particulate material. The proposed technique is based on local space decompositions generated in fractured areas. The contact surfaces of the neighboring particles are defined by the local Voronoi decomposition generated according to the lattice topology employed in computations of the discrete element method. The visual model validation helps to indicate the regions of a highly deformed lattice, where the defects detected between the pairs of the neighboring particles on the lattice connections cannot be directly mapped onto the relevant edges of the Voronoi diagram. The parallel implementation of the visualization technique is based on the domain decomposition and two layers of ghost vertices and connections. The technique is implemented in the distributed visualization software VisPartDEM. Datasets of the elastic solid problem exhibiting non-uniform distribution of fracture force values are considered to validate the performance of the proposed technique. The parallel speed-up of the visualization software is investigated. The superior performance of the applied local technique is compared to the performance observed by using the standard global Voronoi algorithm. | Visualization of cracks by using the local Voronoi decompositions and distributed software |
S096599781500023X | In reinforced concrete (RC) structural experiments, the development of concrete surface cracks is an important factor of concern to experts. One conventional crack observation method is to suspend a test at a few selected testing steps and send inspectors to mark pen strokes on visible cracks, but this method is dangerous and labor intensive. Many image analysis methods have been proposed to detect and measure the dark shadow lines of cracks, reducing the need for manual pen marking. However, these methods are not applicable for thin cracks, which do not present clear dark lines in images. This paper presents an image analysis method to capture thin cracks and minimize the requirement for pen marking in reinforced concrete structural tests. The paper presents the mathematical models, procedures, and limitations of our image analysis method, as well as the analysis flowchart, the adopted image processing and analysis methods, and the software implementation. Finally, the results of applying the proposed method in full-scale reinforced concrete bridge experiments are presented to demonstrate its performance. Results demonstrate that this method can capture concrete surface cracks even before dark crack lines visible to the naked eye appear. | Thin crack observation in a reinforced concrete bridge pier test using image processing and analysis |
S0965997815000265 | Since various existing simulation tools based on multibody system dynamics focus on conventional mechanical systems, such as machinery, cars, and spacecraft, there are some problems with the application of such simulation tools to shipbuilding domains due to the absence of specific items in the field of naval architecture and ocean engineering, such as hydrostatics, hydrodynamics, and mooring forces. Thus, in this study, we developed a multibody system dynamics simulator for the process simulation of ships and offshore structures. We based the simulator on six kernels: the multibody system dynamics kernel, the force calculation kernel, the numerical analysis kernel, the hybrid simulation kernel, the scenario management kernel, and the collision detection kernel. Based on these kernels, we implemented a simulator that had the following Graphic User Interfaces (GUIs): the modeling, visualization, and report GUIs. In addition, the geometric properties of blocks and facilities in shipyards are needed to configure the simulation for the production of ships and offshore plants, so these are managed in a database and connected to a specific commercial CAD system in shipyards. We used the simulator we developed in various cases of the process simulation of ships and offshore plants. The results show that the simulator is useful for various simulations of operations in shipyards and offshore industries. | Multibody system dynamics simulator for process simulation of ships and offshore plants in shipyards |
S0965997815000289 | The problem of integrating the rotational vector from a given angular velocity vector is met in such diverse fields as the navigation, robotics, computer graphics, optical tracking and non-linear dynamics of flexible beams. For example, if the numerical formulation of non-linear dynamics of flexible beams is based on the interpolation of curvature, one needs to derive the rotation from the assumed curvature field. The relation between the angular velocity and the rotation is described by the first-order quasi-linear differential equation. If the rotation is given, the related angular velocity is obtained by the differentiation. By contrast, if the angular velocity is given, the related rotations are obtained by the integration. The exact closed-form solution for the rotation is only possible if the angular velocity is constant in time. In dynamics of non-linear flexible spatial beams, the problem of integrating rotations from a given angular velocity becomes even more complex because both the angular velocity and the curvature need simultaneously be integrated and are both functions of space and time. As the angular velocity and the curvature are assumed to be analytic functions, they must satisfy certain integrability conditions to assure the unique rotation is obtained from the two differential equations. The objective of the present paper is to derive approximate, yet closed-form solutions of the following problem: for a given curvature vector, determine both the rotation and the angular velocity. In order to avoid the singularity of kinematic relations, the quaternions are used for the parametrization of rotations, and the integrations are partly performed in the four-dimensional quaternion space. The resulting closed-form expressions for the rotational and angular velocity quaternions are ready to be used in the finite-element formulations of the dynamics of flexible spatial beams as interpolating functions. The present novel solution is assessed by comparisons of the numerical results with analytical solutions for variety of oscillating curvature functions, as well as with the solutions of the quaternion-based midpoint integrator and the Runge–Kutta-based Crouch–Grossman geometrical methods CG3 and CG4. | Integrating rotation and angular velocity from curvature |
S0965997815000290 | This paper will propose a topology optimization approach for the design of large displacement compliant mechanisms with geometrical non-linearity by using the element-free Galerkin (EFG) method. In this method, the Shepard function is applied to construct a physically meaningful density approximant, to account for its non-negative and range-bounded property. Firstly, in terms of the original nodal density field, the Shepard function method functionally similar to a density filter is used to generate a non-local nodal density field with enriched smoothness over the design domain. The density of any node can be evaluated according to the nodal density variables located inside the influence domain of the interested node. Secondly, in the numerical implementation the Shepard function method is again employed to construct a point-wise density interpolant. Gauss quadrature is used to calculate the integration of background cells numerically, and the artificial densities over all Gauss points can be determined by the surrounding nodal densities within the influence domain of the concerned computational point. Finally, the moving least squares (MLS) method is applied to construct the shape functions using the weight functions with compact support for assembling the meshless approximations of state equations. Since MLS shape functions are lack of the Kronecker delta function property, the penalty method is applied to enforce the essential boundary conditions. A typical large-deformation compliant mechanism is used as the numerical example to demonstrate the effectiveness of the proposed method. | Topology optimization of compliant mechanisms using element-free Galerkin method |
S0965997815000307 | This article discusses the applicability of the three-parameter Kozeny–Carman generalized equation to trigger immiscible viscous fingers and describe it in fractal heterogeneous porous media, during numerical simulations of waterflood operations in oil reservoirs. For that purpose, for the first time this equation was incorporated into a model that describes immiscible flows of incompressible two-phase fluids in porous media. Results were generated from intensive simulations, and viscous fingers were visualized graphically for three different well patterns, typical of oil fields: Line-Drive, Five-Spot and Inverted Five-Spot. Such results suggest that this generalization of the Kozeny–Carman equation can be used in numerical simulations of oil recovery processes susceptible to hydrodynamic instability phenomena. | Applicability of the three-parameter Kozeny–Carman generalized equation to the description of viscous fingering in simulations of waterflood in heterogeneous porous media |
S0965997815000319 | In this paper we present a deferred method for evaluating a complete CSG tree based on triangulated solids. It allows the exact evaluation of the surface of the entire model in a single step, using regularized Boolean classifications. The overall performance with this approach is better than with the classical method, which incrementally evaluates a CSG tree with single Boolean operations. The deferred algorithm does not use any intermediate result for the nodes of the CSG tree. It uses a very simple data structure and an octree that speeds up spatial queries for the entire CSG tree. The algorithm intensively uses multitasking and is ready for working with very complex CSG expressions, including the application of an out-of-core based approach. | Deferred boundary evaluation of complex CSG models |
S096599781500040X | Computational efficiency is still a great challenge for the generation of the Medial Axis (MA) for complicated CAD models. Current research mainly focuses on CPU-based MA generation methods. However, most of the methods emphasize using a single CPU. The highly-efficient methods based on parallel computing are still missing. In this study, a parallel method based on multi-CPU is proposed for the efficient MA generation of CAD models using distance dilation. By dividing the whole model into several parts for which MAs are calculated in parallel and then combined, computational efficiency can be greatly improved in theory and the computation time can be reduced nearly K times if K CPUs are used. Firstly, an adaptive division method is proposed to divide the voxelized model into blocks which have nearly the same number of voxels to balance the computational burden. Secondly, the local Euclidean Distance Transform (EDT) is calculated for each block based on the existing distance dilation method. Thirdly, the complete inter-dilation method is proposed to compute the influence between different blocks to get a global EDT for each block. Finally, each block generates a sub-MA separately and then all the generated MAs are combined to obtain the final MA. The last three processes can be efficiently conducted in parallel by using multiple CPUs. Several groups of experiments are conducted which demonstrate the good performance of the proposed methods in terms of efficiency. | Calculating the medial axis of a CAD model by multi-CPU based parallel computation |
S0965997815000411 | Automotive bumper beam is an important component to protect passenger and vehicle from injury and damage induced by severe collapse. Recent studies showed that foam-filled structures have significant advantages in light weight and high energy absorption. In this paper, a novel bumper beam filled with functionally graded foam (FGF) is considered here to explore its crashworthiness. To validate the FGF bumper beam model, the experiments at both component and full vehicle levels are conducted. Parametric study shows that gradient exponential parameter m that controls the variation of foam density has significant effect on bumper beam’s crashworthiness; and the crashworthiness of FGF-filled bumper beam is found much better than that of uniform foam (UF) filled and hollow bumper beam. The multiobjective optimization of FGF-filled bumper beam is also performed by considering specific energy absorption (SEA) and peak impact force as the design objectives, and the wall thickness t, foam densities ρf 1 and ρf 2 (foam densities at the end and at mid cross section, respectively) and gradient exponential parameter m as design variables. The Kriging surrogate modeling technique and multiobjective particle swarm optimization (MOPSO) algorithm were implemented to optimize the FGF-filled bumper beam. The optimized FGF-filled bumper beam is of great advantages and it can avoid the harmful local bending behavior and absorb more energy than UF filled and hollow bumper beam. Finally, the optimized FGF-filled bumper beam is installed to a passenger car model, and the results demonstrate that the FGF-filled bumper beam ensures the crashworthiness performance of the passenger car while reduces weight about 14.4% compared with baseline bumper beam. | Crashworthiness design for functionally graded foam-filled bumper beam |
S0965997815000484 | The main limits of reanalysis method using CUDA (Compute Unified Device Architecture) for large-scale engineering optimization problems are low efficiency on single GPU and memory bottleneck of GPU. To breakthrough these bottlenecks, an efficient parallel independent coefficient (IC) reanalysis method is developed based on multiple GPUs platform. The IC reanalysis procedure is reconstructed to accommodate the use of multiple GPUs. The matrices and vectors are successfully partitioned and prepared for each GPU to achieve good load balance as well as little communication between GPUs. This study also proposes an effective technique to overlap the computation and communication by using non-blocking communication strategy. GPUs would continue their succeeding tasks while communication is still carried out simultaneously. Furthermore, the CSR format is used in each GPU for saving the memory. Finally, large-scale vehicle design problems are implemented by the developed solver. According to the test results, the multi-GPU based IC reanalysis method has potential capability for handling the real large scale problem and reducing the design cycle. | A multiple-GPU based parallel independent coefficient reanalysis method and applications for vehicle design |
S0965997815000496 | Generally, Computing Aided Engineering (CAE) modeling and simulation of Linear Variable Differential Transformer (LVDT) has drawbacks such as the slow modeling speed and instability in simulation results. In this study, a rapid integrated parametric CAE modeling method is proposed for electromagnetic simulation based on a script template implemented in Maxwell electromagnetic simulation software with Visual Basic, so that the proposed method only requires the establishment of a simplified electromagnetic simulation model of a LVDT. The standard and parametric modeling process of LVDT is initially recorded as a script and then identifiers are added into the script to form a script template and transform Computing Aided Design (CAD) parameters to CAE modeling parameters according to parameter constraints of the model. Finally, parameter values are automatically assigned to identifiers in the script template in order to generate the script file through which the accurate CAE model can be created conveniently. The parametric LVDT simulation can not only be rapidly established but also significantly improves the quality of LVDT design in industry. In addition, the proposed method can improve CAD information availability in realizing seamless integration of CAD/CAE modeling in similar sensor product. | Rapid integrated parametric CAE modeling method of Linear Variable Differential Transformer based on a script template |
S0965997815000502 | In practical applications of structural health monitoring technology, a large number of distributed sensors are usually adopted to monitor the big dimension structures and different kinds of damage. The monitored structures are usually divided into different sub-structures and monitored by different sensor sets. Under this situation, how to manage the distributed sensor set and fuse different methods to obtain a fast and accurate evaluation result is an important problem to be addressed deeply. In the paper, a multi-agent fusion and coordination system is presented to deal with the damage identification for the strain distribution and joint failure in the large structure. Firstly, the monitoring system is adopted to distributedly monitor two kinds of damages, and it self-judges whether the static load happens in the monitored sub-region, and focuses on the static load on the sub-region boundary to obtain the sensor network information with blackboard model. Then, the improved contract net protocol is used to dynamically distribute the damage evaluation module for monitoring two kinds of damage uninterruptedly. Lastly, a reliable assessment for the whole structure is given by combing various heterogeneous classifiers strengths with voting-based fusion. The proposed multi-agent system is illustrated through a large aerospace aluminum plate structure experiment. The result shows that the method can significantly improve the monitoring performance for the large-scale structure. | Structural health monitoring system based on multi-agent coordination and fusion for large structure |
S0965997815000514 | Numerical models for computing low-frequency electromagnetic fields can contain spatial 2D finite elements, which are numerically most demanding due to problem of singularity. In this paper, an advanced time-harmonic quasistatic surface charge simulation method for computation of scalar electric potential and electric field intensity distribution is presented. Subparametric spatial 2D finite elements with an arbitrary number of nodes for description of surface charge density distribution are developed. The problem of singularity that occurs in the double 2D integration over these elements is solved using an originally developed advanced numerical integration based on 2D Gaussian quadrature. Self and mutual coefficients of spatial 2D finite element nodes are numerically computed and included in the system of linear equations for surface charge density distribution computation. The accuracy of the computer program, based on the presented model, is shown in the chosen numerical example with known analytical solution. Numerical model and advanced integration presented herein could be easily extended to non-homogeneous regions and multilayer problems using the image method. | A surface charge simulation method based on advanced numerical integration |
S0965997815000605 | To join a medium or thick plate weldment with a full penetration, a groove is usually prepared in the space between two sections of metal. Because weld metal needs to be deposited within the groove to form the joint, it is expected that different groove type will require different heat input, which may consequently have influence on welding residual stress and deformation. Generally, different groove corresponds to different bead layout, so it can be foreseen that the groove type has a significant effect on temperature history, shape and size of heat affected zone, and region of sensitization in certain alloys such as austenitic stainless steel. The influences of groove type on residual stress, angular distortion and width of sensitization region in a SUS304 butt-welded joint were investigated by means of numerical simulation and experiment. Based on ABAQUS code, a computational approach with considering thermo-mechanical coupling behaviors, moving heat source, strain hardening and annealing effect was developed to simulate temperature profile, stress field and deformation in multi-pass joint. Welding temperature cycles, residual stress distributions and deformations in V, K and X groove joints were calculated through using the proposed computational procedure. Meanwhile, experiments were carried out to obtain residual stress distributions and angular distortions. Through comparing the numerical results and the measured data, the effectiveness and accuracy of the developed computational approach were verified. The simulation results show that groove type has a significant influence on welding residual stress distribution, angular distortion and width of sensitization region. | Influence of groove type on welding-induced residual stress, deformation and width of sensitization region in a SUS304 steel butt welded joint |
S0965997815000629 | Crashworthiness simulation system is one of the key computer-aided engineering (CAE) tools for the automobile industry and implies two potential conflicting requirements: accuracy and efficiency. A parallel crashworthiness simulation system based on graphics processing unit (GPU) architecture and the explicit finite element (FE) method is developed in this work. Implementation details with compute unified device architecture (CUDA) are considered. The entire parallel simulation system involves a parallel hierarchy-territory contact-searching algorithm (HITA) and a parallel penalty contact force calculation algorithm. Three basic GPU-based parallel strategies are suggested to meet the natural parallelism of the explicit FE algorithm. Two free GPU-based numerical calculation libraries, cuBLAS and Thrust, are introduced to decrease the difficulty of programming. Furthermore, a mixed array and a thread map to element strategy are proposed to improve the performance of the test pairs searching. The outer loop of the nested loop through the mixed array is unrolled to realize parallel searching. An efficient storage strategy based on data sorting is presented to realize data transfer between different hierarchies with coalesced access during the contact pairs searching. A thread map to element pattern is implemented to calculate the penetrations and the penetration forces; a double float atomic operation is used to scatter contact forces. The simulation results of the three different models based on the Intel Core i7-930 and the NVIDIA GeForce GTX 580 demonstrate the precision and efficiency of this developed parallel crashworthiness simulation system. | A high performance crashworthiness simulation system based on GPU |
S0965997815000630 | This paper presents an extended surface boundary representation (B-rep), where each topology entity can have dual geometric representations to accommodate various defects (e.g., gaps and overlaps) commonly present in CAD models. Keeping a uniform B-rep and the unsuppressed geometry data enables the use of various existing repairing, defeaturing and meshing algorithms to process CAD models with small gaps and overlaps on surface boundaries. The continuous geometry of the input model remains untouched in the repairing, defeaturing and meshing process, and the output mesh is loyal to this geometry. Such feature is often desirable in numerical simulations that require meshes with high geometry fidelity. | Automatic surface repairing, defeaturing and meshing algorithms based on an extended B-rep |
S0965997815000642 | This paper presents an output only damage diagnostic algorithm based on frequency response functions and the principal components for health monitoring of laminated composite structures. The principal components evaluated from frequency response data, are employed as dynamical invariants to handle the effects of operational/environmental variability on the dynamic response of the structure. Finite element models of a laminated composite beam and plate are used to generate vibration data for healthy and damaged structures. Three numerical examples include a laminated composite beam, cantilever plate made of carbon–epoxy and a laminated composite simply supported plate. Varied levels of delamination of laminated composite plies and matrix cracking at varied locations in the plies are simulated at different spatial locations of the structure. Numerical investigations have been carried out to identify the spatial location of damage using the proposed principal component analysis (PCA) based algorithm. In order to limit the number of sensors on the structure, an optimal sensor placement algorithm based on PCA is employed in the present work and the effectiveness of the proposed algorithm with a limited number of sensors is also investigated. Finally, the inverse problem associated with the detection of delamination and matrix cracking is formulated as an optimization problem and is solved using the newly developed dynamic quantum particle swarm optimization (DQPSO) algorithm. Studies carried out and presented in this paper clearly indicate that the proposed SHM scheme can robustly identify the instant of damage, spatial location, the extent of delamination and matrix cracking even with limited sensor measurements and also with noisy data. | Detection of delamination in laminated composites with limited measurements combining PCA and dynamic QPSO |
S0965997815000654 | The aim of this study was to explore the heat transfer behavior between convection and conduction in the thick wall crude oil pipeline with laminar unsteady state flow using integration of developed computational fluid dynamics model and statistical experimental design. The governing equations were employed to investigate the effects of wall thickness, wall thermal conductivity, surrounding heat transfer coefficient and ambient temperature on transport profile using statistical experimental design and to locate an origin point where wax precipitate in the pipeline (wax appearance distance) by using response surface methodology (RSM). A good agreement between the model and literature experimental data suggests that the proposed numerical scheme is suitable for simulating the transport profile in pipeline and predicting the phenomena for any other conditions. From the statistical analysis, it was found that, surrounding heat transfer coefficient and ambient temperature were the major effect parameters on the wax appearance distance. wall thickness/coded factor of wall thickness (−) pipe thermal conductivity/coded factor of pipe thermal conductivity (−) surrounding heat transfer coefficient/coded factor of surrounding heat transfer coefficient (−) ambient temperature/coded factor of ambient temperature (−) pipe diameter (m) heat transfer coefficient (kW/m2 °C) inner wall heat transfer coefficient (kW/m2 °C) outer wall heat transfer coefficient (kW/m2 °C) thermal conductivity (kW/m°C) pipe length (m) inner wall radius (m) outer wall radius (m) heat resistance (m2 °C/kW) source term time (s) temperature (°C) x-velocity (m/s) y-velocity (m/s) x-direction wall thickness (m) y-direction wax appearance distance (m) dependent variable density (kg/m3) diffusion coefficient ambient fluid/crude oil | Integration of computational fluid dynamics simulation and statistical factorial experimental design of thick-wall crude oil pipeline with heat loss |
S0965997815000666 | A method and an algorithm for numerical estimation of effective mechanical properties of porous materials are presented. The effective properties are sought in the form of the nonlinear relation between the second Piola–Kirchhoff stress tensor and the Green strain tensor for anisotropic materials with second-order nonlinearities accounted for. The effective characteristics of test models are computed by means of a CAE Fidesys program module based on the proposed algorithm. The effective material properties as functions of porosity are examined. The finite element mesh that contained more than a million of elements was used while performing stress analysis of a specimen. To reduce computing time, assembly and solution of the global equation system was done in parallel using CUDA technology. The computations were carried out on NVIDIA Tesla C2050 graphics processors. Our results show that accounting for nonlinear effects is essential for correct estimation of effective properties of porous materials. | Software for estimation of second order effective material properties of porous samples with geometrical and physical nonlinearity accounted for |
S0965997815000678 | Although parallelization of computationally intensive algorithms has become a standard with the scientific community, the possibility of in-core vectorization is often overlooked. With the development of modern HPC architectures, however, neglecting such programming techniques may lead to inefficient code hardly utilizing the theoretical performance of nowadays CPUs. The presented paper reports on explicit vectorization for quadratures stemming from the Galerkin formulation of boundary integral equations in 3D. To deal with the singular integral kernels, two common approaches including the semi-analytic and fully numerical schemes are used. We exploit modern SIMD (Single Instruction Multiple Data) instruction sets to speed up the assembly of system matrices based on both of these regularization techniques. The efficiency of the code is further increased by standard shared-memory parallelization techniques and is demonstrated on a set of numerical experiments. | Acceleration of boundary element method by explicit vectorization |
S096599781500068X | Micro- and nanomanipulators are essential for a broad range of applications requiring precise micro- and nanoscopic spatial control such as those in micromanufacturing and single cell analysis. These manipulators are often manually controlled using an attached joystick and can be difficult for operators to use efficiently. This paper describes a system developed in MATLAB to control a well-known, commercial micromanipulator in a user friendly and versatile manner through a graphical user interface (GUI). The control system and interface allows several types of flexible movement controls in three-axis, Cartesian space, including single movements, multiple queued movements, and mouse-following continuous movements. The system uses image processing for closed loop feedback to ensure precise and accurate control over the movement of the manipulator’s end effector. The system can be used on any electronic device capable of running the free MATLAB Runtime Environment (MRE) and the system is extensible to simultaneously control other instruments capable of serial communication. | Computerized control system and interface for flexible micromanipulator control |
S0965997815000691 | Complex curved surface parts with local geometric feature are usually critical parts in high-end equipments. However, the processing for this kind of parts is usually difficult or inefficient due to the adoption of difficult-to-machine material and special structure. Current approaches cannot satisfy the rapid development of high-end equipments. Due to the existence of the local geometric feature for the parts, processing such parts with constant machining parameters is less applicative, restricting the improvement of machining efficiency. By separating the local geometric feature and generating tool path for the local geometric feature and the remaining processing area separately, the more efficient machining with variable machining parameters will be obtained for the complex curved surface with local geometric feature. In this way, the quick segmentation for the complex curved surface with local geometric feature is of great importance to the NC machining with variable machining parameters for this kind of parts, and a quick segmentation system is developed based on Initial Graphics Exchange Specification (IGES) and Open CASCADE (OCC) platform in this study. The complex curved surface model in IGES format is firstly imported into the system and then trimmed into independent surface patches. After computing the feature size of each surface patch, the segmentation for the complex curved surface is achieved by sorting and classifying the surface patches according to their feature sizes. Taking the whole impeller with small splitter blades for an example, the experimental result shows that the segmentation of small splitter blades from the whole impeller is successful and a serialized processing program could be generated, and then the whole impeller could be machined precisely and efficiently with NC equipment. In the machining experiment, it is proved that the machining with various machining parameters can improve the efficiency by 28.18% in the comparison experiment, 20.14% and 12.33% in the estimation. The research provides an important foundation for the high quality and more efficient machining of the complex curved surface with local geometric feature. | Quick segmentation for complex curved surface with local geometric feature based on IGES and Open CASCADE |
S0965997815000708 | Trajectory planning in robotics refers to the process of finding a motion law that enables a robot to reach its terminal configuration, with some predefined requirements considered at the same time. This study focuses on planning the time-optimal trajectories for car-like robots. We formulate a dynamic optimization problem, where the kinematic principles are accurately described through differential equations and the constraints are strictly expressed using algebraic inequalities. The formulated dynamic optimization problem is then solved by an interior-point-method-based simultaneous approach. Compared with the prevailing methods in the field of trajectory planning, our proposed method can handle various user-specified requirements and different optimization objectives in a unified manner. Simulation results indicate that our proposal efficiently deals with different kinds of physical constraints, terminal conditions and collision-avoidance requirements that are imposed on the trajectory planning mission. Moreover, we utilize a Hamiltonian-based optimality index to evaluate how close an obtained solution is to being optimal. | Simultaneous dynamic optimization: A trajectory planning method for nonholonomic car-like robots |
S096599781500071X | This work presents a contribution on the numerical modelling capabilities for the simulation of fluid flow and heat transfer in cellular solids – in particular we focus on open cell aluminium foams. Rather than applying one of the classical academical or commercial numerical finite volume (FV), finite difference (FD) or finite element (FE) interface tracking methods, we base our models on an interface capturing phase field method (Nestler, 2005). A coupled diffuse interface lattice Boltzmann fluid flow solver (Ettrich, 2014) and a diffuse interface heat transfer approach (Ettrich et al., 2014) are combined in view of dealing with even more convoluted geometries, incorporating the dynamics of interfaces and complex multiphysics applications. Numerical results for the combined fluid flow and heat transfer simulations in open cell metal foams are in very good agreement with experimental data (Ettrich and Martens, 2012; Ettrich et al., 2012). | Diffuse interface method for fluid flow and heat transfer in cellular solids |
S0965997815000721 | This work presents a novel CACD/CAD/CAE integrated framework for design, modeling, and optimization of fiber-reinforced plastic parts, which can greatly enhance the current design practice by realizing partial automation and multi-stage optimization. To support this framework, a new heterogeneous feature model (HFM) has been developed to model the fiber-reinforced objects and to be transferred between engineering modules. To be specific, the CACD (computer-aided conceptual design) module employs the level-set structure and material optimization to produce the initial design with thickness control, and also the initial HFM; the CAD (computer-aided design) module allows manual editing on the HFM to reflect various design intents; then, the injection molding CAE (computer-aided engineering) simulates the manufacturing process, and the response surface method (RSM) is applied to optimize the process parameters of gate location, injection flow rate, mold temperature and melt temperature, to approach the manufactured fiber orientation distribution close to the optimized result produced by the CACD module; besides, the structural analysis CAE module generates the mechanical performance result to support the CACD module, as well as to validate the final design. By applying this framework, the final structural design including the fiber orientation distribution, will perform better in mechanical properties, and consume less matrix and fiber materials; besides, the design maturity can be approached in shorter time. To prove the effectiveness, a plastic gripper design will be comprehensively studied. the energy bilinear form elastic tensor elastic tensor of the matrix material elastic tensor of the fiber elastic tensor of the fiber after coordinate transformation normalization parameter of the global strength measure signed distance function design domain thickness-control functional forward and backward finite difference operators element index strain Young’s modulus of the matrix material Young’s modulus of the fiber along the longitudinal direction local grid node index within the element shape sensitivity density of the thickness-control functional length of the square feature Heaviside function grid node index optimization iteration index Two-dimension grid node index objective function of the level set structural and material optimization the load linear form Lagrange formulation of the optimization problem number of elements boundary unit vector pointing from the material domain outwards shape interpolation function of local grid node g weighted average orientation difference norm parameter body force boundary projection of Z global measure of the elastic energy density the elementary elastic energy density the maximum allowed value of local elastic energy density maximum elementary elastic energy density radius of the circle feature n-dimension space time targeted thickness transformation matrix displacement vector the space of kinematically admissible displacement field test vector velocity for normal boundary propagation adjoint variable gate location injection flow rate mold temperature melt temperature sample vector sample vector center point of shape features sample vector located on the structural boundary sample vector located on ray ∂ Ω Y volume ratio of the fiber shape sensitivity density parameters of the quadratic function adjustment parameter of the weighting factor μ Dirac Delta function Dirac Delta function for auxiliary fiber orientation control adjustment parameter of the penalization factor Λ fiber orientation local tangential direction of the level set contour initial fiber orientation before controlled by the auxiliary feature elementary fiber orientation of the simulation result elementary fiber orientation of the optimized result local boundary curvature the Lagrange multiplier weighting factor of the thickness-control functional Poisson ratio of the matrix material traction force control band width of the auxiliary feature penalization factor of the Lagrange multiplier λ the set of projections of X on ∂ Ω level set function primitive level set functions material domain boundary of the material domain | A novel CACD/CAD/CAE integrated design framework for fiber-reinforced plastic parts |
S0965997815000733 | Conventional finite element analysis (FEA) is usually carried out in offsite and virtual environments, i.e., computer-generated graphics, which does not promote a user’s perception and interaction, and limits its applications. With the purpose of enhancing structural analysis with augmented reality (AR) technologies, the paper presents a system which integrates sensor measurement and real-time FEA simulation into an AR-based environment. By incorporating scientific visualization technologies, this system superimposes FEA results directly on real-world objects, and provides intuitive interfaces for enhanced data exploration. A wireless sensor network has been integrated into the system to acquire spatially distributed loads, and a method to register the sensors onsite has been developed. Real-time FEA methods are employed to generate fast solutions in response to load variations. As a case study, this system is applied to monitor the stresses of a step ladder under actual loading conditions. The relationships among accuracy, mesh resolution and frame rate are investigated. | Real-time finite element structural analysis in augmented reality |
S0965997815000745 | An efficient solver integrating the restarted simpler generalized minimal residual method (SGMRES(m)) with finite volume method (FVM) on triangular grid is developed to simulate the viscoelastic fluid flows. In particular, the SGMRES(m) solver is used to solve the large-scale sparse linear systems, which arise from the course of FVM on triangular grid for modeling the Newtonian and the viscoelastic fluid flows. To examine the performance of the solver for the nonlinear flow equations of viscoelastic fluids, we consider two types of numerical tests: the Newtonian flow past a circular cylinder, and the Oldroyd-B fluid flow in a planar channel and past a circular cylinder. It is shown that the numerical results obtained by the SGMRES(m) are consistent with the analytical solutions or empirical values. By comparing CPU time of different solvers, we find our solver is a highly efficient one for solving the flow equations of viscoelastic fluids. | The simpler GMRES method combined with finite volume method for simulating viscoelastic flows on triangular grid |
S0965997815000757 | Renewable energy technologies are developing rapidly, while in the last decade great interest is encountered in the use of wind energy, especially due to the energy crisis and serious environmental problems appeared from the use of fossil fuels and therefore a large number of wind farms have been installed around the world. On the other hand the ability of nature inspired algorithms to efficiently handle combinatorial optimization problems was proved by their successful implementation in many fields of engineering sciences. In this study, a new problem formulation for the optimum layout design of onshore wind farms is presented, where the wind load is implemented using stochastic fields. For this purpose, a metaheuristic search algorithm based on a discrete variant of the harmony search method is used for solving the problem at hand. The farm layout problem is by nature a constrained optimization problem, and the contribution of the wake effects is significant; therefore, in two formulations presented in this study the influence of wind direction is also taken into account and compared with the scenario that the wake effect is ignored. The results of this study proved the applicability of the proposed formulations and the efficiency of combining metaheuristic optimization with stochastic wind loading for dealing with the problem of optimal layout design of wind farms. | Optimum layout design of onshore wind farms considering stochastic loading |
S0965997815000769 | High-dimensional data is pervasive in many fields such as engineering, geospatial, and medical. It is a constant challenge to build tools that help people in these fields understand the underlying complexities of their data. Many techniques perform dimensionality reduction or other “compression” to show views of data in either two or three dimensions, leaving the data analyst to infer relationships with remaining independent and dependent variables. Contextual self-organizing maps offer a way to represent and interact with all dimensions of a data set simultaneously. However, computational times needed to generate these representations limit their feasibility to realistic industry settings. Batch self-organizing maps provide a data-independent method that allows the training process to be parallelized and therefore sped up, saving time and money involved in processing data prior to analysis. This research parallelizes the batch self-organizing map by combining network partitioning and data partitioning methods with CUDA on the graphical processing unit to achieve significant training time reductions. Reductions in training times of up to twenty-five times were found while using map sizes where other implementations have shown weakness. The reduced training times open up the contextual self-organizing map as viable option for engineering data visualization. | Extending parallelization of the self-organizing map by combining data and network partitioned methods |
S0965997815000770 | The present paper introduces an investigation into simultaneous optimization of the PbLaZrTi-based actuator configuration and corresponding applied light intensity for morphing beam structural shapes. A finite element formulation for multiphysics analysis of coupled opto-electro-thermo-mechanical fields in PbLaZrTi ceramics is derived and verified with the theoretical solution and the commercial software ANSYS. This element is then used to simulate beam bending shape control using the orthotropic PbLaZrTi actuators and the simultaneous optimization. In this procedure, the controlling and geometrical variables are simultaneously optimized via a hierarchical genetic algorithm. A bi-coded chromosome is proposed in a hierarchical mode, which consists of some control genes (i.e. actuator location and number) and parametric genes (i.e. applied light intensity). Whether the parametric gene is activated or not is managed by the value of the first-grade control genes. The numerical results demonstrate that the achieved beam bending shapes correlate remarkably well with the expected ones and the simultaneous optimization of photostrictive actuator locations, numbers and light intensities can result in optimal actuator layout with less PbLaZrTi actuators and irradiated light energy. The simulation results also show that the hierarchical genetic algorithm has more superior performance over the conventional real-coded genetic algorithm. | Simultaneous optimization of photostrictive actuator locations, numbers and light intensities for structural shape control using hierarchical genetic algorithm |
S0965997815000848 | Currently, there are still some big gaps between the CAD system and CAE system, e.g. the different data structure for model representation, which costs lots of time and effort of engineers in the interaction between these two kinds of systems. In order to bridge these gaps, an incorporate software framework is proposed in this paper. In this framework, the unified representation architecture (URA) is presented that makes CAD and CAE to be an organic entity. The URA contains three components: (1) unified data model (UDD) including unified B-rep, unified feature and unified mesh; (2) unified data management (UDM) consisting of unified interaction, unified data structure, unified Constructive Solid Geometry (CSG) history and unified interface; (3) unified display and post-processor (UDP) for both design and performance analysis. The URA facilitates the incorporation by explicitly representing design and analysis information as design features, which maintains their associations through the history chain. Besides the URA, a unified mesh data (UMD) is proposed to unify the mesh of CAD model display and CAE analysis with the purpose of reducing the redundancy of mesh data. The unified mesh data (UMD) is proposed to unify the mesh of CAD model display and CAE analysis, which greatly reduces the redundancy of mesh generation data. Finally, the high efficiency of the proposed framework is demonstrated by engineering examples. | A CAD/CAE incorporate software framework using a unified representation architecture |
S096599781500085X | The present article proposes an advanced methodology for numerically simulating complex noise problems. More precisely, we consider the so-called multi-stage acoustic hybrid approach, which principle is to couple sound generation and acoustic propagation stages. Under that approach, we propose an advanced hybrid method which acoustic propagation stage relies on Computational AeroAcoustics (CAA) techniques. To this end, first, an innovative weak-coupling technique is developed, which allows an implicit forcing of the CAA stage with a given source signal coming from an a priori evaluation, whether the latter evaluation is of analytical or computational nature. Then, thanks to additional innovative solutions, the resulting CAA-based hybrid approach is optimized so that it can be applied to realistic and complex acoustic problems in an easier and safer way. All these innovative features are then validated on the basis of an academic test case, before the resulting advanced CAA-based hybrid methodology is applied to two problems of flow-induced noise radiation. This demonstrates the ability of the here proposed method to address realistic problems, by offering to handle at the same time both acoustic generation and propagation phenomena, despite their intrinsic multiscale character. | An advanced hybrid method for the acoustic prediction |
S0965997815000861 | Soft computing techniques have been widely used during the last two decades for nonlinear system modeling, specifically as predictive tools. In this study, the performances of two well-known soft computing predictive techniques, artificial neural network (ANN) and genetic programming (GP), are evaluated based on several criteria, including over-fitting potential. A case study in punching shear prediction of RC slabs is modeled here using a hybrid ANN (which includes simulated annealing and multi-layer perception) and an established GP variant called gene expression programming. The ANN and GP results are compared to values determined from several design codes. For more verification, external validation and parametric studies were also conducted. The results of this study indicate that model acceptance criteria should include engineering analysis from parametric studies. | Assessment of artificial neural network and genetic programming as predictive tools |
S0965997815000873 | The simulation of a manufacturing process chain with the finite element method requires the selection of an appropriate finite element solver, element type and mesh density for each process of the chain. When the simulation results of one step are needed in a subsequent one, they have to be interpolated and transferred to another model. This paper presents an in-core grid index that can be created on a mesh represented by a list of nodes/elements. Finite element data can thus be transferred across different models in a process chain by mapping nodes or elements in indexed meshes. For each nodal or integration point of the target mesh, the index on the source mesh is searched for a specific node or element satisfying certain conditions, based on the mapping method. The underlying space of an indexed mesh is decomposed into a grid of variable-sized cells. The index allows local searches to be performed in a small subset of the cells, instead of linear searches in the entire mesh which are computationally expensive. This work focuses on the implementation and computational efficiency of indexing, searching and mapping. An experimental evaluation on medium-sized meshes suggests that the combination of index creation and mapping using the index is much faster than mapping through sequential searches. | An in-core grid index for transferring finite element data across dissimilar meshes |
S0965997815000885 | Structural damages caused by natural catastrophic events cover a wide area and it is convenient to supervise the event consequences by vision tools. The aim of this paper is to supply a rapid damage detector designed as a way to aid in risk assessment, damage control and disaster prevention as well as a way to speed the examination of catastrophic effects for emergency studies. The satellite pictures covering the area of interest represent the required bits of information to manage the developed telematics tool. A case study is discussed in order to provide experimental evidence of the proposed procedure potential. Moreover, a multi-view image/video fusion system is integrated in the image process to detect the damage levels of structures to overcome the limitations on the vertical information provided by a satellite. In synthesis, this study shows how a GIS-based real time monitoring system can be effectively used for a rapid evaluation of structural damage and disaster management. | Real-time identification of disaster areas by an open-access vision-based tool |
S0965997815000897 | Nowadays building designers have to face up to new strategies to achieve the best sustainable building designs. Well planned natural ventilation strategies in building design may contribute to a significant reduction on building’s energy consumption. Natural ventilation strategies are conditioned to the particular location of each building. To improve natural ventilation performance of a building, the analysis of the influence of the location and the surrounding buildings on wind flow paths around the design building is a must. New computational tools such as Computational Fluid Dynamics (CFD) are particularly suited for modelling outdoor wind conditions and the influence on indoor air conditions prior to building construction. Hence, reliable methodologies are necessary to support building design decisions related to naturally ventilated buildings prior to construction. This paper presents a case study for the selection of the best future building location attending to natural ventilation behaviour inside the building, conditioned by different evolving environment. A validated CFD model is used to represent outdoor and indoor spaces. The methodology explains how to qualitatively and quantitatively analyze wind paths around and through a building to quantify the natural ventilation performance. The best location, from two real possible solutions, is then selected. | Computational analysis of wind interactions for comparing different buildings sites in terms of natural ventilation |
S0965997815000903 | Occupant responses and injuries are important considerations in the design and assessment of roadside safety devices such as barriers. Although incorporating occupant responses and injuries into the design of safety devices is highly recommended by the current safety regulations, there are limited studies that directly consider occupant responses and injuries. Crash test dummies are seldom equipped in the state-of-the-art crash testing of roadside barriers and thus occupant responses and injury risks are evaluated primarily based on vehicle responses. In the present work, occupant responses and injuries in automotive crash events were investigated by incorporating crash test dummies into the vehicle model that was used in the finite element (FE) simulations of roadside crashes. The FE models of a Ford F250 pickup truck and a Hybrid III 50th percentile crash test dummy were employed and a passive restraint system was developed in the FE model. The FE model was validated using existing experiments including a sled test and a full-frontal impact test. Simulations of the Ford F250 impacting a concrete barrier and a W-beam guardrail were conducted and the occupant responses were analyzed. Furthermore, occupant injuries were quantitatively estimated using occupant injury criteria based directly on dummy responses and compared to those based solely on vehicle responses. The correlations between vehicle responses and occupant injuries were studied. | A numerical study of occupant responses and injuries in vehicular crashes into roadside barriers based on finite element simulations |
S0965997815000915 | Recently building information models have substantially improved the explicit semantic content of design information. Information models are used to integrate the initial phases of project development. On the construction site, however, the designs are still mostly represented as line-based paper drawings or projections on portable displays. A generic technology that can integrate information and situate it in time, place and context is augmented reality. The specific research issues addressed are (1) does augmented reality have a potential use in civil engineering, (2) how big – in comparison to other technologies - is this potential and (3) what are the main barriers to its adoption. The generic research issue was to develop a methodology for evaluation of potentials of technology. A prototype was built. It was tested on a real construction site to evaluate the potential of its use using the action-research method. A set of structured interviews with potential users was then conducted to compare the prototype to conventional presentation methods. Using this methodology it has been found out that augmented reality is expected to be as big a step as the transition from 2D line drawings to photorealistic 3D projections. The main barrier to the adoption is immature core virtual reality technology, conservative nature of construction businesses and size of building information models. | Measuring the potential of augmented reality in civil engineering |
S0965997815000927 | In the paper, two methods for building a 3-dimensional geometry of a wire rope bent over a sheave in Proe™ are presented. In order to obtain the centroidal axes of the wires, the first method is associated with deriving their coordinate equations based on the Serret–Frenet frame and the second method is characterized by using the ‘Variable Section Sweep’ tool in Proe™ to generate a helically twisting surface around the centroidal axis of the king wire or a strand with the two boundary curves being the centroidal axes of two double or triple helical wires. Finally, both methods use the ‘Variable Section Sweep’ tool to generate the geometries of the wires. The two methods can be applied to any helical-strand wire rope. | Computer-aided modeling of wire ropes bent over a sheave |
S0965997815000976 | Spiral triangular strand (STS) and simple straight strand (SSS) are widely used in practical applications, but comparative analyses aimed for a better comprehension of the service behavior are seldom conducted due to the complex geometric configuration of STS. In the present study, a new parametric geometric model of STS, considering the effect of lay angle on the wire cross section, is proposed by means of parametric equations and Pro/Engineer software. Full 3D finite element (FE) models of the STS and SSS are developed with ANSYS software. Under axial tensile and torsional loads, the behaviors of the STS and SSS with the same lay angle and total wire sectional area are comparatively studied, and the comparison are conducted at different lay angles and outer wire diameters. The results of FE analyses show that nonlinear overall behaviors happen to the both kinds of strands. The STS results in smaller axial force and torque, but severer plastic deformation and von Mises stress than the SSS, and the discrepancies increase with increasing lay angle and outer wire diameter. The discontinuous contact lines of the STS lead to the nonuniform distribution of von Mises stress and significant contact pressure. | Parametric modeling and comparative finite element analysis of spiral triangular strand and simple straight strand |
S0965997815001027 | To effectively investigate the mechanical performance of microstructure-based layered composites, an object-oriented software with interactive graphical user interface has been developed. This software, named PCLab, is able to analyze the microstructure evolution and mechanical performance by both Monte Carlo (MC) simulation and the Finite Element method (FEM). The software has integrated preprocessors, solvers and postprocessors. Some examples are tested and explored the functionality of the software package. It shows that the PCLab software with a user-friendly graphical interface provides an efficient tool for faster material analysis, design and application. It also provides a flexible, robust platform for the future extensity in the material multi-physics research. | PCLab – A software with interactive graphical user interface for Monte Carlo and finite element analysis of microstructure-based layered composites |
S0965997815001118 | Modern design process is a complex work which includes many aspects and so CAD/CAM/CAE are widely used now. The next special generation of such software which combines complex geometrical design facilities, micro-models of composite structures and FE analysis, and tools for additive technologies has to be developed. This paper proposes a design methodology of a new 3D raster/vector drawing program to make micro-models with crowding or coarsening of fiber structures. The definitions of the new terms, principles, and algorithms to design such structure as a set of domains are given. Files for additive technology machines and finite element analysis were created. This approach is the convenient means of micro-modeling of FRC complex shape parts. | A methodology to design a 3D graphic editor for micro-modeling of fiber-reinforced composite parts |
S096599781500112X | One of the most important challenges in the computer vision has long been to obtain three-dimensional models from the information given by a projection of the model. In this work we show an automatic system which allows obtaining three-dimensional models from entities that represent the conical projection of a polyhedral model with normalon or quasi-normalon typology. The results obtained on a total of 160 tests, with a success ratio of 100%, make the method a proposal to be considered for obtaining models from conical perspectives automatically. | Obtaining three-dimensional models from conical perspectives |
S0965997815001131 | A global sensitivity analysis and parameter adjustment of a simplified physical fire model applied to a well measured experimental example is developed in order to validate the model. The fire model is a simplified physical 2D wildland fire model with some 3D effects that takes into account the wind, the slope of the orography, the fuel load and type, the moisture content, the energy lost in the vertical direction and the radiation from the flames. The simplicity of the model and the numerical techniques proposed allow very competitive computational times. temperature (K) (T ∞ reference temperature) enthalpy ( J m − 2 ) fuel load ( kg m − 2 ) (M 0 initial fuel load) moisture content (kg of water/kg of dry fuel) density ( kg m − 3 ) heat capacity ( J K − 1 kg − 1 ) natural convection coefficient ( J s − 1 m − 2 K − 1 ) thermal radiation ( J s − 1 m − 2 ) radiation intensity ( J s − 1 m − 2 sr − 1 ) mean absorption coefficient ( m − 1 ) latent heat of evaporation ( J kg − 1 ) flame height (m) half-life time of combustion (s) spatial and temporal scales (m, s) dimensionless temperature ( u = T − T ∞ T ∞ ) dimensionless enthalpy ( e = E M C T ∞ ) mass fraction of solid fuel ( c = M M 0 ) dimensionless natural convection coefficient ( α = H [ t ] M C ) dimensionless thermal radiation ( r = [ t ] M C T ∞ R ) dimensionless latent heat of evaporation ( λ v = M v Λ v C T ∞ ) dimensionless temperature of water evaporation dimensionless temperature of solid fuel pyrolysis dimensionless coefficient of fuel mass variation by pyrolysis ( ln 2 [ t ] t 1 / 2 ) dimensionless wind velocity correction factor | Sensitivity analysis and parameter adjustment in a simplified physical wildland fire model |
S0965997815001143 | The efficient and integrated visualization and reuse of multidisciplinary simulation data are imperative for the development of complex products. However, it is not a trivial task for designers to efficiently acquire, view and then reuse simulation data to improve the product design process. The challenge is that simulation data are always too huge to be transferred and retrieved quickly and they tend to be heterogeneous and tool-specific due to the lack of a uniform representation. In this study, an approach of intermediate model based efficient and integrated visualization of multidisciplinary simulation data for simulation information reuse is proposed to address the above issues. Firstly, the intermediate model based integrated model framework is designed to support the uniform modeling and integrated visualization of multidisciplinary simulation data. Then, the intermediate mesh model is constructed based on the hybrid mesh size (HMS) field to achieve the uniform representation of multidisciplinary simulation data with high-fidelity. Thirdly, a series of strategies such as coarse filtering, fine filtering for incremental transmission and data compression are proposed to improve data transmission efficiency. Moreover, a simulation model descriptor (SMD) based similarity assessment method is developed to support the efficient retrieval of simulation models for reuse. Finally, several experiments are conducted to demonstrate the feasibility and effectiveness of the proposed model and methods. | Intermediate model based efficient and integrated multidisciplinary simulation data visualization for simulation information reuse |
S0965997815001155 | This paper introduces a mesh generation strategy devised and implemented for the volume element model (VEM), and elaborates key contributions of the strategy in enhancing the VEM as a prominent tool in ship thermal modeling and simulation. The VEM mesh generation strategy employs ray crossings and ray– triangle intersection algorithms developed in previous studies, and constructs sufficiently accurate geometric representations of the whole ship within permissible time frame using hexahedral meshes. In addition, this work demonstrates the strategy’s practicality in thermal analysis of a notional all-electric ship, which is characterized by intricate structures and multiple internal components, i.e., thermal loads. Ship thermal solutions obtained in this assessment verify the proposed mesh generation strategy’s ability to improve the overall computational efficiency of the VEM, by allowing it to obtain plausible thermal solutions with respect to time and space using a coarse independent mesh. specific heat (J/kg K) thermal conductivity (W/m K) length (m) total number number normal array of volume element vertex coordinates pressure (Pa) heat transfer rate (W) point ray triangle temperature time volume (m3); vertex Cartesian coordinates divider thickness (m) volume element length (m) mesh refinement relative error plane density (kg/m3) relative humidity energy (J) solution vector convection bottom divider east equivalent generation VE index VE face index maximum minimum mesh north actual component weighted average south top vapor volume element saturation pressure west x-direction y-direction z-direction | Volume element model mesh generation strategy and its application in ship thermal analysis |
S0965997815001222 | In this paper a review of optimal analysis of structures is presented. Different methods of swift analyses are employed for various problem formulations. Depending on the problem at hand, a proper combination of graph products, sub-structuring methods, finite difference method and manipulating the stiffness matrix manipulation is selected to achieve the most efficient design. Design problems can be classified as three types. The first type includes the solution of near-regular structures using graph products and sub-structuring methods. These structures consist of two groups. In the first group, the main structure contains some additional members with respect to its corresponding regular structure while the structures in the second group contain some additional nodes with respect to the corresponding regular structures. The second type of problems includes the simultaneous optimal analysis and optimal design of structures. The presented method is applicable to an arbitrary structure and the optimal solution is obtained by manipulating the stiffness matrices and taking advantages of the iterations during design process. The third type of problems includes the efficient modal analysis of structures using a combined finite difference method and graph products. Boundary-value and initial-value differential equations are solved using finite difference method and graph products, and then the method is applied to the dynamic equations of modal analysis. | Advances in swift analysis of structures: Near-regular structures, and optimal analysis and design |
S0965997815001234 | Based on the recent research concerning the PageRank Algorithm used in the famous search engine Google [1], a new Inverse-PageRank-Particle Swarm Optimizer (I-PR-PSO) is presented in order to improve the performances of classic PSO. The resulted algorithm uses a stochastic Markov chain model to define an intelligent topological structure of the swarm’s population, in which the better particles have an important influence on the others. In the presented experiments, calculations on some benchmark functions classically used to test optimization methods are performed, and the results are compared to different versions of the standard PSO, that is using different topological structures of the population. The experimental results show that I-PR-PSO can converge quicker on the tested functions, and can find better results in the solution domain than its tested peers. | A new hybrid PSO algorithm based on a stochastic Markov chain model |
S0965997815001246 | In this paper, a semi-implicit method for solving pressure coupled equations used to calculate the flow field, and dynamic mesh were employed to simulate the three-dimensional dynamic turbulent flow of whole flow channels, in start transition process and runaway transition process of bulb hydraulic turbine. In above processes, the transition process of pressure field and flow field were realistically modeled and simulated, which reflects the influence of water flow state, after passing through guide vanes on the inflow of the runner blades, and reveals the flow field variations in the transition process. The numerical results show that: during the start transition process, with the increase of guide vane opening, the flow circulation produced by water flowing through the guide vanes becomes smaller; therefore, the rotational acceleration of the runner decreases and the rotational speed value reduces. In the runaway transition process, the hydraulic turbine operating with load has a sudden load rejection and then, the hydraulic turbine rotational speed is rising with the guide vane closing, leading to pressure pulsations and severe vortex phenomenon, which will cause significant vibrations of swings. | Transient hydrodynamic analysis of the transition process of bulb hydraulic turbine |
S0965997815001325 | The increase in the use of biofuels raised new challenges to engineering problems. In this context, the optimization of chemical reactors, particularly bioreactors and photobioreactors, is crucial to improve the production of biofuels in a sustainable manner. This paper reports the development of an optimization method and its application to the design of a continuous flow bioreactor envisaged to be used in industrial fermentation processes. Mass and momentum conservation equations are simulated via CFD and specific a posteriori performance parameters, determined from the flow solution, are fed into a multiobjective evolutionary algorithm to obtain corrections to the parameters of the geometrical configuration of the reactor. This heuristics is iterated to obtain an optimized configuration vis-à-vis the flow aspects portrayed by the performance parameters, such as the shear stress and the residence time variations. An open source computer package (PyCFD-O) was developed to perform CFD simulations and the optimization processes automatically. First, it calls the pre-processor to generate the computational geometry and the mesh. Then it performs the simulations using OpenFOAM, calculates the output parameters and iterates the procedure. The PyCFD-O package has proved reliable and robust in a test case, a ∼1 m3 continuous fermentation reactor. The multiobjective optimization procedure actually corresponds to search for the Pareto frontier in the solution space characterized by its geometric parameters and the associated performance parameters (dispersion o residence times and shear stresses). Optimal design configurations were obtained representing the best tradeoff between antagonistic objectives, i.e. the so-called non-dominant solutions. | Optimal industrial reactor design: development of a multiobjective optimization method based on a posteriori performance parameters calculated from CFD flow solutions |
S0965997815001337 | Building Information Modelling (BIM) is now a global digital technology which is widely believed to have the potential to revolutionise the construction industry. This has been mainly a result of worldwide government initiatives promoting BIM uptake to improve efficiency and quality in delivering construction projects. This push has been accompanied by the release of a tremendous amount of BIM software systems which are now available in the market. Although this can be seen as a positive development, one cannot ignore how it has overwhelmed many professionals who cannot easily distinguish between the uses of these software systems. Previous studies about different BIM systems have generally been limited in scope focusing predominantly on operational issues. This study aims to conduct a comprehensive and critical appraisal of a wide range of BIM software systems currently being used in managing construction project information. To achieve this, five main methods are adopted. These include a systematic review of the literature, a structured questionnaire survey, action learning, focus group discussions and email surveys. It has to be noted that, although it is impossible to examine the totality of BIM systems, the study adopts a holistic approach looking at most of the major BIM system categories and 122 application examples which are common in the architecture, engineering and construction (AEC) industry. | A critical analysis of Building Information Modelling systems used in construction projects |
S0965997815001349 | The success of a flexible assembly line (FAL) depends on efficacious scheduling and control architecture. However, the scheduling and control architectures currently employed in FALs lack the flexibility and reconfiguration capacity to manage disturbances when they occur. Consequently, the system performance rapidly degrades when the system operation is interrupted. The objective of this study is to examine the potential enhancement of FAL performance through the use of a radio-frequency-identification-enabled multi-agent scheduling and control system (RFID-enabled MASCS). A simulation test platform is developed for the examination of an RFID-enabled MASCS in a FAL, and several system performance measures are considered in the simulation test platform. The results indicate that the RFID-enabled MASCS can increase the uptime productivity and production rate of a FAL. A real case-study test is performed, and a 22% decrease in lead time along with significant improvements in other system performance indicators are observed, especially when a series of disturbances occur within the examined assembly machine. | Flexible testing platform for employment of RFID-enabled multi-agent system on flexible assembly line |
S0965997815001350 | Engineering design is a complex and iterative process that involves multiple engineering teams sharing and communicating information during the design process. One aspect of engineering design involves the development of physics-based models and their analysis via numerical simulations that are computationally expensive. To overcome the time constraints due to the complexity of numerical simulations, reduced-order models (ROM) such as proper orthogonal decomposition are being increasingly used. Decreasing the simulation time, however, does not address the inefficiencies in communicating engineering models and analysis during the design process. This paper proposes developing and incorporating a ROM server into the design workflow. The ROM server stores all data associated with a given engineering model and automatically constructs a ROM every time a model is created or updated, thus maintaining a consistent version of information across multiple engineering teams. A common engineering workflow is compared with one using a ROM server. A cost of synchronization metric has been defined based on the parameters of data size, size of the engineering team and design iterations. This metric has been evaluated and compared for the cases with and without a ROM server and it was found that the cost of synchronization is lower when a ROM server is used in the design workflow. It is shown that as the team size increases, the ROM server helps with more efficient information storage and transfer. Finally, an example problem of a heat-exchanger fin shape design is used to demonstrate the ROM server framework. | Integrating a reduced-order model server into the engineering design process |
S0965997815001386 | Convex hulls are fundamental geometric tools used in a number of algorithms. This paper presents a fast, simple to implement and robust Smart Convex Hull (S-CH) algorithm for computing the convex hull of a set of points in E 3. This algorithm is based on “spherical” space subdivision. The main idea of the S-CH algorithm is to eliminate as many input points as possible before the convex hull construction. The experimental results show that only a very small number of points are used for the final convex hull calculation. Experiments made also proved that the proposed S-CH algorithm achieves a better time complexity in comparison with other algorithms in E 3. | Space subdivision to speed-up convex hull construction in E3 |
S0965997815001398 | This paper presents a novel method for mesh color sharpening using the discrete Laplace–Beltrami operator, which is an approximation of the second order derivatives on irregular 3D meshes. The one-ring neighborhood is utilized to compute the Laplace–Beltrami operator. The color of each vertex of the 3D mesh is updated by adding the Laplace–Beltrami operator of the vertex color weighted by a factor to its original value. Laplacian is commonly used in image processing to sharpen 2D images and different discretizations of the Laplace–Beltrami operator have been proposed for geometrical processing of 3D meshes. This paper utilizes several discretizations of the Laplace–Beltrami operator for sharpening 3D mesh colors and applied them to various 3D objects. This method successfully improves the visual appearance of the meshes while keeping the surface geometry intact. Experimental results of the proposed mesh color sharpening method using different discretizations of the Laplace–Beltrami operator demonstrated its effectiveness on improving the visual appearances of 3D meshes. | Mesh color sharpening |
S0965997815001404 | A stripe-patterned surface with different wettability can be effective for the passive control of droplet movement on a vertical surface. We have performed three-dimensional Lattice Boltzmann (LB) simulations to investigate the effect of the pattern characteristics and liquid properties on the droplet movement. The simulation was initiated by imposing gravity on the droplet formed on the surface. The droplet moves along the direction of the pattern when the angle between the gravity and the pattern is small; however, it starts to overrun the stripes when the angle is greater than a certain value, i.e., critical angle. It is shown that the critical angle decreases as the Bond number increases while it increases as the strength of the adhesion/repulsion force increases. The droplet forms a curved asymmetric boundary on the stripe-patterned surface due to gravity and surface forces. The critical angle is also affected by the thickness of the stripes. | Lattice Boltzmann simulation of the movement of droplets on stripe-patterned surfaces having different wettability |
S0965997815001428 | The devastation wrought by Hurricanes Katrina (2005), Ike (2008), and Sandy (2012) in recent years continues to underscore the need for better prediction and preparation in the face of storm surge and rising sea levels. Simulations of coastal flooding using physically based hydrodynamic codes like ADCIRC, while very accurate, are also computationally expensive, making them impractical for iterative design scenarios that seek to evaluate a range of countermeasures and possible failure points. We present a graphical user interface that supports local analysis of engineering design alternatives based on an exact reanalysis technique called subdomain modeling, an approach that substantially reduces the computational effort required. This interface, called the Subdomain Modeling Tool (SMT), streamlines the pre- and post-processing requirements of subdomain modeling by allowing modelers to extract regions of interest interactively and by organizing project data on the file system. Software design and implementation issues that make the approach practical, such as a novel range search algorithm, are presented. Descriptions of the overall methodology, software architecture, and performance results are given, along with a case study demonstrating its use. | SMT: An interface for localized storm surge modeling |
S096599781500143X | The main goal of this paper was to develop an integrated simulation-design of experiments (DOE) model to optimize a petrol station queuing system and sales rate. Initially, the petrol station operating system was simulated using Witness 2014 simulation software©. Then, the responses of simulation were deployed as the input of DOE. Two-level full factorial experiments with center points were performed where the simulated model parameter studied were number of pump, number of cashier and inter arrival times (IATs). The response variables analyzed were queue length and sales rate. The obtained model from experimental design revealed that number of cashier and inter arrival time were significant in determining the queue length while all the factors and their interaction were significantly affecting the sales rate. | Performance evaluation of a petrol station queuing system: A simulation-based design of experiments study |
S0965997815001441 | Feature techniques have played an important role in CAD/CAM integration. These techniques need to be developed for each type of manufacturing process owing to its unique characteristics. Therefore, an approach is proposed in this paper to extract the machining feature of region containing internal sharp points for the process preparation of electrical discharge machining (EDM). The hint feature points are innovatively defined and classified into three types: internal sharp points, cutting-into points and interacting points. Based on this, our approach firstly identifies the faces and the type of the region. Secondly, the interacting region is decomposed into isolated regions through reconstructing the topological structure of the region. Thirdly, the reconstructed faces and original faces are stitched together to form a closed surface, and the CAD models of volumetric features are constructed. Finally, the position and dimension parameters are extracted and saved. The shape and parametric information extracted can be used for subsequent procession preparation, so as to promote the CAD/CAM integration of EDM. | Feature recognition and volume generation of uncut regions for electrical discharge machining |
S0965997815001520 | In this paper, in the framework of OpenFOAM, the density-based steady and unsteady dual-time implicit LU-SGS solvers which are termed as lusgsFoam and lusgsDualFoam are established. The key implementation details of the forward and backward sweep looping process in the LU-SGS approach are introduced. Three typical test cases, i.e. hypersonic airflow across cylinder(steady), subsonic flow over bump (steady) and supersonic forward step flow (unsteady), are used to investigate the performance of these LU-SGS solvers, and the density-based explicit solver, i.e. the rhoCentralFoam in the official OpenFOAM, is adopted as the comparison solver. Through the comparison of the numerical results for the first two steady cases, it is found that, the convergence performance of the LU-SGS solver is significantly superior to explicit solver rhoCentralFoam. Meanwhile, considering the combined effect of time step and the iteration efficiency, the LU-SGS solver, lusgsFoam is significantly more efficient than the explicit solver, rhoCentralFoam. For the third test case, i.e. the unsteady supersonic forward step flow, the spatial accuracy of the unsteady dual time lusgsDualFoam solver is a little lower than the explicit rhoCentralFoam, but overall, this unsteady implicit solver can capture the transient characteristics efficiently. convective Jacobian matrix positive/negative Steger–Warming flux-splitting Jacobian matrix surface element diagonal matrix, the lower-diagonal matrix and the the upper-diagonal matrix convective flux vectors viscous flux vectors identity matrix sets of “owner” and “neighbor” cells which are adjacent to the cell i in OpenFOAM unit normal vector at the interface set of cells which are adjacent to cell i residual of complete spatial discretization term for the discretized governing equation physical time(s) contravariant velocity vector of conservative variable control volume spectral radius of the convective flux Jacobian, Ac L2 norm residual pseudo time step convective; sound speed index of cell interface between cell i and j time level at the current pseudo time Cartesian coordinates inverse time level at the current physical time viscous symbol indicating direction temporary variable | Implementation of density-based implicit LU-SGS solver in the framework of OpenFOAM |
S0965997815001532 | Trajectory planning refers to planning a time-dependent path connecting the initial and final configurations with some special constraints simultaneously considered. It is a critical aspect in autonomously driving an articulated vehicle. In this paper, trajectory planning is formulated as a dynamic optimization problem that contains kinematic differential equations, mechanical/environmental constraints, boundary conditions and an optimization objective. The prevailing numerical methods for solving the formulated dynamic optimization problem commonly disregard the constraint satisfactions between every two adjacent discretized mesh points, thus resulting in failure when the planned motions are actually implemented. As a remedy for this limitation, the concept of minute mesh grid is proposed, which improves the constraint satisfactions between adjacent rough mesh points. On the basis of accurate penalty functions, large-scale constraints are successfully incorporated into the optimization criterion, thus transforming the dynamic optimization problem into a static one with simple bounds on the decision variables. Simulation results verify that our proposed methodology can provide accurate results and can deal with various optimization objectives uniformly. | Precise trajectory optimization for articulated wheeled vehicles in cluttered environments |
S0965997815001544 | This article presents numerical modelling of rural road pavement sections recycled in situ with two materials stabilized with bitumen emulsion. The two materials stabilized with bitumen emulsion are base course materials comprising 25% reclaimed asphalt pavement and 75% natural aggregates with and without 1% cement. A 3D-finite difference model was used to determine the response of these pavement sections when subjected to two types of loads with four types of soil subgrades of varying resistances. A nonlinear elasto–plastic Mohr-Coulomb model was used in the two materials stabilized with bitumen emulsion, and a nonlinear model was adopted in the four soil subgrades. Both the resilient and permanent behaviours of these materials were modelled. An analysis was conducted on rutting and fatigue resistances of the base course materials. The base course material containing 1% cement is more resistant and is apt for use in lightly trafficked rural roads. Both base course materials stabilized with bitumen emulsion will first fail from rutting before fatigue. | Nonlinear elasto–plastic performance prediction of materials stabilized with bitumen emulsion in rural road pavements |
S0965997815001568 | This paper presents a Particle Swarm Optimization-based topology optimization method for the design of negative permeability dielectric metamaterials. As the electromagnetic metamaterials have some physical properties not available in nature, they have attracted a huge scientific research interest for decades. In fact, electromagnetic metamaterials can exhibit simultaneously negative permeability and negative permittivity. The aim of this work is to find an optimal topology of a dielectric metamaterial that achieves negative permeability at a given frequency. A binary Particle Swarm Optimization is developed and applied to a negative permeability dielectric metamaterial topology design problem. The optimization process is achieved using a developed numerical model of the studied metamaterial, which is solved by the Finite Element Method. First, the governing equations and the weak formulation of the electromagnetic problem are presented. Then, the optimization problem to be solved is formulated. The developed binary Particle Swarm Optimization method, and the developed interfacing method are explained. Some numerical examples are presented to demonstrate that the binary Particle Swarm Optimization is adapted to the topology optimization of negative permeability dielectric metamaterials, at given frequencies, to demonstrate the utility and validity of the presented method. | Optimum topological design of negative permeability dielectric metamaterial using a new binary particle swarm algorithm |
S0965997815001581 | Optimum design of real world steel space frames under design code provisions is a complicated optimization problem due to the presence of large numbers of highly nonlinear constraints and discrete design variables. The use of gradient based optimization techniques in finding the optimum solution of such large design problems is cumbersome due to the selection of initial design points and convergence difficulties while metaheuristic algorithms do not suffer such problems. Artificial bee colony (ABC) algorithm is one of the recent additions to the swarm intelligence based meta-heuristic search techniques that mimic natural foraging behavior of honey bees. In this study optimum design problem of steel space frames is formulated according to the provisions of LRFD-AISC and its solution is obtained by using enhanced artificial bee colony algorithm. The performance of artificial bee colony algorithm is improved by adding Levy flight distribution in the search of scout bees. Real world steel space frames are designed with the new algorithm developed in this study to demonstrate its robustness and efficiency. | Design optimization of real world steel space frames using artificial bee colony algorithm with Levy flight distribution |
S0965997815001593 | Recently, a Sequential Optimization and Reliability Assessment (SORA) method was proposed and proven to be effective for solving reliability-based design optimization (RBDO) problems. In the SORA, the optimization loop and the reliability assessment loop are decoupled from each other. This helps improve the efficiency of the SORA significantly. However, the SORA still exists two main drawbacks: (1) the optimal solutions are easily trapped within local extremes and (2) the optimal results depend on the initial trial points. To overcome these drawbacks, this paper integrates the SORA with the Improved Constrained Differential Evolution algorithm (ICDE) to give a so-called SORA-ICDE for solving RBDO problems. Due to the global search mechanism, the SORA-ICDE can easily obtain global solutions regardless of initial points. The numerical results obtained in the paper are compared with available results in the literature to illustrate the efficiency, applicability and precision of the SORA-ICDE in solving the RBDO problems for truss structures. | An effective reliability-based improved constrained differential evolution for reliability-based design optimization of truss structures |
S0965997815001684 | The paper proposes a new data-flow based approach for the identification of backbones in infinite clusters on 2-D percolation site lattices of dimension L × L. The infinite cluster is identified first, then a multi step algorithm is applied for the reduction of the infinite cluster to its backbone. Algorithm performances are evaluated theoretically and experimentally. The algorithm is local and can therefore be efficiently implemented on data-flow parallel platforms in Θ(L) time if applied on percolation lattices near the critical percolation probability or in Θ(L 2) in the worst case. The proposed methodology could resolve the problem of stack overflow at large systems that can appear with classical graph based algorithms, and has potential for a higher execution speed-up on parallel architectures. | Analysis and classification of flow-carrying backbones in two-dimensional lattices |
S0965997815001696 | With several characteristics, such as large scale, diverse predictability and timeliness, the city traffic data falls in the range of definition of Big Data. A Virtual Reality GIS based traffic analysis and visualization system is proposed as a promising and inspiring approach to manage and develop traffic big data. In addition to the basic GIS interaction functions, the proposed system also includes some intelligent visual analysis and forecasting functions. The passenger flow forecasting algorithm is introduced in detail. | WebVRGIS based traffic analysis and visualization system |
S0965997815001702 | This paper presents a new powerful nature-inspired method named Virus Colony Search (VCS). VCS simulates diffusion and infection strategies for the host cells adopted by virus to survive and propagate in the cell environment. With the strategies, the individual in the new algorithm explores and exploits the search space more efficiently. To verify the performance of our VCS, both the unconstrained classic and CEC2014 modern benchmark functions, and constrained engineering design optimization problems are employed. The experimental results, considering both convergence and accuracy simultaneously, demonstrate the effectiveness of VCS for global numerical and engineering optimization problems. | A novel nature-inspired algorithm for optimization: Virus colony search |
S0965997815001714 | The traditional fatigue test of wheel comprising the radial and cornering fatigue tests cannot simulate the real stress state of wheel well. Biaxial wheel fatigue test combining these two traditional tests has become an internationally recognized method that can reproduce the real loading condition of the wheel in service. Since the test is time- and cost-consuming, developing the simulation method on biaxial wheel fatigue test is urgently necessary. In this paper, a new method is proposed to evaluate the fatigue life of commercial vehicle wheel, in which the finite element model of biaxial wheel fatigue test rig is established based on the standards of EUWA ES 3.23 and SAE J2562, and the simulation of biaxial wheel test and fatigue life estimation considering the effects of tire and wheel camber is performed by applying the whole load spectrum specified in ES 3.23 to the wheel. The radial and cornering fatigue tests are also simulated, and the results are compared with ones of the biaxial fatigue test. The research shows that the proposed method provides an efficient tool for predicting the fatigue life of the wheel in the biaxial fatigue test. | Simulation of biaxial wheel test and fatigue life estimation considering the influence of tire and wheel camber |
S0965997815001726 | An innovative procedure for characterizing thermo-mechanical behavior of superalloy using the Eigenfunction Virtual Fields Method (EVFM) was proposed. First, the principle of EVFM for thermo-mechanical constants identification was developed based on the principal components analysis. Then, the strain fields were extracted from finite element (FE) simulation of a superalloy plate with a circular hole under uniaxial tension and uniform temperature increment. In addition, the virtual fields were constructed using the eigenvectors of augmented strain matrix. Finally, the thermo-mechanical constants were inversed from the strain fields, and the effect of mesh size and noise on the inversion results was analyzed. The results show that the thermo-mechanical constants of superalloy inversed from EVFM using these eigenvectors as virtual fields are in excellent agreement with the true values. | Characterizing thermo-mechanical behavior of superalloy using the eigenfunction virtual fields method |
S0965997815001738 | The main factors governing the design of composite laminates are the geometrical dimensions, the stacking sequence –including ply thickness and orientation angles–, the mechanical properties of the materials, the applied loads and the performance requirements. Most of these factors are commonly affected by uncertainty and this should be taken into account when designing these structures. Thus, uncertainty quantification should be used to evaluate the performance requirements and a reliability-based procedure is advisable when the design is optimized. However, these methods present several drawbacks, like the lack of trustworthy information about the uncertainty present in the variables of the model or the high computational cost required to apply the algorithms to medium to large models. This paper evaluates several methodologies for design optimization of composite panels under uncertainty. The uncertainty quantification is performed using stochastic expansion and limit state approximation methods. Monte Carlo sampling is also used to verify reliability results. The optimization process is carried out using gradient-based and genetic algorithms, with either continuous or discrete design variables. Surrogate methods, including polynomial, kriging, multivariate adaptive regression splines, and artificial neural networks, as well as parallel computing, have been leveraged to keep analysis times under acceptable levels. An application example of a stiffened composite panel of an aircraft fuselage is presented to demonstrate the computational performance and the accuracy of the methods. Results show major improvement in analysis time without compromising on precision. | Efficient methodologies for reliability-based design optimization of composite panels |
S0965997815300090 | In this paper, an improvement in the hybrid stochastic/deterministic Pincus-Nelder-Mead optimization algorithm (P-NMA) which enables to solve the target optimization problem of vibration-based damage detection is proposed. The proposed modification consists in reducing the sampling domain of the Pincus formula by assigning a maximum number of damaged elements, i.e., by allowing only a few elements of the sampling vector to be different from 1. Consequently, a new parameter which determines the maximum number of damaged elements (npmax ) is introduced and must be choose by the designer. Such a modification attempts to speed up the convergence of the original version of the P-NMA and thus, reducing its computational cost. A series of numerical examples, all selected from literature, was performed. To test the accuracy and efficiency of the proposed improved optimization algorithm (IP-NMA), its results were compared to those obtained by the P-NMA and the metaheuristic harmony search algorithm (HS). A statistical analysis was also performed in order to test the robustness of the three algorithms. The proposed improved optimization algorithm showed better performance (more accurate and required lower computational cost than the original version of the P-NMA and the metaheuristic HS), emphasizing its capacity in damage diagnosis and assessment. | An improved hybrid optimization algorithm for vibration based-damage detection |
S0965997815300119 | Design pattern is widely used in the software engineering field, which enables designers to reuse existing mature designs from a high level perspective. Inspired by this idea, a novel approach is proposed to extract design patterns in the CAD field. First, the characteristics for a good design pattern are analyzed and the model for representing design patterns is elaborated. Then, given a set of 3D feature-based CAD models, the corresponding extraction approach is proposed, which includes three important phases: (1) extracting reusable regions with high cohesion, low coupling and moderate complexity so as to form a relative integrated function; (2) constructing candidate design patterns by clustering reusable regions using a graph-oriented agglomerative hierarchical clustering algorithm; (3) determining the final design patterns by choosing those candidate design patterns with high frequency and sufficient information. Finally, a design pattern extraction prototype system is developed, and the experimental results are presented to demonstrate the effectiveness of the approach. | Design pattern modeling and extraction for CAD models |
S0965997815300144 | The objective of this research was to use finite element modeling and simulations to evaluate the ballistic resistance of woven fabrics and soft body armor. In the work of this paper, nonlinear finite element (FE) simulations were performed to evaluate the response of single- and multi-layer woven fabrics under ballistic impacts. A shell-element based fabric material model was first validated using perforation tests performed on a single-layer fabric under high-velocity impact by a spherical steel projectile. The validated model was then used to replicate high- and low-velocity impacts by a blunt aluminum projectile on eight-layer Kevlar targets. Results from the multi-layer simulations were shown to have good agreement with experimental data. Finally, the validated fabric model was used to simulate a full-scale ballistic test on a groin protector panel of the interceptor body armor system. The simulation results of both the single- and multi-layer impacts were shown to match well with experimental data in terms of the projectile's residual velocities. This research confirms the effectiveness of the fabric model and can be extended to a wide range of applications involving soft body armors. | A numerical and experimental study of woven fabric material under ballistic impacts |
S0965997816300011 | A simulation software for the assessment of performance, costs and environmental impact of conventional and advanced configuration aircraft has been developed and validated. The software is named PLA.N.E.S. (PLAtform for New Environment-friendly Solutions), and includes a sizing routine and a mission simulator. The simulation is performed with the so-called backward paradigm, i.e. the flight conditions along the mission (altitude and speed versus time) are assumed to be known. Accordingly, the instantaneous power request of the aircraft to meet that flight mission and the corresponding instantaneous fuel consumption are calculated. In the case of advanced powertrains, it is also possible to choose different energy management strategies for the optimal control of the energy flows among engine, secondary equipment and storage systems during the mission. The components currently modeled in PLA.N.E.S. include energy converters (piston and Wankel engines, turboprop, fuel cell, etc.), energy storage systems (batteries, super-capacitors), auxiliaries and secondary power systems. The tool is designed to be integrated with a multi-objective optimization environment. In the present investigation PLA.N.E.S. has been applied to a Medium Altitude Medium Endurance (MAME) Unmanned Aerial Vehicle (UAV) as a case study to compare an experimentally validated Wankel-based powertrain with a proposed turbocharged diesel piston-prop system. auxiliary power Unit brake mean effective pressure brake specific fuel consumption environmental cabin system electricity storage system hybrid electric vehicle internal combustion engine lower heating value more electric aircraft state of charge true airspeed takeoff available distance engine bleed air mass flow rate of fuel acceleration aspect ratio wing span nominal capacity of the battery drag coefficient parasite drag coefficient lift coefficient propeller power coefficient propeller thrust coefficient drag force acceleration distance transition distance propeller diameter rotation distance takeoff distance Oswald's efficiency factor gravity acceleration lift off height propeller advance ratio lift induced drag coefficient lift force mass of the aircraft empty mass fuel mass payload nominal powertrain mass number of engines propeller speed (instantaneous) atmospheric pressure mechanical power requested by accessories electric power required by electric accessories engine power shaft propulsion power propeller power shaft radius of turn wing area time thrust rolling time true air speed open circuit voltage stall speed weight of the aircraft altitude time step of the backward simulator fraction of thrust generated by the propeller compression ratio climb angle engine efficiency generator efficiency propeller efficiency gear efficiency wheel friction coefficient air density corrected density takeoff/sea level/parasite average braking cruise climbing engine nominal sea level takeoff | Development and validation of a software tool for complex aircraft powertrains |
S0965997816300114 | In three-dimensional reconstruction experiments based on stereo vision theory in a glass flume, there is usually more than one medium in the travel path of the light, such as air, glass and water. These media not only degrade image quality, but also change the light route. Large errors are generated if the effects of these media are ignored. To solve the problems of media effects, a new method of object reconstruction for the glass flume is proposed, based on computer vision theory and laws of refraction. Firstly, the light refraction effects are analyzed and a coordinate correction formula is developed. Secondly, correction parameters are obtained based on a stereo vision method to correct the coordinates of a target point. Finally, model experiments in glass flume are described and the errors are analyzed. The experimental results show that the proposed method is effective in correcting refraction distortion, and improves the accuracy of three-dimensional reconstruction of target points. | Study on the reconstruction method of stereo vision in glass flume |
S0965997816300126 | We develop a three-dimensional (3D) shipping information system as a case study for the integration of a dynamic flow field and a 3D virtual geographical environment. A 2D hydrodynamic model is formulated to calculate the waterway depth and velocity distribution by using real-time hydrologic monitoring data. The parallel OpenMP computations take 4min on a 20-core computer. The image-based flow visualization method is used to produce a 2D dynamic flow field on a curved surface, and the integration of dynamic flow fields with a 3D virtual geographical environment was achieved with the OpenSceneGraph rendering engine. Compared with a traditional 2D navigation map, the combination of a flow simulation and a visualization module can integrate flow velocity magnitude and distribution, and enhance ship navigation safety. This functionality will aid the display of integrated scientific information, and will have potential applications within 3D information systems in many domains. | Flow simulation and visualization in a three-dimensional shipping information system |
S0965997816300138 | This paper examines the enhancement of static and dynamic travel range of electrostatically driven microbeams using shape optimization approach. Continuous functions of width and thickness are used for optimizing the geometry of both cantilever and fixed–fixed microbeams. Rayleigh–Ritz energy method is employed to compute the static and dynamic pull-in parameters. Particle swarm optimization and hybrid simulated annealing are used for shape optimization of microbeams. Constraints on design variables are imposed using penalty approach. Enhanced pull-in parameters obtained for variable geometry microbeams have been validated using 3-D finite element analysis. Optimized shapes of microbeams show significant improvement in static and dynamic travel range. Pull-in displacement is increased up to 54.92% for cantilever microbeam and 40.79% for fixed–fixed microbeam with hybrid simulated annealing. Effectiveness of particle swarm optimization is brought out through representative test cases. The convergence of the particle swarm optimization is approximately five times faster as compared to the hybrid simulated annealing, while maintaining the same level of accuracy. | Optimization of static and dynamic travel range of electrostatically driven microbeams using particle swarm optimization |
S096599781630014X | Medial axis (MA) is used as an effective description for objects in many engineering fields. A difficulty for the current methods for the generation of MA of CAD models is the balance between the efficiency and the quality. In this study, an approach to iteratively generating hierarchical multi-resolution MA is proposed. In each iteration, only a small part of MA that affects MA quality is refined, by which the time cost and the space cost are reduced greatly. First, the model is voxelized and its initial MA is generated by distance dilation method. Meanwhile, the MA quality is computed and evaluated. Second, if the MA quality does not satisfy the requirement, upgrade the MA level and re-compute the local MA in the affected region until the MA quality does. Finally, by combining the local MA in the affected region with the reused MA in other regions, hierarchical multi-resolution MA is obtained. Several examples are given to demonstrate the outperformance of the proposed method in terms of time and space. | Generation of hierarchical multi-resolution medial axis for CAD models |
S0965997816300151 | Model simplification is imperative in the process of computer aided design (CAD) and computer aided engineering (CAE) integration. Mid-surface abstraction is the most effective method to simplify the thin-walled models. Many previous research efforts have been focused on the mid-surface abstraction, including the model decomposition based methods, Medial Axis Transform (MAT) based methods and Chordal Axis Transform (CAT) based methods. However, complex thin-walled models cannot be handled well due to the fact that there are some problems including low geometrical precision, poor topological structure, etc., in the above resultant mid-surface models. Especially, these methods are hard to be reused to generate the mid-surface model efficiently. Therefore, a hierarchical semantic mid-surface abstraction method is proposed for the thin-walled model based on rib feature decomposition in this paper. Firstly, a new hierarchical semantic structure is defined and applied on both the thin-walled models and mid-surface models. After that, the model decomposition is conducted based on the identified rib features and the hierarchical semantic information is obtained at the same time. Then, the offset operation and discretization based methods are used to obtain the mid-surface patch for each sub region with different semantic structure respectively. Finally, the mid-surface model with hierarchical semantic information is generated by stitching all discrete patches. Moreover, the above model can be reused to facilitate the rapid mid-surface abstraction of the changed model based on its hierarchical semantic structure. Several examples are given to demonstrate the outperformance of the proposed method. | Automatic hierarchical mid-surface abstraction of thin-walled model based on rib decomposition |
S0965997816300163 | This paper proposes a novel nature-inspired meta-heuristic optimization algorithm, called Whale Optimization Algorithm (WOA), which mimics the social behavior of humpback whales. The algorithm is inspired by the bubble-net hunting strategy. WOA is tested with 29 mathematical optimization problems and 6 structural design problems. Optimization results prove that the WOA algorithm is very competitive compared to the state-of-art meta-heuristic algorithms as well as conventional methods. The source codes of the WOA algorithm are publicly available at http://www.alimirjalili.com/WOA.html | The Whale Optimization Algorithm |
S0965997816300175 | With the constant deepening of research on marine environment simulation and information expression, there are higher and higher requirements for the sense of reality of ocean data visualization results and the real-time interaction in the visualization process. This paper tackle the challenge of key technology of three-dimensional interaction and volume rendering technology based on GPU technology, develops large scale marine hydrological environmental data-oriented visualization software and realizes oceanographic planar graph, contour line rendering, isosurface rendering, factor field volume rendering and dynamic simulation of current field. To express the spatial characteristics and real-time update of massive marine hydrological environmental data better, this study establishes nodes in the scene for the management of geometric objects to realize high-performance dynamic rendering. The system employs CUDA (Computing Unified Device Architecture) parallel computing for the improvement of computation rate, uses NetCDF (Network Common Data Form) file format for data access and applies GPU programming technology to realize fast volume rendering of marine water environmental factors. The visualization software of marine hydrological environment developed can simulate and show properties and change process of marine water environmental factors efficiently and intuitively. | Multi-dimensional visualization of large-scale marine hydrological environmental data |
S0965997816300229 | As nuclear power expands, technical, economic, political, and environmental analyses of nuclear fuel cycles by simulators increase in importance. To date, however, current tools are often fleet-based rather than discrete and restrictively licensed rather than open source. Each of these choices presents a challenge to modeling fidelity, generality, efficiency, robustness, and scientific transparency. The Cyclus nuclear fuel cycle simulator framework and its modeling ecosystem incorporate modern insights from simulation science and software architecture to solve these problems so that challenges in nuclear fuel cycle analysis can be better addressed. A summary of the Cyclus fuel cycle simulator framework and its modeling ecosystem are presented. Additionally, the implementation of each is discussed in the context of motivating challenges in nuclear fuel cycle simulation. Finally, the current capabilities of Cyclus are demonstrated for both open and closed fuel cycles. | Fundamental concepts in the Cyclus nuclear fuel cycle simulation framework |
S0965997816300254 | Rapid development in numerical modelling of materials and the complexity of new models increase quickly together with their computational demands. Despite the growing performance of modern computers and clusters, calibration of such models from noisy experimental data remains a nontrivial and often computationally intensive task. Layered neural networks provide a robust and efficient technique for overcoming the time-consuming simulations of calibrated models. The potential advantages of neural networks include simple implementation and high versatility in approximating nonlinear relationships. Therefore, there were several approaches proposed in literature for accelerating the calibration of nonlinear models by neural networks. This contribution reviews and compares three possible strategies based on approximating (i) the model response, (ii) the inverse relationship between the model response and its parameters and (iii) an error function quantifying how well the model fits the data. The advantages and drawbacks of particular strategies are demonstrated with the calibration of four parameters of an affinity hydration model from simulated data as well as from experimental measurements. The affinity hydration model is highly nonlinear but computationally cheap, thus allowing its calibration without any approximation and better quantification of results obtained by the examined calibration strategies. This paper can be viewed as a guide for engineers to help them develop an appropriate strategy for their particular calibration problems. | Artificial neural networks in the calibration of nonlinear mechanical models |
S0965997816300333 | As simulations are becoming popular in the analysis of the complex behavior of large-scale systems with immense inputs and outputs, there is an increasing demand to efficiently store, manage, and analyze massive simulation outputs. Hadoop and MapReduce have been used in various applications to speed up the process of analyzing large amounts of datasets. In this paper, we present ARLS (After-action Reviewer for Large-scale Simulations), a MapReduce-based output analysis tool for simulation outputs. ARLS clusters distributed storages using Hadoop and automatically composes Map and Reduce functions to process the simulation outputs. ARLS has been applied to our SAM (Surface-to-Air Missile) simulator. The SAM simulator has been developed to analyze the dynamics of a missile in designing air-defense systems. ARLS takes a large amount of unstructured simulation outputs from SAM simulator, automatically generates Map and Reduce functions to analyze the missile and the aircraft component of SAM simulator, and executes Map and Reduce jobs in parallel. The results of our experiments show that ARLS can efficiently analyze a large amount of unstructured simulation datasets by distributing datasets and computations over the cluster of commodity machines. | ARLS: A MapReduce-based output analysis tool for large-scale simulations |
S0965997816300345 | Boundary conditions (BCs)are important parameters of numerical computation for CAE structure analysis. Automatically and correctly reconstructing BCs would evidently improve the design efficiency. In this paper, a novel approach consisting of feature representation of BCs, coding mechanism for BC related topological entity and BC reconstructing mechanism is proposed. BCs treated as features can be adaptive to the changing geometric model in this approach. Coding mechanism guarantees that the specified entities of BCs from the model reconstruction process could be identified. Reconstructing mechanism comprises the maintenance of BC-geometry feature dependency, data consistency and coding transmission, which ensures all the BCs can be automatically updated in terms of the changing geometry. This approach can avoid repeatedly applying BCs to the whole or portion of topological entities. Finally, some representative cases demonstrate that the proposed approach is able to significantly improve the design efficiency. | A novel approach for automatic reconstruction of boundary condition in structure analysis |
S0965997816300436 | This paper presents a new regularized boundary integral equation (BIE) method for three-dimensional (3D) potential gradient field. For this method, we firstly construct two special tangential vectors, and then provide a characteristics theorem with respect to the contour integrations of normal and tangential gradients of the fundamental solution. Finally, a new regularized boundary integral equation with indirect unknowns is derived by using the characteristics theorem and a limit theorem. Compared with the direct boundary element method (BEM), the proposed method has three new features: (1) the continuity requirements of density functions are reduced from C 1, α to C 0, α ; (2) the BIE does not involve the hypersingular (HFP) integral and thus its numerical evaluation is more easy and precise; (3) any potential gradients on the boundary, not limited to normal gradients, can now be calculated. Numerical results illustrate that the present method is computationally efficient, accurate, and convergent with an increasing number of boundary elements. | A new regularized boundary integral equation for three-dimensional potential gradient field |
S0965997816300448 | In this paper, dynamic axial crashing analysis of tailor-welded blanks (TWBs) thin-walled structures with top-hat shaped section under front impact is presented. The crash tests are performed through a sled test in order to model a car-to-car front impact. The strain rate dependence of both high strength steels (DP590 and DP780) is considered to study its influence on acceleration and energy absorption involved into high speed impacting process. The FE model about the front dynamic crashing is conducted, and different weld line modeling types on the dynamic simulation results such as acceleration history are compared. It demonstrates that coincide node (CN) model is considered appropriate for simulating the dynamic impacting. Additionally, the effects of weld line locations and spotweld spacing are also performed. It may be concluded that the material and thickness properties of front end have certain influence on the crashworthiness performance of TWBs. The simulation results show that the acceleration curves of three TWB combinations are insensitive to spotweld spacing. A comprehensive analysis including the crash mode, the acceleration curves and the energy absorption is carried out for crashworthiness assessment. The obtained results can provide some insightful guide information and fundamental supports for light-weight and crashworthiness design of TWBs to a certain extent. | Dynamic axial crashing of tailor-welded blanks (TWBs) thin-walled structures with top-hat shaped section |
S096599781630045X | Photo- and physically realistic techniques are often insufficient for visualization of fluid flow simulations, especially for 3D and time-varying studies. Substantial research effort has been dedicated to the development of non-photorealistic and illustration-inspired visualization techniques for compact and intuitive presentation of such complex datasets. However, a great deal of work has been reproduced in this field, as many research groups have developed specialized visualization software. Additionally, interoperability between illustrative visualization software is limited due to diverse processing and rendering architectures employed in different studies. In this investigation, a framework for illustrative visualization is proposed, and implemented in MarmotViz, a ParaView plug-in, enabling its use on a variety of computing platforms with various data file formats and mesh geometries. Region-of-interest identification and feature-tracking algorithms incorporated into this tool are described. Implementations of multiple illustrative effect algorithms are also presented to demonstrate the use and flexibility of this framework. By providing an integrated framework for illustrative visualization of CFD data, MarmotViz can serve as a valuable asset for the interpretation of simulations of ever-growing scale. cell centroid of a cell or region (m) distance of contour points from a central axis (m) edge feature graph constructed from mesh thickness for feature halos (m) products of inertia tensor for a region (m5) volumetric angular momentum of a region (m5 s−1) number of unmatched regions-of-interest camera projection plane normal octree used for feature matching point on a contour (m) queue used for feature matching region-of-interest position vector (m) strobe silhouette curve bounding contour around a feature time (s) user-specified threshold velocity of a cell, or volume-average velocity of a region (m s−1) volume of a cell or region (m3) spatial coordinates (m) initial value bounding contour around a feature rear point on a contour cell count threshold for regions-of-interest gradient threshold for regions-of-interest counting indices left-most point on a contour inset contour around a feature minimum/maximum values along a contour offset contour around a feature right-most point on a contour estimated value similarity parameter for feature matching (-) user defined time step (s) similarity criterion for feature matching (-) relaxation parameter for feature matching (-) hard lower limit for the feature matching criterion (-) volumetric average angular velocity of a region (s−1) | Framework and algorithms for illustrative visualizations of time-varying flows on unstructured meshes |
S0965997816300473 | In this paper, using a recently developed unified approach, benchmark results are presented for structural optimization when the only source of uncertainty is the variability of the applied load directions. The worst-load-direction oriented framework can be applied to a broad class of engineering optimization problems. In each case, the central element of the solution searching algorithm is a standard multi-load structure optimization problem, which using an appropriate method, can be solved within reasonable time. The varying load directions are handled by additional linear or nonlinear relations, which describe the allowable perturbations of the nominal load directions. The result of the optimization is a performance measure minimal design which is invariant to the investigated uncertainty type and satisfies the response constraints. In order to illustrate the viability and efficiency of the approach, problem-specific models, algorithms and detailed benchmark results are presented for volume minimization of 2D continuum structures with compliance constraints and weight minimization of 2D truss structures with displacement and stress constraints. In each case, the computational cost of the proposed approach is comparable with its fixed load direction oriented equivalent because the worst-load-direction identification process is searching on the space of allowable direction perturbations, which generally means an easier and smaller computational problem than the standard multi-load structure optimization. | Structural optimization under uncertainty in loading directions: Benchmark results |
S0965997816300485 | Shear failure of concrete elements reinforced with Fiber Reinforced Polymer (FRP) bars is generally brittle, requiring accurate predictions to avoid it. In the last decade, a variety of artificial intelligence based approaches have been successfully applied to predict the shear capacity of FRP Reinforced Concrete (FRP-RC). In this paper, a new approach, namely, biogeography-based programming (BBP) is introduced for predicting the shear capacity of FRP-RC beams based on test results available in the literature. The performance of the BBP model is compared with several shear design equations, two previously developed artificial intelligence models and experimental results. It was found that the proposed model provides the most accurate results in calculating the shear capacity of FRP-RC beams among the considered shear capacity models. The proposed BBP model can also correctly predict the trend of different influencing variables on the shear capacity of FRP-RC beams. | A feasibility study of BBP for predicting shear capacity of FRP reinforced concrete beams without stirrups |
S0965997816300497 | The article describes efficient methods to visualize the results from finite element analysis and implementation of these methods in post-processing results. The work is based on premise that computer memory and performance are limited and amount of data processed by complex finite element analysis is enormous. Therefore, some kind of simplification and approximation of resulting data has to be used. Multigrid method was the inspiration for research work and development of post-processor. The stored data from finite element analysis are discrete values. The paper deals with several ways of replacing them by continuous functions suitable for representation in computer graphics, which are different from the approximation functions used in finite element method. Special attention is devoted to approximation errors – difference between these functions. Finite element mesh is decomposed into subdomains with respect to approximation errors. The ways of creating mesh hierarchy are described in details and also the possibilities of nodal value interpolations in simplified mesh are discussed in the text. Besides the approximation of data in space, also the approximation in time is used. Pseudo-code of the approximation algorithm key parts is shown. Various types of approximation functions were investigated to reach the lowest approximation error and the highest compression factor. Results are summarized in the article. | Approximation of large data from the finite element analysis allowing fast post-processing |
S0965997816300503 | Recent earthquakes have demonstrated the high vulnerability of cultural heritage buildings, whose seismic assessment and rehabilitation constitute an important issue in seismic regions around the world. The high nonlinear behaviour of masonry material requires ad hoc refined finite element numerical models, whose complexity and computational cost are generally unsuitable for practical applications. For these reasons many authors proposed simplified numerical strategies to be used in engineering practice. However, most of these alternative methods are oversimplified since based on the assumption of in plane behaviour of masonry walls. In this paper a discrete-modelling approach for the simulation of both the in plane and out of-plane response of masonry structures is proposed. The method is applied to a basilica plan church, which has been partially investigated in the literature. The results show the capability of the proposed discrete element approach to simulate the nonlinear response of monumental structures also in those cases in which the ‘in’ and the ‘out’ of plane response cannot be decoupled, as it happens for many structural layouts typical of churches, ancient palaces and several other monumental structures. | 3D macro-element modelling approach for seismic assessment of historical masonry churches |
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