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Development of a Practical DSP Car Audio System
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Digital signal processors (DSPs) are being used widely for sound field reproduction. However, it is difficult to apply a DSP to a car audio system because of the complicated acoustic characteristics of the passenger compartment. The authors have developed a new car audio system which employs special DSP software and a new speaker layout to provide excellent presence. The DSP has five output channels to generate stereophonic reflection from the front and rear speakers. The DSP software is programmed for each individual car model. A center speaker and A-pillar tweeters are used to produce a natural sound field in front through effective utilization of reflection from the windshield. This system is featured in 1992 Nissan models.
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Cold Start Improvement by use of Latent Heat Stores
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Engine and cabin heating problems associated with cold starts at subzero conditions are greatly reduced by use of a Heat Battery. This is a latent heat store, collecting waste heat from the engine and storing it by use of efficient heat insulation. On the next cold start the heat is released with high initial power. The performance increases with colder environment conditions. Startability of the engine and the warm-up performance are improved. Emissions of hydrocarbons and carbonmonoxide are reduced up to 80 % in the CVS test at -7째C (20째F) and Diesel noise is lowered. The windshield is cleared of ice and frost and kept free of mist. Passenger comfort improves since hot air flows into the cabin within seconds after the Heat Battery is engaged.
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Reconnaissance Capable F/A-18D Optical and Infrared Window Antifog Systems
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Aircraft modifications have been developed to make F/A-18D Hornets capable of being converted to a reconnaissance configuration which includes both optical and infrared sensors. A major design challenge was to prevent fog formation on the two exterior moldline windows used for viewing by these sensors. Antifogging was required during a rapid 7620 m/min (25,000 ft/min) descent into humid atmospheric conditions following a sustained cold soak at altitude. This paper describes the design development and laboratory verification testing of the two unique antifog systems selected to meet this requirement.
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Enhanced Heat Transfer by a Spiral Spring Augmentive Device Inside a Round Tube
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The use of augmentive devices in round tubes to promote heat transfer has been known to the industry for some time. Early work has shown that the improvement in heat transfer in a round tube is considerably greater with an augmentive device when in the heating mode than in the cooling mode. As a result, the bulk of the effort, thus far, appears to be in the heating mode. This work is set to prove that the augmentive devices are as efficient in the cooling mode as in the heating mode. This work also opens the doors to many applications where space and cooling equipment size are a factors to be considered during the design of systems. This study utilizes a spiral spring augmentive device in four wire diameters and in four turns per inch for each wire diameter in a nominal 0.375 diameter copper tube. The coil diameter of the augmentive device was sized to fit inside the tube with a minimum clearance.
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The Effects of Instrument Panel Top Color and Windshield Angle on Veiling Glare
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This Paper summarizes the results of research on the causes of windshield veiling glare in automotive vehicles. A special test apparatus was and built to simulate real-world windshield glare conditions. Four subjects were required to perform identification tasks under various levels of veiling glare. Error frequency and discomfort rating were used as the measurement of glare level. Results show the influence windshield glare from such parameters as solar brightness, solar position, windshield angle and instrument panel top color. Instrument panel color was evaluated using the Munsell attributes of Hue, Value, and Chroma.
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A System Approach to Safe Winter Driving Considerations: The Visual System
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A systems approach is used to analyze the problem of providing optimum visual capabilities to deal with the demands required for safe driving in cold weather. Using a systems analysis approach, the problem is divided into its constituent parts (e.g. road conditions, vehicle features and design, the human components, etc.) and then these components, as they pertained to the defined visual system, are addressed.. Under temperate driving conditions, visual acuity and field of view are two of the most important considerations for safe driving. While these still remain important during winter driving conditions, windshield clarity and the problems associated with it, becomes extremely important. These three requirements have many related characteristics that may be overlooked when a systems approach is not used.
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Vertical Body Panels: Flexible Class A Surface Composites Via Compression or Injection Molding
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Low Profile Class A sheet molding compound (SMC) is recognized as the composite material of choice for horizontal automotive body panels. The excellent surface, dimensional stability, stiffness and coefficient of thermal expansion have made it preferred for hoods, deck lids and roofs. softer thermoplastic and thermosetting (RIM) materials have been more considered for fenders and occasionally doors. recent studies have shown performance problems with these materials and SMC composites are being considered as an alternative. Increased flexibility over standard rigidity SMC is considered desirable for vertical body panels, particularly fenders. This flexibility can be achieved but normally at a major price in surface smoothness. This paper reports on research and development work done to achieve Class A surface flexible SMC/BMC composites that can be either compression or injection molded. these advancements have been made by a combination of shrinkage control agent (low profile additive) chemistry, unsaturated polyester structure, fiber wetting agent and fiberglass size technology. A comparison is made of surface characteristics, flexibility and physical properties which can be obtained via these two processing/molding techniques.
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Improvements and Applications of Permanent Magnet Materials in Automotive Sensors
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Advancement of automotive electronic technology is leading to a greater use of permanent magnet materials. New vehicle specifications demand sensors and D.C. motors to be lighter and more efficient. Magnet manufacturers are developing materials and processes to meet these needs, both for the present and the future. Permanent magnets today are used in a wide range of industrial, domestic, automotive and aerospace applications. Their special, technological importance derives from their ability to act contactlessly on ferromagnetic material, either by attraction or repulsion, and to provide a permanent magnetic flux with no energy input and, hence, at no operating cost. The current usage of permanent magnets in domestic applications averages 50 per household in the United States, as illustrated in Figure 1. Perhaps the most surprising range of permanent magnet uses are the numerous applications in a modern passenger vehicle. These applications include an array of D.C. electric motors such as the starter, heater and air conditioner blower, windshield wiper, window lift, door lock and fuel pump motors. A fully equipped car can have more than 30 D.C. electric motors. Other uses include actuators, gauges and sensors, as shown in Figure 2. In all these examples, higher performance magnetic materials may afford the advantages of increased operating efficiency and reduction in size and weight. The continuing improvement in magnetic materials together with advances in power and integrated electronics has seen the development of a wide range of devices in which field coil windings are replaced by permanent magnets. These developments have also led to a dramatic increase in the use of permanent magnets in automotive sensor applications.
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Automotive Testing Requirements in the Design of a Reverberation Chamber
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The purpose of this paper is to identify various concerns that need to be evaluated prior to the design and construction of a reverberation chamber, such that the chamber can be used for various automotive related acoustical measurements. Some of the concerns involve issues such as room shape and size, the degree of sound and vibration isolation required, the use of conventional building materials versus traditional massive construction, construction cost, and the performance requirements for the test noise generation system. Various uses of a reverberation chamber include random incidence sound absorption measurements, small sample sound transmission loss measurements, vehicle insertion loss tests, dash panel, door, and other ?쐀uck??evaluation tests, and sound power level measurements of small automotive components and devices. These uses have differing and in some cases conflicting requirements that compete in the selection of room design parameters. The paper discusses these issues including the requirements for sound level generation in the chamber for proper measurements. The paper also provides case studies on the use of reverberation chambers for automotive applications.
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Acoustical Performance Testing of Automotive Weatherseals
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Advances in vehicle noise control are leading the automotive industry to place increasing emphasis on weatherseals to block exterior noise. As a result, properly evaluating the acoustical performance of automotive weatherseals is of increasing importance. There is no current specific standard for this testing. Rather, there has been reliance on adaptations of SAE Standard 51400 ?쏬aboratory Measurement of the Airborne Sound Barrier Performance of Automotive Materials and Assemblies??by testing laboratories. However, the 51400 standard addresses testing of flatstock materials and does not readily lend application to pre-formed parts such as weatherseals. For this reason, adaptation of the standard can vary significantly from facility to facility and manufacturer to manufacturer. These differences can be significant and can render comparisons between test results on competing materials very difficult. This paper explores some of the limitations of using SAE J1400 to evaluate weatherseal performances and the likely impact of these limitations on test results. It also offers some considerations on developing a test procedure for an appropriate standard for evaluating weatherseals.
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Automotive Squeak and Rattle Prevention
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Recent advances in automotive sound quality have reduced the general level of noise in the passenger compartment and focused more attention on irritating noises. Traditional methods of prevention and elimination of irritating noises such as squeaks and rattles are no longer sufficient to develop acceptable products in shortened product development cycles. Basic causes, design rules for prevention, and evaluation techniques using integrated digital data acquisition, laboratory simulation, acoustic and modal analysis techniques have been successfully developed to push the prevention process upstream in the development cycle.
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Design of Automotive Audio Systems Using the Acoustic Transfer Function Measurement
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The small, irregular volume of the typical automotive cabin can induce large, unpredictable variations in the low frequency response (<200 Hz) of woofers in the audio system. Acoustic transfer function measurements of these effects, made using a reciprocity technique, show these variations at the listener's position. The response of a subwoofer design at any position in the vehicle can be predicted and optimized through computer aided convolution of the woofer response and the acoustic transfer function. A commercially available loudspeaker acoustic simulator, SPEAK, was used for woofer system design and simulation in an automobile.
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Engineering, Optimization, and Tuning of vehicle interior Sound Absorption and Other mechanisms for Sound Reduction
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This paper treats the engineering, optimization and tuning of vehicle sound absorption with emphasis on headliners. It covers the methodology of measuring sound. The mechanisms for sound reduction damping are discussed. The report compares the acoustical performance of worldwide headliner constructions at different frequencies and leaves it up to the reader to make his/her own evaluation. The Authors discuss means to enhance and optimize and tune headliners to increase the acoustic functionality of the parts. The paper also shows the relative acoustic performance of interior trim parts. Future trends and methodology are explored along with the European trend to eliminate roof bows and the headliner being robotically adhered to the roof to improve acoustics, structural effectiveness and lower cost.
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Vehicle Drive Line Dynamic Behaviour Simulation
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A mathematical model was built up and a computer programme was developped in order to simulate the drive line of a vehicle. Particular attention was given to the possibility to incorporate non linearities such as teeth clearence and torsional stiffness of the clutch plate. With the model it is possible to study rattling and hammering of the gearbox and in particular the influence of the clutch on it. Also the influence of a vibration absorber on resonance frequencies is investigated. Due to a extrapolation of the programme, we are also able to analyse the interaction between the torsional stiffness of the driveline and the axle vibration on his suspension.
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The Application of Bonded Aluminum Sandwich Construction Technology to Achieve a Lightweight, Low Cost Automotive Structure
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Bonded Aluminum Sandwich Construction Technology offers a new approach for automotive manufacturers to rapidly develop low volume niche products that achieve world class results for weight, cost, styling and surface finish with minimal tooling investment. Using sandwich panel construction in the development of their new ultra lightweight sleeper, Western Star Trucks was able to reduce the product weight by 50%, manufacturing costs by 25%, and tooling and development cost by 75%, while significantly reducing development time. In less than one year the company was able to deliver a new family of Star Light Sleepers that replaced a conventional stamped steel body-in-white structure with the same basic body shape but with improved styling detail and surface finish. Additional benefits encountered included increased ease of assembly and interior finishing, and improved reparability and noise and thermal attenuation.
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Aeroacoustics of an Automobile A-Pillar Rain Gutter: Computational and Experimental Study
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Noise due to the flow over an automobile A-pillar rain gutter in isolation was computed using a two step procedure. Initially the flow solution was obtained by solving the Reynolds Averaged Navier Stokes (RANS) equations. Acoustical Sources were extracted from the flow solution and propagated to the far-field using the Lighthill-Curle equation. Experiments were conducted to evaluate the computations. Compared results include steady pressures, time dependent pressures, and sound intensity levels. Computed results and experimental data were reduced in a similar way to ensure a one to one comparison. Computed results are in good agreement with the experimental values. A-weighted noise levels are predicted reasonably well.
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Booming Noise Analysis Method Based On Acoustic Excitation Test
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A method for analyzing and decreasing booming noise in the cabin of a minivan using acoustic excitation tests has been developed. To ensure a pleasant ride for passengers of minivans equipped with four-cylinder engines, decreasing cabin noise from secondary components of engine revolution has become a priority. ?쏝ooming noise??in the cabin originates from engine vibration that passes through engine mounts to shake the body structure and body panels. To decrease the level of sound pressure resulting from this shaking, one effective approach is to reduce the level of the mechanical-acoustical transfer function (MATF) in the interval from engine mounts to passengers' ears. This paper reports on a specific method for reducing the level of MATF. In this method, a speaker is positioned near a passenger's ear to measure the vibration-response level at the points where engine mounts are installed when exciting the body structure, and the level is reduced by modifying the body structure. This method makes use of the relationship between MATF and vibration response during acoustic excitation, which can be considered equivalent according to the reciprocity principle. The following conclusions were reached when applying this method to decreasing 60- to 120-Hz booming noise in minivans that mount the engine under the driver's seat. The pattern of vibration distribution measured when exciting body structure by a shaker is generally different from that measured by acoustic excitation, and the proposed method that modifies body structure to suppress the latter vibration can improve MATF levels in a relatively short time. In other words, when exciting body structure by a shaker or when running the vehicle, the vibration components of body structure that excite the cabin resonance mode and generate booming noise are normally hidden by vibration components that do not result in sound.
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Four Legs in the Morning: Issues in Crew-Quarter Design for Long-Duration Space Facilities
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In designing habitats for long-duration space missions, one of the primary issues to address is that of sleep spaces, commonly known as Crew Quarters. While ergonomic design plays a major role in short-duration crew quarters (CQ) design, longer term missions must take into account the significant effect which environmental factors have on crew productivity; to that end, the establishment of private space for each individual crew member, as well as a range of semiprivate work and rest areas represents a significant departure from established norms in space habitat design. Both for proposed planetary habitats and microgravity habitats, various systems must be studied to enhance the wellbeing of the crewmembers. Improved lighting, color, and acoustic environments as well as the introduction of diurnal simulation systems, virtual windows, flexible partitions and other potential innovations are being investigated by the Space Habitation Design Group as means of developing efficient, high-acceptability crew accommodations.
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Everyday Noise - All Day
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In the Lunar-Mars Life Support Test Project chamber, crewmembers collected various sound level measures starting with the entry day ceremonies and ending with the welcome home celebrations. Crewmembers recorded sample decibel(A) levels in the 80s and 70s in the mechanical area; 70s and 60s in the common living and work areas; and 50s and 40s in the individual crew quarters. Medical personnel evaluated crewmembers for threshold hearing shifts comparing audiometry readings before and after the chamber experience. The discussion relates the chamber findings to the operational requirements for space stations and planetary habitation, as well as for long duration exposures on Earth.
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Aeroacoustic Testing Improvements at Pininfarina
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Aeroacoustics is playing an increasing role in the development of new passenger cars. However, most existing wind tunnels, with few recent exceptions, have been designed and built with little or no attention to their aeroacoustic aspects. Building new wind tunnels with excellent low noise levels is technically feasible today, however it is not often justifiable from an economic standpoint. In the case of the Pininfarina wind tunnel, built in 1972 without any specific noise target, a decision was taken in 1984 to progressively upgrade the facility and the acoustic measuring techniques. A target of reaching a background noise level low enough to allow satisfactory acoustic development work on new cars, with the contemporary use of more modern measuring techniques, was established. This decision implicitly assumed that, to do this development work, it is not necessary to reach the very low noise levels of a pure acoustic wind tunnel. The paper reports a short description of the main modifications made to the facility, in the years 1985-90, and the main results obtained. Then, it describes some of the new measuring techniques which have been set up in the meantime. They are optimized so as to be as efficient as possible in the presence of the background noise. This noise has a relatively low level and a favorable spectrum when compared with other aerodynamic wind tunnels, but this noise still remains worse than that of the acoustic wind tunnels. In order to further improve the existing situation, a new three-year research program has been recently started (mid 1992). Its main aim is to improve the capability of detecting the noise sources on the outer surfaces of cars. To do that, new measuring techniques are in course of development and testing. At the same time, further modifications to the facility are going to be carried out, mainly to its fan-drive system, to reduce the background noise level. An overview of this new research program is reported in the second part of the paper, together with some examples of the latest experimental results.
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Measurement and Prediction of the Sound Transmission Loss of Automotive Glazing Materials
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The transmission of sound through automotive glazing materials was investigated. The sound transmission loss in one-third octave bands of several different automobile windows was measured at a testing laboratory. The materials tested included monolithic (single-layer) glass, monolithic polycarbonate, and a double glazing with an air gap in between the two panes. The experimental data are given in the paper. Subsequently, a computer spreadsheet program was written and developed to predict the sound transmission loss of single-layer glazing materials, using empirical equations found in the literature. The predicted sound transmission loss values showed good agreement with the experimental values. The sound transmission loss spreadsheet is a useful, easy-to-use tool to predict the acoustic performance of automobile window glazing materials.
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Multilayer Laminated Composites for Noise and Thermal Control - PRE FINISH METALS
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Continuous developments in car design and customer attention to performance and comfort have created necessities for improvements in external and internal noise reduction in cars, trucks and busses and thermal control around engine and exhaust areas. Solutions to these ?쐁hallenges??are usually combinations of novel designs and selection of more efficient engineering materials. The authors describe the development of laminated composites consisting of outer metal ?쐓kins??with a specially selected core material between them. Depending on the noise damping and/or thermal insulation properties required by the application, the core materials may be viscoelastic polymers or inorganic materials.. As the result of this development, ?쐄amilies??of different materials for such applications are presented with the description of material properties and potential uses. These material systems include composites for noise reduction of parts in engine compartment, body parts, brakes, and materials for thermal control in under-the-hood, exhaust, and catalytic converter applications.
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In-Car Early Reflection Studies Using In-the-Ear Microphone Techniques
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After prototyping numerous sound systems for automobiles, it is often frustrating for the design engineer to gather a number of listeners and each turns out to have their own perception of the system performance. Some people are sensitive to localization problems in the car yet are unaware of reflection induced frequency response problems. The converse holds true for other listeners that notice small anomalies in frequency but are oblivious to localization difficulties. A trained listener can often balance the frequency and imaging issues though by tilting their head or mentally biasing the acoustical data. The reasons for these differences in listeners is often due to the pinna, which is the visible part of the outer ear. In-The-Ear??microphones, recently developed by Etymotic Research [1], are placed in the ear canals of several listeners to measure these influences in hope of understanding why these contrasting opinions exist.
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Experimental Investigaton of Radio Antenna Wind Noise
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Recent advances in the field of vehicle noise control have subjected the automobile to the ?쐂rained swamp syndrome?? Quieter engines, powertrains and bodies, combined with passive sound treatments for the interior have unearthed the stumps; radio antenna wind noise is one of them. This has prompted various innovative designs and redesigns for radio antennas that have been employed by major manufacturers in recent vehicles. This paper aims to determine the optimal antenna design through experimental testing both on the road and in the laboratory.
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Engine Sound Quality in Sub-Compact Economy Vehicles: A Comparative Case Study
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A comparative study was undertaken to investigate engine noise in sub-compact vehicles under typical highway operating conditions. Baseline acoustical testing was performed. Typical sound quality metrics indicated that passenger cabin noise levels and sound quality were similar among all vehicles tested. However, poorer subjective sound quality in a vehicle equipped with a 3-speed automatic transmission was related to a higher degree of perceived periodicity than in other models. Further study of the 3-speed vehicle indicated that installing a 4-speed transmission would reduce noise more effectively than any substantial changes to the vehicle structure or engine mounting system. Damping or barrier treatments applied to the firewall or toe pan did not provide significant benefit.
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Design and Test of Voice Interfaces in Cars
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Voice interfaces are of much interest for car designers: they are a safe way to operate various devices. However car compartments are very hostile environments for voice capture and emission because road noise is very loud. For every new car much time must be spent on their optimization which involves tools for quality evaluation. Comparing configurations is not practical while driving. A simple model of voice interfaces based on impulse responses makes reliable tests much easier to implement. This paper describes its practical application and shows a few objective results.
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Effects of On-Road Turbulence on Automotive Wind Noise: Comparing Wind-Tunnel and On-Road Tests
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For high-speed driving conditions, the air flow around a car creates wind noise that is transmitted into the cabin, which can dominate other noises. If an atmospheric wind is present, it will create a turbulent cross wind, which not only changes the air flow velocity and direction as experienced by the vehicle, but leads to continuously varying wind noise, as heard inside the car. The purpose of this paper is to look at how the on-road wind environment affects wind noise, and to evaluate the need to simulate real on-road conditions such as fluctuating yaw angles and velocities in vehicle wind tunnels.
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Assessment of Air Bag Module Durability Test Specifications Using CAE Techniques
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Several air bag module vibration testing issues are identified. Eight OEM air bag module vibration test specifications are compared in terms of predicted fatigue lives using computer simulation. The specifications differ significantly in the type of loading (sine sweep, fixed sine and random), frequency range, and test duration. The comparison results indicate large variation in the relative severity of specifications based on the computed fatigue lives. This variation indicates that a more standardized approach for deriving representative vibration test specifications is desirable. The unrepresentative specifications can lead to overdesigned components, diminishing the value of the air bag system. Experimental results used to validate the analytical predictions are presented along with the simulation results. A computer program developed to perform the fatigue life calculations for both sine sweep and random vibrations is also described. Several suggestions for developing representative specifications are provided.
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Importance of Sealants for Interior Noise Control of Automobiles
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Sealant materials are used in todays automobiles for many applications such as, sealing of body seams, sealing access holes and the filling of hollow cavities. The primary reasons for these applications are to prevent corrosion, prevent water intrusion, and to reduce the noise level in the passenger compartment. However, the noise control capabilities of sealant materials have not been explored until recently. This paper discusses the requirements that a noise control material must possess, and reviews how a sealant material can fulfil these requirements. Properly designed sealant materials can possess sound transmission loss (barrier) properties, vibration damping properties over a given frequency and temperature range of interest, and often sound absorption properties with proper formulation. This paper provides case studies to substantiate the acoustical capabilities of sealant materials.
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Automotive Rollover Angular Rate Sensors and Evaluation
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This paper presents a test methodology for evaluating angular rate sensors used for detecting vehicle rollover. The key electrical parameters over temperature are tested with a rate table. Immunity to linear accelerations is evaluated at room temperature with a vibration table and a thruster. The vibration test provides mechanical resonance information and rough road performance, while the thruster test provides g-sensitivity parameters under severe impact conditions such as with vehicle frontal and side impact events. The vehicle level evaluation includes severe vehicle maneuvers, rough road and gravel road tests, as well as full-scale vehicle rollover tests.
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Vehicle Passenger Door Hinge Systems
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The scope of this SAE Recommended Practice is to establish recommended uniform test procedures and minimum static load requirements for vehicle passenger door hinge systems. Tests are described that can be conducted on test fixtures and equipment in laboratory test facilities. The test procedures and minimum performance requirements outlined in this recommended practice are based on currently available engineering data. It is intended that all portions of the recommended practice be periodically reviewed and revised as additional knowledge regarding vehicle hinge system performance under impact conditions is developed.
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Application of Formable and Self-Skinning Polyurethane Foams in Headliners
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The initial function of headliners in automobiles was to conceal the rough appearance of the exposed roof construction. As the roof construction evolved towards solid metal, the requirements for headliners grew to include acoustic and styling properties. Today, fiberglass-based headliners have the major share of the North American market in high and mid-line vehicles. However, there is a recent trend to find substitutes for fiberglass headliners because of their skin irritation effects on assembly workers. Headliners based on formable and self-skinning polyurethane foam have gained wide acceptance in Europe as an alternative to fiberglass. This paper discusses the different PUR processes involved and the characteristics of the finished headliners produced with these PUR foams.
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Simple, Passive, Non-Contact Class A Multiplexing Method Using Programmable Surface Acoustic Wave Devices
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This paper describes a novel technique for class A sensor-to-module multiplexing using surface acoustic wave (SAW) technology. This technique converts information on the status of N switches to a series of N pulses in the time domain. The basic enabling technology is a programmable SAW reflector, which may be programmed to either a nonreflecting or partially reflecting state by closing or opening a switch connected to the reflector. The SAW device consists of a transducer and N programmable reflectors printed on a piezoelectric substrate such as lithium niobate. To read the status of the switches, an electronic module sends an interrogating rf pulse to the transducer. At a series of later times determined by the spacing of the reflectors from the transducer and the SAW velocity, return pulses are generated whose amplitudes are determined by the corresponding switch settings. Coupling between the electronic module and SAW device utilizes a pair of coupling coils. This allows the status of switches on a rotating or moving object such as a steering wheel, tire, or door, to be read without making any electrical contact to the moving object. Only the switches, the SAW device, and a coil, all passive components, need to mounted on the moving object. A system to read 15 switches on a steering hub has been developed utilizing a simple SAW device and low-cost electronics, and it is straightforward to extend the system to a higher number of switches.
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Use of Continuously Annealed Bake Hardenable Steels for Automobile Outer Panels
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The automotive industry's ongoing effort to improve quality and reduce weight without added cost has led to the investigation of many medium strength steels. This study presents a comparison of continuously annealed Bake Hardenable Steels (BHS) with current DQSK production materials for outer panel applications. While all steels exhibit strength increases from work hardening during forming, BHS has a unique and ideal characteristic which produces an increase in yield strength due to strain aging during the paint baking process at the automotive assembly plants. This results in an increase in dent resistance. BHS is a desirable material for relatively flat outer panels which often receive only small strains during forming such as in doors, hoods and decklids. Improved durability against dents, dings, and palm printing are obtained in the BHS parts. Similarly, quality improvements are realized in the stamping and assembly plants by a decrease in handling and transit damage.
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A Multilayer Membrane-Tension Automotive Door-Barrier System
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An alternative device based on the membrane-tension principle was developed to improve the resistance of vehicle doors to side impact. The device is comprised of several layers of sheets. The outermost layer is essentially flat and the other layers are corrugated, each with the same pitch but with a successively greater depth. The ends of each layer are attached to tabs which are connected to the door frame in a manner suitable for developing the required forces. In this concept, the side impact pushes inward on the outer sheet and causes it to develop membrane tension because its axial movement is restrained at its ends. As the inward intrusion increases, the outer sheet stretches inelastically and eventually ruptures. This action continues as successive sheet layers are stretched to rupture. The computer program, DOOR1, was developed to aid in designing the device to suit various geometries and packaging criteria. Tests were conducted on prototype specimens and compared to a companion test of an existing system. The tests indicated that the new door barrier device acting alone can deform up to 18 inches and reach a maximum load of at least 11,000 pounds in a typical three-layer, 46-1/2-inch span configuration. Details can be selected so that the load-deformation curve can be engineered to provide a desired shape. Because it appears that the new device could potentially improve crash resistance, full-scale tests on a vehicle are planned.
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Characteristics of Box-Annealed Bake-Hardenable Steels
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Bake-hardenable steel optimizes the combination of higher formability (low strength and high ductility) needed for part formation and higher final strength needed for dent resistance in the finished part. In outer panel design, it is important to understand the bake-hardening mechanism and its relationship to strain states in the part, bake temperatures and time. Bake-hardening steel exhibits carbon strain-aging that significantly increases the material's strength after part formation. The aging mechanism is created in box-anneal sheet product by the control of annealing parameters and heat composition. Property data from bake-hardenable material currently being used on a door outer application is discussed. Two different aging studies show the relationships between bake hardenability and the variables of strain, baking temperature and baking time. A third study demonsrates that, once strain is induced, strain-age hardening begins to occur at room temperature.
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Soft and Light Door Trim by Using Double Slushed Skin and Glass Mat Reinforced Rigid Polyurethane Foam Core
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As for recent market needs, there is an increasing demand for the total coordination of the vehicles interior trims, the enhancement of adaptability for freer designs, soft touch and weight reduction. In order to meet these demands, we have developed a door trim reflecting this new concept. This door trim is manufactured by foaming rigid polyurethane foam as the core material after the double slush skin (1st layer: PVC, 2nd layer: PVC foam) and the glass mat are set together in the foaming mold. Employment of double slushed skin allows an improvement in flexibility of design, softer materials to be manufactured and further coordination of color, gloss and grain pattern with those of instrument pad. In addition, we have succeeded in reducing the weight by using glass mat reinforced rigid polyurethane foam. Since the center ornament fabric is formed together with the skin, the look at the joint section of the fabric and skin has been improved remarkably compared to conventional products. We also succeeded in reducing the number of processes by abolishing the ornament assembly process and by improvement in the treatment of periphery and terminal of parts.
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Turnkey Processes for Window Encapsulation
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As window encapsulation technology advances, the requirement for process improvements to decrease cycle time, improve part quantity, and to minimize labor requirements becomes very important to the manufacturers. Traditional module systems have advanced to include closed-loop control metering units; fast acting, reliable presses; and SPC data collection systems. Turnkey automatic systems include robotic load/unloading, centering station, automatic/semi-automatic priming station, and robotic IMC/mold release. The demands to reduce overall costs has led manufacturers to consider several alternatives that prove best for their application. This paper is to list and expand on these alternative solutions.
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Passive Venting for Alleviating Helicopter Tail-Boom Loads
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The tail boom of a single-rotor helicopter is subjected to a complex flow field that includes the wakes of the main and tail rotors, the freestream, and the wake from the forward fuselage. Hovering and sideward flight present the operational regimes that are most critical with respect to adverse sideward and downward loads on the tail boom. These adverse loads necessitate additional engine power, thereby reducing payload, performance, and available yaw-control margins. In addition, nonlinear side-force gradients near conditions of boom stall can make precise yaw control very difficult for the pilot. The addition of strakes to the tail boom is one method that has been used to modify the flow field and reduce these adverse loads.
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A Flexible Lateral Seam Riveting System for Circular Aircraft Structures
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The need for a flexible and automated seam riveting system has opened the door for a new approach to machine design. The Flexible Lateral Seam Riveting system (FLSR) proposed by Gemcor will be able to automatically, under CNC and tracer control, rivet both lateral and radial joints without the use of dedicated and fixed machine track systems. The FLSR system is adaptable to a wide range of part diameters and configurations with lengths up to 10m (394 inches). Applications include aircraft fuselage sections as well as any other circular section which is assembled with rivets or other standard aerospace fastener systems including interference fit type.
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Study on Test and Product Variations of Noise Reduction Capabilities of Headliners
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This paper discusses the importance of studying different variabilities (test and product variations) that may affect the noise reduction capabilities of automotive headliners, constructed from different materials. For this purpose, interior noise measurements were made at a position approximating the operator ear level, with different headliner materials under various operating conditions. For better understanding of the effect of different variabilities on acoustical performance, various single number values were computed from the measured data reduced in 1/3 octave band frequencies. Statistical data analyses show that the acoustical performance evaluation of headliners is affected by the product variation from one headliner to another, as well as experimental variation due to vehicle performance and test variation.
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A Mathematical Model for Calculating the Dent Initiation Loads at the Door Centers
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A computational procedure is presented to evaluate the static dent resistance at the center of a steel door panel. Using the design parameters of geometric shape, thickness and the stress-strain relations of the steel, the static dent initiation load can be calculated. The method is based on the concept of plastic work which is the non-recoverable energy dissipated in the panel by the applied load. A threshold value of plastic work of 0.02 joule is used to signal the dent initiation. A comparison of the computed and measured dent initiation loads of ten experimental panels shows the maximum deviation is less than 20 newtons.
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Automobile Aerodynamic Noise
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As engine, tire, and other automobile noise is reduced and as driving speeds increase, aerodynamic noise sources on ground vehicles are becoming relatively more important. They often dominate at cruise speeds above 60 mph. Aspiration and leak noise are strong sources but generally can be controlled by known methods. Turbulent pressure fluctuations due to separated and vortical flows are also strong sources. Much interior noise is caused by transmission of these external pressure fluctuations through windows and other surfaces. The paper presents the variety of aeroacoustic sources on automobiles and reviews the state of experimental data, of analysis methods, and noise reduction principles. A new correlation method for predicting external fluctuating pressures in separated regions is presented.
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Built-In Speaker Car Sound System
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The acoustic characteristics of the sound field inside a vehicle cabin were analyzed. On the basis of the analysis results, a three-way horn speaker system for vehicles was developed, comprising a woofer, a mid-range, and a tweeter. For a woofer, we developed a speaker system utilizing resonation of acoustic tubes, in which the acoustic tubes provide acoustic impedance well matched to the acoustic impedance of a vehicle cabin space. In this paper, to identify the influence of standing waves inside a vehicle cabin, we evaluate the sound field reactivity in terms between sound field reactivity and sound image localization or the frequency characteristics. For a mid-range, we developed a speaker system with its directivity controlled by a sound source with a rectangular shape, thereby realizing a well-diffused sound field even in a restricted narrow cavity providing us with the tendency of an expanding sound image. For comparison with the conventional speaker system, data including the accumulative power characteristics and binaural correlation characteristics of this speaker system are presented in this paper. For a tweeter, we developed a system which combines a directivity controlled multi-horn speaker and a digital filter, thus realizing an improved asymmetric sound field and definite sound image localization. For this development, we analyzed the sound field inside a vehicle cabin using the acoustic ray tracing method, and the wave front in the horns by the finite element method. With the above systems, a car audio system has been realized which permits definite sound image localization just in front of a listener, and stereophonic balanced sound reproduction for both the driver's and passenger's seats, for all frequency ranges.
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Combining Materials and Functions for Low Cost Manufacturing of Headliners
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Headliners are large parts that must be lightweight, sound absorbent and sturdy enough to carry a complement of other interior components as well. And as the dashboard becomes loaded with more and more technologies, there is a drive to spread some of that complexity over the rest of the interior of the car. Automotive headliners offer an opportunity for slashing vehicle production costs by integrating components and functions in a one-step operation. The headliner is the ideal candidate not only to accept sun visors, lighting systems and hand grips, but also garage door openers, cellular telephones and audio speakers. This paper will discuss the use of low pressure injection molding as a way to reduce headliner production costs while expanding functionality. It will also examine the equipment requirements and the implications of this process for designers and manufacturers of vehicle headliners.
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Agricultural Cab Operator Comfort
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Modern agricultural machines are very complex, requiring extensive monitoring of multiple operations at the same time as they travel over very rough terrain. Hence, the cabs must be designed to provide not only good visibility of all monitors and easy access to all controls, but operator comfort and safety as well. This includes climate control (temperature, humidity, dust, noise, etc.), vibration damping, easy access on to and off of the tractor, good visibility from the cab and no controls jutting out where they could constitute a hazard. Good cab design promotes efficiency, comfort and safety.
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Gantry 5 Axis DNC/CNC High Speed Milling and Drilling Machine with Integrated Multiflexible Universal Holding Fixture for the Aerospace Industry
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An airplane fuselage structure basically consists of many individual fuselage panels which differ considerably in size and shape. Each individual panel is automatically assembled from individual components, such as the panels, frames, stringers, clips, shear ties, window frames, etc.
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The Modern Chassis Dynamometer as a Testing Device in the Acoustic Laboratory
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Development work for the reduction of vehicle noise Is mostly performed in laboratories. The paper describes testing equipment of the latest state of the art that is used in a laboratory for vehicle acoustics. The test specimen and testing equipment are installed in an acoustic chamber. All design measures for noise reduction will be described. The equipment for noise measurement and analysis is included in the chassis dynamometer control and automation system. Noises and vibrations are picked up by special measuring devices and analysed in a separate computer, which is linked to the test stand computer. The results of measurement will be presented and explained.
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Recycling Polyurethanes - An Industry Update from the Polyurethanes Recycle and Recovery Counsel (PURRC)
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The Polyurethanes Recycle and Recovery Council (PURRC), a unit of the Polyurethane Division of the Society of the Plastics Industry, Inc., continues to evaluate the technical and commercial viability of current and evolving technologies to recover and recycle polyurethanes. This report will update key PURRC projects targeting automotive polyurethane recovery and recycling issues. Candidate part applications will be reviewed. A project was completed in 1994 to collect post consumer seats from salvage yards and to recover the flexible foam. Process economics and seat collection viability were evaluated. Acoustical foams derived from rigid, semi-flexible and flexible foam scrap combinations are being evaluated. Flexible Slabstock foam production using up to 18% seating scrap has been demonstrated. PURRC is currently recovering polyurethane foam from instrument panels and evaluating techniques to process this scrap into acoustical padding, rebond carpet underlay and industrial structural parts. A study is underway to evaluate the most effective methods to grind flexible polyurethane scrap into powder to be used in the production of seating and headrests.
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Key Considerations when Engineering a Ten Year Instrument Panel
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This paper outlines field performance shortcomings historically observed in automotive instrument panels (I/Ps) and discusses the role materials play in these deficiencies. Additionally, specific material development requirements for a ten year instrument panel are discussed. While design and the placement of adjacent vehicle components, such as windshield glass, play key roles in affecting the durability of an I/P, functional and cosmetic performance in large part depend on the materials chosen for construction. Tradeoffs in short term performance (processability during manufacture) and long term performance (field weatherability) often exist for the chemical constituents comprising instrument panel assemblies. In order to obtain an optimal combination of properties, specific performance criteria must be identified and prioritized. Well-defined test methods must be clearly documented and correlated with actual field performance in order to have a methodology to evaluate various material choices. Hopefully, this paper will serve as a framework for discussions focusing on instrument panel constructions for extended vehicle life.
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Data and Methods for Estimating the Severity of Minor Impacts
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Front, rear, lateral and side-swipe collisions were staged to correlate passenger vehicle damage to motion. Data from the staged collisions are used to develop severity-prediction methods for the four collision types. Human volunteers were present in many of the vehicles tested. Their responses, and the responses of human volunteers to staged impacts in other studies, are discussed in terms of impact severity. For front and rear impacts, data are presented that correlate the post-impact condition of bumper systems to impact severity. These data build on data previously presented1,2,3. A method for computing velocity change (?V) for vehicle to vehicle collisions from vehicle to barrier data is presented. Data from staged low-speed lateral collisions correlate target and bullet vehicle damage to linear and angular velocity change (?V, ??), impact location, pavement friction and collision force. It is shown how momentum, energy and restitution principles can be used to predict ?V and ?? from damage. For staged side-swipe collisions, damage details are correlated to the target vehicle acceleration-time history. The vehicle motion is characterized as a vibration dose.
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A Survey of Automobile Aeroacoustic Activities in Germany
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This survey reports on the salient features of the approaches being pursued in Germany by automobile manufacturers, research organizations etc. to control and inhibit the noise emission from automobiles. The results reviewed are those presented by a number of experts from industry, research organization and universities during a Symposium held in February 1994 in Germany. Topics of concern were among others: sources of noise in automobiles, noise emission measurement techniques, aeroacoustic optimisation of car body and air conditioning equipment, design of and operational experience with new aeroacoustic wind tunnels in Germany.
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Silicone Elastomer Reduces Noise, Vibration, and Squeaks in Vehicle Instrument Panels
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Felt tape has traditionally been used as a cushion material between thermoplastic instrument panel (IP) components such as bezels, steering column covers, and trim to reduce noise, vibration, and squeaks that normally develop when plastic materials are adjacent to one another. However, felt tape is expensive as a raw material, and its application is labor intensive. While searching for an alternative cushion material, exploration showed that the use of a one-part, room-temperature vulcanizing (RTV) silicone elastomer offered lower raw material and labor costs versus the felt tape. The RTV silicone elastomer also did a superior job of reducing noise, vibration, and squeaks and provided improved fit for a higher level of overall quality. This paper will describe the process of evaluating the silicone elastomer as a desirable alternative and the cost comparisons of both silicone and felt tape materials. The actual process of applying the silicone elastomer as a cushioning material on the IPs of 1995 General Motors C/K light truck and sport utility vehicles will also be described. Background material on the chemistry of silicone RTVs and some of their other applications in the automotive industry will be presented as well.
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Occupant Retention Glazing for Automotive Sidelites
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This paper summarizes joint efforts by Monsanto Company and Excel Industries to develop a cost effective integrated system for automotive sidelites to achieve improved occupant retention. A cost/ performance analysis of a proprietary polyurethane RIM attachment system in combination with two candidate laminate structures (Monsanto ?쐃xperimental plastic?? tempered bilaminate + annealed glass/polyvinyl butyral/ annealed glass trilaminate) was completed. While both systems yielded high energy containment capabilities, the trilaminate system was rated higher because it showed superior membrane characteristics after impact and significantly lower fabrication costs. It was determined that such a system could be implemented for an incremental cost of < $100 per vehicle.
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Establishment of Countermeasures in Side Impact by Simulations
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To check sharply increasing traffic accident casualties, activities have been underway to analyze accidents and develop safety equipment Automobile makers have placed a great emphasis on improving safety in collision. In this situation, a new side impact standard was introduced in FMVSS 214 in October 1990 and will be applied to passenger cars in 1993 model year. The standard requires an additional full scale dynamic test in which an aluminum honeycomb moving deformable barrier (MDB) simulating the front end of a car is crashed at 33.5 mph into the side of a standstill car at an angle of 27 degrees. The Side impact Dummy's (SID) Thoracic Trauma index (TTI(d)), which is the average of the maximum rib acceleration and the maximum lower spine acceleration, is limited to 90 g's for a 2-door passenger car and 85 g's for a 4-door car. The dummy's pelvic maximum acceleration must remain no greater than 130 g's for both types of cars. Because most compact cars have no more than 300mm crash space between the door and the dummy, this new standard is even more stringent than the frontal impact requirements. This is especially so for a 2-door car, of which lateral rigidity is normally lower than that of a comparable 4-door car, and there have in fact been few makes which met the new standard. In order to ensure compliance with the new FMVSS 214. We have reviewed our conventional development method carefully so that necessary countermeasures for 2-door cars can be incorporated into prototypes and thus much time and money can be saved by avoiding unnecessary design reworks and retests. Previously, we used experimental methods to work out safety provisions on vehicles, but such methods could be time-consuming and expensive, and variations in test had to be always taken into account, often causing delay in engineering release for prototypes. Therefore, the method of numerical simulations was chosen to quickly perform a series of operations from factor analysis to verification of countermeasures worked out As a result goals were achieved in a relatively short time. This paper presents the method of numerical simulation.
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Correction of Finite Element Model for Vibration Analysis Using the Identification System
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At the early stage of a new automobile or a new motorcycle development, it is important to grasp and improve its vibration characteristics. To satisfy this demand, finite element method has been applied to vibration analysis in recent years. However, a poor finite element model can cause not only insufficient vibration estimation but also additional development period. Conventionally, an inaccurate finite element model is corrected by trial and error technique to correspond with the experimental results. In this study, a finite element model identification system referring to experimental modal parameters has been developed. The system mainly consists of structural analysis, sensitivity analysis, numerical optimization technique, and evaluation of mode shape correlation. All these processes collectively minimize the difference of calculated and experimental natural frequencies. The system has been applied to automobile and motorcycle structures, and is confirmed to be effective in correcting a finite element model.
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Challenges To Meet Heavy Duty Diesel Engine Euro II And US 1998 Emission Regulations
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The paper presents results of engine development and research activities demonstrating the potential of technology currently being developed to meet forthcoming emission regulations for heavy-duty diesel engines in Europe and USA. Development strategies demonstrated in the paper concentrate primarily on the reduction of NOx and PM exhaust emissions while maintaining engine fuel economy and durability. Furthermore, decisive aspects of engine competitiveness are considered, such as minimum necessary complexity of the technical solution in order to minimize production costs, and low engine noise characteristics.
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Tools For Sound Quality Analysis In Complex Sound Fields
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As worldwide competition for agricultural and construction equipment increases, manufacturers need to distinguish their products in areas such as operator comfort and perceived quality. Advances in digital audio recording and high speed computers have presented the noise and vibration engineer with the possibility of new tools and techniques for analyzing and processing sound. This paper discusses some of the recent developments in sound quality analysis in passenger cars and how they can be applied to similar engineering problems in off-highway vehicles.
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A New Test Cell Computer for Exhaust and Evaporative Emission Testing
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For the increased requirements on computer automatization and data evaluation in the field of emission testing, new programming / computer - technologies are required. To fulfill the requirements of the programmer and the user of the software, Windows NT with object oriented programming was found to provide the best possibilities to control such highly automated, complex systems. Under these directions the new Emission Test Cell Computer (short ETCC) was developed with use of the latest software and hardware technology. The Test Cell Computer provides a control system with integrated storing and paperless documentation of all relevant test data as well as protocols with all today's possibilities to create printouts. Also the managing work necessary for multiple tests running in parallel at the same time in different rooms with progress monitoring is included. The ETCC can easily be integrated into network environments and connected e.g. to existing networks. Data evaluation stations for research and development work can operate on the same network. With the integrated client/server-database, all evaluation stations have access to available data even with multiple test cell computers connected in the network. This was realized by using new technologies for the man machine interface, based on the well known Windows operating interface.
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Investigation Into the Noise Associated With Air Bag Deployment: Part I - Measurement Technique and Parameter Study
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High-amplitude, short-duration noise is called impulse noise. A large body of literature on impulse noise has been developed primarily by military researchers for multiple exposures such as those caused by weapons firing. Some research into the impulse noise associated with air bag deployments was performed in the late 1960's and early 1970's to ascertain the risk of hearing loss. Several criteria for risk of noise-induced hearing loss were proposed and much was learned about the sources of the noise. Unfortunately, the instrumentation used to measure the noise in many of those studies lacked adequate low frequency response characteristics. Perhaps more importantly, results from experiments with human volunteers do not seem to agree with the proposed criteria. For this study, a new system consisting of commercially available pressure transducers and microphones was assembled and a new software package was developed. This system allows analysis of the pressure-time data using two analysis methods and criteria proposed in the early 1970's. A series of experiments using this system was run over a four year period to investigate the parameters that affect the impulse noise associated with a deploying air bag. Some observations are presented and conclusions drawn from the data.
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Mathematical Simulation of Driver and Restraint Systems in Racing Saloon Car Impacts
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MADYMO 3D software was used to model a racing driver with helmet, racing harness and competition seat, and to evaluate injury parameters in a racing saloon car under European Type Approval impact conditions. Parametric changes in the safety systems were evaluated. The systems protected the driver well, although high neck torques were predicted in frontal impact. Loads on the head restraint were substantially higher than the strength required in regulations. In side impact the head passed through the open window. A window net prevented this, but the predicted loads exceeded the strength of a net tested in the laboratory.
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Noise Attenuation for Polyamide Intake Manifold
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Noise Attenuation for Polyamide Intake Manifolds Since the stiffness of polyamide is lower than aluminum, special techniques have been developed to increase local and global stiffnesses of polyamide intake manifolds. The increased stiffness results in parts with noise emissions equal to or less than equivalent aluminum intake manifolds with twice the wall thickness. These special techniques enable engineers not only to attenuate noise, but to ?쐔une??the remaining noise emissions for a desirable sound quality.
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The Aero-Acoustic Wind Tunnel of Stuttgart University
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The noise emission of cruising vehicles essentially consists of tire/road noise, drivetrain noise (engine with intake and exhaust system, transmission and driving axle) and aerodynamic noise due to the flow around bodywork, chassis, wheels and cooling air flow (fan). Engines and drivetrains have become quieter due to many man-years of engineering attention and tire noise has also been reduced - at least the noise reaching the passenger compartment. Consequently, the aerodynamic noise of ground vehicles has become dominant at driving speeds above 100 kph both in interior and exterior noise. In order to determine the contribution of aerodynamic noise to the overall noise, measurements are carried out more and more in specially equipped automotive wind tunnels. Besides wind tunnels in which aeroacoustic testing was already envisaged in the specification and design phase, existing wind tunnels can be upgraded to acoustic testing by a suitable treatment of the tunnel airpath and the plenum chamber. The existing 22.45 m2 Open-Jet Automotive Wind Tunnel of Stuttgart University - Institute of Internal Combustion Engines and Automotive Engineering (IVK) - built in 1988 was converted into an aeroacoustic wind tunnel in 1993 by a novel silencing concept. In the return duct of this G철ttingen-type wind-tunnel two U-bend silencers were installed upstream and downstream of the fan, using membrane absorbers as thin and smooth vertical splitters (for the low frequency range) in conjunction with profiling the turning vanes with coated porous Polyesterfoam (for the middle and high frequency range). An anechoic plenum chamber was achieved with a new type of broadband absorbers, mounted on the plenum walls and ceiling. Due to its very low self-noise level the IVK Aero-Acoustic Wind Tunnel provides a high potential for the acoustic rating of design optimizations in the development of future vehicles.
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New Acoustic Feedback System
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The acoustic feedback (AFB) system is to detect the acoustic signals radiated from a loudspeaker with a microphone, and feed them back to the previous stage of the amplifier. However, there were many problems to put it into practical use. A new AFB system has been developed, where the above problems are solved by setting the microphone at the optimum position and adopting a new feedback method. This was achieved by reviewing the loudspeaker performance from a new point of view. Thus, a wide-range feedback and the improvement in the speaker response have been obtained. Also, the problems of oscillation have been solved.
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A Numerical Investigation of Two-Dimensional Cavity Flow
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Results are presented for the application of an acoustic/viscous splitting technique to die computation of flowfields within two-dimensional rectangular cavities for moderate Reynolds numbers. This technique has been previously applied to cavity flows but results were studied only in die acoustic far field and limited to low Reynolds numbers. Implementation of a large eddy simulation model has allowed the Reynolds number range to be extended and direct comparison of computations with wind tunnel results for the cavity near field demonstrates that this technique, which is two-dimensional, may be used to study three-dimensional cavities, provided such cavities are fairly large in their transverse direction. In addition, the flowfield calculation is shown to be sensitive to such parameters as boundary layer thickness, filter width used in the large eddy simulation implementation, and incoming velocity profile.
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Road Noise Modelling Using Statistical Energy Analysis Method
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A mathematical model was developed to evaluate design options for control of road noise transmission into the interior of a passenger car. Both air-borne and structure-borne road noise over the frequency range of 200-5000 Hz was able to be considered using the Statistical Energy Analysis (SEA) method. Acoustic and vibration measurements conducted on a laboratory rolling road were used to represent the tire noise ?쐓ource??functions. The SEA model was correlated to in car sound pressure level measurements to within 2-4 db accuracy, and showed that airborne noise dominated structure-borne noise sources above 400 Hz. The effectiveness of different noise control treatments was simulated and in some cases evaluated with tests.
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Acoustic Modeling and Optimization of Induction System Components
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Several aspects of the acoustic design optimization of induction systems are considered. The important role of the inlet manifold in the induction system is shown by constructing mathematical models of two levels of sophistication. A plane wave representation of the manifold is adequate when the geometry of the manifold supports only longitudinal acoustic modes. When the geometry supports transverse modes it is necessary to include the acoustic modal structure in the mathematical model comparing three mathematical models. The manifold with a conventional runner arrangement is shown to introduce harmonics of the firing frequency other than the generally assumed multiples of the number of cylinders. A manifold with runners coupled in a common plane is considered as a means of eliminating undesirable harmonics. It is shown by considering the ninth harmonic (order 4.5), that harmonics other than the integer multiples of the number of cylinders are drastically reduced in amplitude. The difficult problem of generating a good source model for the inherently nonlinear aeroacoustic source at the inlet valve is approached by the use of a simple linear model with source strength and source impedance adjusted to match with data over limited frequency ranges. The car body transfer function is shown to be an important element in the design optimization process which is based on the reduction of driver's ear noise, rather than on snorkel noise. The design process is systematized by using a SIMPLEX optimization scheme in conjunction with a plane wave modeling code. The design procedure is shown to depend heavily on access to acoustic data from a prototype vehicle. This data is required to calibrate the noise source, to establish background noise levels which limit the benefits achievable by induction system optimization, and to provide a transfer function for the car body.
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Blower Motor Whining Noise - A Case Study
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Vehicle interior sound quality is regarded as a major quality attribute by automobile consumers and manufacturers. Whining noise, due to its steady state and tonal nature, is easily perceived as an annoyance to normal driving comfort. The blower motor in the climate control air-handling system can be a source of whining noise, especially when the motor is located in the passenger compartment. This paper describes a systematic case study carried out to identify the major noise generating mechanisms of a whining noise from the climate control air-handling system. The paper discusses the use of commonly available tools and techniques to resolve typical automotive NVH concerns resulting in improved sound quality. Particular measurement and analysis techniques presented include sound field mapping using acoustic intensity, resonance identification using transfer functions, three-axis spectrum analysis, and some physical modifications to the source and propagation paths. A variety of objective noise and vibration data is presented and explained. The investigation concludes the source of the whining noise as a type of brush noise. The path is identified as structureborne noise transmitted from the brush-commutator interface, through the motor support structure, to the blower assembly casing, where it is radiated from various positions as airborne noise. The recommended solution is to mount the motor so that it is vibration isolated. Data measured on an iso-mount design is presented to confirm this solution.
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Analytical and Empirical Evaluation of the Impact of Solar Control Glazing on the Thermal Environment in Vans
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Spectrally selective glazings that reduce the amount of solar energy entering a vehicle have been developed by PPG to enhance overall passenger comfort and help automotive designers and engineers manage the thermal environment in vehicles. That environment is being affected by such factors as the use of larger glass surfaces, smaller engines, fuel economy goals and refrigerant issues. To quantify the effects of a variety of solar control glazings on passenger comfort and thermal environments, PPG has conducted in-vehicle tests in Arizona evaluating the following glazing systems: the SUNGATE짰 Automotive windshield, which uses a transparent infrared-reflective coating; SOLARGREEN짰 Glass, a special composition that reduces infrared energy transmittance, and GL-20??Glass, a deep-tint privacy glass. The evaluations included measurements of passenger compartment air temperatures, material temperatures, air flow, heat flux through non-glass surfaces, passenger comfort and air conditioner performance. Test results show that these glazing systems are effective in reducing maximum temperatures in parked vehicles, improve cooldown performance following static exposure and reduce compressor work loads. This all leads to improved passenger comfort, improved fuel economy and less damage to interior materials. While desert testing will continue to play a role in assessing in-vehicle performance of glazing systems, there is a need to provide such information in real time as auto manufacturers continue to reduce their development cycle. To that end, a predictive analytical model has been developed. The foundation for that approach is a thermal simulation code that has been modified to allow changes in orientation and the capability to use short time step boundary conditions. Initial efforts in this project, both analytically and empirically, have been focused on simulation of the minivan vehicles. The dynamic nature of both the simulation and the empirical drive test required observation of additional temperature, flow and heat flux sensors throughout the vehicle. Comparisons of the simulation models to empirical results confirm that the analytical approach captures the measured performance of new glazing products in vehicles.
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Acoustics and Microgravity Flight
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The effects of acoustic levels in manned space vehicles was not thoroughly appreciated until the STS 40 mission, Spacelab Life Sciences 1 (June, 1991). Previous to that mission, waivers were submitted and equipment operated without overwhelming effect on ongoing flight activities. The factors of multiple pieces of noise producing equipment operating simultaneously, operating in the vicinity of crew sleep stations, and operating for this long of a mission (10 days) became relevant in crew tolerance, fatigue, communication, and permanent shifts in hearing thresholds. Because this was a life sciences mission, accurate instrument measurements were obtained of acoustic levels in the middeck, flight deck and spacelab during flight and physiological measurements were obtained from the crew members during all phases of the mission. Due to the STS 40 results, a Spacelab/Payloads Acoustics Working Group (SPAWG) was formed post flight to address acceptable acoustic limits. The charter of this group was to: Identify and assess orbiter, spacelab, subsystems, and experiment hardware with the objective of reducing the overall acoustic levels on the Middeck and within the Spacelab module to acceptable flight levels. Members of the group represented NASA headquarters, field centers, and payload developers. This paper will briefly address the acoustic impact on crew persons during STS 40, the recommendations of the SPAWG, and current means of addressing acoustic issues within life sciences hardware flown on microgravity missions.
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Customer Based Holometric Analysis
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This paper describes a test-based process used to identify structural characteristics of a vehicle windshield wiper system that contribute to customer impression of the sound. The method of paired comparisons determined which wiper system sounds customers preferred. Annoyance ratings of sound components then identified contributors to customer preference. Wiper motor noise was identified as the major annoyance factor affecting system sound quality. This information guided a study of the structures responsible for radiated motor noise. Laser based test methods were used to interrogate the structures clearly identifying transmission paths into the surrounding structure. Paths were then modified reducing structure-borne motor sound as measured with acoustic retests. Thus, a logical technique for hardware testing and modification guided by customer perceptions is presented allowing efforts to be focussed on the most critical aspects of vehicle sound quality.
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Objective Analyses of Binaural Recordings
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Aurally-adequate sound measurement technology makes use of both present psychoacoustic knowledge, e.g. loudness, roughness, fluctuation, sharpness and so forth, and Artificial Head measurement technology with transmission characteristics comparable to human hearing. By taking into account psychoacoustic evaluation parameters very often good results for judging sound events with regard to sound quality, as compared to subjective impressions, can be achieved. If a sound situation is relatively complex, i.e. if it consists of various single sound sources at different spatial positions, significant level and phase differences between the left and right ear occur which - in comparison with a monaural evaluation - can yield different results. Such effects have been observed for some time already. Speech intelligibility in a noisy environment, e.g., depends on the positions of the sound sources. Furthermore, investigations into noise in workplaces showed that binaural recordings as compared to monaural recordings caused significantly different physiological reactions of the test subjects. Moreover, it became evident that noise annoyance of single sound sources in a complex mixture of sounds does not only depend on absolute parameters such as A-weighted SPL, loudness etc., but also on their localization. In the interior of a car, for instance, the individual engine orders can produce significant amplitude and phase differences between the left and the right ear, due to wave and multipath propagation, influencing the subjective evaluation. There are no objective measurement procedures available at present. In the last decades a lot of scientific basic research was done on binaural signal processing. Due to the complexity of signal processing in human hearing there have been no complete models yet which simulate binaural signal processing in a simple way and thus constitute a basis for the objective determination of sizes, derived from a binaural measurement to describe subjectively perceived sound quality. Therefore, investigations aiming at the selection of certain signal components from a complex mixture of sounds were carried out, based on additional information such as directional sound incidence of the sound sources under test or engine r.p.m. for selecting individual engine orders. On the basis of known models to predict speech intelligibility in a noisy environment, binaural models for the objective determination of sound quality, based on these simple application examples and Artificial Head recordings, were developed.
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Engine Noise Reduction Using Narrowband Feedback Control
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A narrowband feedback control is developed to cancel periodic noise. The method consists of digital bandpass filters centered at a reference frequency and its harmonics. Each of these bandpass filters is then followed by a finite impulse response (FIR) filter which changes the phase of the control signal to achieve the 180째 phase shift in the open loop system. A gain is applied to the control signal to adjust the overall noise reduction, considering reasonable stability margins in the system. In a set of experiments the proposed technique was compared with the filtered-x adaptive feedforward control method. The periodic noise, introduced by a noise speaker, inside a reverberant box was controlled (reduced) using both techniques. With the gain properly adjusted, the amount of noise reduction at the microphone was slightly less than that achieved by the filtered-x adaptive control, but the stability characteristics of the feedback control system was considerably better. The feedback system was able to maintain a gain margin of about 6 dB's and a phase margin of 45째 over the entire frequency range of interest while the feedforward controlled system became unstable at a few frequencies even with very slow adaptation rates. The proposed feedback technique was also used to attenuate the interior noise, due to the firing of the engine, in an automobile. The reduction of up to 8 dB's in sound pressure level at the driver's head was achieved.
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Application of Noise Control and Heat Insulation Materials and Devices in the Automotive Industry
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Automotive noise control involves many aspects of the total vehicle design - the powertrain, body structure, chassis and so forth. Noise control materials in conjunction with intelligent vehicle design can help produce a pleasant, desirable vehicle. Understanding the basic functions and uses of noise control materials is one of the objectives of this paper. In some situation, thermal insulation materials are combined with or used in conjunction with noise control materials, and an understanding of the thermal properties of materials can be useful. Vibration isolators are important devices in controlling the transfer of sound and vibration energy and these are discussed.
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Investigation of Different Techniques for Quantifying Automotive Panel Noise Radiation
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In the process of determining optimal treatment locations and compositions for automotive noise control parts, it is necessary to know both low frequency and high frequency sound contributions of automotive interior sheet metal panels. Several techniques of experimentally assessing individual panel contributions to coherent, low frequency noise as well as incoherent, high frequency noise are investigated. These include use of a sound intensity probe, a pressure gradient microphone and an accelerometer for measurement of panel vibrations. Acoustical insulation of all interior surfaces except a particular surface of interest (the ?쐗indowing??method) and boundary element modeling (for exclusively low frequency characterization) are also investigated. While no one technique is ideally suited to determining contributions in the entire audible frequency range, the boundary element method was found to be particularly useful for coherent source characterization, while the more traditional ?쐗indowing??method is well-suited to incoherent source characterization.
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Sound Quality Assessment of Powered Seat Adjusters
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With the extensive improvements achieved in vehicle driveline and road noise quality manufacturers are turning their attention to component and ancillary noise sources and expecting their suppliers to include sound quality in the assessment of their designs. This paper describes an investigative project into the principal components contributing to the perceived sound quality of powered seat adjusters in passenger vehicles and the statistical methods of analyzing jury preference data.
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The Ford Motor Company Advanced Engineering Center
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The Ford Motor Company Advanced Engineering Center contains 100,000 square feet of sound and vibration laboratories, induding full vehicle chassis dynamometers, powertrain dynamometers, and sound quality evaluation chambers. The facility houses the first U.S. All-Wheel-Drive NVH Chassis Dynamometer (4 independent motor drive), the first U.S. All-Wheel-Drive NVH Powertrain Dynamometer (4 independent motor drive) and other unique elements, such as innovative wedge construction for the acoustic chambers.
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The Chrysler 3/8-Scale Pilot Wind Tunnel
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The Chrysler 3/8-scale model automotive wind tunnel is a pilot facility for a planned full-size tunnel of the same design. The 3/8-scale tunnel, which has a complete compliment of instrumentation including a pressure system and high-precision balance, will also be used for 3/8 model aerodynamic development testing of vehicles after piloting is complete. The tunnel is convertible from a slotted-wall test section to a semi-open jet test section. Commissioning, calibration, and piloting results show the performance of some features being piloted including slotted-wall effectiveness, open jet collector performance, and tunnel background noise levels. Calibration results include static and dynamic pressure distributions.
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On the Induced Noise of Test Sections in Different Wind Tunnels and in the Cabin of a Passenger Car
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An acoustic comparison test of eleven European and two American full-scale automotive wind tunnels was carried out with a passenger car. The scope of investigation comprised in-flow and out-of-flow background noise measurements of the empty test sections as well as interior noise measurements inside the passenger compartment of a standard type Volkswagen Passat Variant CL. For this purpose seven different vehicle configurations were investigated in the various wind tunnels. The aim of this experimental investigation was to establish physical criteria in order to carry out a suitable acoustic comparison between wind tunnels with different types of test sections and to establish upper limits of wind tunnel background noise levels where acoustic measurements inside a passenger compartment are questionable.
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Measurement and Analysis of Gaseous Exhaust Emissions from Recreational and Small Commercial Marine Craft
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In general, propulsion systems used in recreational and small commercial marine craft exhibit some unique design and installation characteristics, which demand special attention from the standpoint of emissions measurement and data interpretation. For example, the exhaust system is often a compact folded design which terminates partially or completely underwater. Also, water is normally present throughout much of the exhaust ducting in order to provide cooling, noise reduction, and tailored exhaust tuning characteristics. Marine industry efforts have led to the development of a measurement standard (ICOMIA 34-88) which is being used to evaluate marine propulsion systems in anticipation of future exhaust emission regulations. This paper discusses the rationale used to develop the measurement and data analysis procedures, and presents the complete ICOMIA standard as an appendix.
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Standardization of a Test Track Surface for Use During Vehicle Noise Testing
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A group within the International Organization for Standardization has worked out a standard for a road surface intended to be used during vehicle noise measurements according to the ISO 362 and 7188 procedures. The surface should be equally suited for use in similar measuring procedures where full-throttle operation of vehicles is needed and where the influence of the surface on noise emission and propagation must be kept at a minimum. Several test tracks have been laid according to the proposed specifications. A Round Robin Test has been conducted in which five cars and one truck were run on a number of test tracks in Europe and Japan. The results show that the surface meets the basic requirements of giving low tire/road noise while still having negligible sound absorption characteristics. Also, the site-to-site variability is low. In this paper, the convener of the working group presents the work and a preliminary proposal. The final proposal is scheduled to be presented in the summer of 1991.
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Active Control of Simulated Road Noise
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Active noise control is a potential method for controlling troublesome low frequency road noise in the passenger cabin of automobiles. In this investigation, the control of simulated road noise in a four door automobile is studied. Active control of road noise requires that the inputs to the controller sense a significant part of the energy causing the noise. Only the coherent energy between the input sensors and the performance microphone is controllable. An investigation is conducted of the control achievable using accelerometers mounted at various positions near the rear wheel of the vehicle as inputs to the controller. The best input sensor location was used with a commercial active noise controller to reduce simulated road noise near the driver's head location. The measured reduction is compared with the results predicted using the coherence. Additional controller simulations were developed to predict and better understand the performance of various controller types in this automobile.
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Acoustic Analysis of Truck Cab
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This paper presents the results of acoustic analyses of light duty truck cabs by actual vehicle testing and by numerical analysis utilizing the boundary element method (BEM). In the resonance mode analysis using BEM, by taking into account the vibration characteristics of cab panels, the presence of the modes other than the purely acoustic cavity resonance modes were confirmed. The contribution of the panel vibrations to booming noise that occurs in actual light duty trucks was analyzed. BEM analysis showed that some of the panel vibration had a negative contribution to booming noise. In other words, decreasing vibration in such a section was shown to increase sound pressure. The results of the BEM analysis match well with actual test results. It has thus been demonstrated that BEM is an effective method for analyzing truck interior noise reduction.
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Integrated Flight-Propulsion Control Concepts for Supersonic Transport Airplanes
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Integration of propulsion and flight-control systems will provide significant performance improvements for supersonic transport airplanes. Increased engine thrust and reduced fuel consumption can be obtained by controlling engine stall margin as a function of flight and engine operating conditions. Improved inlet pressure recovery and decreased inlet drag can result from inlet control system integration. Using propulsion system forces and moments to augment the flight-control system and airplane stability can reduce the flight-control surface and tail size, weight, and drag. Special control modes may also be desirable for minimizing community noise and for emergency procedures. The overall impact of integrated controls on the takeoff gross weight for a generic high speed civil transport is presented.
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Development and Application of Simulation for Low-Frequency Boom Noise and Ride Comfort
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This paper investigates a new approach to the quantification technique for road induced vehicle interior noise and vibration within the frequency range up to 40 Hz. By employing the least squares method, both vertical and fore-aft load to each wheel were quantified using transfer function and actual vibration response of the vehicle driven on a road. The coupled structural-acoustic vehicle model using the finite element method, which is also detailed in this paper, is combined with the quantified input load to simulate road induced interior noise and vibration response. Experimental verification, which indicates reasonable accuracy of the simulation, and an application for the prototype development are also presented.
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Development of Composite Materials Applications to Production Nacelle Component Structures
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The main engineering problems requiring solution in a development programme aimed at the application of composite materials to selected nacelle components are reviewed. The components chosen were characterised by important special features including acoustic performance, fireproof capability and resistance to fan-blade off effects. The subsequent application of the developed technology to meet production nacelle requirements and Airworthiness compliance needs is discussed.
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Corrosion Protection of Galvanized Steel Sheet-Corrosion Investigation of Field Vehicle
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Three doors from three field vehicles made with one-side galvanized steel on the inside of the outer panels were investigated for perforation corrosion using microscopic and analytical methods after 8 or 10 years' field exposure in the snow-belt areas of North America. Perforation of these doors occurred within the lapped part of the door hems. Outer panel perforation began at the zinc layer on the inside surface of the outer panel at the lapped part and/or at the ?쐀ent part??of the outer panel of the door hems. Details of the micro corrosion behavior for the inside surface of the outer panel were made clear using EPMA analyses. The corrosion products on the inside surface of the outer panel were identified with X-ray diffraction. Initially, zinc corrosion begins at the zinc coating layer of the upper side at the wax-free zone of the lapped part. Eventually zinc corrosion occurred beneath the wax layer as ?쏹nder-film corrosion?? proceeding gradually from the bottom to the top of the lapped part. The zinc is transformed into ZnO from the protective ZnCl2쨌4Zn(OH)2 initial product. Eventually, the steel substrate corrodes after the zinc coating loses its sacrificial corrosion protection. The steel is transformed into Fe3O4 and 慣, 款-FeOOH. It was found that this corrosion behavior was a common phenomena for the observed door hems.
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Rollover Crash and Laboratory Tests of Ejection Reduction By Glass-Plastic Side Windows and Windshields
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About one fourth of the occupant deaths in passenger cars in the United States involve either complete or partial ejection. Approximately one half of these ejections are through glazing areas. This paper presents research results which demonstrate the potential of glass-plastic glazing to significantly reduce ejections through motor vehicle windows. Four passenger car and four light truck and van rollover experimental crashes were conducted. All the vehicles had glass-plastic front side window glazing. One of these included the improved glazing with a movable encapsulated ?쐎ffset T-edge??design. Two in addition had glass-plastic windshields. Even with glass breakage and window frame distortion, the glass-plastic glazings maintained their ?쐓afety net??ejection reduction function. Laboratory dummy drop and sled tests of the movable glass-plastic glazing side windows are reported. Component tests are discussed which use 10 pound and 40 pound, eight inch diameter, chamois - covered spheres as test devices to evaluate the characteristics of the improved glazing relative to the Head Injury Criterion, laceration, and ejection reduction. Research remains to be carried out to assure sufficient deformation of the safety net glazing system to provide acceptable neck loads under severe glazing contact conditions.
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Carbon Epoxy Perforated Skin for Nacelle Acoustic Treatment
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The acoustic treatment requirement for jet engine nacelle inner flowpath leads to using perforated skin. Formerly in light alloy these skins are now composite and new techniques have been developped to achieve the perforation. After reviewing different possible techniques (mandrel tool, abrasion, stamping, mechanical drilling,?? one process is chosen and described in terms of skin mechanical properties, cost, and production facilities.
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Parameter Identification for Noise Prediction in Car Structures
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The investigation of the static behaviour of structures, especially car bodies, by analytical methods is a very important and widely used tool in the automotive industry. It is much more difficult to predict noise phenomena. The key point is that many physical quantities determine the sound in the car (1)*. The relevant physical effects must be identified in order to get a reliable mathematical model. The paper describes how this can be done by a combination of experimental and analytical works. The frequency range of interest is up to 200 Hz
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Using Fiber Optics and Laser Fluorescence for Measuring Thin Oil Films with Application to Engines
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A new method has been developed for measuring the oil films on cylinder walls in engines that offers benefits in improved understanding of oil transport and consumption. The unique aspect of this work is that fiber optics and laser induced fluorescence are combined to measure the oil film thickness. As a result the system is much less intrusive than previous methods using windows to observe the fluorescence. Static tests were used to demonstrate the characteristics of the technique. Dynamic tests, performed on a Cameron Plint wear tester, showed the capability of the system to measure thin films under dynamic conditions and at high loads and temperatures. Finally, the system was installed in a diesel engine and used to measure oil film thicknesses under fired conditions.
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Side Impact Crashworthiness Design: Evaluation of Padding Characteristics Through Mathematical Simulations
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The National Highway Traffic Safety Administration (NHTSA) has developed a lumped mass computer model which simulates the interaction of a struck car door and an adjacent two dimensional seated dummy in side impacts. This model was used to investigate the effect of various vehicle design parameters on occupant responses and to define various methods to improve vehicle safety performance. This paper discusses the effectiveness of door padding and side structural stiffness to minimize potential for occupant thoracic injuries in 90째 side impacts. Occupant response data were obtained with the aid of the computer model for a Moving Deformable Barrier striking a car at lateral velocities of 25, 30 and 35 mph. To determine the optimal padding and structure needed to minimize potential occupant injury, the Thoracic Trauma Index (TTI) was mapped in terms of different levels of struck car side stiffness and padding characteristics.
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About the Threshold for Fatal or Potentially Fatal Injuries in Car-to-Car Side Collisions - A Comparison Between Real Accidents and PMHS-Tests
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This analysis is part of a retrospective real accident study of 670 occupants in 428 cars. In most cases the real accidents were reconstructed from police reports by means of photographs, accident drawings and descriptions of the damaged cars. In fatal crashes the cars, and in most cases the sites of the accidents were examined. Among 272 occupants involved in car side collisions, we found 41 belt protected near side front passengers, whose cars were impacted by another car with main impact points at the front passengers' doors and B-pillars. The analysis of the correlation between technical parameters of the real accidents and injuries of the passengers showed a high significant discrimination between MAIS and some regional AIS 0-3 on one hand, and MAIS and some regional AIS 4-6 on the other hand already for each of the technical variables EES, delta v and maximum deformation. The comparison between these 41 real accident cases and 57 PMHS (postmortem human subjects) tests (15)* proved a significant difference between the thresholds for fatal injuries in respect to maximum deformation. The mean values of maximum deformation for fatal injuries in the real accidents were significantly higher than in the PMHS-tests. The possible causes of the differences are discussed.
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Cold Start Improvements With a Heat Store
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The Heat Battery, a latent heat store, accumulates waste heat of the engine and preserves it by efficient heat insulation. On the next cold start, after a day or a weekend, the heat is released with an initial power of 50 to 100 kW. This energizes the vehicle heating system within seconds, allowing for hot air to flow instantly to the cabin and to the windshield. The passenger comfort is immediately felt, and the windshield can be defrosted or demisted without manual help. Due to the high heating power the engine will warm up within 30 seconds so that the tailpipe emissions of carbon monoxide are reduced up to 50% and unburnt hydrocarbons up to 30% in the first bag of the CVS-Test.
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Overview of a Study on Direction-of-Motion Stereotype Strengths for Automobile Controls
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Virginia Polytechnic Institute and State University recently conducted an SAE sponsored research study investigating directional stereotypes of six types of automobile controls: power mirrors, power windows, manual windows, stalks, generic controls, and power door locks. The objective was to determine stereotype strength and the reasons for the strengths. Two hundred subjects participated in this study. This paper provides an overview of the results of the study and recommendations made therefrom.
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A Plan to Prevent ESD Damage on Electronic Components at an Auto Radio Process Assembly
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Everybody has already had the ungrateful experience of walking on a carpet tile and receiving an electric shock just by touching a door knob. What many people don't know is that, simply the fact of walking a few meters over the carpet can generate some kilovolts of electrical charge and cause a damage of some thousand dollars on electronic devices such as computers, radios, electronic controls, etc, due to the fact that they have components sensitive to a few hundred volts or less. The most common way of generating Electrical Static Charge is frictioning two different materials against each other. Electrons are transfered from one surface to the other making one more positive then the other this imbalance can easily reach the order of some hundred volts. Today, the automotive industry uses a large quantity of a wide range of electronic components in its products (cars, trucks, etc.) not only for entertainment, but also on the drive control area, (engine, powertrain control etc.). Where no failure can be admitted because driveability and safety can not be jeopardized. So, it is very easy to undestand why an Electronic Assembly Plant that uses millions of sensitive devices every year needs a well defined plan to prevent the effects of Electrostatic Discharge.
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Use of One ST9 Timer for Handling a J1850 50 Kbit/Sec. Implementation
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This paper describes a mixed hardware and software implementation for the SAE-J1850 protocol (1). This implementation is general and can be adapted to most J1850 based systems. Each node is entirely managed by one ST9 microprocessor. That means that the same micro controls the application and the bus. To interface with the bus the micro uses one ST9 16-bit timer and two register banks. As a result this system can be implemented using any ST9 microprocessor. Only a simple external circuitry is needed to drive and buffer the bus, as well as filtering the incoming signals. Bit decoding, CRC check/generation and consistency checks are done internally to the micro, thanks to the sophisticated hardware of the standard ST9 16-bit timer. The data link, network, transport, session and presentation layers are implemented by software. Therefore this implementation is perfectly suited for nodes with application layers of medium complexity, such as doors, lights, speed control, A/C control, instrumentation, distributed audio modules, etc.
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Temperature Measurements During Flash Welding Thin-Walled Door-Frame Components
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This study was conducted to examine the effect of flashing conditions on the resulting temperature profile during flash welding automobile door frames. Previous work on temperature profiles of flash welds has shown that at some point in the welding cycle a steady state temperature is reached, minimizing the need for further flashing. The indication of such a minimum flashing time allows flashing conditions for any application to be optimized. Unfortunately, previous work has been limited to rather heavy section materials, and the results could not be directly applied to the flash welding thin sections typical for door frames. This program was a preliminary study to examine the effects of initial flashing velocity and flashing acceleration on the resulting temperature profiles in U-shaped channel sections. Work was done on a cam driven flash welding machine supplied. Flashing conditions were varied by using cams with different profiles. The first cam was a linear cam typical of that used for production of this part. In addition, three new cams were prepared. These included a cam with a linear flashing profile using twice the initial flashing velocity of the production cam, and two cams with parabolic flashing profiles. Both parabolic cams profiles used half the initial flashing velocity of the original cam. All cams used roughly the same flashing time, resulting in different degrees of burn-off. Temperature measurements were made by locating thermocouples at increasing distances from the original interface. During welding, temperature was recorded from these thermocouples as temperature versus time data. For each set of flashing conditions, separate experiments were run to characterize temperature profiles on the three sides of the channel section. Resulting temperature versus time data was then transformed to temperature versus distance from the flashing interface data. This data was curve fit to an exponential expression, and the results of that curve fit used to calculate effective forge depth of the workpiece. The results of this program show that the parabolic cams reach steady state temperature faster than the linear cam, and are consistent with the published literature on heavier section flash welding. However, it was also noted that excessive flashing velocities (as a result of either a high initial flashing velocity or too high a flashing acceleration) tended to overheat the part. Higher flashing velocities result increase the rate of heat generation during flash welding. It is believed that the relatively long stick-out lengths used in this application, and the relatively poor conductivity of the dies prevented heat from being extracted at a sufficient rate to maintain a stable temperature profile. Apparently, heat generation needs to be balanced between that necessary to achieve stable temperature conditions in a reasonable time, while not overheating the workpiece.
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Advances in Thermoset Injection Molding
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Injection molding of thermosetting materials such as low profile SMC/BMC composites found increasing application in the transportation industry in the eighties. Such automotive parts as front end panels and rear/hatchback doors have grown in usage. The rear doors have reached exceptional production levels of 2500/day in a single plant. The injection process offers the advantages of greater automation for the mass production of body panel parts compared to compression molding. However, the injection molding of fiber reinforced low profile composites suffers from a severe reduction in physical properties. This is particularly true for impact strength which can be one-third that of similar compression molding materials. A primary reason for this is due to the degradation of the reinforcement during the processing/molding. Efforts at increasing the physical properties through processing changes have many times caused problems with the surface smoothness of the moldings. Should major improvements in impact strength be coupled with excellent surface appearance the injection process could be applicable to automotive hoods, doors, deck lids, etc. The resultant application of automation could provide a more favorable cost structure for these composites versus metal even at high volumes of production. This paper reports on a concerted study of this problem involving examination of the organic matrix system, shrinkage control materials, interfacial agents, glass sizing changes, chemical thickening and various processing parameters and injection molding machines. This work has resulted in truly super Class A surface molding at impact strengths 80% above those of the best standard injection materials. Progress of this nature signals the beginning of a new day in low profile thermoset injection molding.
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Gas Injection Molding of Thermoplastic Composite Window Guidance Channel
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Gas injection molding of reinforced engineering plastics for structural applications is a very innovative approach, but is still in an infancy stage. The requirements for window guidance channel are: dimensional stability, high strength to weight ratio, no warpage and low wear. The composite materials with hollow tubular structure can only meet these requirements based on FEA analysis. We evaluated 30% glass filled polyester (short and long glass fibers). The part and tool designs are the key parameters for successful results which are discussed. Information on current gas injection molding technologies is discussed. The new software ?쁂-Gas flow analysis??was used to optimize gate design and process parameters. The design of experiments based on Taguchi method was used. Both available technologies, i.e., gas through nozzle and gas through runner or cavity were tested. The cross section analysis was done using CAT Scan. This is the first structural application of gas injection technology which is fully tested and approved according to GM specifications. We received Society of Plastic Industries (SPI) ?쁀ward of Excellence??for design and application development in February 1990.
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