Search Results

The addition of nickel-coated graphite to silicon carbide particulate reinforced aluminium alloys imparts unique properties to the new composite GrA-Ni™; the graphite makes it useful in high wear applications where it behaves analogously to flake graphite in grey cast iron. Graphite improves scuffing resistance and significantly increases the critical load at which the transition from mild wear to severe wear occurs. The graphitic silicon carbide MMC has better machinability and can be machined at higher metal removal rates than other existing SiC reinforced composites. Fatigue life was determined to be similar to A356-15% SiC composite.

The Simulation Model of Automobile Collisions (SMAC) computer program, developed in the early 1970's, includes a complex collision algorithm for monitoring, detecting and modeling the collision interactions of motor vehicles. A detailed review of some aspects of the logic, rationale and, in particular, limitations of the original SMAC collision algorithm is presented. This paper presents refinements in the definition of the collision interface, the definition of collision type, the vehicle proximity and collision detection logic, and the form of supplementary impulsive constraints on relative motions. The effects of the modifications of the SMAC algorithm on reconstruction results are presented in the form of direct comparisons of results obtained with the original and modified algorithms.

The trajectory solution procedures of the original CRASH program included both the SPIN routine and an exploratory trajectory simulation option to approximate and refine the linear and angular velocities at separation. The resulting separation speeds were then used to determine the impact speeds by means of application of the principle of conservation of linear momentum. This paper presents a detailed review of the logic, rationale and limitations of the trajectory solution procedures of the original CRASH program and discusses a number of refinements including: incorporation of the principle of conservation of angular momentum, approximations of the effects of changes during collision in the positions and orientations of the two vehicles and of the effects of external forces and moments that act on the two-body system during the collision, and adaptations of optimization techniques for error reduction and convergence in iterative solutions.

This paper examines the dynamic displacement-crushing force and dynamic displacement-absorbed energy behaviour of eight cars in full width barrier, 45% overlap rigid barrier and 30° angled barrier tests at 56, 50 and 56 kph respectively. This study shows the frontal crush behaviour of these cars can be divided into three regions or zones of constant force, these zones being associated with crushing of the front structure as far as the engine, the engine and rear front structure and the occupant compartment. The highest average crushing force is associated with crushing of the engine and rear front structure with lower average crushing forces required for the extreme front of the car and for the occupant compartment. It is hypothesised that the energy absorbed-dynamic displacement behaviour in the full width barrier test represents the energy absorbed-mean displacement for all other crush configurations.

When the vacuum-powered brake booster in a passenger vehicle becomes disabled, the brake force gain of the system is reduced significantly, and the brake pedal force required to lock the tires increases beyond the ability of some adults. In such cases, the maximum braking deceleration acheived by those individuals will be something less than the upper boundary as defined by available traction. This paper's goal is to review the design of vacuum boosters, the literature concerning human ability to depress a brake pedal, and FMVSS 105 requirements which must be met by vehicle manufacturers, and to present performance data with and without the booster operational for four passenger vehicles. Furthermore, the application of this information to accident investigations involving disabled boosters will be discussed.

In order to reduce the cost of engine cooling systems in particular the turbo Diesel engines with charge air coolers, we want to understand the relationship between oil sump temperatures and engine coolant temperatures and their impact on one another. Several cars have been tested in the climatic wind tunnel. The following are the cooling specifications: hill climbing with 12% grade with or without a trailer at a 20°C ambient max. speed at 35°C ambient. The main results of these studies were: a great variation of oil sump temperature versus coolant temperature a small variation of coolant temperature versus oil sump temperature a very small variation of heat flux in the oil, in the coolant and the output of engine versus oil sump and coolant temperature.

Test results have been obtained on the thermal performance of aqueous mixtures of propylene-glycol and ethylene-glycol for conditions simulating automotive engine operation. For the present study, thermal performance is defined as the test section surface temperature for a given set of operating conditions. In addition to testing over a wide range of surface heat fluxes up to 2.3 MW/m2, data were also obtained at different mixture concentrations. For all cases considered, both coolant mixtures provided similar results.

On highway and proving ground vehicle tests were conducted in the Southwestern United States to compare the performance of propylene glycol and ethylene glycol based coolants. A cross-section of vehicles encompassing pickup trucks, large and small cars, a minivan and a sport utility vehicle from various manufacturers were included in the program. Test protocols were completed with vehicles ballasted to curb weight with a four passenger load, with and without maximum recommended weight trailers. On highway driving schedules were run simultaneously with each vehicle pair. Two sets of tests were completed with each pair; once with ethylene glycol/water coolant and once with propylene glycol/water coolant. This was done in an AB/BA test sequence to reduce the impact of different ambient conditions between test. Ambient temperatures during the testing ranged from 35°C to 50°C.

There are many collisions in which the “standard” analysis methods are not sufficient to complete an analysis. Many times the points of rest for the vehicles are not documented or the vehicles were “driven” to the points of rest. There are also cases in which one of the vehicles is repaired prior to being documented. In these cases, there is a method that can be used to establish the approximated speed change of the vehicles. This method involves using the crush profile of one of the vehicles and balancing the opposing forces across the crush profile to determine an equivalent crush depth on the undocumented vehicle. Using this “balanced forces” method requires a detailed crush profile of one of the vehicles and good stiffness data for both vehicles. The method is not as accurate as standard methods because of the unknowns, but does yield reasonable results for the speed change severity for the vehicles involved.

The market needs for quieter and more compact engine cooling modules have led Valeo to develop a complete simulation based design (SBD) for its future fan technology. Its purpose is not only to improve the performances of the existing range, but also to reduce the design times significantly, and therefore to cut down the development costs. The current SBD involves using state-of-the-art CFD as a backbone. From an initial guess for a given design point based on a ducted flow approach, 2D blade cascade Navier-Stokes computations are performed to improve and optimize the initial profile. 3D Navier-Stokes computations are then performed to get the final stacking that will match the objective performances. All computations presented here have been achieved with TASCflow by ASC.

Central to the problem of heat exchangers design is the prediction of pressure drop and heat transfer in the exchanger passages. In order to make such predictions for non-Newtonian fluids, it is necessary to know the relation between the viscous properties of the fluid and the wall shear rate. This is done by assuming a constitutive equation which relates the local apparent viscosity of the fluid to the local shear rate. An often used constitutive equation because of its simplicity is the power law equation which however is only valid for particular fluids over a limited wall shear rate (or duct Reynolds number) range. This study concerns the limits of applicability of the power law equation. The method involves a considerations of a more general equation which has power law and Newtonian behavior as asymptotes. The more general equation contains an operating and property parameter whose values specify the operating shear rate range and thus the appropriate viscous properties.

The numerical optimization techniques coupled with a three-dimensional Navier-Stokes solver have been developed to design an automotive cooling fan. The conjugate gradient method is used to look for the search direction and the golden section method is used for the one dimensional search. Concerning the constraints, exterior penalty functions are employed. In the applications of this numerical optimization technique to the design of an automotive cooling fan, using the object functions defined as an increase in the pressure coefficients and a ratio of production rate of turbulent kinetic energy to the pressure head, the final shapes are obtained after sixth and seventh changes of shape function, respectively.

Instruments and analytical techniques are described for in-vehicle monitoring of amounts of air (void fraction) in engine coolant systems and for evaluating the performance of degas reservoirs. This method, based on electrical conductivity measurements of flowing air / coolant mixture, provides measurement, acquisition and display of coolant system temperature, pressure, flow rate, instantaneous void fraction and rate of air removal by degas bottle. Embedded temperature compensation equations are used for essentially real time display of the void fraction.

Advanced automatic transmissions are controlled by electronic control units (ECUs) which perform the gear change and furthermore a lot of complex control and diagnostic functions. Hardware-in-the-loop simulation (HIL) is a powerful tool to develop and test the control algorithms implemented in the ECUs. The simulation is based upon mathematical models of the different power train components, adapted to the real-time requirements. In this paper an improved real-time model of an automatic transmission with a Ravigneaux planetary gear train is presented. This transmission contains among other components numerous clutches and brakes. The time-variant states of these nonlinear elements (sliding and static friction) lead to numerical problems with respect to real-time simulation. In the suggested model the transferred torques of the different clutches and brakes are calculated using the methods of multi-variable control.

This paper describes the development of a Matrixx Model of an electronically controlled on-demand 4 Wheel-Drive (4WD) Transfer Case. The model was partially validated with respect to available vehicle test data and subsequently used for control system design and evaluation.

Computer imaging and animation can be extremely useful in analyzing vehicle accidents and illustrating the results. However the admissibility of computer images and animations in court is a concern. It is within the trial judge's discretion to decide whether a computer animation may be shown. Courts have accepted them in some cases and have rejected them in others. Aside from the legal issues, courts need to be sure that the images and motions are accurate and are based on recognized principles. Juries need to know these same things. This paper discusses the requirements which should be met to make computer images acceptable in a court of law and discusses methods for presenting an adequate foundation in court and the necessary explanations to a jury. The paper presents a systematic approach to laying the foundation for a court of law based on the author's own experience which employs the use of still images, photos, and diagrams. Case references are provided.

This paper provides an accident investigation protocol for the examination of a vehicle having an inflatable restraint (air bag) system. The topics covered are beyond what is normally required for a routine vehicle examination. Included are points on administrative preparation, such as safety precautions, information research, logistics and equipment preparation, and photo documentation equipment. The examination protocol covers exterior damage, under hood inspection, and examination of the vehicle interior. Passenger compartment integrity, intrusion, occupant contact, evidentiary transfers, seating, seat belts, and components of the inflatable restraint system are addressed, along with component removal and recovery, for shipment to a laboratory.

EDVSM is a 3-dimensional vehicle simulator developed for the HVE simulation environment. The EDVSM vehicle model was based on the original HVOSM model, developed at Calspan for the Federal Highway Administration. This paper describes the vehicle and tire models used by EDVSM. The basic model is unchanged from the original HVOSM model, however, tire-road modeling has been substantially improved by the model's integration into the HVE environment. This paper provides the details of the integration procedure. The paper also includes a validation study, comparing results between EDVSM, HVOSM and real-world handling studies. Comparison reveals the results are substantially similar. Finally, applications and limitations of the model are addressed.

Research performed in the 1970's revealed significant limitations in the available documentation of vehicle crush information and trajectory spinout information. As a result a series of full-scale crash tests were performed which became known as the Research Input for Computer Simulation of Automobile Collisions (RICSAC) crash tests. Previous research using the RICSAC test results, particularly in relation to the validation of accident reconstruction computer programs, has varied widely in acceptance, interpretation and presentation of the RICSAC test results. This paper presents a detailed review and decipherment in useable form of the original 12 crash tests that were performed within the RICSAC program. A new method of analyzing accelerometer data from arbitrary sensor positions, on the basis of discrete measures of the vehicle responses rather than complete time-histories, is defined.

Effects of restitution on damage interpretations are compounded by the fact that restitution acts to reduce the amount of residual deformation, for a given maximum dynamic crush, while also acting to increase the total impact speed change. This paper presents a revised analytical procedure to include restitution effects for the CRASH program and refinements to the restitution modeling within the SMAC program. The conversion of vehicle impact test results into inputs for the two revised programs is also included. The effects of the refinements to the damage analysis procedures on reconstruction results are illustrated by direct comparisons with corresponding results produced by the original SMAC and CRASH programs and with measured data from full scale vehicle impact tests.