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In performing stochastic simulations using computer models, the method of sampling is important. It affects the quality and the convergence speed of the results. This paper discusses one special case: sampling of spot-weld locations from potentially thousands of spot welds on a vehicle body. This study is prompted by the need of evaluating the effect of missed spot welds on the structural integrity, identifying critical welds, and optimizing weld locations. A balanced random sampling algorithm based on the concept of Latin-Hypercube sampling is developed for this application. We also present a case study in which the efficiency of three different sampling methods is compared using a car joint stiffness example. The new method, called the Balanced Latin-Hypercube Sampling (BLHS), has shown significantly faster convergence over the other two.

The approaches used to develop an NVH package for a vehicle have changed dramatically over the last several years. New noise and vibration control strategies have been introduced, new materials have been developed, advanced testing techniques have been implemented, and sophisticated computer modeling has been applied. These approaches help design NVH solutions that are optimized for cost, performance, and weight. This paper explains the NVH practices available for use in designing vehicles for the new millennium.

The more noise and vibration improvements are incorporated into our vehicles, the more customers notice squeaks and rattles (S&R). Customers increasingly perceive S&R as a direct indicator of vehicle build quality and durability. The high profile nature of S&R has the automotive industry striving to develop the understanding and technology of how to improve the S&R performance in the vehicle. Squeaks and itches make up a significant amount of Squeak and Rattle complaints found in today's vehicles. Squeaks and itches are the result of stick slip behavior between two interacting surfaces. Squeak itch behavior is dependent upon a large number of parameters including but not limited to: the material itself, temperature, humidity, normal load, system compliance, part geometry, velocity, surface roughness, wear, contaminants, etc. This paper will describe the analysis of sound data and friction data and the relationship between them.

The overall vision of this project was to develop a new technology that will be an enabler to reduce design and development time of HVAC systems by an order of magnitude. The objective initially was to develop a parametric model of an automotive HVAC Windshield Defrost Duct coupled to a passenger compartment. It can be used early on in the design cycle for conducting coarse packaging studies by quickly exploring “what-if” design alternatives. In addition to the packaging studies, performance of these design scenarios can be quickly studied by undertaking CFD simulation and analyzing flow distribution and windshield melting patterns. The validated geometry and CFD models can also be used as knowledge building tools to create knowledge data warehouses or repositories for precious lessons learned.

This paper documents the development process of the 2001 Pontiac Aztek body structure for improved noise & vibration performance. Successful vehicle development under an accelerated timing schedule demands clearly defined body structure vibration performance targets and critical dependence on the math based modeling process. Specifications for global body structure vibration performance were generated through a two step process. First, a benchmarking activity was undertaken to comprehend competitive vehicle performance. Secondly, a frequency domain “mode map” was constructed to minimize vehicle subsystem interaction. Computer simulation models were developed to predict the body structure performance. A coarse full body structure model was used to define body structure section size and joint requirements. Detailed analysis models of body joint areas were used to synthesize the joint design.

This study was initiated to evaluate the thermal characteristics of a vehicle underbody using math-based computational fluid dynamics (CFD) simulation based on 3-D configuration. Simulations without heat shields were carried out for different vehicle operating conditions which placed several areas at risk of exceeding their thermal design limits. Subsequently, simulations with several heat shield designs were performed. Results show that areas at risk without shields are well within thermal design limits when shielded. Part of the CFD simulation results were compared with experimental data, with reasonable correlation. The CFD approach can provide useful design information in a very short time frame.

Aspirating airbag modules are unique from other designs in that the gas entering the airbag is a mixture of inflator-delivered gas and ambient-temperature air entrained from the atmosphere surrounding the module. Today's sophisticated computer simulations of an airbag deployment typically require as input the mass-flow rate, chemical composition and thermal history of the gas exiting the canister and entering the airbag. While the mass-flow rate and temperature of the inflator-delivered gas can be obtained from a standard tank test, information on air entrainment into an aspirated canister is limited. The purpose of this study is to provide quantitative information about the aspirated mass-flow rate during airbag deployment. Pressure and velocity measurements are combined with high-speed photography in order to gain further insight into the relationship between the canister pressure, the rate of cabin-air entrainment and the airbag deployment.

CFD (Computational Fluid Dynamics) has been used to analyze vehicle air flow. In cross wind conditions an asymmetrical flow field around the vehicle is present. Under these circumstances, in addition to the forces present with symmetric air flow (drag and lift forces and pitching moment), side forces and moments (rolling and yawing) occur. Issues related to fuel economy, driveability, sealing effects (caused by suction exerted on the door), structural integrity (sun roof, spoiler), water management (rain deposit), and dirt deposit (shear stress) have been investigated. Due to the software developments and computer hardware improvements, results can be obtained within a reasonable time frame with excellent accuracy (both geometry and analytical solution). The flow velocity, streamlines, pressure field, and component forces can be extracted from the analysis results through visualization to identify potential improvement areas.

This paper describes the design, synthesis-analysis and development of the unique vehicle structure architecture for the fifth generation Chevrolet Corvette, ‘C5’, which starts in the 1997 model year. The innovative structural layout of the ‘C5’ enables torsional rigidity in an open roof vehicle which exceeds that of all current production open roof vehicles by a wide margin. The first structural mode of the ‘C5’ in open roof configuration approaches typical values measured in similar size fixed roof vehicles. Extensive use of CAE and a systems methodology of benchmarking and requirements rolldown were employed to develop the ‘C5’ vehicle architecture. Simple computer models coupled with numerical optimization were used early in the design process to evaluate every design concept and alternative iteration for mass and structural efficiency.

This paper introduces for the first time a fully connectorized passive optical star for use with plastic optical fiber that addresses all automotive application requirements. A unique mixing element is presented that offers linear expandability, uniformity of insertion loss, and packaging flexibility. The star is constructed of all plastic molded components to make it low cost and produceable in high volume and is single-ended to facilitate vehicle integration. The star is connectorized to facilitate assembly into the vehicle power and signal distribution system.

The common occurrence of impulsive sounds in automobiles and the recent emphasis on producing vehicles with a “quality sound” has increased the need for a method for measuring the pitch of impulsive sounds. Using Zwicker’s Loudness Patterns as a basis, a data reduction method was developed which summarizes the frequency content of each pattern. The method yields time varying quantities called Percentile Partial Loudness Frequencies from a time series of Loudness Patterns. Several “simple” impulsive sounds, representing a range of pitches, were investigated using this method. Visual inspection of the results has identified trends which seem to rank the impulsive sounds in agreement with subjective pitch rankings of a listening jury. In addition, the method appears to be capable of ranking the early portion of the impulse as a sharp or dull attack. Further investigations are needed to confirm these observations and refine the technique.

Defining or sizing the basic components in a vehicle brake system is done to satisfy specific requirements such as vehicle stopping distance, pedal travel and effort; braking efficiency as well as thermal considerations, cost, and packaging. This paper presents a flow-down method for computing brake system design parameters directly from those requirements. Relationships are also developed that enable the designer to understand trade-offs between requirements and system parameters.

A practical methodology is presented for the synthesis of Chassis Systems and their integration into a vehicle design to achieve a specified vehicle dynamic performance. By focusing on the fundamental performance requirements of gain, response time, and stability in midrange handling and the higher level design parameters of front and rear cornering compliance it is possible to find optimum values for these design parameters. The balancing of these higher level design parameters, in the context of overall vehicle performance, determines primary system requirements for the front suspension, rear suspension, tires, and steering system which may in turn be met by a variety of specific hardware designs.

The primary objective of Central Port Fuel Injection is to be a low cost multi-point fuel injection system with the additional attributes of compactness, packaging flexibility, and reliability. Performance of this fuel system closely resembles that of a simultaneous multi-point fuel injection system in flow control, dynamic range, cylinder-to-cylinder distribution, idle quality, transient response, and emissions. The system provides significantly improved performance in the areas of hot fuel handling, cold startability, vacuum and voltage sensitivity and system noise. This performance comes at a significant cost savings and greater packaging and targeting flexibility over a conventional multi-point fuel injection system.

A front suspension laboratory test procedure was developed to reproduce time-correlated fatigue damaging events from a light truck road durability test. Subsequently, the performance of front suspension systems for the GMT 400 light truck program were evaluated in terms of customer reliability. Both prototype and pilot testing, as well as computer modeling, were used in the evaluation.

This paper presents a method for modeling large deformations of structures using scale plastic models. The method was used to predict the dynamic barrier crash performance of a proposed vehicle structure with the aid of a computer simulation of the collision. The use of the technique can provide design direction in the early stages of the vehicle design process.

A Collision Damage Severity Scale, comprehensive with regard to direction and horizontal and vertical location of collision damage and suitable for computerized storage and retrieval, is described. This is an extension of earlier damage severity scales, developed to provide narrower classification of vehicle damage types to permit closer comparisons of results from different professional accident investigation teams.

A requirement for larger trucks and higher operating speed is indicated. The present report presents wind tunnel data on drag of a Chevrolet truck-trailer combination. Possible means of drag reduction are examined. Although side force and yawing moment data are presented, their effect on directional stability are not, at present analyzed.

SPECIFICATIONS of the new Chevrolet Turbo Thrust V-8 engine described in this paper are: