Search Results

General Motors Powertrain Division has developed the next generation big block V8 engine for introduction in the 1996 model year. In addition to meeting tighter emission and on-board diagnostic legislation, this engine evolved to meet both customer requirements and competitive challenges. Starting with the proven dependability of the time tested big block V8, goals were set to substantially increase the power, torque, fuel economy and overall pleaseability of GM's large load capacity gasoline engine. The need for this new engine to meet packaging requirements in many vehicle platforms, both truck and OEM, as well as a requirement for minimal additional heat rejection over the engine being replaced, placed additional constraints on the design.

This paper is intended to give a general overview of the key aerodynamic developments for the 2006 Chevrolet Corvette C6 Z06. Significant computational and wind tunnel time were used to develop the 2006 Z06 to provide it with improved high speed stability, increased cooling capability and equivalent drag compared to the 2004 Chevrolet Corvette C5 Z06.

General Motor's Corvette product engineering was given the challenge to find mass reduction opportunities on the painted body panels of the C6 Z06 through the utilization of carbon fiber reinforced composites (CFRC). The successful implementation of a carbon fiber hood on the 2004 C5 Commemorative Edition Z06 Corvette was the springboard for Corvette Team's appetite for a more extensive application of CFRC on the C6 Z06 model. Fenders were identified as the best application for the technology given their location on the front of the vehicle and the amount of mass saved. The C6 Z06 CFRC fenders provide 6kg reduction of vehicle mass as compared to the smaller RRIM fenders used on the Coupe and Convertible models.

This paper presents a comparison of methods for the identification of a reduced set of useful variables using a multidimensional system. The Mahalanobis-Taguchi System and a standard statistical technique are used reduce the dimensionality of vehicle ride based on consumer satisfaction ratings. The Mahalanobis-Taguchi System and cluster analysis are applied to vehicle ride. The research considers 67 vehicle data sets for the 6 vehicle ride parameters. This paper applies the Mahalanobis-Taguchi System to forecast consumer satisfaction and provides a comparison of results with those obtained from a standard statistical approach to the problem.

A new process is developed for the aerodynamic shape optimization of racing cars using Computational Fluid Dynamics (CFD). The process is based on using the mesh morphing techniques to create new designs for analysis by morphing the CFD mesh of the original design. The resulting improvements in the analysis turnaround time allow a quick exploration of the design parameters for determining the optimum aerodynamic design. The approach is used to perform a parametric study to optimize a racing car shape for maximum downforce. The analysis procedure used for the CFD analysis is tuned to ensure grid independence and accuracy of the predictions. The parametric study shows that the morpher-based process can quickly and precisely create designs for the CFD analysis. This process can become the foundation for the automated aerodynamic design optimization of the racing cars.

The battery support in a small car is an example of a subsystem that lends itself to mounted component dynamic fatigue analysis, due to its weight and localized attachments. This paper describes a durability analysis method that was developed to define the required enforced motion, stress response, and fatigue life for such subsystems. The method combines the large mass method with the modal transient formulation to determine the dynamic stress responses. The large mass method was selected over others for its ease of use and efficiency when working with the modal formulation and known accelerations from a single driving point. In this example, these known accelerations were obtained from the drive files of a 4-DOF shake table that was used for corresponding lab tests of a rear compartment body structure. These drive files, originally displacements, were differentiated twice and filtered to produce prescribed accelerations to the finite element model.

A novel lateral sliding vehicle bucket seat was developed to address consumer needs for improved facile access to third row seats in minivans and sport utility vehicles. The concept provides for a second row bucket seat to slide laterally across a vehicle floor by roller mechanisms that roll across steel rails that transverse the vehicle floor. The system consists of two T-section type steel rails mounted parallel to each other at a distance equal to the seat riser support attachment features. The seat risers contain a roller mechanism that enables contact with the cylindrical portion of the steel rails. Each steel rail contains rectangular openings spaced appropriately to allow the seat latching mechanisms to engage securely. The seat riser supports at the rear include a releasable clamping mechanism hook that engages and disengages into the rectangular openings of the steel rails.

In developing the 2007 Model Year Saturn VUE Green Line hybrid vehicle, a vehicle model for prediction of fuel economy and performance was developed. This model was developed in Matlab / Simulink / Stateflow by augmenting an existing conventional vehicle model to include hybrid components and controls. The generic structure and the functionalities of the model are presented. This simulation model was used for rapid concept selection and requirements balancing early in the vehicle development process. Engine usage and energy distributions are shown based on simulation results. Fuel economy breakdown was also discussed.

Over the past 20 years, polyvinyl chloride (PVC) has almost replaced metal in stationary glass reveal moldings with dramatic part cost savings on cars and trucks world-wide. The process of assembly is generally simple and convenient but to replace a reveal molding can be difficult. Many times, in order to replace the molding, it may also be necessary to replace or reseal the glass. In short, PVC reveal moldings, relatively inexpensive parts, are very expensive to service. Outside of general assembly and processing issues, there are 5 variables that may cause a failure in the performance of a stationary glass reveal molding. They are as follows: material degradation, crystallization, plasticizer loss, material properties, and molded-in stress. Because of modern standard PVC formulations and the material requirements of most automotive companies, material degradation, crystallization and plasticizer loss do not commonly cause failure. Material properties and molded-in stress do.

In automotive body manufacturing, there are two processes are often applied, Nominal Build and Functional Build. The Nominal Build process requires all individual stamping components meet their nominal dimensions with specified tolerances. While, the Functional Build process emphasizes more on the tolerances of the entire assembly as opposed to those of the individual stamped parts. The common goal of both processes is to build the body assemblies that meet the specified tolerances. Although there is strict tolerance specified for individual stamping parts the finished stampings frequently are released to assembly process with certain levels of dimensioning deviations, or they are within the specified tolerances but require heavy clamping during assembly. It is of high interest to predict the dimensional deviations in the stamping sub-assembly or body-in-white assembly process.

To cope with the conflict requirements between the stability and handling performance, and the high-order and complex vehicle-trailer plant, a model tracking method is proposed. With this approach, a feedback control is designed to “decouple” the vehicle and the trailer plant, such that each tracks a well-defined second-order reference model independently yet coordinately. A feedforward control is designed to maintain its system steady-state performance. As a result, the proposed approach not only improves the system transient responses, but also its steady-state performance. This approach further yields a simple yet analytical control derivation that provides more insight to the system dynamics.

The equipment for collecting dilute exhaust samples involves the use of bag materials (i.e., Tedlar®) that emit hydrocarbons that contaminate samples. This study identifies a list of materials and treatments to produce bags that reduce contamination. Based on the average emission rates, baked Tedlar®, Capran® treated with alumina deposition, supercritical CO2 extracted Kynar® and supercritical CO2 extracted Teflon NXT are capable of achieving the target hydrocarbon emission rate of less than 15 ppbC per 30 minutes. CO2 permeation tests were also performed. Tedlar, Capran, Kynar and Teflon NXT showed comparable average permeation rates. Based on the criteria of HC emission performance, changes in measured CO2 concentration, ease of sealing, and ease of surface treatment, none of the four materials could be distinguished from one another.

In recent years, the slip lock-up mechanism has been adopted widely, because of its fuel efficiency and its ability to improve NVH. This necessitates that the automatic transmission fluid (ATF) used in automatic transmissions with slip lock-up clutches requires anti-shudder performance characteristics. The test methods used to evaluate the anti-shudder performance of an ATF can be classified roughly into two types. One is specified to measure whether a μ-V slope of the ATF is positive or negative, the other is the evaluation of the shudder occurrence in the practical vehicle. The former are μ-V property tests from MERCON® V, ATF+4®, and JASO M349-98, the latter is the vehicle test from DEXRON®-III. Additionally, in the evaluation of the μ-V property, there are two tests using the modified SAE No.2 friction machine and the modified low velocity friction apparatus (LVFA).

When pickup trucks are driven on concrete paved freeways, freeway hop shake is a major complaint. Freeway hop shake occurs when the vehicle passes over the concrete joints of the freeway which impose in-phase harmonic road inputs. These road inputs excite vehicle modes that degrade ride comfort. The worst shake level occurs when the vehicle speed is such that the road input excites the vehicle 1st bending mode and/or the rear wheel hop mode. The hop and bending mode are very close in frequency. This phenomenon is called freeway hop shake. Automotive manufacturers are searching for ways to mitigate freeway hop shake. There are several ways to reduce the shake amplitude. This paper documents a new approach using hydraulic body mounts to reduce the shake. A full vehicle analytical model was used to determine the root cause of the freeway hop shake.

General Motors is developing a hybrid electric concept vehicle from its “Precept” high efficiency vehicle architecture, to satisfy requirements of the Partnership for a New Generation of Vehicles (PNGV) program. This Technology Demonstration Vehicle (TDV) features fundamental architecture that is unconventional compared to contemporary passenger car design, or even to other hybrid vehicles. This paper describes this unique architecture and how the vehicle's most significant features complement each other in harmonious design. It also notes how these features contribute to robustness of efficiency.

Effects of the wind tunnel blockage in a closed-wall wind tunnel were investigated using computational fluid dynamics (CFD). Flow over three generic vehicle models representing a passenger sedan, a sports utility vehicle (SUV), and a pickup truck was solved. The models were placed in a baseline virtual wind tunnel as well as four additional virtual wind tunnels, each with different size cross-sections, providing different levels of wind tunnel blockage. For each vehicle model, the CFD analysis produced an aerodynamic drag coefficient for the vehicle at the blockage free condition as well as the blockage effect increment for the baseline wind tunnel. A CFD based blockage correction method is proposed. Comparisons of this method to some existing blockage correction methods for closed-wall wind tunnel are also presented.

An automatic optimization process for the aerodynamic design of automotive vehicle shapes is presented. The Computational Fluid Dynamics (CFD) mesh generation and the analysis software packages are coupled for transfer of data and information between the two packages. This communication enables an automated process in which designs are created and analyzed for the aerodynamic drag. New designs are created by morphing the CFD model for the baseline design. The automated process is applied to perform a parametric study on a generic automobile sedan shape. The results show that the process can be used for aerodynamic optimization of any automotive vehicle shape. The turnaround for the automated process is at least an order of magnitude less than the conventional analysis process.

For automotive applications at elevated temperatures, the need for sufficient creep resistance of Mg alloys is often associated with retaining appropriate percentages of initial clamp loads in bolt joints. This engineering property is often referred to as bolt-load retention (BLR); BLR testing is a practical method to quantify the bolt load with time for engineering purposes. Therefore, standard BLR test procedures for automotive applications are desired. This report summarizes the effort in the Structural Cast Magnesium Development (SCMD) project under the United States Automotive Materials Partnership (USAMP), to provide a technical basis for recommending a general-purpose and a design-purpose BLR test procedures for BLR testing of Mg alloys for automotive applications. The summary includes results of factors influencing BLR and related test techniques from open literature, automotive industry and research carried out in this laboratory project.

Computational fluid dynamics (CFD) was used to simulate the flow field over a pickup truck. The simulation was based on a steady state formulation and the focus of the simulation was to assess the capabilities of the currently used CFD tools for vehicle aerodynamic development for pickup trucks. Detailed comparisons were made between the CFD simulations and the existing experiments for a generic pickup truck. It was found that the flow structures obtained from the CFD calculations are very similar to the corresponding measured mean flows. Furthermore, the surface pressure distributions are captured reasonably well by the CFD analysis. Comparison for aerodynamic drags was carried out for both the generic pickup truck and a production pickup truck. Both the simulations and the measurements show the same trends for the drag as the vehicle geometry changes, This suggests that the steady state CFD simulation can be used to aid the aerodynamic development of pickup trucks.

Development and integration of the cooling system for an automotive vehicle requires a balancing act between several performance and styling objectives. The cooling system needs to provide sufficient air for heat rejection with minimal impact on the aerodynamic drag, styling requirements and other criteria. An optimization of various design parameters is needed to develop a design to meet these objectives in a short amount of time. Increase in the accuracy of the numerical predictions and reduction in the turn-around time has made it possible for Computational Fluid Dynamics (CFD) to be used early in the design phase of the vehicle development. This study shows application of the CFD for robust design of the engine cooling system.