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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.

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.

Any equipment system or vehicle component like the Convenience Organizer storage system needs to be retained within the cargo compartment without intruding into the passenger compartment for occupant safety during a high speed impact. This paper outlines a test method to evaluate the retention of such a system in a rear impact environment. The method utilizes a low speed barrier to simulate a high speed RMB (Rear Moving Barrier) impact. The content of the low speed RMB impact test setup was developed utilizing DYNA3D analytical simulation results from a full vehicle model subjected to high-speed RMB impact. The retention of the equipment developed through this test method was confirmed on a full scale rear impact test.

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.

The super-ultra-low-emission-vehicle (SULEV) non-methane organic gas (NMOG) hydrocarbon exhaust standard as legislated by the state of California LEV II regulations is 10 milligrams per mile. This requires that the associative instrumentation must be capable of accurately and precisely determining total hydrocarbons (THC) concentrations on the order of 10 parts per billion-carbon (ppbC) for vehicle tests run under optimum conditions on a bag mini-diluter (BMD) test site. The flame ionization detector (FID) is the standard instrument used in the measurement of THC. Currently, there are many instrument manufacturers that produce these types of analyzers. This paper studies the limit of detection and accuracy capabilities of one of these instruments, the Beckman 400A FID. In addition, the paper shows evidence that supports that this “state of technology” as described by this instrument, is sufficient to meet the demands of the today's most stringent, vehicle emission standards.

This paper presents the fundamental principles of variation analysis and robust design for dimensional datum schemes. The kinematics equations for rigid body motions are simplified through linearization. The simplified formulations explicitly relate the dimensional deviations of a rigid part with its datum scheme configuration and dimensional variations at datum target points. This simplified approach can be used with either the first order Taylor series approximation or Monte Carlo simulation to study the statistical characteristics of datum scheme variations. A headlamp case study is presented that shows the application procedures and demonstrates that both Taylor series and Monte Carlo methods generate comparable results, but the former offers more efficiency and convenience due to its close form formulation. This approach has found many applications especially in on-site problem solving and fast what-if studies.

This paper describes an axle gear whine noise reduction process that was developed and applied using a combination of experimental and analytical methods. First, an experimental Transfer Path Analysis (TPA) was used to identify major noise paths. Next, modeling and forced response simulation were conducted using the Hybrid FEA-Experimental FRF method known as HYFEX [1]. The HYFEX model consisted of an experimental FRF representation of the frame/body and a finite element (FE) model of the driveline [2] and suspension. The FE driveline model was calibrated using experimental data. The HYFEX model was then used to simulate the axle noise reduction that would be obtained using a modified frame, prior to the availability of a prototype. Hardware testing was used as the final step in the process to confirm the results of the simulation.

A vehicle concept finite-element model is experimentally assessed for predicting structural vibration to 50 Hz. The vehicle concept model represents the body structure with a coarse mesh of plate and beam elements, while the suspension and powertrain are modeled with a coarse mesh of rigid-links, beams, and lumped mass, damping, and stiffness elements. Comparisons are made between the predicted and measured frequency-response-functions (FRFs) and modes of (a) the body-in-white, (b) the trimmed body, and (c) the full vehicle. For the full vehicle, the comparisons are with a comprehensive set of measured FRFs from 63 tests of nominally identical vehicles that demonstrate the vehicle-to-vehicle variability of the measured FRF response.

Brake squeal has been a persistent quality issue for automobile OEMs and brake system suppliers. The ability to model and measure brake squeal dynamics is of utmost importance in brake squeal reduction efforts. However, due to the complex nature of brake squeal and the wide frequency range in which it occurs, it is difficult to accurately correlate and update analytical models to experimental results. This paper introduces a systematic and rigorous correlation and updating process that yields FE models, which can accurately reproduce high-frequency brake squeal dynamics.

This paper presents a project that was done to solve an integration problem between a brake system and a cruise control system on a GM vehicle program, each of which was supplied by a different supplier. This paper presents how the problem was resolved using a CAE tool which was a combination of formulated MS/Excel spreadsheet, Overdrive (GM internal code), and iSIGHT of Engineous Software Inc, which is a process integrator and process automator. A sensitivity study of system reliability was conducted using iSIGHT. The most sensitive factor was found through the sensitivity study. Thereafter, a Robust design was obtained. The recommended Robust Design was implemented in the vehicle program, which led to a substantial cost saving. The CAE software tool (the combination) developed through the problem solving process will be used to ensure quality of brake and cruise system performance for future vehicle programs.

In addition to the thermal comfort of the vehicle occupants, their safety by ensuring adequate visibility is an objective of the automotive climate control system. An integrated dew point and glass temperature sensor is widely used among several other technologies to detect risk of fog formation on the cabin side (or inner) surface of the windshield. The erroneous information from a sensor such as the measurement lag can cause imperfect visibility due to the delayed response of the climate control system. Also the high value, low cost vehicles may not have this sensor due to its high cost. A differential equation based model of the cabin air humidity is proposed to calculate in real-time specific humidity of the passenger compartment air. The specific humidity is used along with the windshield surface temperature to determine relative humidity of air and therefore, the risk of fog formation on the interior surface of a windshield.

A numerical investigation of automobile sunroof buffeting on a prototype sport utility vehicle (SUV) is presented, including experimental validation. Buffeting is an unpleasant low frequency booming caused by flow-excited Helmholtz resonance of the interior cabin. Accurate prediction of this phenomenon requires accounting for the bi-directional coupling between the transient shear layer aerodynamics (vortex shedding) and the acoustic response of the cabin. Numerical simulations were performed using the PowerFLOW code, a CFD/CAA software package from Exa Corporation based on the Lattice Boltzmann Method (LBM). The well established LBM approach provides the time-dependent solution to the compressible Navier-Stokes equations, and directly captures both turbulent and acoustic pressure fluctuations over a wide range of scales given adequate computational grid resolution.

This paper presents a study of roof rack wind noise using commercial Computational Fluid Dynamics (CFD) software. The focus is to predict the noise generated from the roof rack cross bars mounted on a realistic vehicle geometry. Design iterations are created by altering the cross bar orientation. Results from the CFD simulations include frequency spectra of Sound Pressure Level (SPL) for comparison to typical wind tunnel measurements. Aerodynamic results of body lift, drag, and transient flow visualization are also produced to support the noise data. The CFD and physical experiments compare very well with respect to tonal noise generation, tonal frequency content, and relative magnitudes. It is concluded that the CFD method is suitable for predicting relative performance, ranking design concepts, and optimizing large scale geometry parameters of vehicle roof racks in a production-engineering environment.

The complexity of vehicle-pedestrian collisions necessitates extensive validation of pedestrian computational models. While body components can be individually simulated, overall validation of human pedestrian models requires full-scale testing with post mortem human surrogates (PMHS). This paper presents the development of a full-scale pedestrian impact test plan and experimental design that will be used to perform PMHS tests to validate human pedestrian models. The test plan and experimental design is developed based on the analysis of a combination of literature review, multi-body modeling, and epidemiologic studies. The proposed system has proven effective in testing an anthropometrically correct rescue dummy in multiple instances. The success of these tests suggests the potential for success in a full-scale pedestrian impact test using a PMHS.

The close-fitting cockpit of the modern Indy car single seat race car has the potential to provide a high level of head and neck impact protection in rear and side impacts. Crash investigation has shown that a wide variety of materials have been used as the padding for these cockpits and, as a result, produced varying outcomes in crashes. Additionally, these pads have not always been positioned for optimal performance. The purpose of this study was to investigate the head impact performance of a variety of energy-absorbing padding materials under impact conditions typical of Indy car rear impacts and to identify superior materials and methods of improving their performance as race car head pads. An extensive series of tests with the helmeted Hybrid III test dummy head and neck on an impact mini-sled was conducted to explore head padding concepts.

The Automotive Aluminum Alliance in conjunction with SAE ACAP founded a corrosion task group in 2000 with a goal to establish an in-laboratory cosmetic corrosion test for finished aluminum auto body panels, which provides a good correlation with in-service performance. Development of this test involves a number of key steps that include: (1) Establishing a reservoir of standard test materials to provide a well-defined and consistent frame of reference for comparing test results; (2) Defining a real-world performance for the reference materials through on-vehicle tests conducted in the U.S. and Canada; (3) Evaluating existing laboratory, proving ground, and outdoor tests; (4) Conducting statistically designed experiments to evaluate the effects of cyclic-test variables; (5) Comparing corrosion mechanisms of laboratory and on-vehicle tests; and (6) Conducting a round robin test program to determine the precision of the new test. Several of these key steps have been accomplished.

Since 2000, an Aluminum Cosmetic Corrosion task group within the SAE Automotive Corrosion and Protection (ACAP) Committee has existed. The task group has pursued the goal of establishing a standard test method for in-laboratory cosmetic corrosion evaluations of finished aluminum auto body panels. A cooperative program uniting OEM, supplier, and consultants has been created and has been supported in part by USAMP (AMD 309) and the U.S. Department of Energy. Prior to this committee's formation, numerous laboratory corrosion test environments have been used to evaluate the performance of painted aluminum closure panels. However, correlations between these laboratory test results and in-service performance have not been established. Thus, the primary objective of this task group's project was to identify an accelerated laboratory test method that correlates well with in-service performance.

A co-operative program initiated by the Automotive Aluminum Alliance and supported by USAMP continues to pursue the goal of establishing an in-laboratory cosmetic corrosion test for finished aluminum auto body panels that provides a good correlation with in-service performance. The program is organized as a task group within the SAE Automotive Corrosion and Protection (ACAP) Committee. Initially a large reservoir of test materials was established to provide a well-defined and consistent specimen supply for comparing test results. A series of laboratory procedures have been conducted on triplicate samples at separate labs in order to evaluate the reproducibility of the various lab tests. Exposures at OEM test tracks have also been conducted and results of the proving ground tests have been compared to the results in the laboratory tests. Outdoor tests and on-vehicle tests are also in progress. An optical imaging technique is being utilized for evaluation of the corrosion.

This paper documents the development of the 2002 Buick Rendezvous body structure for optimum noise & vibration performance. Accelerated vehicle development timing demanded clearly defined body structure vibration performance targets, with critical dependence on math based modeling. The 2002 Buick Rendezvous was truly a fast-to-math program enabled partially by borrowing some of its structural features from the recently launched Pontiac Aztek Competitive performance data collected for the Aztek was tailored to the Rendezvous for setting major global body structure targets. Architectural differences in overall vehicle size and body opening configuration led to adjustments in body matchboxing, bending and torsional requirements. The frequency domain “mode map” was modified to these requirements taking into account the Buick Brand Character. Computer simulation models were used exclusively to predict body structural performance.