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There is an increasing interest in transient thermal simulations of automotive brake systems. This paper presents a high-fidelity CFD tool for modeling complete braking cycles including both the deceleration and acceleration phases. During braking, this model applies the frictional heat at the interface on the contacting rotor and pad surfaces. Based on the conductive heat fluxes within the surrounding parts, the solver divides the frictional heat into energy fluxes entering the solid volumes of the rotor and the pad. The convective heat transfer between the surfaces of solid parts and the cooling airflow is simulated through conjugate heat transfer, and the discrete ordinates model captures the radiative heat exchange between solid surfaces. It is found that modeling the rotor rotation using the sliding mesh approach provides more realistic results than those obtained with the Multiple Reference Frames method.

Contamination protection of brake rotors has been a challenge for the auto industry for a long time. As contamination of a rotor causes corrosion, and that in turn causes many issues like pulsation and excessive wear of rotors and linings, a rotor splash protection shield became a common part for most vehicles. While the rotor splash shield provides contamination protection for the brake rotor, it makes brake cooling performance worse because it blocks air reaching the brake rotor. Therefore, balancing between contamination protection and enabling brake cooling has become a key critical factor when the splash shield is designed. Although the analysis capability of brake cooling performance has become quite reliable, due to lack of technology to predict contamination patterns, the design of the splash protection shield has relied on engineering judgment and/or vehicle tests. Optimization opportunities were restricted by cost and time associated with vehicle tests.

Two-stage turbochargers are a recent solution to improve engine performance, reducing the turbo-lag phenomenon and improving the matching. However, the definition of the control system is particularly complex, as the presence of two turbochargers that can be in part operated independently requires effort in terms of analysis and optimization. This work documents a characterization study of two-stage turbocharger systems. The study relies on a mean-value model of a Diesel engine equipped with a two-stage turbocharger, validated on experimental data. The turbocharger is characterized by a VGT actuator and a bypass valve (BPV), both located on the high-pressure turbine. This model structure is representative of a “virtual engine”, which can be effectively utilized for applications related to analysis and control. Using this tool, a complete characterization was conducted considering key operating conditions representative of FTP driving cycle operations.

Finite element analysis (FEA) predictions of magnesium beams are compared to load versus displacement test measurements. The beams are made from AM60B die castings, AM30 extrusions and AZ31 sheet. The sheet and die cast beams are built up from two top hat sections joined with toughened epoxy adhesive and structural rivets. LS-DYNA material model MAT_124 predicts the magnesium behavior over a range of strain rates and accommodates different responses in tension and compression. Material test results and FEA experience set the strain to failure limits in the FEA predictions. The boundary conditions in the FEA models closely mimic the loading and constraint conditions in the component testing. Results from quasi-static four-point bend, quasi-static axial compression and high-speed axial compression tests of magnesium beams show the beam's behavior over a range of loadings and test rates. The magnesium beams exhibit significant material cracking and splitting in all the tests.

Magnesium alloy extrusions offer potentially more mass saving compared to magnesium castings. One of the tasks in the United States Automotive Materials Partnership (USAMP) ?Magnesium Front End Research and Development? (MFERD) project is to evaluate magnesium extrusion alloys AM30, AZ31 and AZ61 for automotive body applications. Solid and hollow sections were made by lowcost direct extrusion process. Mechanical properties in tension and compression were tested in extrusion, transverse and 45 degree directions. The tensile properties of the extrusion alloys in the extrusion direction are generally higher than those of conventional die cast alloys. However, significant tension-compression asymmetry and plastic anisotropy need to be understood and captured in the component design.

Magnesium alloys are the lightest structural metal and recently attention has been focused on using them for structural automotive components. Fatigue and durability studies are essential in the design of these load-bearing components. In 2006, a large multinational research effort, Magnesium Front End Research & Development (MFERD), was launched involving researchers from Canada, China and the US. The MFERD project is intended to investigate the applicability of Mg alloys as lightweight materials for automotive body structures. The participating institutions in fatigue and durability studies were the University of Waterloo and Ryerson University from Canada, Institute of Metal Research (IMR) from China, and Mississippi State University, Westmorland, General Motors Corporation, Ford Motor Company and Chrysler Group LLC from the United States.

Over the last five years, the automotive industry has experienced a trend towards niche performance vehicles equipped with high-output powertrains. These high performance vehicles also demand higher output braking systems. One method used to provide enhanced pedal feel and fade performance is to equip vehicles with higher apparent friction linings. The challenge then becomes how to design and manufacture these brake systems without high-frequency disc brake squeal and without paying a significant mass penalty. One alternative is to design disc brake rotors with increased damping. There are several options for increasing rotor damping. The classical approach is to increase the rotor's cast iron carbon content, thus increasing the internal material damping of the rotor. However, this methodology provides only a small increase in rotor damping. Alternatively, the rotor damping can be increased by introducing friction, sometimes referred to as Coulomb damping.

A study was conducted by General Motors at its crash test facility located at the Milford Proving Ground. The intent of this study was to expand upon the currently available research regarding the safety belt buckle environment during full scale planar crash tests. Buckle accelerations and webbing tensions were measured and recorded to characterize, in part, buckle responses in a crash environment. Previous studies have focused primarily on the component level testing of safety belt buckles. The crash tests included a variety of vehicles, impact types, seating positions, Anthropomorphic Test Devices (ATDs), impact speeds, and impact angles. Also included were various safety belt restraint systems and pretensioner designs. This study reports on data recorded from 100 full scale crash tests with 180 instrumented end release safety belt buckles. Acceleration measurements were obtained with tri-axial accelerometers mounted onto the buckles.

Although rollover crashes represent a small fraction (approximately 3%) of all motor vehicle crashes, they account for roughly one quarter of crash fatalities to occupants of cars, light trucks, and vans (NHTSA Traffic Safety Facts, 2004). Therefore, the National Highway Traffic Safety Administration (NHTSA) has identified rollover injuries as one of its safety priorities. Motor vehicle manufacturers are developing technologies to reduce the risk of injury associated with rollover collisions. This paper describes the development by General Motors Corporation (GM) of a suite of laboratory tests that can be used to develop sensors that can deploy occupant protection devices like roof rail side air bags and pretensioners in a rollover as well as a discussion of the challenges of conducting this suite of tests.

A methodology involving Design for Six Sigma (DFSS) and Multi-body dynamic simulation is employed to tune a body-on-frame vehicle, for improved ride (shake) performance. The design space is limited to four sets of symmetric body mounts for a vehicle. The stiffness and damping characteristics of the mounts are the control factors in the virtual experiment. Variation of these design parameters from the nominal settings, as well as axle size, tire and wheel combinations, tire pressure, shock damping, and vehicle speed constitute the noise factors. This approach proves to be an excellent predictor of the vehicle behavior, by which much insight as to influence of each parameter on vehicle performance is gained. Ultimately, specific recommendations for the control factor settings are provided. Subsequent hardware builds show excellent agreement with the analytical model and suggested tuning.

Constrained Layer Damping (CLD) treatments have long provided a means to effectively impart damping to a structure [1, 2 and 3]. Traditionally, CLD treatments are constructed of a very thin polymer layer constrained by a thicker metal layer. Because the adhesion of a thin polymer layer is very sensitive to surface finish, surfaces that a CLD treatment can be effectively applied to have historically been limited to those that are very flat and smooth. New developments in material technology have provided thicker materials that are very effective and less expensive to apply when used as the damping layer in a CLD treatment. This paper documents the effectiveness of such a treatment on a cast aluminum front cover for a V6 engine. Physical construction of the treatment, material properties and design criteria will be discussed. Candidate applications, the assembly process, methods for secondary mechanical fastening will be presented.

Robust optimization usually requires numerous functional evaluations, which is not feasible when the functional evaluation is time-consuming. Examples in automobile industry include crash worthiness/safety and fatigue life simulations. In practice, a response surface model (RSM) is often used as a surrogate to the CAE model, so that robust optimization can be carried out. However, if the error in the RSM is significant, the solution based on the RSM can be invalid. This paper proposes a method of finding multiple candidate solutions, all of which have similar predicted performances. This approach is effective in finding the close-to-optimum solutions when the model has error, and providing design alternatives. Examples are provided to illustrate the method.

The application of Statistical Energy Analysis (SEA) to vehicle development is discussed, with a new technique to implement noise path analysis within a SEA model to enable efficient solution and optimization of acoustic trim. A whole vehicle Performance-Based SEA model is used, in which Sound Transmission Loss (STL) and acoustic absorption coefficient characterize subsystem performance. In such a model, the net contribution from each body panel/path, such as the floor, to a specific interior subsystem, such as the driver's head space, is extremely important for vehicle interior noise development. First, it helps to identify the critical path to root-cause potential problems. Second, it is necessary in order to perform balancing of path contributions. With current software, the power based noise contribution analysis is for direct paths/adjacent subsystems.

Airbag systems have been part of passenger car and truck programs since the mid-1980's. However, systems designed for medium and heavy duty truck applications are relatively new. The release of airbag systems for medium duty truck has provided some unique challenges, especially for the airbag sensing systems. Because of the many commercial applications within the medium duty market, the diversity of the sensing environments must be considered when designing and calibrating the airbag sensing system. The 2003 Chevrolet Kodiak and GMC TopKick airbag sensing development included significant work, not only on the development of airbag deployment events but also non-deployment events – events which do not require the airbag to deploy. This paper describes the process used to develop the airbag sensing system deployment events and non-deployment event used in the airbag sensing system calibration.

Fundamental differences exist between sheet metal forming and hydroforming processes. Sheet metal forming is basically a one step metal fabrication process. Almost all plastic deformation of an originally flat blank is introduced when the punch is moved normal to a clamped sheet metal. Hydroforming, however, consists of multiple steps of tube making, pre-bending, crushing, pressurization, etc. Each of the above mentioned steps can introduce permanent plastic deformations. The forming limit diagram obtained for sheet metal forming may or may not be used in hydroforming evaluations. A failure criterion is proposed for predicting bursting failures in tube hydroforming. The tube material's stress-strain curve, obtainable from uniaxial tensile test and subjected to some postulations under large stress/strain states, is used in judging the failure.

Reducing the high cost of hardware testing with analytical methods has been highly accelerated in the automotive industry. This paper discusses an analytical model to simulate the driveline bending integrity test for the longitudinal 4WD-driveline configuration. The dynamic stresses produced in the adapter/transfer case and propeller shaft can be predicted analytically using this model. Particularly, when the 4WD powertrain experiences its structural bending during the operation speed and the propeller shaft experiences the critical whirl motion and its structural bending due to the inherent imbalance. For a 4WD-Powertrain application, the dynamic coupling effect of a flexible powertrain with a flexible propeller shaft is significant and demonstrated in this paper. Three major subsystems are modeled in this analytical model, namely the powertrain, the final rear drive, and the propeller shafts.

By design, frontal New Car Assessment Program (NCAP) tests focus on a narrow portion of the spectrum of field crash events. A simple, high level parsing of towaway crashes from NHTSA's National Automotive Sampling System - Crashworthiness Data System (NASS-CDS) files shows that only a small fraction of occupants (but a somewhat larger portion of their harm as measured by ISS) find themselves in crash circumstances remotely similar to NCAP crash conditions. Looking only at seat location, area of damage, direction of force, distribution of damage, and estimated delta-V filters significantly restricts the relevance of NCAP even before critical factors like belt use and vehicle crash partner are considered. Given the limited scope of frontal NCAP it should not be surprising that it has limited usefulness in discriminating among various vehicles' overall performance in the field.

Many traffic collisions are the result of the driver's failure to notice the other vehicle. It is often cited in police reports that the driver "looked but did not see.'' The purpose of Daytime Running Lights (DRLs) is to increase the visual contrast of DRL-equipped vehicles. Visual contrast, which is the difference in brightness between two areas, is an important characteristic enabling a driver to detect objects. This paper begins with a brief regulatory history of DRLs in the U.S. and how General Motors Corporation (GM) introduced DRL-equipped vehicles. It also describes a DRL effectiveness study conducted by Exponent Failure Analysis Associates of San Francisco for General Motors Corporation. The study compared the collision rates of specific General Motors Corporation, Saab, Volvo and Volkswagen vehicles before and immediately after the introduction of DRLs. Since DRLs are not visible from behind a vehicle, rear-end collisions were not included in the study.

Brake squeal has been analyzed by finite elements for some time. Among several methods, complex eigenvalue analysis is proving useful in the design process. It requires hardware verification and it falls into a simulation process. However, it is fast and it can provide guidance for resolving engineering problems. There are successes as well as frustrations in implementing this analysis tool. Its capability, robustness and reliability are closely examined in many companies. Generally, the low frequency squealing mechanism is a rotor axial direction mode that couples the pads, rotor, and other components; while higher frequency squeal mainly exhibits a rotor tangential mode. Design modifications such as selection of rotor design, insulator, chamfer, and lining materials are aimed specifically to cure these noise-generating mechanisms. In GM, complex eigenvalue analysis is used for brake noise analysis and noise reduction. Finite element models are validated with component modal testing.

This paper documents a joint development process between General Motors and Dow Automotive to improve primary body structure frequencies on the GM family of midsize vans by utilizing cavity-filling structural foam. Optimum foam locations, foam quantity, and foam density within the body structure were determined by employing both math-based modeling and vehicle hardware testing techniques. Finite element analysis (FEA) simulations of the Body-In-White (BIW) and “trimmed body” were used to predict the global body structure modes and associated resonant frequencies with and without structural foam. The objective of the FEA activity was to quantify frequency improvements to the primary body structure modes of matchboxing, bending, and torsion when using structural foam. Comprehensive hardware testing on the vehicle was also executed to validate the frequency improvements observed in the FEA results.