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Automotive structural components are exposed to high loads, impact situations and corrosion. In addition, there may be temperature excursions that introduce creep as well as reduced modulus (stiffness). These issues have limited the use of light metals in automotive structural applications primarily to aluminum alloys, and primarily to cast wheels and knuckles (only a few of which are forged), cast brake calipers, and cast control arms. This paper reports on research performed at Chongqing University, Chongqing China, under the auspices of General Motors engineering and directed by the first author, to develop a protocol that uses wrought magnesium in control arms. The goal was to produce a chassis part that could provide the same engineering function as current cast aluminum applications; and since magnesium is 33% less dense than aluminum, would be lighter.

Measured vehicle loads have traditionally been used as the basis for development of component, subsystem and vehicle level durability tests. The use of measured loads posed challenges due to the availability of representative hardware, scheduling, and other factors. In addition, stress was placed on existing procedures and methods by aggressive product development timing, variety in tuning and equipment packages, and higher levels of design optimization. To meet these challenges, General Motors developed new processes and technical competencies which enabled the direct substitution of analytically synthesized loads for measured data. This process of Virtual Road Load Data Acquisition (vRLDA) enabled (a) conformance to shortened product development cycles, (b) greater consistency between design targets and validation requirements, and (c) more comprehensive data.

There is an increasing demand in automated manufacturability analysis of metal castings at the initial stages of their design. This paper presents a system developed for virtual manufacturability analysis of casting components. The system can be used by a casting designer to evaluate manufacturability of a part designed for various manufacture processes including casting, heat treatment, and machining. The system uses computational geometrics and geometric reasoning to extract manufacturing features and geometry characteristics from a part CAD model. It uses an expert system and a design database consisting of metal casting, heat treatment and machining process knowledge and rules to present manufacturability analysis results and advice to the designer. Application of the system is demonstrated for the manufacturability assessment of automotive cast aluminum components.

In order to assess the possible ways of energy transfer from the various sources of excitation in a vehicle assembly to a given target location, frequency based substructuring technique and transfer path analysis are used. These methods help to locate the most important energy transfer paths for a specific problem, and to evaluate their individual effects on the target, thus providing valuable insight into the mechanisms responsible for the problem. The Source-Path-Receiver concept is used. The sources can be from the road surface, engine, transmission, transfer case, prop-shaft, differential, rotating components, chain drives, pumps, etc., and the receiver can be driver/passenger ears, steering column, seats, etc. This paper is devoted to identify the noise transfer paths and the force transmissibility among the interfaces of different components in the vehicle for the low to mid frequency range.

Maximizing reuse of existing software assets is a common goal for companies as they move to new projects and products. Typically, reuse is complicated by changes to the context in which the software executes; the software architecture. As in all development areas, software architects are seeking continuous improvement to their designs either through internal innovation or established external standards. However, changes to the software architecture (e.g. interfaces, services, scheduling etc.) can prove to be a driver of fundamental, large-scale change to software if reuse strategies are not planned into the product line. This paper describes a reuse strategy that maximizes the preservation of existing assets while focusing effort on the development of transformation rules that generate software targeting a new architectural context.

This paper presents subjective and objective methods for evaluating transient vehicle dynamics characteristics in four sections: (1) Definition of transient behavior in terms of four traits-agility, stability, precision, and roll support; (2) Description of subjective evaluation methods; (3) Implementation of Design for Six Sigma principles to the development of a steering robot controlled objective test for transient performance; (4) The final section of this paper uses data from simulation and road tests to demonstrate how chassis design parameters can affect transient handling performance.

Delivering the appropriate material data for CAE analysis of plastic components is not as straight forward as it would seem to be. While a few of the properties typically used by resin manufacturers and material engineers to describe a plastic are useful to the analysis community (density, CLTE), most are not (flexural modulus, notched izod). In addition some properties such as yield stress are defined differently by the analysis community than by the materials community. Lastly, secondary operations such as painting or chrome plating significantly change the behavior of components with plastic substrates. The materials engineering community and the CAE analysis community must work together closely to develop the material data necessary to increase the capability of the analysis. This paper will examine case studies where these issues have required modifications to the material property data to increase the fidelity of the CAE analysis.

This study evaluates utilizing an accelerated test method that correlates customer interaction with a vehicle seat where bagginess and wrinkling is produced. The evaluation includes correlation from warranty returns as well as test vehicle results for test verification. Consumer metrics will be discussed within this paper with respect to potential application of this test method, including but not limited to JD Power ratings. The intent of the test method is to aid in establishing appropriate design parameters of the seat trim covers and to incorporate appropriate design measures such as tie downs and lamination. This test procedure was utilized in a Design for Six Sigma (DFSS) project as an aid in optimizing seat parameters influencing trim cover performance using a Design of Experiment approach.

Temperature effects on the deformation and fracture of a commercially produced transformation-induced plasticity (TRIP) steel subject to a two-step quenching and partitioning (Q&P) heat treatment are investigated. Strain field evolution at room temperature is quantified in this 980 MPa grade Q&P steel with a stereo digital image correlation (DIC) technique from quasi-static tensile tests of specimens with 0°, 45°, and 90° orientations. Baseline tensile properties along with the variation of the instantaneous hardening index with strain were computed. Variations of the bake-hardening index were explored under simulated paint bake conditions. Tensile properties were measured at selected temperatures between -100°C and 200°C and the TRIP effect was found to be temperature-dependent due to stress-induced martensitic transformation at lower temperatures versus strain-induced transformation at higher temperatures.

As mass reduction becomes an increasingly important enabler for fuel economy improvement, having a robust structural development process that can comprehend Vehicle Dynamics-specific requirements is correspondingly important. There is a correlation between the stiffness of the body structure and the performance of the vehicle when evaluated for ride and handling. However, an unconstrained approach to body stiffening will result in an overly-massive body structure. In this paper, the authors employ loads generated from simulation of quasi-static and dynamic vehicle events in ADAMS, and exercise structural finite element models to recover displacements and deflected shapes. In doing so, a quantitative basis for considering structural vehicle dynamics requirements can be established early in the design/development process.

Experimental decklids for the Cadillac STS sedan were made with Al AA5083 sheet outer panels and Mg AZ31B sheet inner panels using regular-production forming processes and hardware. Joining and coating processes were developed to accommodate the unique properties of Mg. Assembled decklids were evaluated for dimensional accuracy, slam durability, and impact response. The assemblies performed very well in these tests. Explicit and implicit finite element simulations of decklids were conducted, and showed that the Al/Mg decklids have good stiffness and strength characteristics. These results suggest the feasibility of using Mg sheet closure panels from a structural perspective.

Magnesium and aluminum alloys offer lightweighting opportunities in automotive applications. Joining of dissimilar materials, however, generally requires methods that do not involve fusion. This paper explores the use of self-pierce riveting (SPR) to join magnesium to aluminum alloys for structural and closure applications. The preliminary results indicate that SPR is a viable option for joining aluminum extrusions to magnesium die castings, as well as stamped sheet aluminum to quick-plastic-formed (QPF) sheet magnesium.

Roof racks are designed for carrying luggage during customers' travels. These rails need to be strong enough to be able to carry the luggage weight as well as be able to withstand aerodynamic loads that are generated when the vehicle is travelling at high speeds on highways. Traditionally, roof rail gage thickness is increased to account for these load cases (since these are manufactured by extrusion), but doing so leads to increased mass which adversely affects fuel efficiency. The current study focuses on providing the guidelines for strategically placing lightening holes and optimizing gage thickness so that the final design is robust to noise parameters and saves the most mass without adversely impacting wind noise performance while minimizing stress. The project applied Design for Six Sigma (DFSS) techniques to optimize roof rail parameters in order to improve the load carrying capacity while minimizing mass.

Developing a robust model that can simulate all real world conditions a vehicle can experience can be extremely difficult to predict. When working through the engineering process, Computer Aided Engineers (CAE) traditionally set modeling parameters and conditions to a nominal setting. This is done to simplify the models so that it avoided inputting too much tedious details into the system and wasting so much engineering time preparing the work. It was soon realized that this strategy did not capture all the possible conditions a hood on a vehicle could experience. There was a need to develop a formal approach and method to correlate an analysis model to real world conditions. The Design for Six Sigma (DFSS) process was utilized to develop robustness in the techniques used to accurately understand the vehicle environment. The DFSS process is normally used to design and develop robustness into physical parts.

This paper presents a method to reduce the number of occurrences of vehicle deceleration disturbances due to the reduction of regenerative braking in the presence of wheel slip. Usually, regenerative braking is disabled when wheel slip is detected in order to allow the ABS system to efficiently cycle brake pressure. When this happens, the vehicle will momentarily lose deceleration due to the reduction in both regenerative brake torque and friction brake pressure, until friction brake pressure is reapplied. Some ABS activations can be defined as nuisance events, in which full ABS control is not necessary and is exited rapidly; for example, a vehicle driving through a pothole. In these cases it is desirable to continue regenerative braking in order to keep vehicle deceleration as smooth as possible.

The imperative to get to the market faster with new and better products, has determined all automotive OEM to rethink their product development cycle, and, as a result, many hardware based processes were replaced and/or augmented with virtual, software based ones. However, the virtualization itself does not guaranties better and faster products. In the area of vehicle dynamics, we concentrate on improving the multi-body model development process, facilitating comprehensive virtual testing, and verifying the robustness of the design. The authors present a highly flexible and efficient environment that encourages, enforces, and facilitates model sharing, reusing of components, and parallelization of vehicle dynamics simulations, developed on top of an existing commercial off-the-shelf engineering software application.

GM has recently developed two kinds of vehicle electrification architectures. First is VOLTec, a heavy electrification architecture, and second is eAssist, a light electrification architecture. An overview, of IGBT power modules & inverters used in VOLTec and eAssist, is presented. Alternative power modules from few cooperative suppliers are also described in a benchmarking study using key metrics. Inverter test set up, procedure and instrumentation used in GM Power Electronics Development Lab, Milford are described. GM electrification journey depends on Power Electronics lab' passive test benches; double pulse tester, inductive resistive load bench and active emulator test cell without electric machines. Such test benches are preferred before dyne test cells are used for inverter software/hardware integration and motor durability tests cycles. Specific test results are presented.

Decoratively plated plastic parts continue to be in high demand. One of the essential and challenging features of these finished goods is the adhesion between the metal plating and the plastic. As is the case with any bond between metals and plastics, combating the force from dissimilar thermal growth is an ongoing concern. When a plated plastic part is frozen and the plastic contracts, the failure mode for the plating manifests as a blister or “worm track”. On the other hand, when high heat causes plating failures from growth of the plastic, the problem is one of cracking in the plating. In this study, two methods are discussed that provide insight into the strength of the bond between the metal plating and the ABS and ABS+PC plastics. Peel testing is one means to evaluate the strength of the plating to plastic bond. Peel testing methodology and results are reported for both ABS and ABS+PC samples. A second means to evaluate the bond strength is through thermal cycle testing.

The present study defines the functional requirements for a liftgate and the body in order to avoid rattle, squeak, and other objectionable noises. A Design For Six Sigma (DFSS) methodology was used to study the impact of various constraint components such as bumpers, wedges, and isolated strikers on functional requirements. These functional requirements include liftgate frequency, acoustic cavity frequency, and the stiffness of the liftgate body opening. It has been determined that the method of constraining the gate relative to the body opening has a strong correlation to the noise generated. The recommended functional performance targets and constraint component selection have been confirmed by actual testing on a vehicle. Recommendations for future liftgate design will be presented.

As customer dissatisfaction with interior trim components is tracked by the JDPowers question on “surface durability”, there is a need to increase the durability of the parts that are molded in color. In particular, door trim panel lowers are susceptible to surface damage which results in an unfavorable appearance. To address this issue, an assessment of the various factors that can affect surface durability was conducted using talc filled TPO materials in order to determine the optimum set of physical properties. The team used Design for Six Sigma (DFSS) methodology. A Taguchi orthogonal experiment was used and included control system factors of material, grain, gloss, and color. Noise factors included molding process parameters, aging, and piece to piece variation. The output was a measure of the scratch resistance of the molded plaque which was defined by a Delta L calculation.