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Technical Paper

Material Damping Properties: A Comparison of Laboratory Test Methods and the Relationship to In-Vehicle Performance

This paper presents the damping effectiveness of free-layer damping materials through standard Oberst bar testing, solid plate excitation (RTC3) testing, and prediction through numerical schemes. The main objective is to compare damping results from various industry test methods to performance in an automotive body structure. Existing literature on laboratory and vehicle testing of free-layer viscoelastic damping materials has received significant attention in recent history. This has created considerable confusion regarding the appropriateness of different test methods to measure material properties for damping materials/treatments used in vehicles. The ability to use the material properties calculated in these tests in vehicle CAE models has not been extensively examined. Existing literature regarding theory and testing for different industry standard damping measurement techniques is discussed.
Technical Paper

Mercury Switches in Underhood and Trunk Lamp Applications: A Detailed Environmental and Economic Analysis of Alternatives

The largest application of mercury in automotive applications occurs in underhood and trunk lamp activation switches. A reduction of mercury in this application will have a significant impact on automotive mercury usage. Using environmentally conscious design and manufacturing principles, this paper will investigate functional alternatives for the activation of underhood (U/H) and trunk lamp applications. Five alternatives to perform the activation function will be analyzed in four areas over their life cycles: Environmental Economic Engineering Manufacturing Each alternative will be ranked on criteria in each of these four areas using documented LCA processes. Totals will be generated for each area, then weighted and added to arrive at an overall score. Four groups of weightings will be used based on the vehicle type: small cars, mid-size cars, large/luxury cars, and trucks.
Technical Paper

A New Approach to Evaluating Spot Welds for Automotive Durability

The need for accurate virtual prototyping prediction is well documented in the literature. For welded body structures one notable shortcoming has been the ability for finite element analysis (FEA) to accurately predict the failure of welded joints due to cyclic loading. A new approach to representing spot-welds for durability evaluation in automotive sheet metal structures is presented here. Excellent correlation with spot-weld failures in actual tests have been observed through this modeling approach. We present a method of representing spot-welds using the finite element method. This method has shown to be able of predicting the behavior of spot-welds prior to the build of any prototypes or testing. Further, for spot-weld failures we present evidence that reveals which radial quadrant of the spot-weld will contain the failure. This method also allows engineers to determine the mechanism of failure. This paper describes in detail the spot-weld modeling method.
Technical Paper

Failure Evaluation of Clinched Thin Gauged Pedestrian Friendly Hood by Slam Simulation

In order to reduce the number of head injuries sustained by pedestrian accidents, safety engineers are developing pedestrian friendly hood systems through gauge optimization of the hood inner panel. In this study, the clinch method was employed to assemble a pedestrian friendly hood with a 0.5mm thick inner panel. Static and dynamic analyses were carried out to determine the clinch experiencing the highest loads and to understand the fatigue behavior of a clinched hood during a slam event. The macroscopic failure modes of clinched joints by hood slam were studied by means of a scanning electron microscope. A simple equation was derived to correlate the hexahedron spot weld model as a substitute for clinching in order to obtain an equivalent stiffness for a clinched joint within the linear region of an F-D curve. The F-D curve was obtained by lap shear testing.
Technical Paper

Numerical Simulation of Unsteady Natural Convection in a Simplified Engine Bay Enclosure under Soak Conditions

At the onset of soak, air and surface temperatures in an engine bay enclosure are elevated since temperature of heat sources are high while convective cooling is sharply reduced as a result of airflow being shut off from the inlet grilles of the vehicle leading to temperature spikes. Accurate simulation of this important thermal and flow regime that is natural convection driven, highly transient and complex is therefore very important. In this investigation, we simulate flow in the engine bay at the onset of soak with fixed thermal boundary conditions where the geometries representing the engine bay and components are simplified. Good agreement was observed with detailed experimental data available in references for both velocities and temperatures.
Technical Paper

An Experimental Study on the Interaction between Flow and Spark Plug Orientation on Ignition Energy and Duration for Different Electrode Designs

The effect of flow direction towards the spark plug electrodes on ignition parameters is analyzed using an innovative spark aerodynamics fixture that enables adjustment of the spark plug gap orientation and plug axis tilt angle with respect to the incoming flow. The ignition was supplied by a long discharge high energy 110 mJ coil. The flow was supplied by compressed air and the spark was discharged into the flow at varying positions relative to the flow. The secondary ignition voltage and current were measured using a high speed (10MHz) data acquisition system, and the ignition-related metrics were calculated accordingly. Six different electrode designs were tested. These designs feature different positions of the electrode gap with respect to the flow and different shapes of the ground electrodes. The resulting ignition metrics were compared with respect to the spark plug ground strap orientation and plug axis tilt angle about the flow direction.
Technical Paper

Noise and Vibration Measurement Methods for Large Diameter Single-Piece Aluminum Propeller Shafts

This paper describes recently developed test methods and instrumentation to address the specific noise and vibration measurement challenges posed by large-diameter single-piece tubular aluminum propeller (prop) shafts with high modal density. The prop shaft application described in this paper is a light duty truck, although the methods described are applicable to any rotating shaft with similar dynamic properties. To provide a practical example of the newly developed methods and instrumentation, impact FRF data were acquired in-situ for two typical prop shafts of significantly different diameter, in both rotating and stationary conditions. The example data exhibit features that are uniquely characteristic of large diameter single-piece tubular shafts with high modal density, including the particular effect of shaft rotation on the measurements.
Technical Paper

Root Cause Identification and Methods of Reducing Rear Window Buffeting Noise

Rear Window Buffeting (RWB) is the low-frequency, high amplitude, sound that occurs in many 4-door vehicles when driven 30-70 mph with one rear window lowered. The goal of this paper is to demonstrate that the mechanisms of RWB are similar to that of sun roof buffeting and to describe the results of several actions suspected in contributing to the severity of RWB. Finally, the results of several experiments are discussed that may lend insight into ways to reduce the severity of this event. A detailed examination of the side airflow patterns of a small Sport Utility Vehicle (SUV) shows these criteria exist on a small SUV, and experiments to modify the SUV airflow pattern to reduce RWB are performed with varying degrees of success. Based on the results of these experiments, design actions are recommended that may result in the reduction of RWB.
Technical Paper

Experimental Characterization of the Unsteady Flow Field behind Two outside Rear View Mirrors

The unsteady flow fields behind two different automobile outside side rear view mirrors were examined experimentally in order to obtain a comprehensive data base for the validation of the ongoing computational investigation effort to predict the aero-acoustic noise due to the outside rear view mirrors. This study is part of a larger scheme to predict the aero-acoustic noise due to various external components in vehicles. To aid with the characterization of this complex flow field, mean and unsteady surface pressure measurements were undertaken in the wake of two mirror models. Velocity measurements with particle image velocimetry were also conducted to develop the mean velocity field of the wake. Two full-scale mirror models with distinctive geometrical features were investigated.
Technical Paper

Life Cycle Assessment of Advanced Materials for Automotive Applications

Substituting alternative materials for conventional materials in automotive applications is an important strategy for reducing environmental burdens over the entire life cycle through weight reduction. Strong, light carbon composites and lightweight metals can potentially be used for components such as body structure, chassis parts, brakes, tie rods, or instrument panel structural beams. There are also proposed uses in conventional and alternative powered vehicles for other advanced materials, including synthetic graphite, titanium, and metals coated with graphite composite, that have special strength, hardness, corrosion resistance, or conductivity properties. The approach used in this paper was to compare the environmental life cycle inventory of parts made from carbon fiber-thermoplastic composites, synthetic graphite, titanium, and graphite coated aluminum, with parts made from conventional steel or aluminum.
Technical Paper

Weathering of Black Plastics for Automotive Exteriors

Ten mold-in-color black polymers were evaluated for exterior weathering in an attempt to improve the specifications for exterior mold-in-color plastics to meet five year durability for a 95th percentile sunbelt customer. Four different weathering methods were utilized including Arizona exposure, Florida exposure, and Xenon arc exposures per the GMNA and the GM Europe methods. Colorfastness, gloss retention and other material property changes due to weathering were measured and analyzed against two GM durability standards. For the appearance attributes, correlations between actual exposure and accelerated exposure were attempted. Test results before and after polishing were also analyzed. Finally, in addition to comparing the performance of the ten polymers, the four weathering methods are compared and discussed with recommendations for the preferred testing regimen.
Technical Paper

A Robust Procedure for Convergent Nonparametric Multivariate Metamodel Design

Fast-running metamodels (surrogates or response surfaces) that approximate multivariate input/output relationships of time-consuming CAE simulations facilitate effective design trade-offs and optimizations in the vehicle development process. While the cross-validated nonparametric metamodeling methods are capable of capturing the highly nonlinear input/output relationships, it is crucial to ensure the adequacy of the metamodel error estimates. Moreover, in order to circumvent the so-called curse-of-dimensionality in constructing any nonlinear multivariate metamodels from a realistic number of expensive simulations, it is necessary to reliably eliminate insignificant inputs and consequently reduce the metamodel prediction error by focusing on major contributors. This paper presents a robust data-adaptive nonparametric metamodeling procedure that combines a convergent variable screening process with a robust 2-level error assessment strategy to achieve better metamodel accuracy.
Technical Paper

Application of Modal Transient Dynamics to Calculate Body Fatigue Life

The methodology of predicting analytical fatigue life of automotive body structures using two commercially available computer codes, NASTRAN and NCODE is described. Modal transient durability simulations are improved with use of residual vectors incorporating inertia relief basis functions. Simulations consisting of hundreds of thousand finite elements and hours of road loads are routine.
Technical Paper

Windowed Selected Moving Autocorrelation (WSMA), Tri-Correlation (TriC), and Misfire Detection

In this paper, two correlations, Windowed Selected Moving Autocorrelation (WSMA) and Tri-Correlation (TriC), are introduced and discussed. The WSMA is simpler than the conventional autocorrelation. WSMA uses less data points to obtain useful signal content at desired frequencies. The computational requirement is therefore reduced compared to the conventional autocorrelation. The simplified TriC provides improved signal to noise separation capability than WSMA does while still requiring reduced computational effort compared to the standard autocorrelation. Very often, computation resource limitation exists for real-time applications. Therefore, the WSMA and TriC offer more opportunities for real-time monitor and feedback control applications in the frequency domain due to their high efficiencies. As an example, applications in internal combustion (IC) engine misfire detection are presented. Simulation and vehicle test results are also presented in this paper.
Technical Paper

GM's Evolving Epsilon Midsize Car Platform

This paper reviews the history of the General Motor's Epsilon Platform from a Body Structure perspective. From the time that it was conceived in 1996 to the present, the platform has evolved to meet many changing requirements. The focus of this paper will cover basic body requirements such as crash performance, modal requirements, packaging issues, changes for wheelbase and powertrains, mass, different body styles, etc, including the differences between European and US requirements. It will demonstrate that this globally developed platform met all its initial requirements and continued to evolve over time to meet additional changing requirements.
Technical Paper

Target Detection Distances and Driver Performance with Swiveling HID Headlamps

Twent-two participants of varying ages detected roadside targets in two consecutive dynamic evaluations of a horizontally swiveling headlamp vehicle and a vehicle with the same headlamps that did not swivel. Participants detected targets as they drove unlighted low-speed public roads. Scenarios encountered were intersection turns, and curves with approximate radii of 70-90m, 120-140m, 170-190m, and 215-220m. Results from the first study found improved detection distances from the swiveling headlamps in left curves, but unexpectedly decreased detection distances in larger radius right hand curves. The swiveling algorithm was altered for the second study, and the headlamps used did not have the same beam pattern as in the first study. Results from the second study again found improved detection distances from the swiveling headlamps while in the larger radius right hand curves fixed and swivel were not statistically different.
Technical Paper

Discomfort Glare Ratings of Swiveling HID Headlamps

Sixteen participants aged 55–65yrs provided deBoer scale ratings of discomfort glare for a vehicle with horizontally swiveling HID headlamps and a vehicle with the same headlamps that did not swivel in eight scenarios staged in a darkened parking lot. Participants, who were seated in the driver’s position of a stationary vehicle and instructed when to look, viewed the oncoming test vehicles in scenarios of 180m left turn, 180m right turn, 80m left turn, 80m right turn, left turn beside participant vehicle, crossing left in front of participant vehicle, right turn beside participant vehicle, and straightaway, in counterbalanced presentation orders. The swiveling headlamp vehicle provided statistically lower glare ratings in both 180m curves and the 80m right curve and statistically lower or similar in the intersection scenarios than the fixed headlamp vehicle.
Technical Paper

The Use of in Vehicle STL Testing to Correlate Subsystem Level SEA Models

For the assessment of vehicle acoustics in the early design stages of a vehicle program, the use of full vehicle SEA models is becoming the standard analysis method in the US automotive industry. One benefit is that OEM's and Tier 1 suppliers are able to cascade lower level acoustic performance targets for NVH systems and components. Detailed SEA system level models can be used to assess the performance of systems such as dash panels, floors and doors, however, the results will be questionable until test data Is available. Correlation can be accomplished with buck testing, which is a common practice in the automotive industry for assessing the STL (sound transmission loss) of vehicle level components. The opportunity to conduct buck testing can be limited by the availability of representative bodies to be cut into bucks and the availability of a transmission loss suite with a suitably large opening.
Technical Paper

Use of Single Point Interface Measures for Characterization of Attachments

Often components or subsystems are attached to other systems through multiple fasteners at multiple locations. Examples may include things like compressors, alternators, engine cradles, powertrain mounting systems, suspension systems, body structures or almost any other interface between components or subsystems. Often during early design stages, alternative component or subsystem configurations are being considered that can have very different interface characteristics, such as alternators with different number of mounting fasteners, or suspension systems with different number of body structure interface attachments. Given these different mounting configurations, it can be difficult to meaningfully compare the interface performance of the two components or subsystems.
Technical Paper

CFD Based Lumped Parameter Method to Predict the Thermal Performance of Brake Rotors in Vehicle

The objective of the paper is to outline a CFD based lumped parameter method that compares the thermal performance of brake rotors, predicts the transient temperatures and brake lining wear in vehicle. A two-pronged approach was developed for this purpose. A rotor stand-alone model was used to predict rotor performance curves. Simultaneously heat transfer coefficients of the brake rotor were computed corresponding to the rotor performance curves and the appropriate heat transfer correlations were established. The second part of this approach involved developing a brake model in a vehicle and solving for the air flow through rotors in different vehicles at various speeds. These rotor flows were cross-referenced with the rotor performance curves, generated earlier for that rotor, to compute the heat transfer coefficients in the vehicle.