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Brake torque variation is a source of objectionable NVH body/chassis response. Such input commonly results from brake disk thickness variation. The NVH dynamic characteristics of a vehicle can be assessed and quantified through experimental modal testing for determination of mode resonance frequency, damping property, and shape. Standard full vehicle modal testing typically utilizes a random input excitation into the vehicle frame or underbody structure. An alternative methodology was sought to quantify and predict body/chassis sensitivity to brake torque variation. This paper presents a review of experimental modal test methodologies investigated for the reproduction of vehicle response to brake torque variation in a static laboratory environment. Brake caliper adapter random and sine sweep excitation input as well as body sine sweep excitation in tandem with an intentionally locked brake will be detailed.

Tailor welded steel blanks have long been applied in stamping of automotive parts such as door inner, b-pillar, rail, sill inner and liftgate inner, etc. However, there are few known tailor welded aluminum blanks in production. Traditional laser welding equipment simply does not have the capability to weld aluminum since aluminum has much higher reflectivity than steel. Welding quality is another issue since aluminum is highly susceptible to pin holes and undercut which leads to deterioration in formability. In addition, high amount of springback for aluminum panels can result in dimension control problem during assembly. A tailor-welded aluminum blank can help reducing dimension variability by reducing the need for assembly. In this paper, application of friction stir and plasma arc welded blanks on a liftgate inner will be discussed.

In automotive testing, a chassis dynamometer is typically used, during cell testing, to evaluate vehicle performance by simulating actual driving conditions. The use of indoor cell testing has the advantage of running controlled tests where the cell temperature and humidity and solar loads can be well controlled. Driving conditions such as vehicle speed, wind speed and grade can be also controlled. Thus, repeated tests can be conducted with minimum test variations. The tractive effort required at the wheels of a vehicle for a given set of operating parameters is determined by taking into account a set of variables which affect vehicle performance. The forces considered in determination of the tractive effort include the constant friction force, variable friction force due to mechanical and tire friction, forces due to inertia and forces due to aerodynamic and wind effects. In addition, forces due to gravity are considered when road grades are simulated.

Brake judder, which is a low frequency excitation of the suspension and thus, the body structure during low-G braking, is mainly felt at the steering wheel and throughout the vehicle structure. Brake judder is a problem that costs manufacturers millions of dollars in warranty cost and undesirable trade offs. The magnitude of judder response depends not only on the brake torque variation, but also on the suspension design character-istics. This paper discusses the judder simulation process using ADAMS software to investigate the suspension design sensitivity to the first order brake judder performance. The paper recommends “tuning knobs” to suspension designers and vehicle development engineers to resolve issues in the design and development stages. Various suspension design varia-bles including geometry and compliances as well as brake related characteristics were investigated.

In this study, a full vehicle with durability tire model established with ADAMS is applied to simulate the dynamic behavior of the vehicle under severe rough road proving ground events, where the shock force-velocity characteristics are modeled as nonlinear curves and multi-stage representations, respectively. The shock forces and velocities at each corner are resolved and through full factorial DOE, the shock forces and velocities response surface models are established to analyze the sensitivities of shock force and velocity to the shock damping characteristics.

For a vehicle or repairable system, incidents (conditions) are neither necessarily independent nor identically distributed. Therefore, traditional statistical distributions like Weibull, Normal, etc, are no longer valid to estimate reliability. The Non-homogeneous Poisson process (NHPP) model can be used to predict reliability and warranty of the field product. It can also measure the reliability improvement during the development cycle. The NHPP model is discussed in this paper. In applying a NHHP model to reliability data on a repairable system, one may have few or no failures. This paper presents the I/100 and reliability derivations when the parameter β in the ROCOF function is assumed to have a known value.

Load data representing severe customer usage is required during the chassis development process. One area of current research is the use of road profiles for predicting chassis loads. The most direct method of predicting these loads is to run dynamic simulations of the vehicle using numerous road profiles as the excitation. This onerous task may be avoided, and a greatly reduced number of simulations would be required, if roads having similar characteristics can be grouped. Currently, road profiles are characterized by their spectral content. It has been noted by several researches, however, that road profiles are generally nonstationary signals that contain significant transient events and are not well described in the spectral domain. The objective of this work, then, is to develop a method by which the characteristics of the road can be captured by describing these constitutive transient events.

Rapid wear out of a disk brake due to phenomena commonly known as hot spots is one of various problems faced by brake manufacturers. Hot spots are localized high temperature areas generated on the frictional surface of a disk brake during braking. The non-uniform surface expansion caused by hot spots on the disk surface may cause pedal pulsation or known as thermal judder. This effect in the long run will shorten a brake's life. Numerical simulation of a disk brake requires the use of nonlinear contact mechanics approach. The simulation is computationally very expensive and difficult to perform. A computer simulation technique has been developed at the DaimlerChrysler Brake Core Group to investigate the hot spot phenomena since 1997. The technique was implemented on 3-D finite element models to simulate frictional contacts between the disk and its pads. Computer code ABAQUS is used for these analyses and computations are performed in Silicon Graphics, Origin 2000 machines.

One of the major NVH concerns for automobile manufacturers is the response of a vehicle to the impact of the tire as it encounters a road discontinuity or bump. This paper describes methods for analyzing the impact response of a vehicle to such events. The test vehicle is driven on a dynamometer, on which a bump simulating cleat is mounted. The time histories of the cleat impact response of the vehicle can be classified as a transient and a repeated signal, which should be processed in a special way. This paper describes the related signal processing issues, which include converting the time data into a continous spectrum, determination of the correct scaling factor for the analyzed spectrum, and smoothing out harmonics and fluctuations in the signal. This procedure yields a smooth frequency spectrum with a correctly scaled amplitude, in which the frequency contents can be easily identified.

Over 250 million tires are scrapped in the United States each year. Tires have been a problematic scrap because they have been designed to resist destruction, and have a tendency to float upwards in landfills. Improper storage has resulted in tire fires1--an even more problematic environmental concern than unsightly piles which can serve as breeding grounds for insect vectors. A better solution is to recover materials for use in new components. Not only does this resolve the landfill issue, but it also serves to conserve resources, while returning an economic benefit to society. This paper traces the introduction of tire material recovery at NRI Industries and DaimlerChrysler Corporation (DCC), the development of the infrastructure and materials, and the launch of the Jeep Grand Cherokee thermoplastic elastomer (TPE) radiator seals, comprised of post consumer tire crumb.

A traction test machine, developed for evaluation of traction-CVT fluids for the automotive consortium, USCAR, provides precision traction measurements to stresses up to 4 GPa. The high stress machine, WAMhs, provides an elliptical contact between AISI 52100 steel roller and disc specimens. Machine stiffness and positioning technology offer precision control of linear slip, sideslip and spin. A USCAR traction test methodology includes entrainment velocities from 2 to 10 m/sec and temperatures from -20°C to 140°C. The purpose of the USCAR machine and test methodology is to encourage traction fluid development and to establish a common testing approach for fluid qualification. The machine utilizes custom software, which provides flexibility to conduct comprehensive traction fluid evaluations.

A design is robust when the performance targets have been achieved and the effects of variation have been minimized without eliminating the causes of the variation such as manufacturing tolerances, material properties, environmental temperature, humidity, operational wear etc. In recent years several robust design concepts have been introduced in an effort to obtain optimum designs and minimize the variation in the product characteristics [1,2]. In this study, a probabilistic design analysis was performed on a catalytic converter substrate in order to determine the required manufacturing tolerance that results in a robust design. Variation in circularity (roundness) and the ultimate shear stress of the substrate material were considered. The required manufacturing tolerance for a robust design with 1,2 and 3 sigma quality levels was determined. The same manufacturing tolerance for a reliability based design with reliability levels of 85%, 90% and 95% was also determined and compared.

The goal of an OEM electrical/electronics (E/E) platform organization is to release reliable E/E systems that achieve high levels of customer satisfaction with minimum investment and system cost. Achieving this goal is made more challenging by rapid advances in E/E technology and features which impact the vehicle development business environment. This paper discusses the evolution of an OEM platform organization striving to achieve E/E system integrity in an ever-changing world and eventually achieved the world class electrical quality as measured by J. D. Power. The organizational evolution progresses through a series of philosophies and methodologies, adapting new initiatives and enablers seeking continuous improvement. The result is an OEM organization with: knowledge based on lessons learned, an understanding of E/E system architecture, and enabled by models and tools to provide high levels of customer satisfaction.

Mechanical properties of as-rolled steels used in a vehicle vary with many parameters including gages, steel suppliers and manufacturing processes. The residual forming and strain rate effects of automotive components have been generally neglected in full vehicle crashworthiness analyses. Not having the above information has been considered as one of the reasons for the discrepancy between the results from computer simulation models and actual vehicle tests. The objective of this study is to choose the right material property for as-rolled steels for stamping and crash computer simulation, and investigate the effect of forming and strain rate on the results of full vehicle impact analyses. Major Body-in-White components which were in the crash load paths and whose material property would change in the forming process were selected in this study. The post-formed thickness and yield stress distributions on the components were estimated using One Step forming analyses.

This paper dis cusses the development of a nonlinear shock absorber model for low-frequency CAE-NVH applications of body-on-frame vehicles. In CAE simulations, the shock absorber is represented by a linear damper model and is found to be inadequate in capturing the dynamics of shock absorbers. In particular, this model neither captures nonlinear behavior of shock absorbers nor distinguishes between compression and rebound motions of the suspension. Such an inadequacy limits the utility of CAE simulations in understanding the influence of shock absorbers on shake performance of body-on-frame vehicles in the low frequency range where shock absorbers play a significant role. Given this background, it becomes imperative to develop a shock absorber model that is not only sophisticated to describe shock absorber dynamics adequately but also simple enough to implement in full-vehicle simulations. This investigation addresses just that.

This paper describes the performance improvement and cost savings achieved by the Stamping Technology Department at DaimlerChrysler Corporation (Chrysler group), in migrating from Unix workstations with RISC technology to Linux PCs with Intel Pentium technology. Performance comparisons of various engineering applications running on these two system configurations are analyzed. The major aspects such as hardware configuration, operating system, software availability, compatibility, reliability, accuracy and consistency of simulation results are discussed. The improvement in computing speed and deviations in simulation results between MPP LS-Dyna and SMP LS-Dyna are presented.

In the automotive industry, in order to characterize and evaluate damping treatments, it is a common practice to employ Oberst bar tests as specified by ASTM E756 and SAE J1637. The ASTM standard provides equations for sandwiched Oberst bars. These equations allow engineers to extract the properties of the visco-elastic core. For certain type of automotive constrained-layer damping treatments, such as the Aluminum Foilback, it is often convenient and desirable to prepare the Oberst bar samples with production-intent configuration. Unfortunately, these configurations are often asymmetric. Therefore, the composite Oberst bar data cannot be post-processed by employing the ASTM equations. In this study, the ASTM equations for sandwiched bars are modified to accommodate for asymmetric Oberst bar configurations. The finite element method is used to validate the derived equations by performing a “Virtual Oberst Bar test.”

Most products are designed to operate for a long period of time, and in such case, life testing is a relatively lengthy procedure. Lengthy tests tend to be expensive and the results become available too late to be of much use. To reduce the experimental cost significantly and provide an efficient tool to assess the life distribution for highly reliable product, a step-stress accelerated test (SSAT) was developed. An example of a rear suspension aft lateral link is used to validate the SSAT method.

Knowledge of the loads experienced by a leaf spring suspension is required for the optimal design of the suspension components and frame. The most common method of representing leaf springs is the SAE 3 link model, which does not give good results in the lateral direction. In this paper, a beam element leaf spring model is developed. This model is validated using data obtained from laboratory tests done on leaf spring assemblies. The model is then subjected to actual road load data measured on the Proving Ground. Lastly, results from the beam element model are presented and compared with results obtained from proving ground tests. Overall, the beam element model gives good results in all directions except in situations where it is subjected to high fore/aft acceleration and high reverse braking events.

In this paper, a comprehensive evaluation index for impact harshness (IH) is proposed. A mid-sized uni-body SUV is selected for this study, with the acceleration responses at the various vehicle body locations as objective functions. A sensitivity study is conducted using an ADAMS full vehicle model with flexible body structure representation over an IH event to analyze the influence of various suspension tuning parameters, including suspension springs, shock damping, steer gear ratio, unsprung mass, track-width, and bushing stiffness.