Search Results

Low frequency torsional vibrations can be a significant source of objectionable vehicle vibrations and in-vehicle boom, especially with changes in engine operation required for improved fuel economy. These changes include lower torque converter lock-up speeds and cylinder deactivation. This paper has two objectives: 1) Examine the effect of increased torsional vibrations on vehicle NVH performance and ways to improve this performance early in the program using test and simulation techniques. The important design parameters affecting vehicle NVH performance will be identified, and the trade-offs required to produce an optimized design will be examined. Also, the relationship between torsional vibrations and mount excursions, will be examined. 2) Investigate the ability of simulation techniques to predict and improve torsional vibration NVH performance. Evaluate the accuracy of the analytical models by comparison to test results.

During the design process for a vehicle, the CAD surface geometry becomes available at an early stage so that numerical assessment of aerodynamic performance may accompany the design of the vehicle's shape. Accurate prediction requires open grille models with detailed underhood and underbody geometry with a high level of detail on the upper body surface, such as moldings, trim and parting lines. These details are also needed for aeroacoustics simulations to compute wall-pressure fluctuations, and for thermal management simulations to compute underhood cooling, surface temperatures and heat exchanger effectiveness. This paper presents the results of a significant effort to capitalize on the investment required to build a detailed virtual model of a pickup truck in order to simultaneously assess performance factors for aerodynamics, aeroacoustics and thermal management.

The need for efficient space utilization has provided a framework for the design of a 248mm family of torque converters that supports a wide choice of engine and transmission combinations. The axial length of the part and its weight have been substantially reduced while the performance range has been broadened without degradation of efficiency. The new converter operates in an expanded slipping clutch mode. It significantly contributes to the performance and fuel economy improvements of related vehicles. To meet the cost target, the comprehensive lineup and the resulting complexity have required a high level of component interchangeability. During the design phase, the manufacturing core competencies were scrutinized and process redundancies eliminated, both resulting in optimization of material selection and applicable technology.

This paper identifies the difference in powertrain cooling system content levels using a nominal and a +3 Standard deviation maximum temperature design approach. Variation simulation analysis tools are used along with a 1-D cooling system performance model to predict resulting temperature distribution for different combinations of input variable populations. The analysis will show differential in powertrain cooling system content, mass, and impact to fuel economy for a nominal vs. +3 sigma design approach.

In this paper, tow hook systems and their functional objectives are briefly introduced. General analysis considerations in strength prediction of a tow hook system are described. These considerations contain nonlinear, clamping and material property simulations. Connections and loading simulation of a tow hook system model are discussed in details. A correlation example of a tow hook system is illustrated. This study shows that detailed modeling of a tow hook system is a fundamental requirement for accurate strength prediction and good correlation between finite element analysis and testing.

In this paper, the methodology of finite element analyses of fastened joints in automotive engineering applications is described in detail. The analyses cover a) the possibility of slippage of the spacer with the design/actual clamp load, and under critical operating loads; b) the strength of the fastener and other structural components comprising the joint under the maximum clamp load. The types of fastened joints, the mechanical characteristics of the joints, the relationship of clamp load to torque, the design and maximum clamp loads, the finite element model meshing and assembly, the non-linearity due to contact, the determination of gaps and stack-up, and the nonlinear material simulation and loading procedures are described. An analysis example of a fastened joint on chassis is also illustrated.

The objective of this paper is to investigate the effect of stamping process on oil canning and dent resistance performances of an automotive roof panel. Finite element analysis of stamping processes was carried out using LS-Dyna to obtain thickness and plastic strain distributions under various forming conditions. The forming results were mapped onto the roof model by an in-house developed mapping code. A displacement control approach using an implicit FEM code ABAQUS/Standard was employed for oil canning and denting analysis. An Auto/Steel Partnership Standardized Test Procedure for Dent Resistance was employed to establish the analysis model and to determine the dent and oil canning loads. The results indicate that stamping has a positive effect on dent resistance and a negative effect on oil canning performance. As forming strains increase, dent resistance increases while the oil canning load decreases.

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.

In September 2003, the Mercedes Car Group set another milestone by introducing the fifth generation of automatic transmissions developed and manufactured in-house since 1960. The world's first 7-speed automatic transmission 7G-TRONIC is featured in the Mercedes-Benz S, SL, CL and E-Classes with V8 gasoline engines. Deduced from the demands of the requirement specifications, the 5-speed automatic transmission was decisively improved; the result is a clear increase in spontaneity, agility, fuel economy, and driving comfort for the customer. And because of the harmony between the vehicle and its powertrain, excellent results in the areas of performance, reduced emissions, comfort, and acoustics are obtained.

A methodology for topology and performance redesign of complex structures by LargE Admissible Perturbations (LEAP) has been developed since 1983 in the Department of Naval Architecture and Marine Engineering, the University of Michigan. LEAP theory has successfully solved various redesign problems for performance and simultaneous topological and performance changes. The redesign problem is defined as a two-state problem that consists of two structural states, States S1 and S2. State S1 has undesirable characteristics or performance which does not satisfy designer specifications. The unknown State S2 has the desired structural response and/or performance. The relation between State S1 and State S2 is highly nonlinear with respect to its response or topology. So far, LEAP algorithms have solved various redesign problems for large structural changes (on the order of 100%–500%) of State S1 with only one finite element analysis.

Modern high power density gasoline fueled engines place an ever-increasing demand on the engine lubricant. In this study, it is shown that advances in engine design to increase performance, improve fuel economy and lower emissions have outpaced the development of typical commercial engine lubricants. Advanced designed engines began to experience oil starvation as a result of a combination of driving cycles, oil quality and poor maintenance practices. The cause was traced to excessive increases in borderline pumping viscosity as measured by MRV TP-1 (ASTM D4684). Used oil analysis for MRV TP-1 showed viscosity greatly increased in excess of stay-in-grade requirements and in many cases the crankcase lubricant was solid at the temperature appropriate for its viscosity grade. However, at the same time CCS values were in grade or only slightly (1W grade) elevated.

Loads generated during assembly may cause significant stress levels in components. Under test conditions, these stresses alter the mean stress which in turn, alters the fatigue life and critical stress area of the components as well. This paper describes the Finite Element Analysis (FEA) procedure to evaluate behavior of a cast aluminum wheel subjected to the rotary fatigue test condition as specified in the SAE test procedure (SAE J328 JUN94). Fatigue life of the wheel is determined using the S-N approach for a constant reversed loading condition. In addition, fatigue life predictions with and without clamp loads are compared. It is concluded that the inclusion of clamp load is necessary for better prediction of the critical stress areas and fatigue life of the wheel.

Finite Element Analysis (FEA) has been successfully used in the simulation of sheet metal forming process. The accurate prediction of the springback is still a major challenge due to its sensitivity to the geometric modeling of the tools, strain hardening model, yield criterion, contact algorithm, loading pattern, element formulation, mesh size and number of through-thickness integration points, etc. The objective of this paper is to discuss the effect of numerical parameters on springback prediction using dynamic explicit FEA codes. The example used in the study is from the Auto/Steel Partnership High Strength Steel Rail Springback Project. The modeling techniques are discussed and the guidelines are provided for choosing numerical parameters, which influence the accuracy of the springback prediction and the computation cost.

For the 2003 model year DaimlerChrysler Corporation (DCC) will introduce an all-new 5.7L V8 truck engine manufactured at the new Saltillo II Engine Plant (SEPII) in Saltillo, Mexico. The product will debut in the new RAM series of pick-up trucks and marks the return of the hemispherical combustion chamber architecture. This paper covers the engine design features, simulation methods, development, and manufacturing processes. Also reviewed are the project objectives and the organizational processes used to manage and deliver the program.

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.

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.

Springback study on a Dodge Ram fender outer panel is detailed in this paper. A simple measurement fixture is designed for the panel, wherein non-contact laser scan technology is applied The measurement data are compared with the original CAD design surface and deviation contour maps are obtained. Consistency of measurement is studied at different sections among three samples. Details of FEA simulations are outlined. The comparison between measurement and simulation prediction is summarized. A method to describe the consistency of measurement and the accuracy of simulation prediction is proposed. The targets for measurement consistency and simulation accuracy are verified. A sensitivity analysis is also performed to investigate various simulation input parameters.

Laminated steel sheets sandwiched with a polymer core are increasingly used for automotive applications due to their vibration and sound damping properties. However, it has become a major challenge in finite element modeling of laminated steel structures and forming processes due to the extremely large differences in mechanical properties and in the gauges of the polymer core and the steel skins. In this study, circular cup deep drawing and V-bending experiments using laminated steels were conducted in order to develop a modeling technique for laminate forming processes. The effectiveness of several finite element modeling techniques was investigated using the commercial FEM code LS-Dyna. Furthermore, two production parts were selected to verify the modeling techniques in real world applications.

One way to improve vehicle's fuel economy is to reduce its weight. Reducing weight, however has other consequences. One of these is reduced vehicle size. Almost invariably, lighter vehicles are smaller. Reducing vehicle weight has also been associated with a reduction in occupant protection; the lighter the vehicle, the greater the chance of injury when a crash occurs. For this study, a data-based model is used to evaluate the independent effects of size and weight. This model is constructed using the NASS database and information obtained from NCAP tests. The results indicate that although mass is the dominant factor, size also has an effect; some of the observed reduction in safety benefits associated with mass reduction is actually an effect of size reduction. The model is also used to evaluate the effects of varying stiffness.

This paper deals with the effects of various approaches for modeling of strain rate effects for mild and high strength steels (HSS) on impact simulations. The material modeling is discussed in the context of the finite element method (FEM) modeling of progressive crush of energy absorbing automotive components. The characteristics of piecewise linear plasticity strain rate dependent material model are analyzed and various submodels for modeling of impact response of steel structures are investigated. The paper reports on the ranges of strains and strain rates that are calculated in typical FEM models for tube crush and their dependence on the material modeling approaches employed. The models are compared to the experimental results from drop tower tests.