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Due to several indeterminate factors, the assessment of the durability performance of a vehicle body is traditionally accomplished using test methods. An analytical fatigue life prediction method (four-step durability process) that relies mainly on numerical techniques is described in this paper. The four steps comprising this process include the identification of high stress regions, recognizing the critical load types, determining the critical road events and calculation of fatigue life. In addition to utilizing a general purpose finite element analysis software for the application of the Inertia Relief technique and a previously developed fatigue analysis program, two customized programs have been developed to streamline the process into an integrated, user-friendly tool. The process is demonstrated using a full body, finite element model.

During frontal and rear end type collisions, very large forces will be imparted to the passenger compartment by the collapse of either front or rear structures. NCAP tests conducted by NHTSA involve, among other things, a door openability test after barrier impact. This means that the plastic/irreversible deformations of door openings should be kept to a minimum. Thus, the structural members constituting the door opening must operate during frontal and rear impact near the elastic limit of the material. Increasing the size of a structural member, provided the packaging considerations permit it, may prove to be counter productive, since it may lead to premature local buckling and possible collapse of the member. With the current trend towards lighter vehicles, recourse to heavier gages is also counterproductive and therefore a determination of an optimum compartment structure may require a number of design iterations. In this article, FEA is used to simulate front side door behavior.

Automotive product development requires higher degree of quality upfront engineering, faster CAE turn-around, and integration with other functional requirements. Prediction of potential durability concerns using analytical methods for sheet metal structures subjected to road loads and other customer uses has become very important. A process has been developed to provide design direction based upon peak loads, simultaneous peak loads, and vehicle program analytical or measured loads. It identifies critical loads at each input location and load sets for multiple input locations, filters load time histories, selects critical areas and analyzes for fatigue life. Several case studies have been completed. The results show that the variations are consistent with the accuracies in finite element analysis, road load data acquisition, and fatigue calculation methods.

One of the many computer oriented structural programs which utilizes the finite element technique is briefly discussed. Examples are presented to demonstrate the application of this program to actual product engineering structural problems. Correlation between predicted deflections and stresses and those obtained in the laboratory are presented. Computer graphics provide a unique method of visually interrogating input data and displaying output data. Graphs, stress contours, and deflected structures obtained by this method are presented.

The European safety regulation plan regarding frontal barrier offset impact calls for 30° angular impact protection in 1995 and a perpendicular 40% offset deformable barrier impact protection in the 1998 time frame. However, various other governmental and private agencies are looking at alternative test conditions. The Auto Motor and Sport Magazine and other insurance agencies have been conducting rigid barrier front impact tests at 40 and 50% offsets. In this study various test conditions were examined analytically. Detailed finite element models were developed to understand the implications of these impact conditions. The models provided insight into energy management mechanism, load transfer and vehicle deformation patterns due to offset impacts on to perpendicular and angular barriers. Several potential offset conditions were simulated using the FEA models.

Failure to provide consistent results in the parallel implementation of a crash simulation can render the simulation code unusable as a design heuristic. This paper describes a parallel implementation of a crash simulation package, FCRASH, which was designed from inception for parallel implementation. An example will be given which illustrates the variation a CAE crash analyst may encounter if the problem of parallel consistency is ignored. Techniques used in FCRASH to deliver consistent results in a parallel environment on a CRAY T90 parallel supercomputer will be discussed. This work has resulted in a robust crash simulation code that delivers consistent results in parallel environments on a variety of shared memory processors. Finally, problems remaining for delivering the same level of robustness in a distributed memory message passing version of an explicit crash simulation program will be examined.

One of the methods used to mechanically fasten a component such as a radio, cluster or finish panel to a plastic instrument panel substrate involves driving a screw through a metal push-nut which has been inserted into an opening in the plastic instrument panel substrate. A primary failure mode which has been observed for this type of joint is cracking of the plastic substrate surrounding the metal push-nut. Finite Element Analysis (FEA) has been employed to optimize the design of the push-nut opening in a polycarbonate substrate and minimize the potential for cracking of the plastic. For the FEA, the implicit version of the ABAQUS program was used. It was determined that the induced stress in the plastic instrument panel substrate from the fastening process can be minimized by controlling the dimensions of the push-nut opening such that push-nut recess is minimized and the thickness of the substrate in the region whether the push-nut engages is optimized.

This paper presents the final phase of a study to develop the modeling methodology for an advanced steering assembly with a safety-enhanced steering wheel and an adaptive energy absorbing steering column. For passenger cars built before the 1960s, the steering column was designed to control vehicle direction with a simple rigid rod. In severe frontal crashes, this type of design would often be displaced rearward toward the driver due to front-end crush of the vehicle. Consequently, collapsible, detachable, and other energy absorbing steering columns emerged to address this type of kinematics. These safety-enhanced steering columns allow frontal impact energy to be absorbed by collapsing or breaking the steering columns, thus reducing the potential for rearward column movement in severe crashes. Recently, more advanced steering column designs have been developed that can adapt to different crash conditions including crash severity, occupant mass/size, seat position, and seatbelt usage.

Test methods to measure mechanical properties of adhesives and sealers such as elastic and shear moduli, Poisson's ratio and damping terms are reviewed. Both standard methods for determining true bulk mechanical properties and methods for determining engineering estimates of mechanical properties of adhesives and sealers “as used” in automotive applications are presented. Mechanical properties are important parameters for designing adhesively bonded and damped automotive structures. Properties such as modulus are typically used in finite element analysis modelling to aid design and optimization of automotive structures. This paper is given as a companion paper to “FEA (Finite Element Analysis) Modelling for Body-In-White Adhesives” by David Wagner, see SAE Paper #960784.

Optimal material selection for a part becomes quite challenging with dynamically changing data from various sources. Multiple manufacturing locations with varying supplier capabilities add to the complexity. There is need to balance product attribute requirements with manufacturing feasibility, cost, sourcing, and vehicle program strategies. The sequential consideration of product attribute, manufacturing, and sourcing aspects tends to result in design churns. Ford R&A is developing a web based material recommender tool to help engineers with material selection integrating sourcing, manufacturing, and design considerations. This tool is designed to filter the list of materials for a specific part and provide a prioritized list of materials; and allow engineers to do weight and cost trade-off studies. The initial implementation of this material recommender tool employs simplified analytical calculators for evaluation of structural performance metrics of parts.

This paper details the lightweighting efforts of the Ford Research & Advanced Transmission team as part of the Multi Material Lightweight Vehicle Project. The Multi Material Lightweight Vehicle (MMLV) developed by Magna International and Ford Motor Company is a result of a US Department of Energy project DE-EE0005574. The project demonstrates the lightweighting potential of a five passenger sedan, while maintaining vehicle performance and occupant safety. Prototype vehicles were manufactured and limited full vehicle testing was conducted. The Mach-I vehicle design, comprised of commercially available materials and production processes, achieved a 364kg (23.5%) full vehicle mass reduction, enabling the application of a 1.0-liter three cylinder engine resulting in a significant environmental benefits and fuel consumption reduction.

Thermoplastics and composites are increasingly becoming popular among automotive design engineers because of their high specific stiffness and flexibility in manufacturing. While plastics like composites are orthotropic, unfilled thermoplastics like ABS Cycolac may be considered isotropic as they show little variation in properties between the flow direction and the direction transverse to the flow. However, this assumption is not enough to treat the latter as metals in finite element analysis. Metals like mild steel, offer considerable ductility, while thermoplastics show limited ductility and begin to fracture with several cracks appearing on the surface. Therefore, in the case of such plastics, it is important to consider the degradation of material properties in nonlinear finite element analysis using Damage Mechanics material law.

A joint system for a dual inlet muffler has been designed which allows the muffler system to be better aligned during assembly. The system uses a slip-fit joint coupled with a ball-and-flair joint. This combination decreases variations in manufacturing and assembly thus, improving tailpipe variability in the vehicle build. The slip-fit/ball-flair joint was compared to conventional inlet systems of flat flanges and flex-couplings. A Variable Simulation Analysis (VSA) audit, finite element analysis of the joint strengths, and variable cost study all showed advantages for the slip-fit/ball-flair system.

The evolution of computer technology has made CAE ( Computer Aided Engineering ) an integral part of the total vehicle development process. Particularly for crash development, up-front input is crucial in determining vehicle architecture, performing trade off studies and setting design targets. Detailed FEA ( Finite Element Analysis ), although more accurate, is not always suitable at this stage due to (1) the lack of Detailed design information and (2) the large amount of modelling and analysis efforts. Concept/Hybrid models, however, can provide important input to make early design decisions without a detailed design. This paper uses a concept model to illustrate the above mentioned point. The model contains, the interior structure of a pick-up truck, driver occupant, restraints, and a detailed steering column assembly. Correlation with a physical test demonstrates the reliability of the model. Several restraint parameters which influence occupant performance are identified.

A side impact study carried out on a particular vehicle has been described and used as a case study to represent a methodology for incorporating side crashworthiness in a new vehicle concept design. In the automotive design environment, it has proved difficult to include side crashworthiness satisfactorily in the initial stages of the passenger car design. Lack of vehicle data at such a stage does not allow detailed finite element analysis. It is, however, possible to suggest the required collapse properties for individual components within the structure so that, through a coarse finite element idealization, a design for crashworthiness can be carried out. The crash properties of the structure can be arrived at by parametric studies of individual components that are absorbing the major portion of the crash energy.

Drive shaft modelling effects frontal crash finite element simulation. A 35 mph rigid barrier impact of a body on frame SUV with an one piece drive shaft and a unibody SUV with a two piece drive shaft have been studied and simulated using finite element analyses. In the model, the drive shaft can take significant load in frontal impact crash. Assumptions regarding the drive shaft model can change the predicted engine motion in the simulation. This change influences the rocker @ B-pillar deceleration. Two modelling methods have been investigated in this study considering both joint mechanisms and material failure in dynamic impact. Model parameters for joint behavior and failure should be determined from vehicle design information and component testing. A body on frame SUV FEA model has been used to validate the drive shaft modeling technique by comparing the simulation results with crash test data.

Pump whine as well as other NVH issues related to power steering system can become customer concerns at the vehicle level. In order to avoid that, proposed treatment of the pump structure and its installation on the engine should be performed. This is particularly important because most vane pumps have a wide range of excitation that can reach 1000 Hz (30th order @ 6000 rpm). This requires maximizing the ‘as installed’ frequencies of the pump to avoid coincidence with the engine and other FEAD harmonics.

The backlite molding squeak noise is caused by the stick-slip type of friction between the window molding and the body panel. To predict if the molding would squeak a finite element analysis technique which uses the nonlinear explicit code LS-DYNA3D has been developed. The three dimensional finite element simulation technique is based on the threshold displacement velocity spectrum and the relative movement of the window glass with respect to the body panel. Comparisons between FEA analysis and tests are also presented in this paper.

This paper first describes an experimental analytical approach and numerical procedures used to establish crushable foam material constants needed in finite element (FE) analysis. Dynamic compressive stress-strain data of a 2 pcf Dytherm foam, provided by ARCO Chemical, is used to determine the material parameters which appears in the foam constitutive equation. A finite element model simulating a 15 mph spherical headform impact with a foam sample 6 in. x 6 in. x 1 in. fixed against a rigid plate is developed. The predicted force-deflection characteristic is validated against test data to characterize the initial loading and final unloading stiffnesses of the foam during impact. Finite element modeling and analysis of 15 mph spherical headform impact with component sections of upper interior structures of a passenger compartment is presented.

The use of die cast magnesium for automobile transmission cases offers promise for reducing weight and improving fuel economy. However, the inferior creep resistance of magnesium alloys at high temperature is of concern since transmission cases are typically assembled and joined by pre-loaded bolts. The stress relaxation of the material could thus adversely impact the sealing of the joint. One means of assessing the structural integrity of magnesium transmission cases is modeling the bolted joint, the topic of this paper. The commercial finite element code, ABAQUS, was used to simulate a well characterized bolt joint sample. The geometry was simulated with axi-symmetric elements with the exact geometry of a M10 screw. Frictional contact between the male and female parts is modeled by using interface elements. Material creep is described by a time hardening power law whose parameters are fit to experimental creep test data.