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This paper discusses the ongoing real-world effects on the wearers of restraint systems which are subject to a retractor's failure to lock in a timely manner. Investigation of the ELR performance using both detailed physical examination and inductive methods enables accurate assessment of successful ELR locking at the first opportunity in the crash sequence. Available methods to determine the reliability of the ELR's crash performance are considered and analyzed for assessment of reliability to enable adequate seat belt wearer protection. Corrective measures are analyzed to probe the feasibility of federal safety regulation amendments to mandate a reliability analysis on the propensity for the ELR's failure to lock in a timely manner.

An experimental method for nondestructive estimation of damage in joints due to high mileage degradation in cars is presented. The method estimates damage by comparing transfer functions of the same car at zero and at high mileage. The potential of the method is demonstrated analytically using a three dimensional concept Finite Element Model (FEM) of a car body to simulate the transfer functions of this car body at zero and at high mileage. The results demonstrate that the method is effective for identifying the damaged joints as well as the relative degree of degradation.

A hybrid approach to predict road-induced loads in vehicle structures is presented. The technique involves full vehicle dynamic simulation using measured wheel forces, absolute wheel vertical displacements, and steering angle as input. The wheel vertical displacement is derived from the measured wheel acceleration. This approach avoids the use of tire-road interface modeling. It also improves the conventional loads measuring process with minimum instrumentation and data acquisition. Existing load data from a test vehicle is used to validate this approach. Computed component loads show good agreement with measurements.

One powerful tool for the optimization of engineering components is solution 200 of MSC/Nastran. The user is able to define nearly every kind of objective function and restriction with the help of synthetic responses, in addition to the usual responses. For sizing problems, solution 200 is well-established and reasonably user-friendly. This is not the case in the field of shape optimization. The main problem is the creation of basis vectors, which are needed to describe the shape variations. There are some methods included in solution 200 to create these vectors, but for complex engineering components these methods are difficult to use and very time-consuming. The program Shape200 has been developed to reduce the effort required to create basis vectors.

In the current design process, the designer generates the detailed geometry of the component based on experience. Prototypes of this design are built and tested to verify the performance. This design - build - test iterative process is continued until performance targets/criteria are met. Computer Aided Engineering is often used to verify the design. This paper presents a new product development process to substantially reduce the number of design - analysis - build - test iterations. This Upfront Analysis Driven Design process incorporates several state of the art technologies in finite element structural analysis, optimization, and Computer Aided Design. This process ensures a near optimum design in the first design level itself.

In this paper we present a numerical shape optimization method of continua for solving min-max problems and identification problems. The min-max shape optimization problems involve minimization of maximum stress or maximum displacement; the shape identification problems involve the determination of shapes that achieve a given desired stress distribution or displacement distribution. Each problem is formulated and sensitivity functions are derived using the Lagrangian multiplier method and the material derivative method. The traction method, which is a shape optimization method, is employed to find the optimal domain variation that reduces the objective functional. The proposed numerical analysis method makes it possible to design optimal structures for maximizing strength and rigidity and for controlling stress and displacement distributions. Examples of computed results are presented to show the validity and practical utility of the proposed method.

The current study is application of an acoustic emission sensing technique in fatigue damage measurement. It focuses on fatigue damage of the below-threshold cycles when they are excited by overloads. Acoustic emission (AE) is monitored while cracks are propagating. Some studies are carried out to reduce and isolate noises from the fatigue acoustic emission signal. Results shows that below-threshold cycles do cause fatigue damage measured by acoustic emission activities under the variable-amplitude loading condition. Acoustic emission signals from fatigue propagation are of an intermittent nature.

A mathematical model was developed for the analysis of a fuel filler door with a torsional spring. The model calculates performance indices such as opening and closing forces, kinetic energy during opening and closing and the maximum spring stress. The model was integrated with an optimization program. Two types of optimization problems were formulated: the traditional problem which does not include the effects of random design parameters, and the stochastic type optimization, which does. An example shows how the mathematical model, in conjunction with optimization techniques, can help determine fuel filler door designs.

This paper presents a method to obtain improved foam/pillar structural designs to help enhance occupant interior impact protection. Energy absorbing foams are used in this study with their thickness and crush strength being selected as primary design variables for optimization. The response surface techniques in the design of experiment are used in the optimization process. Head impact analyses are conducted by a CAE model with explicit, nonlinear, dynamic finite element code LS-DYNA3D. A baseline model is developed and verified by comparing the simulation results with the experimental data. Based on this model, the anticipated effects of stiffness of the pillar structure and the trim on the Head Injury Criterion (HIC) results are also assessed. The optimization approach in this study provides a comprehensive consideration of the factors which affect the HIC value.

To reduce the low frequency noise, a new method in optimal stiffener design is presented in this paper. A Microstructure-based Design Domain Method is employed to formulate a topology optimization problem. Using the MDDM, sensitivity of coupled system can be easily derived. The optimal stiffener design is solved using a sequential convex approximation method called Generalized Convex Approximation (GCA). Examples from this approach are presented to demonstrate its effectiveness.

Low frequency vibration characteristics of a vehicle are mainly influenced by the stiffnesses of the beam type structures such as pillars and rockers, and by the stiffnesses of the joint structures, at which several beam structures are jointed together. In the early design stage of the car body structure a simple FE model has been used, in which joints are modeled as linear springs to represent the stiffnesses of the joint structures. In this paper a new modeling technique for the joint structure is presented using an equivalent beam, instead of using a spring. The modeling technique proposed is utilized to design optimal joint structures that meet the required vibration performance of the total vehicle structure.

The air passages in tailpipe end geometries are investigated with Computational Fluid Dynamics (CFD) simulations. The overall objective of the simulations is to select an optimum design which has a mimimum capacity for noise generation. This is accomplished by comparing pressure drops between inlet and outlet and by examining the turbulent kinetic energy levels in the flow domain. Two designs for the tailpipe end geometries were evaluated. It was found that turbulent kinetic energy levels and pressure drops were lowest in a single pipe design which had relatively smooth internal contours. We conclude that the present CFD approach can provide useful design information in a short time frame (a few weeks) for exhaust pipe tip geometries for reduced pressure drop and noise generation.

The lattice Boltzmann (LB) method, which is closely related to the lattice Gas (LG) method, will be investigated in detail in this paper. The LG method is boolean in nature using only bits to indicate the presence or absence of a particle moving in a particular direction and speed. The absence of floating point operations gives the LG method unconditional numerical stability but restricts it to specialized hardware that can perform the Boolean logical operations efficiently. The Boolean character also results in a noisy signal that must be averaged over space/time for reliable estimates. The LB method, on the other hand, tracks the distribution functions (or time averages) of the particles. As a result, floating point numbers have to be used and so the method is not boolean. While this makes the LB method susceptible to instabilities due to accumulation of round-off errors, it allows the LB method to use a variety of existing computer platforms.

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.

The paper presents the new ‘universal’ coach safety twin seat (patent pending). It carries three-point belts, but also protects occupants sitting behind whether empty or fully loaded and whether the rear occupants are unbelted or lap-belted. The extreme 12 g reverse acceleration pulse was applied with seat spacing of 750 mm and 650 mm. The ECE Regulation 80 injury criteria were met in both Hybrid II and Hybrid III dummies (50 %ile, 5 %ile and 95 %ile), as well as the Hybrid III neck injury levels. The seat passed the 76/115/EEC belt anchorage test. With mass of 36.3 kg, conventional materials and production methods, the technical and commercial concept feasibility of such seats was fully demonstrated.

Side impact dummy (SID) is a human-like test device used in the National Highway Transportation Safety Administration (NHTSA) mandated side impact test of vehicles sold in the USA. A finite element model of SID has been developed at GM as a part of a project to simulate the side impact test. The objective is to better predict physical test results by replacing traditional rigid-body lumped parameter models with a finite element model. The project included, besides mesh generation, the development of new LS-DYNA3D constitutive models for rubber and foam-like materials, and enhancements of contact interface and other algorithms. This paper describes the GM SID finite element model and its performance in side impact test simulations.

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.

Focal Project I (FP-I) of the Automotive Composites Consortium (ACC) was initiated in early 1990 to focus on the use of composites in a vehicle's front end structure to perform crash energy management. The project is a continuation of a proprietary Ford project to replace the entire front structure of a production 1984 Escort with a molded composite front structure. Although FP-I uses existing RTM molding tools, the project focuses on the development of a completely new reinforcement architecture which emphasizes production feasible preforming methods: triaxially braided glass fibers over foam cores make up the upper and lower rails and the connecting panel can be formed from either thermoformed continuous strand mat or directed fiber. The process uses a vinyl ester resin. The front structure of the Escort has been redesigned and replaced with production-feasible composite components designed for crash energy management requirements as well as other overall structural considerations.

A finite element model for hybrid III dummy's lower torso is presented. All details of the dummy's knee structure are carefully considered. In order to justify the finite element model, numerical results are made to compare with the experimental results from both knee impact test and knee slider impact test. It is found that the finite element results agree very well with their experimental counterparts.

A scheme which addresses the determination of the time step for time integration of non-linear explicit structural dynamic equations is described. Explicit time integration algorithms based on nodal partitions and mass scaling for crash applications are presented. This allows for greater advantage to be taken of local stability criteria, and thus improves the efficiency of the explicit time integrator. Consistency, convergence and stability analyses of this algorithm for first order systems are given. Issues relating to the effect of user selection of the proper technique on the outcome of the analysis, are discussed. The adequacy of the technique is evaluated by measuring its performance in various benchmark model problems. Example problems are included to demonstrate the accuracy and stability of the method. The stability conditions for general integration parameters in an element partition are also discussed.