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It is important to predict the crashworthiness of a body frame in order to design the structure which absorbs the impact energy effectively at the front or rear structure member of the body. We have been analyzing the crashworthiness with the following methods to establish a fundamental concept on the buckling characteristics of the frame at the initial design stage of vehicle development. 1) The method to introduce the empirical formulas considered with the effective width theory 2) The finite element method (FEM) based on the plastic joint method 3) The buckling analysis considered with the initial strain and the inertia force of engine Nowadays, it is possible to conduct a large deformation analysis of a crashworthiness by using the Super Computer.

A new concept, a parameter U*, is introduced to express load transfer in a structure. Two cases of U* analysis for a floor structure of a passenger compartment are examined. In the first case, three conditions of U* are introduced as objective functions, and GA structural optimization is applied. The emergent floor structure after the GA calculation has a unique shape in which a member connects the frontal part of an under-floor member and the rear part of a side-sill. In the second case, the U* values and the load paths in a floor structure under collision are calculated by use of PAM-CRASH. As the collision progresses, the under-floor member becomes the principal load path, and in the final stage of the collision the roll of the under-floor member becomes dominant.

A Finite Element Method (FEM) simulation was conducted to predict energy-absorbing characteristics in an impact of a head form against plastic plates. Static and dynamic material tests were conducted in order to determine material properties of the plastics. The properties were applied in an explicit FEM code. The FEM results were validated through the impact tests by the head form against the same plastic plates. It was proved that the FEM could simulate the test result well, when the precise material properties were introduced in the simulation. The method can be expected to be available to predict energy-absorbing characteristics during the impact by the head form against automobile plastic components such as shell portions of instrument panels.

This paper presents a numerical analysis technique for application to shape optimization problems of linear elastic structures subject to multiple loading conditions. The problems dealt with here are a mean compliance minimization problem in relation to individual load cases and a fully stressed design problem. The proposed technique is based on the traction method which analyzes the domain variation. A shape optimization system was developed and applied to fundamental problems in two and three dimensions. The computed results confirmed the validity and usefulness of the proposed technique.

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.

It has become possible to calculate impact phenomena of comlex body structures by utilzing of a supercomputer and recent progress of computational mechanics including the Finite Element Method (FEM). However there are some problems to rely heavily on these methods for the analysis of crashworthiness from the view of time and cost in modeling or in calculation. It is important to develop each specific say of calculation for corresponding to various crashworthiness in early design stages. This papaer describes some FEM analyses for the various crashworthiness in statics and/or dynamics, regarding the body structure as resultant of components such as a side frame and subassembly such as a frontal structure. As a result, it is important to select optimum methods from FEM analysis for static and/or dynamic crash. It is also discussed that the difference between static and dynamic calculations is observed in deformation mode of body structure in collision.

The objective of this paper is to present one of the application of the finite element method (FEM) in early stages of vehicle development to calculate larger deflections of body sheet panel. The stiffness of sheet metal shells is defined in conjunction with the local elastic buckling instability under concentrated loads. Considerable amount of weight reduction of outer panels could be obtained by optimizing metal gauges, radii, peripheral conditions and reinforcing manner of the panel. Among several outer panels of an automobile, a roof panel is picked up as an example and its stiffness is calculated by FEM analysis. The results shows satisfactory coincidence with the experimental ones. Regarding the calculation procedure, Central Processor Unit (CPU) time of finite elements was found to be reduced by varying and optimizing supporting conditions of the panel. Furthermore, the stiffness analysis program during the initial design stages of vehicle development is described.