Tohru Nishimura

Impact response of thin-walled frame structures

Abstract This paper describes a finite-element method which was developed to predict the impact response of three-dimensional thin-walled frame structures. The softening effect of the load-deformation characteristics for thin-walled beams under combined axial compression, bending and torsional loads during impact is simulated by making use of a nonlinear Maxwell model. The large deformation of a structure is calculated by using updated nodal coordinates and internal forces, and the flexibility matrix for a curved beam element. Crash tests against a flat barrier were made on three-dimensional frame models. Comparisons between the calculated and experimental force-time relations and the deformed shape of the frame are discussed.

Impact response of thin-walled plane frame structures

Abstract A numerical study of the impact response of plane frame structures with thin-walled members was performed to predict the deformation and absorbed energy of automobiles under crash loading. The collapse characteristics of thin-walled members under axial compression or bending loads are considered in the present analysis. The load-displacement relations are given for curved beam members, and the inelastic deformations of members are described in terms of equivalent internal loads and their histories. Crash tests on simplified plane frame models impacted against a flat barrier were performed to verify the proposed method. Numerical analyses were also made of an oblique barrier impact of an automobile underframe structure and a rear end collision of a vehicle structural system. The analytical predictions were compared with the corresponding test results.

Shear Deflection of Anisotropic Plate

In the thin plate theory, shear deformation is neglected. This theory is unreliable for plates of considerable thickness in the vicinity of the point of application of load, and sandwich plates with shear rigidity which is very low compared with bending rigidity. A widely accepted theory which includes the effects of shear deformation was developed by Reissner and Mindlin. In recent years, composite materials have been widely employed as structure elements, and it is important to understand their characteristics for designing structures. Plates of composite material are characterized by strong anisotropy and low out-of-plane shear rigidity. This paper provides a convenient representation for the stiffness matrix of the finite element in order to analyze a sandwich plate with an anisotropic face plate and core. The formulation is based on the non-conforming element of Zienkiewicz and is obtained with a modified stiffness matrix in the condition in which the out-of-plane shear strain is constant in two directions within an element.

Identification of the bending stiffnesses of an orthotropic lamina.

In this paper, the authors describe a method that identifies four bending stifnesses of an orthotropic plate. A circular plate is used to carry out the static test of three points bending. Its deformation is measured in several cases of supporting and loading conditions. Then, from the measured values and some initial set ones, four bending stiffnesses are determined by the least square method using a personal computer.

A static and a dynamic stress intensity factor of a lug with cracks.

A simple procedure for obtaining a stress intensity factor using FEM proposed by the authors was applied to analyze the problem of a lug with cracks. First, to confirm its usefulness for the present method, a problem for a rectangular plate with an edge crack subjected to three point bending was calculated by the present method. The present results were compared with present photoelastic experimental results or usual results. Next, a dynamic calculation for the same problem and a problem for a lug with cracks were carried out by the present method, and the results were compared with the present experimental results using a strain gaga method. Consequently, as the usefulness of the present method was recognized, the static and the dynamic stress intensity factor of the lug with cracks was investigated by the present method varying a pin hole diameter or a crack length systematically. Furthermore, the relation between the static stress intensity factor and the dynamic one was presented.