Hideki Kumamoto

Study on the crashworthiness of rail vehicles

Crashworthiness requirements are appearing more frequently in rail vehicle technical specifications. These requirements represent an effort to reduce the number of injuries and fatalities to rail passengers in collisions. There are relatively few published studies which provide methodologies for analyzing the crash behavior of rail vehicles. This paper presents car-body crash test results. Crash behavior is shown to be predictable using Kawasakis analysis method, which employs LS-DYNA.

A simple estimation of notch stress and strain under hardening-creep laws by using the small-scale-creep concept

Abstract Simple expressions are proposed for predicting the notch stress and strain under hardening-creep laws by applying the concept of the state of small-scale creep proposed by the present authors and by Riedel and Rice for a crack under creep conditions. In the case when the creep strain-rate is expressed by the time-hardening law, a simple equation is obtained, which predicts the time variation of a stress-concentration factor under the small-scale-creep conditions from the elastic stress-concentration factor. When the strain-hardening law is employed, an ordinary differential equation is derived, which can be solved for the stress-concentration factor. An equation for predicting the variation of a strain-concentration factor at notches with time is also proposed. Finite-element calculations have shown that the small-scale-creep predictions agree well with the results of the finite-element analyses in the case of plane stress, plane strain, and axial symmetry.