Structural optimization for improvement of train crashworthiness

A better train design was obtained through this study to improve train crashworthiness that is defined as decreasing deformation of crew areas and the maximum deceleration for crews and passengers in crush accidents. This study uses finite elements to model a train that has a crushable zone between crew and passenger areas, which is usually used for automobiles and can improve automobile crashworthiness. In previous study, a lumped mass and nonlinear spring model with a crushable zone was analyzed to know macroscopic characteristics of a crushable zone to decrease deformation and maximum deceleration. As a result, it was found that the decreasing maximum compressive load and the decline-rate, which is the ratio of the maximum compressive load to the average compressive load in the load-displacement curve of crushable zone, effectively improved train crashworthiness. Then, a finite element model of crushable zone was optimized to obtain a crushable zone design in detail. The Response Surface Method and Sequential Quadratic Programming were used in the optimum design. The objective function was to decrease the maximum compressive load and the decline-rate in the load-displacement curve of crushable zone, which had holes in longitudinal members to absorb crush energy, in semi-static finite element analysis. Design variables were the displacement and the radius of holes in the crushable zone. The results of optimization show that one larger hole was more effective to ensure the crashworthiness of rolling stock.