Abstract
This work proposes a new optimization based methodology for the design of train crashworthy structural subsystem arrangements that can be used during the early phases of the design. A multibody code, which allows for the analysis of all important features of the train and the contacts among their components, serves as the basis for the design tool. The gross motion of the system is described using a 2D Cartesian coordinate formulation, the large plastic deformations of the structure are included using the plastic-hinge modeling approach and the contacts are represented by a penalty contact model. An optimization analysis procedure, which uses the multibody code for the analysis, is implemented to support the train design. The novel features of the optimization procedure consist on the use of analytical sensitivities obtained through the application of an automatic differentiation tool. The difficulties and remedies on the evaluation of the sensitivities obtained in this form are discussed here. The design variables used in the optimal problem are the masses of the cars involved in the train crash and the characteristics of the force-displacement curves of crushable and structural devices in the interfaces between cars of the same rake. The methodology is demonstrated through the design of an experimental train crash test to appraise the energy absorption performance of the buffers located in the cars extremities and acting between cars in the same rake. The corresponding optimal solution is obtained and the results discussed not only in face of their relevance in a practical vehicle design but also in terms of the robustness of the overall methodology in what the use of analytical sensitivities versus numerical sensitivities are concerned.
