Simulation-based design process for railway metallic structures

Abstract

The German Aerospace Center (DLR) develops pioneering rail vehicle concepts that enable improvements in terms of energy and resource efficiency, as well as wear and comfort. For passenger car bodies, the focus is on lightweight construction and new materials. However, the use of lightweight structures due to their stiffness and vibration behavior involves a conflict of objectives with regard to passenger comfort. To meet these challenges, suitable design methods and verification concepts are needed that fully exploit the lightweight potential of the materials used. So far, static equivalent loads are generally used in the design of rail vehicles in accordance with the fatigue strength verification defined in the standards, as for instance EN 12663-1. However, this procedure assumes metallic materials, and it is not suitable for adequately considering the dynamic loads that actually occur during operation. This can lead to unnecessary oversizing of the vehicles, which runs counter to the goal of lightweight construction. We developed then a methodology in which design and strength verification are carried out using dynamic loads from flexible multi-body simulation and fatigue strength calculation. This can pave the way for the application of lightweight construction concepts for railway vehicle car bodies. Our method consists first to perform a model reduction in order to extract the flexible body of our car body vehicle. Then, multi-body simulations are carried out to determine realistic dynamic loads and stresses that occur during operation. The results of this stress analysis are directly used for a fatigue simulation. In addition, aerodynamic loads from CFD simulations are considered for the fatigue analysis. For the last step of our method, the welds are defined directly in the fatigue analysis software and a structural durability analysis is done. This last simulation allows us to detect the first damaged location on the structure and finally adapt it for the required life time.