Design and analysis of hollow section extrusion of the underframe part of a railroad vehicle using mismatching refinement with domain decomposition

In order to reduce the weight of a high-speed railroad vehicle, the main bo dy has been manufactured by hollow section extrusion using aluminium alloys . A porthole die has been utilized for the hollow section extrusion process , which involves complicated die geometry and flow characteristics. The des ign of the porthole die is very difficult because of this complexity. Three -dimensional finite element analysis for a complicated hollow section is al so an arduous task from the viewpoint of appropriate mesh construction and computational time. In the present work, mismatching refinement, an efficie nt domain decomposition method with a different mesh density for each subdo main, is implemented fur the analysis of the hollow section extrusion proce ss. In addition, a modified grid-based approach with the surface element la yer is utilized for three-dimensional mesh generation of a complicated shap e with hexahedral elements. The effects of porthole design are discussed th rough simulation of the extrusion of an underframe part of a railroad vehic le. An experiment has also been carried out for comparison. Comparing the v elocity distribution at the outlet with the thickness variation of the extr uded part, it is concluded that the analysed results can provide reliable m easures for deciding on whether the die design is acceptable to obtain unif orm wall thickness. The analysis results are then successfully extended to industrial porthole die design.