Calculation method on circumferential out-of-plane bending moment distribution in railway carbody composed of aluminum alloy hollow extruded profiles

In order to achieve both lightweight and better ride comfort in railway vehicles, this study proposes a method enabling even less-experienced designers to intuitively identify directions for structural modification and analyze solutions derived from machine learning, The method proposes calculation method on circumferential out-of-plane bending moment distribution in carbody shells composed of aluminum hollow extrusions. The method is proposed with beam theory using surface sheet axial forces discretized at intersections of ribs and surface sheets. Validation by simplified cantilever model shows good agreement with theoretical solutions with a maximum error below 5% except under singular conditions. Application to an actual structure involved comparison of structural moment distributions with deformation modes at five cross-sections. It shows consistency with finite element analysis results on out-of-plane deformation trends and relative magnitudes among sections. Based on the obtained moment distribution, plate thickness was adjusted to appropriately set the moment of inertia of area, resulting in a 0.3% mass reduction with a 0.4% improvement in equivalent bending stiffness. These findings confirm that the proposed method is sufficiently practical and effective for structural design of railway carbody to achieve both lightweight and better ride comfort.