Analysis of the Modal Effects on Vibration Fatigue in a Full‐Scale Welded Carbody for High‐Speed Train

ABSTRACT Structural fatigue failure is closely linked to vibration modal characteristics and dynamic response; thus, analyzing their relationship is essential for fatigue‐resistant design. A full‐scale finite element model of the vehicle body is developed, and the modal characteristics of the empty and fully loaded states are compared to identify the causes of local modes. Under random multiaxial loads, modal displacement responses are calculated, and the truncation order is confirmed within an acceptable error range. Critical modes are determined by evaluating their contribution to fatigue damage. Fatigue damage at weld locations is then assessed using two stress‐based approaches within the modal superposition framework. The results show that truncation based on relative error is effective, modes with larger displacement responses have a greater impact on fatigue damage, and the structural stress method provides higher accuracy in fatigue life prediction than the nominal stress method.