Fatigue evaluation of bus welded joints under realistic loading: a dual-criterion approach

Fatigue failures in vehicles and their structural parts due to random loading represent a major concern in product development, particularly during the design phase. In this context, the aim of the present study is twofold. First, it seeks to optimise the fatigue life of a specific case study - namely, a welded joint in the thin-walled profiles of a bus bodywork - by evaluating three different geometric variants of the joint. This optimisation is carried out using a time-domain random fatigue criterion. The analysis begins with experimental service stress-time histories recorded at the critical location of the bus bodywork, corresponding to two distinct travelled road types and two loading conditions. These data are used in the time-domain fatigue analysis to identify the most suitable welded joint variant capable of meeting the required service fatigue life. Once the optimal joint configuration - identified as variant 1 - is selected, both time-domain and frequency-domain fatigue criteria are applied to predict the fatigue life. This second phase considers four additional service stress-time histories obtained from two special testing tracks, under both empty and fully bus loading conditions, in order to evaluate the consistency and reliability of the two fatigue assessment approaches.