Abstract: The conventional method of fatigue prediction under random loading traditionsily involves two data processes of cycle counting and damage summation. This paper introduces an effective fatigue life prediction method for the welded structures under random loading. According to the method, the fatigue fife prediction for welded structures under random loading can be made directly only from a knowledge of the Power Spectral Density (PSD) of the stress history and conventional fatigue data. Even though the designer of structures does not know the stress-time history at the design stage, but with the exact inputs of the structures, the fatigue life prediction for the designed structures can still be made since the PSD of structures response function of the structural system. The method described in the paper is applied to an extraheavy mining truck frame. The enlaslated fatigue life is basically the same as that with the practice.

Key words: Fatigue life, Power spectral density, Truck frame, Welded structure