ANALYSIS OF FATIGUE-STRENGTH ON NON-LOAD-CARRYING AND LOAD-CARRYING FILLET WELDED-JOINTS

An attempt has been made to study, theoretically, the difference in th e fatigue behaviour of non-load-carrying and load-carrying fillet weld ed cruciform joints. In the former case, the pre-existing flaws produc ed during the welding process will always propagate from the weld toe. Accurate stress analysis using the boundary element method on the loa d-carrying fillet welded cruciform joints shows that the weld throat, h, should not be less than 1.414T, or the weld leg length, w, should n ot be less than 2.0T, where T is the main plate thickness, for the cra cks to initiate from the weld toe. Furthermore, the values of M(k), th e correction factor to to take into account the presence of the weld, are found to decrease when the weld size is increased for the load-car rying fillet welded joints. The Paris crack propagation law is then co mputed numerically to obtain the S/N (signal-to-noise) curves for the two welded joints. The non-load-carrying fillet welded joints give 5 p er cent higher fatigue life than the load-carrying ones for an applied stress range of 100 N/mm2.