Size Effect on Fatigue Strength of Welded Joint : Effect of Specimen Width

Abstract

In order to obtain the effect of specimen width on the fatigue strength of welded joint, repeated tensile loading fatigue tests were carried out on the two kinds of notched specimens having three different specimen width, and strain behaviours at notch root, initiation of fatigue cracks and behaviours of crack propagation were observed. Then the same tests and observations were performed for the non-load carrying fillet welded specimen. And the followings are concluded by comparing the crack initiated position with the distribution of strain range, the strain restraint and those variation with load cycling. 1) On the crack initiation and failure lives of the notched specimen, the effect of specimen width was negligible small. 2) The crack initiation and failure lives of welded specimen are affected by specimen width, and the fatigue strength reduction factor (η) to the fatigue strength of the specimen with B/t=1 is obtained as follows B/t<__-8 for failure life (N_f) η=1-1/7(1-1.762N_j^<-0.0589>)(B/t-1) for crack initiation life (N_c) η=1-1/7(1-3.462N_c^<-0.1174>)(B/t-1) where B is specimen width and t is plate thickness.