Fatigue behaviour of load-carrying fillet-welded cruciform joints of austenitic stainless steel

ABSTR A C T Recently, considerable advances have been globally reported on stainless-steel bridges. Fatigue performance is an important design factor. The fatigue damage of stainless-steel bridges mostly occurs in fillet-welded joints, espe-cially in load-carrying fillet-welded (LCFW) cruciform joints. In this study, the fatigue behaviour of LCFW cruci-form joints, manifested by fatigue strength, S-N curve, crack shape, fatigue crack growth rate, and the fatigue life predicted method, were investigated. Constant range fatigue and beach-marking fatigue tests were conducted. The fatigue experimental data were regressed to the S -N curve, and were compared with the fatigue classification references from common standards. The crack shape and evolution were studied based on fractographical anal-ysis, and the crack depth and width were then determined. Furthermore, the fatigue crack growth rate and the coefficients of the Paris equation were determined based on crack sizes, and fatigue life was predicted based on fracture mechanics. The results of the fatigue behaviour of LCFW cruciform joints of austenitic stainless steel were as follows: (1) The free slope regression S -N curve is more suitable for the test data. (2) The crack growth rate is lower than that in the structural steel weld and is similar to that of the base metal of structural steel. (3) The fatigue crack of LCFW cruciform joints of austenitic stainless steel is semi-elliptic crack, which is dif-ferent from that of LCFW structural steel. Semi-elliptic crack has lower stress intensity factor and higher fatigue life. (4) The fatigue strength of the LCFW cruciform joints of austenitic stainless steel (55 MPa) is higher than that of structural steel (36 MPa) according to the Eurocode 3 (EC 3) and International Institute of Welding (IIW) recommendations. (c) 2021 Published by Elsevier Ltd.