Size effect and life estimation for welded plate joints under low cycle actions at room and low ambient temperatures

To understand the size effect and the low temperature effect on the low-cycle fatigue behaviour of welded plate joints, this study reports a series of low-cycle fatigue tests of welded cruciform joints with different geometries under the room temperature (28oC) and the low temperature (−60oC). The experimental results reveal the opposing size effect during the fatigue crack initiation and propagation stages. The comparison of the fatigue life under different temperatures implies a negligible influence caused by the low temperature on the total low-cycle fatigue life of welded plate connections. In addition, this study predicts numerically the low-cycle fatigue life for the welded specimens based on the continuum damage mechanics and achieves a reasonable agreement with experimental results. To simplify the numerical estimation of the local energy-based fatigue driving force at the weld toe, this paper proposes an improved modified Neuber's rule (IMNR), which quantifies the effect of the yield strength for connections under intermediate fatigue driving force. The improved modified Neuber's rule enhances the accuracy of evaluating the local inelastic stress and strain state at the weld toe.