In this paper, fatigue tests of butt-welded joints, under four-point bending cyclic load, were conducted to investigate the influence of welding deformation on fatigue crack initiation life. It is found that the distribution of residual stress around the weld toe is changed depending on the welding deformation. Meanwhile, welding deformation has an effect on stress concentration factor in the corner. So FEM was used to obtain the stress concentration factor of butt joints considering the

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... deformation. A modified Neuber method was adapted to predict fatigue crack initiation life. Moreover, the fatigue notch factor was defined and on which the influence of mean stress and residual stress were considered. Finally, the evaluated results with the modified formula and the test results were compared. It is showed that welding deformation in the corner has an important influence on fatigue crack initiation life. The effect of welding deformation cannot be neglected in the life estimation.