Experiment and modeling on fatigue of the DP780GI spot welded joint

•Fatigue of DP780GI spot welded joints is experimentally investigated and numerically modelled.•A crack growth model is developed to evaluate fatigue life of the spot welded joint.•The SIFs for crack front points are calculated by using FEM and subsequent fitted equations.•The plastic zone is taken into account in the update of crack length.•The calculated results of fatigue life show good agreement with experiment ones, within five times error band.