Damage parameters of two-spot welds using variation of natural frequency

On the basis of finite element analysis, the variation of natural frequency is studied for shear loaded two-spot welded specimens during the crack propagation process. The crack area is used to define the damage, with which established the relationship between the damage and the natural frequency variation ratio. The residual fatigue lives of specimens undergone a certain stage of fatigue damage are predicted according to the damage evolution principle in damage mechanics. The results showed that the proposed damage parameter can describe the fatigue process for the two-spot welded joints.