Fatigue damage model based on the natural frequency changes for spot-welded joints

On the basis of FEM analysis, the variation of natural frequency during crack propagation process was investigated for single-spot and double-spots tensile-shear spot-welded specimens. The crack area was used to define the fatigue damage, with which established the relationship between damage area and natural frequency ratio. The residual fatigue life of specimen undergone a certain fatigue damage was predicted by means of the damage evolution principle of damage mechanics. The results showed that the proposed damage parameter can describe the fatigue process for spot-welded joints.