The demotic spirit as living normality which mainly embody living spot and spirit state of bottom society, it protect the basic of China and load all China's weight.

Considering the tangential force applied on a contact spot, the critical area demarcating the elastic and plastic regimes is obtained by comparing the normal elastic load with the normal plastic load.

With the welding spot fatigue lifetime pre-estimation method, by combination of the finite element analysis and stress calculation, the welding spot fatigue damage under actual load can be calculated.