Applied fatigue damage mechanics and finite element method to study the fatigue crack initiation life problems of component. Fatigue crack initiation life is obtained by using the method of additional load, just a stiffness matrix calculation, greatly reducing the workload of calculation. With the damage degree of the critical element partitioning step of the damage evolution, the damage degree increases unceasingly obtains the corresponding, corresponding to the stress field, strain field and the load matrix, and then to calculate the equivalent stress, the application of damage evolution equation for calculating fatigue crack forming life corresponding. Until the damage degree of the critical element to 1 so far, the fatigue crack initiation life is obtained by adding the fatigue crack initiation lives with different damage variable.

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Abstract-The damage mechanics-effective stress method are used to predict the life of the structure under the interaction of creep and fatigue. The effective stress method is used to calculate the stress field of the component, and the repeated modification of the stiffness matrix is avoided, and the calculation efficiency is improved. The closed effect of compression is taken into account when calculating the equivalent stress of damage. Using APDL, the two development tool of ANSYS, to compile the program, combining the life prediction method based on damage mechanics with the structural analysis of ANSYS, the damage calculation and life prediction of components are realized. The FGH95 specimens of high temperature nickel based powder metallurgy materials were calculated and compared with the experimental results, which proved the feasibility of this method. At the same time, it is verified that creep damage is the main factor under high temperature and low cycle fatigue cycle.