Abstract: In order to solve the problem of large estimation error in traditional two-state reliability assessment, a life prediction method of threestate mechanical products was proposed based on the two-phase Gamma process model under the condition of impact load. Firstly, based on the study of the continuous degradation trajectory of the product, a two-phase Gamma process model was used to describe the continuous degradation of the product, and the discrete degradation caused by external random impact was described based on compound Poisson process. Then, based on the cumulative damage model, the reliability estimation model of mechanical products under the competitive condition of impact failure and degradation failure was established, and the residual life of mechanical products was predicted by using the model. Finally, the correctness and effectiveness of the proposed method were verified by the simulation analysis of the degradation process of the crack growth performance of metal materials. The research results indicate that comparing with the traditional two-state reliability evaluation model, the proposed three-state life prediction method has higher accuracy for the reliability evaluation results.

Key words:  two-phase Gamma process model; three state mechanical products; compound Poisson process；lifetime prediction；reliability evaluation