Abstract: Based on Manson-Coffin relationship, a strain fatigue damage parameter is defined. And, by combined with the Miner linear accumulative damage theory, an elastic-plastic finite element method to predict fatigue crack propagation(FCG) is given. What’s more, a new FCG prediction model is presented either. During the finite element analysis stages, the fatigue process zone equals the plastic zone under monotonic straining near the crack tip, and the fatigue damage is consisted of elastic-plastic strain damage. Besides, in order to obtain an explicit prediction formula, the fatigue process zone is defined as the plastic zone under cyclic straining, in which only the plastic strain damage is considered. By applying both the finite element prediction method and the FCG prediction model to three materials：Cr2Ni2MoV steel, TA12 alloy and 304 stainless steel, it is found that the prediction results are consistent with the corresponding test results. Meanwhile, compared to the finite element simulation method, the prediction ability of the FCG prediction model has larger prediction range and higher accuracy. Therefore, it is easier to be applied to directly obtaining the FCG formula of opening mode crack based on the Manson-Coffin formula from the reference manual in engineering.

Key words: Fatigue crack growth, Fatigue process zone, Low cyclic fatigue strain damage, contact stiffness, fractal theory, langasite, quartz, structure function, Piezoelectric sensors/ force-sensitive