Finite element prediction of fatigue lifetime for different hole making strategies

Residual stresses and surface roughness are known to be the surface integrity parameters most affecting the fatigue life in machining processes. It has always been tried to obtain a correct correlation between these parameters and fatigue life. In this study, an FE model based on damage mechanics was developed to estimate the fatigue life of specimens made by drilling, drilling+predrill, and helical milling processes. First, hole making strategies were simulated to obtain the induced residual stresses. The specimens were then exerted under cyclic uniaxial loading, while damage mechanic was applied in the model. Experimental models were also used to modify the predicted fatigue life based on surface roughness. Validation tests showed capability of the proposed model to predict the fatigue life of holed samples with the maximum difference of 13.1 <^>. In addition, the predicted crack initiation site was consistent with the fractography analysis.