Low-Cycle Fatigue Life Prediction of Pure Copper Based on Slip Deformation Inhomogeneity Analysis

Tension-compression strain fatigue tests and observations on the mesoscopic evolution of deformation inhomogeneity were conducted on T2 pure copper. By combining the representative volume element (RVE) with the crystal plasticity finite element method (CPFEM), the entire processes of grain-level inhomogeneous deformation of the specimens under fatigue cycles at seven strain amplitudes were simulated. On this basis, the parameters characterizing the deformation inhomogeneity and their correlation with material fatigue were investigated. Three sets of fatigue indicator parameters (FIPs) based on slip deformation inhomogeneity were proposed: (1) the mean value Γ¯ and standard deviation Γ^ of the sum of the absolute values of the resolved shear strains of the slip systems at the tensile peak point; (2) the standard deviation ω^ of the sum of the products of the resolved shear strains and resolved shear stresses of the slip systems; (3) the mean value Ξ¯ and standard deviation Ξ^ of the product of the sum of the absolute values of the resolved shear strains and the sum of the absolute values of the resolved shear stresses of the slip systems. These three sets of FIPs can be utilized for fatigue life prediction in material testing. Error evaluation confirms that the predicted fatigue lives obtained using this method all fall within a factor of 1.5 of the experimental values.