Fracture of Pearlite under Conditions of High Deformation Fatigue

The theory of Kettunen and Kocks allows us to obtain a description of the relationship between the saturation stress amplitude, the saturation plastic strain range, and the number of cycles to fracture that fit the experimental data for fully annealed SAE 1038 steel with at least as comparable agreement as that obtained by the Coffin-Manson law. The parameters C and p of the Kettunen and Kocks relationship can be predicted fairly well from two types of tests: the monotonic stress-strain test and the incremental step test. The method of analysis through the linear multiple regression proposed by Bucher and Grozier for ferritic-pearlitic steels satisfactorily predicts the monotonic properties of the material, and the resistance to total strain cycling can be reliably predicted by the Feltner and Landgraf prediction criterion. When controlled strain amplitudes are greater than ±0.37% instantaneous strain hardening is observed during cyclic straining. For smaller strain amplitudes, cyclic softening occurs.