Experimental research on strain-hardening effect of 40CrMnMo in turning process based on the Oxley-Welsh theory

Based on the Oxley-Welsh theory, this paper focuses on the influence of strain-hardening behavior of oil country tubular goods (OCTG) 40CrMnMo (workpiece material) on a cutting model and the influence of cutting parameters on a stress distribution in the shear zone and the chip formation in turning processes by establishing a reasonable cutting experimental platform. Then a relationship model between the shear flow stress and the hydrostatic stress in the shear zone is built, and the size effect and strain-hardening effect of the shear zone in the turning process are explained reasonably, especially for the influence of them on the chip morphology. The research results show that the slope K of the relationship model is not caused by the Bridgman effect but results from a synergistic action of the size effect and the strain-hardening effect in the shear zone of the workpiece material. The workpiece 40CrMnMo in the shear zone can obtain a better resistance to the inhomogeneous plastic deformation under a certain cutting condition.