Generation mechanism of work hardened surface layer in metal cutting (3rd report, effect of cutting edge roundness on work hardened surface layer)

In the ultra-precision machining, the smaller the undeformed chip thickness is, the more the machined surface integrity is affected by the cutting edge roundness of the cutting tool. In this research, the work hardened surface layer was dealt with as an evaluation of the machined surface integrity and the effect of the mechanical factors on work hardening was investigated experimentally in orthogonal cutting. In the case of a rounded cutting edge, unlike a sharp one, it makes the generation mechanism of the work hardened surface layer complicated. Therefore, it is difficult to predict the depth of the work hardened surface layer by using the previously presented prediction equation for the sharp cutting edge. However, it is possible to predict it by using the ratio of the undeformed chip thickness to the cutting edge roundness. That is because the equivalent shear angle changes according to the ratio of the undeformed chip thickness to the cutting edge roundness.