Prediction of serrated chip formation in metal cutting process with new flow stress model for AISI 1045 steel

Abstract

Adiabatic shear bands have been observed in the serrated chip during high strain rate metal cutting process of carbon medium steel. The recent microscopic observations have shown that thermal softening occurs in the narrow adiabatic shear bands. However, the conventional flow stress models in general fail to predict the occurrence of thermal softening such as dynamic recrystallization in the shear bands or thermal softening effects accompanied by thermal softening. In the present study, we suggest a new flow stress model based on some assumptions on large deformation process with very high speed and high temperature during cutting process and attempt to predict the serrated chip formation. The finite element analysis with this proposed flow stress model shows that the temperature of the shear band during cutting process rises to initiate dynamic recrystallization, dynamic recrystallization lowers the flow stress, and that adiabatic shear localized bands and the serrated chips are formed. FEA is also used to predict and compare chip formations of two flow stress models in orthogonal metal cutting with AISI 1045 steel.