Research on the Analytical Modeling of Critical Conditions of Serrated Chip Formation Based on Thermal-Mechanical Coupled Material Behavior

In this study, the critical condition of serrated chip formation of 42CrMo quenched and tempered steel considering thermal-mechanical coupled material behavior was studied. It was found that the balance of the strain strengthening and temperature softening of the materials dominated the mechanism of different types of chip formation. Thus, the material constitutive model of 42CrMo quenched and tempered steel considering the items of strain strengthening and temperature softening was established by the Split Hopkinson Pressure Bar (SHPB) tests. The initial condition and final condition for the tooth generation of serrated chips were derived by using the material constitutive model, combining with slip line theory which was used to calculate the local stress. It was found that the critical plastic strain of the serrated chip formation under the different cutting speeds was almost constant. The final strain of the serrated chip formation gradually increased with the increase of cutting speeds. Therefore, the chip types under different cutting conditions could be predicted according to the proposed mathematical model in this study.