An experimental study on influences of material brittleness on chip morphology

Though several material properties such as hardness, thermal conductivity, specific heat, strain hardening, and thermal softening ability have been studied in terms of influencing segmental or serrated chip formation process, rare study about material brittleness affecting the chip formation process has been carried out. In this paper, an orthogonal cutting experiment with four steels with different brittleness was carried out. The effect of workpiece material brittleness on segmental chip formation and consequent chip morphology was investigated. The experimental results show that the material brittleness heavily affects chip formation process and chip shape. A novel chip formation model was developed to explain the mechanism of material brittleness working on the chip formation process. The mechanism is that material brittleness lowers the value of failure strain and thus makes the maximum stress in flow stress curve occur earlier, which leads to the catastrophic shear instability in primary shear zone and consequent segmented chip.