Fundamental analysis of the mechanism of built-up edge formation based on direct scanning electron microscope observation

Abstract

Direct scanning electron microscope (SEM) observation of the dynamic behaviour of the built-up edge (BUE) and local strain analysis around the BUE were carried out to investigate fundamentally the mechanism of BUE formation for low carbon steel. There are two types of crack which play significant roles in the mechanism of BUE formation: one forms below the flank face of the tool and the other forms subsequently ahead of the rake face of the tool. The former starts at the machined surface, a few tens of micrometres from the cutting edge of the tool, and grows in the primary shear zone accompanied by severe strain concentration. The latter occurs along the secondary shear zone and is caused by extensive shearing a certain distance away from the cutting edge of the tool. The morphology of the BUE is determined by the formation of both cracks, its growth depending on the strain concentration and the growth of the cracks.