Investigation of the Influence of Built-Up Layer on the Stress State in the Primary Shear Zone Using Particle Image Velocimetry Analysis

In this study, a novel methodology was proposed to investigate the influence of the built-up layer (BUL) formation on the stress state distribution in the primary shear zone (PSZ) using analytical model and particle image velocimetry (PIV) analysis. Orthogonal cutting tests were performed under a range of uncut chip thicknesses and cutting speeds using two uncoated cemented carbide tools with different rake angles. A series of shear strain, shear strain rate, and velocity distributions in PSZ were obtained by PIV analysis. Al7075-T6511 was used as the workpiece. Subsequently, the influences of cutting conditions on the BUL/built-up edge (BUE) formation and the plastic deformation in PSZ were investigated. Using these results, the parameters of the proposed analytical model were identified, and the influences of the BUL/BUE formation on the stress state distribution were investigated. From the experimental results, it was found that in the cutting speed range below 2 m/min, only BUE is formed, and the uncut chip thickness and tool rake angle have a significant influence on its formation. The agreement between the measured and calculated results demonstrated the effectiveness of the proposed methodology. The results confirmed that the BUE formation has little effect on the bell-shaped distribution of shear strain rate, but has a significant influence on the thickness of PSZ, chip sliding velocity near the outlet boundary of PSZ, maximum shear strain rate, stress state, and temperature in PSZ. It was also confirmed that the stress triaxiality plays an important role in the BUE formation. These results provide a deeper understanding of the BUL/BUE formation.