Investigation of the effects of constitutive law on numerical analysis of turning processes to predict the chip morphology, tool temperature, and cutting force

Abstract

Turning process is one of the most complex manufacturing processes to simulate. The ability to accurately simulate turning processes depends on the availability of accurate workpiece material properties as well as the workpiece flow stress behavior change with deformation parameters such as strain, strain rate, and temperature. The goal of this paper is to determine the parameters of constitutive equation of flow stress for hardened AISI630 steel according to Johnson-Cook (JC) and power viscosity law (PVL) models. The numerical analysis of turning process has been done based on the finite elements method (FEM). Predicted results have been compared with experimentally determined data like, cutting force, tool tip temperature, and chip shape to validate the FE models. The numerical simulation results indicate that the adeptness of PVL model in forecasting the plastic behavior of AISI630 steel is quite acceptable and the predicted results are very close to experimental results in comparison with JC model. In addition, the results showed that the serrated chip morphology was accurately predicted over a large range of machining parameters using PVL model. Furthermore, FE analysis and PVL model have been used to predict cutting forces and tool temperature during different turning conditions. It has been found that for low feed rates, the chip form will be changed from continuous to saw-tooth form, e.g., at 0.1 mm/rev feed, with increasing cutting speed from 28 to 62 m/min the chip form was changed from continuous to saw-tooth type. In addition, during machining at cutting speed of 28 m/min, the cutting force is stable, while at cutting speed of 62 m/min, the resultant cutting force is fluctuating. This fluctuating force along with the build-up edge formation increases machined surface roughness at a speed of 62 m/min unexpectedly.