Collaborative formation pattern of surface topography and residual stress in hard turning of steels

Abstract

High-performance manufacturing (HPM) is essential for high-quality equipment and parts manufacturing, which requires not only geometric accuracy but also control of surface integrity to satisfy functional performance. Surface topography and residual stress are important elements of surface integrity. However, they are always investigated individually, and their collaborative formation pattern has been ignored for a long time. In this study, surface topography will be measured by a 3D laser scanning microscope and analyzed from the perspective of spectral wavelength (λ) along with its corresponding amplitude. Whereas the residual stress (RS) is going to be analyzed by X-Ray diffraction and finite element (FE) model. Thereafter we introduce the formation pattern of both surface topography and RS. Hereby, simulated points clouds of machined surface topography are generated by superimposing the normally distributed random numbers that take into account the springback of the workpiece material response on tool kinematics and geometry. Furthermore, the RS is divided into mechanical loads induced (RSM) and thermal loads induce (RST) according to the mechanism of formation, which were obtained in cutting speed (Y-direction) and feed direction (Z-direction) by the Mohr circle. Our experimental and numerical results showed that an increase in the feed rate (from 0.05 mm/r to 0.15 mm/r) significantly increases the surface roughness and cutting temperature. The increase in temperature increased the RST by up to 286.1%, resulting in a reduction of compressive RS in Z-direction and an increase of tensile RS in Y-direction. Moreover, the increase in cutting speed (from 40 m/min to 80 m/min) results in a more regular surface and a reduction in surface roughness because of the smaller springback. At the same time, it also leads to a decrease of RSM in Z-direction and an increase of RSM in Y-direction. In addition, the increment in cutting speed leads to a minor increase in temperature and RST (maximum increase of 47.0%). Combining the effects of RSM and RST, RS in both directions increases slightly.