Chip Formation Mechanism and Surface Roughness of SiCp/Al Composites by Ultrasonic Vibration-assisted Turning

SiCp/Al is a metal matrix composite. It has excellent properties such as wear resistance, high temperature resistance, and fatigue resistance, and is widely used in fields such as aerospace, automobiles, electronics. The excellent physical and chemical properties of SiCp/Al composite materials have attracted widespread attention from the industry. With the application of SiCp/Al composite materials in these fields, there is an urgent demand for their precision machining technology, as well as research on machining methods and cutting mechanisms to improve surface quality. In the processing of SiCp/Al composite materials, the smooth discharge of chips and the prevention of chip fragmentation and adhesion on the processed surface can effectively improve the surface quality of the work piece. The effect of chip formation mechanism on the machining process was explored. Ultrasonic vibration assisted cutting technology improved the chip size and shape through the quasi-intermittent cutting characteristics of tool vibration, thereby improving the surface quality of machining. The chip morphology of SiCp/Al composite materials was analyzed through comparative experiments of conventional cutting and ultrasonic vibration assisted cutting. The particle distribution in the shear deformation zone stage and the effect of cutting parameters on chip morphology were studied. The chip morphology of conventional and ultrasonic vibration assisted cutting was compared from three aspects: feed rate, cutting depth and rotational speed. Due to the presence of SiC particles in SiCp/Al composite materials, the material began to deform along the boundaries of the particles, and the effective stress reached the material yield strength for the first time. During the deformation process, the increase of stress might cause particle movement and fracture. Therefore, during the cutting process, due to the continuous changes in the position of the particles cut by the tool, the angle of the boundary line at the beginning of deformation changed, leading to fluctuations in the shear angle within a certain range. And the chip segmentation degree Gs was introduced for quantitative comparison between conventional cutting and ultrasonic vibration assisted cutting experiments. It was found by comparison that the sawtooth degree of conventional cutting was 0.264-0.685, and the sawtooth degree of ultrasonic vibration assisted cutting was 0.085-0.364. The sawtooth shaped chips formed by ultrasonic vibration assisted cutting were not obvious, which avoided the fracture of the free surface of the chip at the crack. Finally, the particle damage forms of the chip free surface and the tool chip contact interface were described to visually describe the chip formation process in conventional cutting and ultrasonic vibration assisted cutting of SiCp/Al composites. Ultrasonic vibration assisted turning with more obvious elastic recovery was beneficial for reducing chip thickness. The chips obtained by ultrasonic vibration assisted cutting are more continuous, avoiding chip fragmentation and promoting the smooth discharge of chips. By observing the surface morphology of the work piece after processing, it is concluded that the smaller and more continuous the chip size, the smaller the surface roughness of the machined surface, while the surface roughness for conventional cutting is 0.805 μm. The surface roughness of ultrasonic vibration assisted turning is 0.404 μm. Compared with traditional turning, ultrasonic vibration assisted turning can reduce surface roughness by 49.8%. By observing the morphology of chips and selecting the optimal cutting parameters, the surface quality of work piece processing can be effectively improved. © 2024 Chongqing Wujiu Periodicals Press. All rights reserved.