On understanding the cutting mechanism of SiCp/Al composites during ultrasonic elliptical vibration-assisted machining

Abstract

SiCp/Al composites play a significant role in achieving equipment lightweight, but its mechanical properties weaken the machinability. Ultrasonic elliptical vibration-assisted machining (UEVM) is a potential way to improve the machinability of difficult-to-cut materials, provides an efficient and precise solution for SiCp/Al composites in industrial manufacturing. However, the removal mechanism of SiCp/Al composites during UEVM and the effective guidance for practical machining are rarely investigated. In this paper, the cutting mechanism of SiCp/Al during UEVM is analyzed through theoretical analysis, finite element (FE) simulation and systematic experiments. Specifically, a multi-phase 2D microscopic FE simulation model is implemented and verified through systematically scratching tests. The research results indicate that particle stress distribution is influenced by variable tool-particle relative position during UEVM, promoting particle fracture and forming high-density zone of broken particles. Segmented chips with shorter length and greater curvature are the main form during UEVM, and dense layered structure appears on free surface of chips. Surface defects include cavities, crushing particles and scratches, while subsurface damage is dominated by pits and crack invasion. In addition, removal rate affects the surface formation, especially under very low scratching speed. Higher scratching speed weakens the ability of particle crushing under vibration effect, which is not helpful for improving surface integrity. Therefore, a reasonable cutting speed of 200 mm/min should be set during UEVM. This paper brings in a deeply understanding on cutting mechanisms of SiCp/Al composites, provides a theoretical guidance for the design and optimization of the vibration assisted processing of metal matrix composite.