Generation mechanism and dual-dynamics simulation of surface patterns in single-point diamond turning of single-crystal copper

Abstract

Single-crystal copper (Cu), whose atom arrangement is in the same direction and has no grain boundary, is widely used in defense technology, civil electronics and network communication. As a diamond machinable material, fan-shaped patterns are commonly generated on the machined surface in single-point diamond turning (SPDT), which affects the machined surface quality and the optical function it carries. Previous studies on the surface generation mechanism in SPDT of single-crystal copper were limited to experimental analyses, while there is a lack of fundamental understanding in the generation mechanism and suppression method of fan-shaped pattern. In the present study, the fan-shaped patterns, surface quality, cutting force and chip morphology generates during SPDT of typical crystal planes (100), (110) and (111) of single-crystal copper were studied both from theoretical and experimental analyses. A molecular dynamics (MD) simulation was conducted to present the fundamental generation mechanism of the fan-shaped patterns from atom arrangement directions and its angle changing with the primary cutting direction in micro scope, while a cutting dynamics model was established to simulate the generation of fan-shaped patterns on the machined surface in macro scope. Based on theoretical and experimental analysis, it was found that the different atom density arrangement directions of single-crystal copper and main cutting direction of SPDT caused fluctuations in the friction coefficient, which further caused the vibration of the cutting system and generated the fan-shaped patterns. The SPDT of crystal planes (100) can achieve the best surface quality. The present research provides a fundamental understanding of fan-shaped pattern formation on the machined surface, and provides a reference to obtain better surface quality in machining of single-crystal copper.