The investigation of mechanism of serrated chip formation under different cutting speeds

Chip type is determined by the coupled effects of workpiece material property, cutting speed, uncut chip thickness, feed rate, and tool edge geometry. The understanding of chip formation plays a critical role in studying surface integrity and optimization of machining process variables. Serrated chip, one of the major important chip type, is usually formed in hard cutting at high speed. In this study, a new analytical model has been proposed to better understand the formation of serrated chip, and the simulations have been acquired using ABAQUS/Explicit in machining AISI 1045 during different speeds (from 60 to 6000 m/min). The workpiece material property is modeled with the Johnson-Cook model, and the experiments have been conducted with AISI 1045 during speeds from 60 to 1200 m/min. It has been shown that flow stress is influenced simultaneously by the strain rate hardening and temperature softening. When the speed reaches very high, the temperature softening will fail, and the strain rate hardening will play a more important role. Also, it can be found that the hardening ratio increases when the cutting speed rises. The results of the simulations and experiments correlated well. The cutting force and thrust force both decrease as the cutting speed increases, and the difference between them will shrink when the machining speed reaches a high level.