Study on the transient thermo-mechanical coupling mechanism at tool-chip interface in ultrasonic vibration assisted chip formation process under sustainable dry machining conditions

Dry machining has become one of the most promising and sustainable manufacturing processes in mechanical machining. One of the main puzzles for industrial applications of dry machining is tool wear, which are closely related with the transient thermomechanical characteristics of tool-chip interface (TCI). Simultaneously, those characteristics at micro scale can provided the critical insight of cutting mechanics and tool wear in ultrasonic vibration assisted cutting (UVC). However, reports in literature appear to be scarce. In this study the transient model of thermomechanical behavior in TCI is proposed, with a consideration of characteristics changes induced by ultrasonic vibration, as well as a focus on the transient cutting mechanism, as well as stress and friction. The proposed model is validated by comparison with the experimental and published analytical results. Obtained results from the proposed model indicate that the distribution of normal stress and average shear stress are similar to those that are predicted by Zorev's model. However, a noticeable apparent discrepancy appears between the two models regarding the distribution of shear stress. Apparently, the ultrasonic vibration changes the friction via alternating normal and shear stresses, and delays the time for the cutting force and the stress to reach their peak point. Additionally, it is confirmed that the fluctuation and increment of friction coefficient is due to the cutting force reduction in UVC under sustainable dry conditions.