高速切削过程绝热剪切局部化断裂的特性试验

Experimental Study on Characteristics of Adiabatic Shear Localization Fracture in High Speed Machining

高速切削过程中绝热剪切局部化断裂的发生是第一变形区绝热剪切演化的结果。研制了高速车削刀-屑快速分离装置,对切屑根部试样进行金相显微观察,探讨绝热剪切局部化断裂的速率相关特性,建立绝热剪切局部化断裂过程的物理模型。结果表明,高速切削过程的绝热剪切演化随切削速度的提高主要经历了绝热剪切的发生、形变带、转变带和绝热剪切局部化断裂。绝热剪切局部化断裂是第一变形区能量聚集和释放的周期性循环过程,随着剪切带能量的不断聚集,当剪切带所能承受的能量达到饱和极限时,剪切带就会以断裂的形式释放能量,结果导致锯齿形切屑沿剪切带完全分离。

The occurrence of adiabatic shear localization fracture in high speed machining is a result of adiabatic shear evolution in primary shear zone. A tool-chip quick separation device applied in high speed turning is developed to obtain the chip roots. The characteristics and induced mechanism of the occurrence of adiabatic shear localization fracture are discussed through micro-examination. The physical model of adiabatic shear localization fracture is built up. The results show that with the increase of cutting speed, adiabatic shear evolution is mainly through the occurrence of adiabatic shear, deformed band, transformed band and adiabatic shear localization fracture. Adiabatic shear localization fracture in high speed machining is a periodic cycle process from energy convergence to energy release of primary shear zone. With the energy convergence in shear band, shear band will fracture to release energy when the energy convergence in band exceeds the energy saturation limit, which leads to serrated chip fracture along shear band completely.