硬质合金刀具断续切削切出破损原因的探讨

Cause of Brittle Tool Exit Failure in Intermittent Cutting

分析了负剪切产生的机理，并给出了负剪切长度的计算公式以及产生负剪切时切削力的表达式；通过对刀具刃区应力分析得知：由于负剪切的形成造成切削力的作用方向发生偏转，使得刀具应力场恶化，导致刀具破损；用弹塑性力学分析了热裂纹的发生及裂纹扩展机制，并给出了防止刀具切出破损的措施。

Forming mechanism of negative shear is analyzed, and an expression of cuttingforce during negative shear is given. According to stress analysis of tool wedge zone, the followingconclusion is drawn: the negative shear makes the direction of cutting force deflect so that stressfield of tool get worse which results in tool failure. The causes of thermal cracks and crack exten-sion are analyzed by means of elastic-plastic mechanics, and effective measures preventing thetool from exit failure are presented.