超声振动和切削液联合作用下的刀刃非物理锐化

Non-physical Sharpening of Cutting Edge Induced by the Joint-use of Ultrasonic Vibration and Cutting Fluid in Metal-cutting

超声辅助切削和切削液的联合使用能减小切削力和降低表面粗糙度,试图说明其机理,目的是为开发精密和超精加工技术打下基础。超声辅助切削和切削液的联合使用,从性质上改变了刀刃施加给工件表面的作用力,包括摩擦力和压力:在无切削液情况下,刀刃切入时,前刀面和后刀面施加给被切削面的摩擦力方向是指向刀刃;在有切削液情况下,刀刃切入时,前刀面和后刀面施加给被切削面的摩擦力方向是背向刀刃。背向刀刃的摩擦力,相对于指向刀刃的摩擦力而言,会导致剪切角增大,等效于更锋利的刀刃所产生的剪切角;切削液的存在使得刀刃施加给工件的力更加集中,等效于圆角半径更小的刀刃所能达到的效果;切削液在刀尖部位的压力分布不利于工件表面产生微裂纹。也就是说,超声辅助切削和切削液的联合使用起到了更锋利即更小圆角半径刀刃所起的效果,称之为非物理锐化。

The joint-use of ultrasonic vibration and cutting fluid in metal machining is able to decrease cutting-force and surface roughness. Though the phenomenon has been observed and well utilized, its mechanism has not been clear. The mechanism is revealed in order to establish foundation for the research and development of the next generation of precision and ultra-precision machining technologies. The joint-use of ultrasonic vibration and cutting fluid changes the way in which a cutting tool exerts cutting forces, friction force and compression force, on a workpiece： when cutting fluid is not applied, the friction force direction exerted on a cutting-chip surface by a cutting tool are away from its cutting edge; but when cutting fluid is applied, the friction force direction is towards to the cutting edge. The friction force whose directions away from the cutting edge leads to an increase in shear angle, which is equivalent to the effect that a sharpened cutting tool bring about; the pressure distribution of cutting-fluid is on a narrower zone surrounding the cutting edge than the zone of the cutting force exerted by cutting edge alone without cutting fluid, which is equivalent to the effect that a cutting edge with a reduced radius can do; the pressure distribution of cutting fluid in front of the cutting tip demote the formation of micro cracks. Because the above mentioned advantages can also be brought about by a shaped cutting tool with its cutting edge＇s radius reduced, the effects of the joint-use of ultrasonic vibration and cutting fluid is called as non-physical sharpening.