中文摘要：

汽车覆盖件模具精加工中,精加工余量较小,较小的精加工余量与刀具刃口钝圆半径处于相同数量级,为了实现汽车覆盖件模具的高品质加工,刀具刃口钝圆半径的影响应当引起重视。刀具刃口钝圆半径存在,使得塑性材料加工中存在最小切削厚度,当实际切削厚度小于模具材料最小切削厚度时,刀具与工件之间将出现滑擦,导致汽车覆盖件模具的加工精度和表面质量难以保证。提出一种确定最小切削厚度的新方法,该方法基于球头铣削方式,并验证所提出方法的有效性;以汽车覆盖件模具常用材料淬硬钢AISI D2为研究对象,采用所提出的最小切削厚度确定方法,确定不同硬度淬硬钢AISI D2材料的最小切削厚度值,研究速度效应对淬硬钢AISI D2材料最小切削厚度的影响规律,研究结果表明：在所选切削参数范围内,温度效应对淬硬钢AISI D2材料成屑的影响大于应变率效应的影响,此时随着切削速度的增加,最小切削厚度值增大。

英文摘要：

The machining allowance is small in finish-machining of automobile panel dies （APD）. The small finish-machining allowance is of the same order of magnitude as the cutting edge radius. In order to realize the high quality machining of APD, the influence of cutting edge radius should be paid attention to. Because of the existence of cutting edge radius, there is the minimum cutting thickness （MCT） in plastic material machining. When the actual cutting thickness is smaller than the minimum permitted cutting thickness of the die material, as a result, the tool will slide on workpieces. Therefore, the machining accuracy and the surface quality of the APD are hard to be guaranteed. A new method based on ball end milling is provided to determine the MCT, and the practicability of the method is verified as well. The common hardened AISI D2 steel is used to determine the MCTs under different hardness by using the method. The influence of cutting speed on the MCT of hardened AISI D2 steel is studied as well. The study results show that the temperature effect caused by cutting speed has greater influence than the strain rates effect in the hardened AISI D2 steel chips forming process. In this state, as the cutting speed increases, the MCT increases as well.