碳/碳复合材料机械加工残余应力实验研究与规律分析

Experimental and Theorital Investigation on Residual Stress in Machining of C/C Composites

采用适宜于测试复合材料的残余应力测试方法钻孔法,通过二次通用旋转组合设计实验,采用电镀金刚石刀具铣磨加工碳/碳复合材料,选取切削深度、切削宽度、切削速率、进给量四个因素进行实验。实验结果分析表明,回归得到基于二次多项式的数学模型,进一步分析了残余应力随各加工参数的变化规律,整体寻优得到了残余应力的极值。研究表明,铣磨加工碳/碳复合材料,残余应力皆为压应力。伴随着切削速率的增长,残余应力存在渐进值。本次实验中,残余应力趋于-16 MPa稳定。伴随着切削宽度、切削深度、进给量的增大,机械加工残余应力表现为先增大后减小(压应力即残余应力的绝对值先减小后增大)。本次实验中,各加工参数的变化分界点分别为:切削宽度aw=6 mm;切削深度ap=0.5 mm;进给量f=200 mm/min。

The residual stress caused by machining directly related to machining deformation and machining damage. Being limited to measuring technique of machining residual stress and characteristics of composite, there are seldom＇paper about machining residual stress on composites. In this paper, hole-drilling method that is suitable for measuring the machining residual stress of composites has been adopted. C/C composites are machined by means of milling-grinding. The cutting tool is grinding head that is electroplating emery on, by means of quadratic general rota- ry unitized design. Four factors including cutting speed, cutting width, cutting depth and feed are selected for this ex- periment. The regression mathematical model based on quadratic polynomial is obtained through the analysis of experi- mental results. The variation of mac residual stress along with the change of processing parameters is analyzed The extreme value is obtained by searching optimization. It shows that mac residual stress is all compressive stress. Along with the increase of the cutting speed, residual stress tends to an asymptotic values that is -16MPa in this experiment. Along with the increase of the cutting width, cutting depth and feed, residual stress first increased and then decreased. The demarcation of parameters are cutting width ： aw = 6 mm ; cutting depth ： ap = 0. 5 mm ; feed ： f= 200 mm/min.