高体积分数SiC_(p)/Al复合材料的螺旋铣削试验研究

Experimental Study of Helical Milling of High Volume Fraction SiC_(p)/Al Composites

目的分析体积分数为55%的SiC_(p)/Al复合材料在螺旋铣削加工条件下的材料去除机理,提高制孔的孔径精度和表面质量,降低表面粗糙度,为螺旋铣削加工提供一定理论基础。方法首先,基于螺旋铣削运动规律分析复合材料中单一碳化硅颗粒的受力状况及不同去除形式。其次,对铝基体、碳化硅颗粒以及刀具进行建模,模拟碳化硅颗粒在加工过程中的去除形式,并分析3种典型去除形式对表面粗糙度的影响。再次,以螺旋铣削的方式,采用直径为4mm的PCD铣刀在8mm厚的SiC_(p)/Al复合材料上制备直径为6mm的孔。通过响应面法,以主轴转速、进给速度和螺距作为优化变量,孔径精度和表面粗糙度作为优化指标,建立相应的响应分析模型,得到切削参数与优化指标的多元回归方程,研究各工艺参数之间的交互作用。最后,对响应面法得到的较优工艺参数进行试验验证。结果当主轴转速为3388 r/min(切削速度为42.575m/min)、进给速度为175mm/min、螺距为0.26mm时,制孔满足孔径H7的技术要求,表面粗糙度Ra值为1.5303μm。结论适当提高切削速度可增大颗粒被切断的概率,相较于颗粒被挤压和颗粒被拔出,颗粒被切断时已加工表面质量更好。

The work aims to analyze the material removal mechanism,simulation and experimental results of SiC_(p)/Al composites with a volume fraction of 55%under the conditions of helical milling machining,to summarize the rules affecting the accuracy of the hole diameter and the surface quality,to meet the technical requirements of the hole diameter H7 and reduce the surface roughness,and at the same time,to provide a certain theoretical basis for the helical milling machining of SiC_(p)/Al composites with high volume fractions.Firstly,the force condition of single silicon carbide particles in SiC_(p)/Al composites and three different removal forms of particle removal were analyzed based on the rule of motion of helical milling.Secondly,the aluminum matrix,silicon carbide particles and the tool were modeled separately to ensure that the particles were randomly and uniformly distributed inside the Al matrix,to simulate the removal of silicon carbide particles in the machining process,and to analyze the effects of the three typical removal forms on the surface roughness.Then,a helical milling experimental study was carried out on SiC_(p)/Al composites with a volume fraction of 55%using a VDF850A vertical machining center,and holes with a diameter of 6 mm were made in 8 mm-thick SiC_(p)/Al composites using a 4 mm-diameter PCD milling cutter.An inner diameter micrometer,a SJ-210 handheld roughness tester,a VHX-500F super depth of field microscope and SEM3100 electron microscope equipment were used to measure and observe the experimental results.Through the response surface method,spindle speed,feed rate and pitch were selected as optimization variables,and hole diameter and surface roughness as optimization indexes.A response analysis model was established to obtain the multiple regression equations of cutting parameters and optimization indexes,and to study the interaction between each process parameter.Finally,the better process parameters obtained from the response surface method were experimentally validated.For the SiC_(p)/Al composite material,compared with drilling,the hole making helical milling had better advantages,reflected in the smaller exit edge defects,which could reduce the size of the drill cap chip to a greater extent.When the spindle speed is 3388 r/min(the cutting speed is 42.575 m/min),the feed speed is 175 mm/min,the pitch is 0.26 mm,the hole size is 6.018 mm,and the surface roughness Ra is 1.5303μm,which is a combination of the parameters to satisfy the technical requirements of the hole diameter H7 and the surface roughness of the process.The most significant effect on the surface roughness of SiC_(p)/Al composites with high volume fraction after machining is the pits created when the SiC particles are pulled out,when the peak of the surface roughness is close to the radius of the SiC particles.Compared with particles being extruded and particles being pulled out,particles being cut off can get better surface quality,and appropriately increasing the cutting speed can increase the probability of particles being cut off.