【作者】 葛英飞；

【导师】 徐九华；

【作者基本信息】 南京航空航天大学 ， 机械制造及其自动化， 2007， 博士

【摘要】 碳化硅颗粒增强铝基复合材料(SiC_p/Al复合材料)具有比强度和比模量高、耐高温、耐磨损、耐疲劳、热膨胀系数小、尺寸稳定性好等优异的综合性能,已在航空航天、汽车、光学精密仪器等领域获得日益广泛的应用,其中通过精密、超精密加工获得的SiC_p/Al零部件主要应用于卫星轴承/天线、激光反射镜、惯性导航系统等。近年来,有关SiC_p/Al复合材料的超精密切削技术受到人们的极大关注,但关于该类材料的超精密切削机理及表面形成机制研究尚处于起步阶段。本文开展了SiC_p/Al复合材料超精密车削机理及工艺的研究,完成了以下颇具创新性的研究工作:1. SiC_p/Al复合材料超精密车削切屑形成机制对锯齿型切屑变形时的应力、应变进行了计算,并结合切屑内部不同位置的显微硬度测试分析,探明了该材料超精密车削时第一、第二变形区材料的变形规律。通过切屑形态及切屑根部组织的观察,并结合SiC_p/Al复合材料的本身特性以及切削时剪切区的应力、应变和温度环境,研究了剪切区微裂纹的动态萌生和扩展机制,以及此种动态行为对切屑形态及切屑形成过程的影响。探讨了切屑厚度准周期变化的内在机制,将剪切角周期变化和微裂纹的动态影响相结合,建立了适应含不同颗粒体分比的该材料的切屑形成过程模型。2. SiC_p/Al复合材料超精密车削表面形成及加工表面缺陷从工件材料膨胀侧流、刀具-工件相对振动、进给量和刀具圆弧半径组成的进给波纹、增强颗粒含量及尺寸、增强颗粒的去除方式等角度探讨了SiC_p/Al复合材料超精密车削表面形成机制。研究了切削用量、冷却条件、刀具刃口半径、基体和界面两者强度关系、刀具磨损状况等对增强颗粒去除方式的影响。阐述了SiC_p/Al复合材料超精密车削表面形成过程与加工表面缺陷的关系,并对SiC_p/Al复合材料超精密车削表面缺陷进行了全面的评估。3. SiC_p/Al复合材料超精密车削表面粗糙度研究研究了增强颗粒含量、尺寸及分布,切削用量、冷却条件、刀具材料及其几何参数、刀具磨损状况等对SiC_p/Al复合材料超精密车削表面粗糙度Ra的影响,为超精密车削该材料时工艺参数的选择和制定提供了重要依据。4. SiC_p/Al复合材料超精密车削金刚石刀具磨损研究观察和分析了聚晶金刚石(PCD)、单晶金刚石(SCD)刀具超精密车削SiC_p/Al复合材料时的典型刀具磨损形态,并对刀具磨损机理进行了探讨,为SCD刀具车削不同种类SiC_p/Al复合材料时的前、后刀面合理定向提供了重要依据。更多还原

【Abstract】 Silicon carbide particle reinforced aluminum matrix composites (SiC_p/Al) have many outstanding properties of high specific stiffness/strength, high wear resistance, low density, high thermal conductivity and low thermal expansion, which make them find inceasing applications in some precision or ultra-precision fields, such as inertial guidance systems, satellite antennae/bearing and laser reflection mirror. Therefore, researchers have paid great attention to the ultra-precision machining of this kind of material. At present, the research about ultra-precision machining of SiC_p/Al composites is still at its initial stage. The present study intends to focus on ultra-precision turning mechanisms and technology for SiC_p/2024Al and SiC_p/ZL101A composites. The following original researches have been performed:1. Chip formation in the ultra-precision turning of SiC_p/Al compositesShear strain/strain rate during the course of serrated chip formation have been calculated. Combined with microhardness measurement on different part of the chip, the deformation characteristics of material in the premier and second shear zone were understood. Chip appearance and chip root metallographic structure were studied and strain, strain rate and local temperature rise were computed to investigate the dynamic generation and spread mechanisms of microcracks in the shear zone. The relationship between this dynamic behavior of microcracks and chip shape/chip formation process was discussed. The mechanisms of semi-periodic variation of chip thickness were discussed, and combining with shear angle changing and dynamic behaviour of microcracks, models of chip forming process were established for SiC_p/Al composites with different reinforcement volume fraction.2. Surface generation mechanisms and machined surface defectsFrom the angle of material swelling and side flow, tool-workpiece relative vibration, feed rate and tool nose radius, SiC particle volume fraction and size, removal mode of SiC particles, surface generation mechanisms when ultra-precision turning SiC_p/Al composites was discussed. Surface generation mechanisms and its relationship with machined surface defects were expounded and the machining induced defects were evaluated comprehensively.3. Factors that affect ultra-precision turning surface roughnessThe influences of cutting tool material, reinforcement volume fraction and size, feed rate and tool nose radius, cooling and tool wear conditions on surface roughness Ra have been investigated when ultra-precision machining of SiC_p/Al composites, which provided important references for selecting the rational machining parameters and tools.4. Diamond tool wear pattern and its mechanismsThe wear pattern and its mechanisms of Single Crystal Diamond (SCD) and Polycrystalline Diamond (PCD) tools have been investigated. The results of this study have offered important rules for selecting rational crystal orientation when SCD tool ultra-precision turning of different SiC_p/Al composites.更多还原