【作者】 张国栋；

【导师】 邓建新；

【作者基本信息】 山东大学 ， 机械制造及其自动化， 2015， 硕士

【摘要】 C/C-SiC复合材料作为一种先进的复合材料,具有硬度高、密度低、耐腐蚀、抗氧化性能好、优异的高温力学性能和热物理性能等优点,逐渐成为新型高温结构材料和功能材料而在航空航天、汽车等领域得到广泛的应用。但是C/C-SiC复合材料力学性能各向异性、层间强度低,使得其切削时在切削力的作用下容易产生分层、撕裂、崩边等缺陷,而且C/C-SiC复合材料由于基体SiC的存在,其硬度高,容易导致加工刀具的磨损与失效,钻削加工更严重,是典型的难加工材料。本文以C/C-SiC复合材料为研究对象,对其力学性能、微观结构进行研究,并对其钻削过程中产生的轴向力、钻削孔的质量和刀具磨损开展了相关的试验研究。通过对C/C-SiC复合材料性能的测定及微观结构的观察分析,结果表明：SiC含量较高的C/C-SiC复合材料,其抗弯强度、断裂韧性等性能较低。在同一试样材料下,当压力方向与碳纤维铺层方向垂直时的性能要明显优于压力方向平行于碳纤维铺层方向的性能；C/C-SiC复合材料的断裂形式主要是脆性断裂,表现为碳纤维的整齐脆性断裂、纤维拨出、纤维分离等。利用钎焊金刚石钻头与电镀金刚石钻头对C/C-SiC复合材料进行钻削试验,研究刀具材料、加工参数等对钻削轴向力的影响。结果表明：在同一加工参数下,相比电镀金刚石钻头,钎焊金刚石钻头钻削C/C-SiC复合材料所产生的轴向力较小；进给量对钻削轴向力的影响较大,在同一转速下,轴向力随着进给量的增大而增大；在同一进给量下,轴向力随着转速的增大而有下降趋势；轴向力随着孔加工个数的增加,而呈现逐渐增大趋势。SiC含量较高的C/C-SiC复合材料钻削加工时产生的轴向力也越大；碳纤维铺层与钻削进给方向垂直时的钻削轴向力要明显小于碳纤维铺层与钻削进给方向平行时的轴向力。通过扫描电镜观察孔的加工质量,对比了不同加工参数下孔的加工质量,分析得出孔的加工缺陷主要有崩边、撕裂及分层等。孔的加工质量随着进给量的增大,加工质量越来越差；随着转速的增大,孔的加工质量越来越好,且入口质量明显优于出口质量。采用钎焊金刚石钻头加工孔的质量要优于电镀金刚石钻头；SiC含量较低的材料加工出孔的质量较好；在钻削参数为n=5500r/min, f=20mm/min时孔的加工质量最好。崩边缺陷既与材料本身的加工缺陷有关,又和材料中碳纤维方向与切削方向的角度有关。撕裂及分层缺陷主要发生在孔的出口处,在出口处设置石墨垫板及采用小的进给量可以获得较好的孔加工质量。利用扫描电镜对金刚石钻头的磨损形貌进行观察,研究了不同参数下金刚石钻头的磨损形态。结果表明：金刚石钻头的磨损形态主要包括金刚石颗粒的破碎、断裂及脱落。钎焊金刚石钻头的磨损程度要小于电镀金刚石钻头；加工Sic含量较高的C/C-SiC复合材料时,金刚石颗粒的磨损程度较大；当进给方向与碳纤维铺层方向垂直时,金刚石颗粒的磨损程度要小于进给方向与碳纤维铺层方向平行时金刚石颗粒的磨损。此外,分析了金刚石钻头的磨损机理,由于金刚石颗粒不同的分布情况,造成了金刚石颗粒不同的磨损形式；与结合剂的结合强度不同,其磨损形式及磨损程度也会不同。更多还原

【Abstract】 C/C-SiC is a kind of advanced composite material. Featuring in high hardness, low density, corrosion resistance, anti-oxidant performance, preferable mechanical property at high temperature and thermal physical property excellent, this kind of composite material has been increasingly and widely applied as a new high-temperature structural material and functional material in fields including aerospace and automobile. Nonetheless, C/C-SiC has the characteristic of anisotropy in terms of its mechanical property; what’s worse, with the mal condition for machining and its low interlaminar strength, the delamination, dilaceration and edge collapse may easily appear during the process of C/C-SiC cutting under the effect of cutting force. On the other hand, with the characteristics of high intensity and high hardness of C/C-SiC due to the existence of SiC, the cutting tools would easily be worn and even lose efficacy; besides, the drilling process would be more difficult. Therefore, C/C-SiC is a kind of typical difficult-to-machine material. Focusing on the C/C-SiC composites, this thesis studies its mechanical property and microstructure and performs experimental study on the axial force produced during the cutting process, the quality of the draw bore and tool wear condition.Through determining the properties of C/C-SiC and the observation and analysis to its microstructure, the thesis draws the conclusion that C/C-SiC with a relatively high content of SiC presents the characteristics of relatively low bending strength and quite poor breaking toughness. Under the same sample material, the property of C/C-SiC presented on the condition that pressure direction goes perpendicular with carbon fiber placement direction would significantly outperformed that of C/C-SiC presented on the condition that pressure direction goes parallel with carbon fiber placement direction. The fracture mode of C/C-SiC is mainly brittle fracture with the manifestation of neat brittle fracture, fiber pull-out and fiber separation in terms of carbon fiber.With brazed diamond bit and electroplated diamond bit, the drilling experiment on C/C-SiC is performed to study the effects of tool material and machining parameter on cutting force. The result indicates that under the same machining parameter, cutting force caused by brazed diamond bit is smaller than caused by electroplated diamond bit, cutting force is significantly affected by feed, which means that under that same rotate speed, axial force would be on increase with the increase of feed and that under the same feed, axial force shows the tendency of decrease as rotate speed increases; in addition, with the increase of hole machining, drilling force presents the tendency of gradual increase. With a relatively high content of SiC, the drilling force produced during the drilling process would accordingly become greater, at the same time, the drilling axial force on the condition that carbon fiber placement direction goes perpendicular with drilling feed direction would be significantly smaller than the drilling force on the condition that carbon fiber placement direction goes parallel with drilling feed direction.Observe the processing quality of hole thorough scanning electron microscopy and compare the processing quality of holes based on different parameters. Then after analysis, we concluded that the main processing defects are edge collapse, tear and delamination. Along with the increase of feed, the processing quality is getting poor. As the speed increases, the processing quality of the hole is getting better and the quality of entrance is much better than that of the exit. The quality of holes processed by brazed diamond bit is better than that by electroplated diamond bit. The quality of holes made from materials whose content of SiC is low is much better. The quality of holes is best when the drilling parameters are n=5500r/min and f=20mm/min. The edge collapse defects are not only related to processing defects of materials themselves but also related to carbon fiber direction and cutting direction. Tear and delamination often occur at the exit of the hole. To gain better processing quality, we can set graphite plate to the exit and reduce input.Observe the wearing conditions of diamond particles through scanning electron microscopy and study about them with different parameters. The results show that the wearing conditions of diamond particles mainly include crushing, fracture and shedding. The wearing degree caused by brazed diamond bit is lower than that caused by electroplated diamond bit. The wearing degree caused by electroplated diamond bit of those C/C-SiC composite materials which contains much more SiC is higher. The wearing degree caused by brazed diamond bit when the feed direction and carbon fiber ply direction are vertical is lower than that when the two directions are parallel. Besides, the wearing mechanism is analyzed in this paper. Due to the various distribution of diamond particles, the wearing forms of diamond particles are also different. Unlike the bonding strength of binders, the wearing forms and degree are also different.更多还原