摘要
当前碳化硅陶瓷类硬脆材料磨削损伤形成机理研究主要是基于经典压痕断裂力学基础理论,然而对于具有复杂显微结构的陶瓷材料,磨削亚表面裂纹损伤形式和萌生扩展机理未必遵循经典压痕断裂力学理论。有鉴于此,重点从陶瓷材料显微结构层面开展碳化硅陶瓷磨削损伤形成机理研究,采用单颗金刚石磨粒轴向进给磨削试验方法,借助聚焦离子束、透射电镜等设备,分析碳化硅陶瓷磨削损伤特点,发现穿晶裂纹具有显著择优取向性,晶界对裂纹萌生具有显著诱导作用、对裂纹扩展具有显著阻碍作用;提出了SiC陶瓷磨削亚表面晶界裂纹系统,揭示了位错在晶界处塞积是晶界裂纹系统产生的机理;随磨削进行,SiC陶瓷磨削亚表面晶界裂纹系统分别经历位错激发、位错运动至晶界处堆积、晶界处微裂纹萌生、晶界处微裂纹扩展汇合形成宏观沿晶裂纹和穿晶裂纹、裂纹扩展至磨削表面形成破碎凹坑五个跨尺度演化过程;基于位错塞积理论建立了晶界裂纹系统一般性的断裂力学模型,解析裂纹萌生与扩展临界条件;建立了晶粒尺度单颗金刚石磨削多晶SiC陶瓷有限元仿真模型,验证了SiC陶瓷磨削亚表面晶界裂纹系统模型的准确性。
The previous studies on the crack damage formation mechanism of the brittle materials grinding are mainly based on the classical indentation fracture mechanics. However, due to the microstructural heterogeneity of ceramics, the typical cracks generated in the ground surface/subsurface of Si C ceramics are not in accordance with the median/radial cracks system produced in the indentation process, the indentation fracture mechanics may not be valid for the analysis of the crack initiation and propagation during grinding SiC ceramics. Hence, the present research mainly focuses on the crack damage formation mechanism of SiC ceramics grinding from the microstructure perspective. A single diamond grinding method with axial feeding was applied on sintered silicon carbide(SSiC) to explore the role of microstructure on the crack damage formation mechanism. A scanning electron microscope and a transmission electron microscope were used to examine the surface and subsurface morphologies of the grinding groove, respectively.It is found that the propagation of semi-trangranular cracks has preferred direction, and the grain boundaries have distinct induction on the crack initiation and evident obstruction on the crack propagation. The grain boundary crack system is proposed on the subsurface of the ground SSiC, which was caused by the dislocation pileups at grain boundaries. As grinding proceeds, the trans-scale evolution of the grain boundary crack system experiences five stages: dislocation activating, dislocation moving to grain boundary and piling up,microcrack initiating at grain boundary, microcracks propagating and merging into macro intergranular crack and transgranular crack at grain boundary, intergranular crack and transgranular crack propagating to ground surface forming fractured pit. Based on the dislocations pile-up theory, a general fracture mechanics model of the grain boundary cracks system was built, and the critical conditions of the cracks initiation and propagation were analyzed. Finally, an FE model of single diamond grinding polycrystalline SiC ceramics is built to verify the grain boundary cracks system model.
作者
戴剑博
苏宏华
王忠宾
丁文锋
傅玉灿
陈佳佳
DAI Jianbo;SU Honghua;WANG Zhongbin;DING Wenfeng;FU Yucan;CHEN Jiajia(College of Mechanical and Electrical Engineering,China University of Mining and Technology,Xuzhou 221008;Jiangsu Collaborative Innovation Center of Intelligent Mining Equipment,China University of Mining and Technology,Xuzhou 221008;College of Mechanical and Electronical Engineering,Nanjing University of Aeronautics and Astronautics,Nanjing 210016;College of Mechanical and Electronical Engineering,Nanjing Forestry University,Nanjing 210037)
出处
《机械工程学报》
EI
CAS
CSCD
北大核心
2022年第13期307-320,共14页
Journal of Mechanical Engineering
基金
江苏省基础研究计划(自然科学基金)(BK20210495)
中国博士后科学基金(2020M681761)
江苏高校优势学科建设工程(苏政办发[2018]87号)资助项目。
关键词
碳化硅陶瓷
亚表面裂纹损伤
显微结构
晶界裂纹系统
silicon carbide ceramics
subsurface crack damage
microstructure
grain boundaries cracks system
