基于尖角效应的工程陶瓷边缘破碎研究

Study of engineering ceramic edge chipping based on corner effect

表面微裂纹与边缘碎裂是工程陶瓷磨削加工技术研究的热点。推导了陶瓷台阶过渡圆角的应力集中数值分析模型,并采用有限元仿真结果表明:表面凸台阶高度H越大或过渡圆角R半径越小,圆角根部的最大应力集中系数越高,其边缘越容易发生脆性破碎。开展了基于尖角效应的陶瓷单晶压痕边缘破碎实验研究了凹槽深度、凹槽根部的过渡圆角半径对Si3N4陶瓷的脆性断裂力值影响关系,其结果与应力集中数值分析模型和有限元仿真分析相一致。此外,随着压力加载速度越快,Si3N4陶瓷的脆性断裂力值会变小,且其力与位移曲线形状发生本质变化。对陶瓷边缘破碎形貌分析,磨削缺陷会导致应力集中,使过渡圆角上某区域成为最为薄弱裂纹源,并适用动态损伤演化方法描述边缘破碎的整个过程。

Surface micro - crack and edge broken is the hot spot for grinding process of engineering ceramics. It de- duces the stress concentration numerical analysis model of step transition fillet on ceramic sur- face. Combined with results of the finite element simulation, it proves that the maximum stress concen- tration coefficient on fillet root is higher when the convex step height H more or fillet radius R smaller, which causes edge of ceramic is easy to be fracture. The single crystal indentation of edge chipping based on comer effect, finds that fillet radius and depth of groove is how to affect the brittle fracture force of Si3N4 ceramic, the result of experiment is the same to the stress concentration analysis model and the fi- nite element simulation analysis. What is more, the force of ceramic brittle broken is smaller and the curve figure of force and displacement will change when the increasing loading speed of pressure makes the impact force increases. Microscopic observation of edge chipping parts prove that grinding defects lead to stress concentration, which make the fillet region become the most weak crack source. It applies the dynamic damage evolution method to describe the whole process of edge chipping.