The Studies On Evaluation Of Ground Surface Mechanical Damage Of Ceramic And Grinding Based On Crack Damage Control

In a grinding process, ceramics generate an intense grindingforce and are prone to engender mechanical damages because ofhis high hardness and brittleness. It is central content of thedissertation how to evaluate mechanical damage that ceramicengender in a grinding process and to set up a grinding modelbased on damage control. The dissertation consists of seven chapters. In the firstchapter, an introduction is given about advanced ceramics,precision grinding technique and material remove mechanism ofceramic grinding. Ceramic grinding experiments and data processmethods are introduced in the second chapter. From the third tothe fifth chapter, surface mocroirregularities damage, surfaceintegrality damage and surface/sub-surface crack damage ofceramic test pieces are evaluated and a new index system isbrought forward. A study on grinding model based onsurface/sub-surface crack damage control is made in the sixthchapter. The seventh chapter is summarization of thedissertation. The main conclusions and work are as follow:1. Based on the study of ground test pieces, definitions on surface mocroirregularities degradation index----surface factor of stress concentration Da , surface integrality degradation index----surface fragmentation area ratio Ds and surface/sub-surface crack degradation index----depth of crack damage layer Dc are made and a new mechanical damage evaluation system is set up in the dissertation. II天津大学硕士学位论文2. In experiment, a few of experiment data processing methods and damage measure methods are used. For example,the grinding force signal processing method using spectrum analyzing wave filtering, the calculation method of surface fragmentation area using computer image processing and the measure method of ceramic crack damage using polishing inclined section plane.3. By analysis of stress field, configuration of single-point grain stress field, which is made up of elastic component and residual component of the single-point grain stress field, is opened out. The residual component of the single-point grain stress field is remained in ceramic and becomes a component of the surface residual stress field of ceramic piece. Quantum of the residual component is computed.4. By analysis on crack damage mechanism of ceramic, prediction model and grinding model based on surface/sub-surface cracks damage control are brought forward. A machining experiment of Si3N4 is made using prediction model and grinding model based on surface/sub-surface cracks damage control.