DEM Simulation And Experimental Investigation Of Ceramics Cracks In Machining Process

For their excellent mechanical and chemical behaviors, ceramics have been very widely used in modern industry. With the increasing requirements of the machining precision, the precision and ultra-precision machining of ceramics have been developed very fast, especially the research focusing on the machining mechanism has been becoming a hot issue. Reducing the cracks damage induced during the machining process is a difficult but key important project. There has been no research method can simulate and analyze the cracks initiation and propagation during the machining process. This thesis firstly applied the Discrete Element Method (DEM) into the research area of the ceramics precision machining through founding the Bonded-Particle Model (BPM) of ceramics and using several simulation tests to calibrate the model. Based on the BPM, indentations of SiC ceramic under different conditions have been simulated and the effects of different indentation conditions on the cracks propagation have been analyzed as well. The DEM simulations of cutting process of SiC ceramics explained the existence of inelastic area during the machining process successfully; a useful method was proposed to analyze the cracks and inelastic area; the cracks number and depth, the formation mechanism of the debris and the effects of the cutting tool's rake angle under different cutting conditions were discussed in detail. The later part of this thesis introduced the three dimensions DEM simulations of the alumina scratch tests and compared the simulation results with other researchers' work. At last, a scratch experiment of alumina was done to investigate the surface and subsurface cracks and to verify the DEM simulation results. It is the most important result that using DEM to simulate the cracks in machining process is prosperous and this thesis provides a new method for researching the ceramics machining technology.