Simulation And Experimental Research On The Failure Mechanism Of Polycrystalline Diamond Micro End Mills

With the continuous development of material science, a large number of newmaterials are widely used in biomedical, aerospace, drilling, etc. Application of thosenew materials with high strength and high hardness promote the development ofpolycrystalline diamond cutting tool materials. Compared with the traditional cuttingtools, machining precision and machining quality will be worse when fracture andwear of PCD micro end mills occurred during the process of machining. In order toprovide certain theoretical support in improving the micro end mills design and thequality of tool machining, this dissertation is research on the failure mechanism on themicro-and macro-scale. The main contents of paper are shown as follows.Using two-dimensional discrete dislocation dynamics and finite element couplingmethod, the two-dimensional micro/nano indentation model was established by thefinite element software to investigate the dislocation distribution under the differentsituation such as different particle size, indenter position and the volume of diamondparticles. The effect of crack length to the crack tip stress intensity factor was studiedand the cloud picture of dislocation distribution of crack tip was obtained. At last, thepropagation of crack was observed by the method of XFEM.The three-dimensional milling model of PCD was built and the dynamic millingprocess was obtained to investigate mechanical characteristics and force distribution;Based on the wear model of Archard, the wear characteristics were researched underdifferent milling conditions, using the maximum wear depth of tool surface to measuretool wear level.The particle size effect of polycrystalline diamond was studied by the nanoindentation experiment. The morphology of indentation was analyzed under thedifferent granularity of PCD and different indentation hardness tester’s pressure; Thewear and fracture were studied by the milling experiment. The correctness of thesimulation model was preliminary verified through the experiment.