Study On Mechanical Properties Of Silicon Carbide Ceramic By Numerical Simulation Considering The Micro Crack Damage

The damage and fracture process of brittle materials such as ceramics have always been a hot topic and a challenging problem for researchers. Silicon carbide ceramic is a typical brittle material with excellent mechanical, thermal and chemical properties, such as high flexural strength, excellent oxidation resistance and low coefficient of friction, and it has been widely used in machinery, microelectronics and other industries. Previously, the research on the mechanical properties and failure process of brittle materials was mostly based on the understanding of materials from the macro level, it was always assumed to be a heterogeneous ideal continuum material in the subsequent modeling and simulation. To some extent, this simplification can meet the needs of engineering practice, but it is difficult to investigate the crack initiation, propagation and penetration of brittle materials under the external load, and it is also difficult to clarify the damage and failure process from meso level to macro level. With the deepening of the study, the investigation of fracture process of brittle materials from the meso scale has become an unavoidable problem for scholars. Especially with the rapid development of computer technology, the numerical simulation method provides abundant research means to investigate of the crack initiation, propagation and penetration, and the device's macro fracture of brittle materials.In this paper, the effect of random micro crack damage on the mechanical properties of silicon carbide ceramic was studied based on the discrete element method. The main research contents are as follows:Firstly, the research established a center oblique crack model of silicon carbide ceramic by the discrete element method, and studied the influence of the center oblique crack on the mechanical properties of the specimen. It analyzed the changing of force chains in failure process of silicon carbide ceramic, and obtained the influence of different crack angles on the angle distribution of the force chain. At the same time, the effect of the pre-stress on the crack propagation, failure mode and mechanical properties were investigated.Secondly, this research extended the isometric collinear cracks model and the multiple random distribution cracks model from the center oblique crack model. The effects of crack angles and crack spacing of the isometric collinear cracks model on the mechanical properties of the sample were studied. This study established the crack density function of silicon carbide ceramic discrete element model. The influences of crack density on the failure mode of the specimen and the mechanical properties of uniaxial compression were studied. This research showed that the simulation results of the multiple random distribution cracks model are consistent well with the theoretical results of Mori-Tanaka method. By changing the distribution of the preset crack, the effects of different crack distribution on failure modes and mechanical properties of uniaxial compression were obtained, and the influence of pre-stress on the mechanical properties of the specimens with cracks was also studied.Finally, the crack system model was introduced into the cutting process model of silicon carbide ceramic, and the effects of pre-stress, cutting speed, and cutting depth on cutting process under different conditions of crack density were investigated.