Discrete Modeling Of The Propagation Characteristics Of Cracks In Brittle Materials

Brittle materials are widely used in various industries due to their outstanding properties such as high fracture strength and hardness and good heat resistance.However,cracks which might lead to the catastrophic failure of bulk material can be formed inside brittle materials under very small strain condition.Thus,for the purposes of better design and optimization of the microstructure of brittle material so as to improve its fracture toughness,it is critical to get a thoroughly understanding of the initiation and propagation behavior of crack.In this work,the propagation behavior of crack inside brittle material was investigated from the component grain scale by performing Discrete Element Method(DEM)simulations.The contact force models of DEM adopted in this work were first introduced.The correctness of DEM simulation was then evaluated though modelling the mechanical responses of partially sintered ceramics.The predicted Young's modulus and fracture strength were then compared with experimental results reported in literature and quantitative agreements were achieved,demonstrating that the developed DEM simulation framework can present quantitatively correct results.The interactions between crack and pore were discussed.The simulation results showed that,depending on its spatial arrangement,pore could either promote or postpone the propagation of the pre-set crack.Comparing with sample without pore,proper arrangement of pore in front of the pre-set crack could notably increase the fracture strain.Such results hint that the fracture toughness of brittle material could be improved by optimizing the microstructure of the material.The propagation behavior of pre-set crack inside ceramics under tensile loading condition was investigated.The simulation results indicated that depending on the loading velocity,the propagation of crack could be in straight,branching or fishbone type.Qualitatively,such results are consistent with experimental observations and peridynamic simulation results reported in the literature.Detailed analyses suggested that the instability of crack propagation was closely related to the accumulation of energy in the crack-tip region rather than the propagation velocity of crack or the grain velocity/stress distribution around the crack tip.