Brittle Fracture Analysis of Porous Ceramics Based on Initiation of Micro Damages
Tomoyuki FUJII, Yoshiaki AKINIWA and Takafumi AMATA
Abstract:Numerical simulation method for analyzing fracture behavior of porous ceramics is developed on a basis of initiation of micro-cracks. The deformation and fracture behavior are numerically simulated under four-point bending. A mixed mean stress model is adopted as a condition of the initiation and propagation of micro-cracks. Analytical models are made of an aggregation of circular grains whose are average size is 150ƒÊm. The micro-cracks are located in a bond of each grain. In a stress - strain relationship, as a notch depth and porosity increase, the stress-strain curve becomes nonlinear. The micro-cracks initiate near large pores and a main crack propagates intricately. When the notch depth is small, the fracture occurs not from the notch root. Size of a non-damaging defect can be evaluated by the proposed method. R - curve calculated is independent of the notch depth. These results calculated agree very well with experimental results. Key Words:Numerical analysis, Porous ceramics, Brittle materials, Fracture, Micro-crack, R -curve, Nonlinearity, Stress intensity factor