WANG Lizhi, MA Dejun, SUN Liang, SHI Xinzheng, GAO Tengteng

(Academy of Armored Force Engineering, Beijing 100072, China)

Abstract: According to the indentation crack parameters and loading-unloading curves obtained by Berkovich indentation test on silicon nitride, the elastic modulus and yield strength of silicon nitride are calculated by finite element method, and then the crack tip stress intensity factor (KI) is calculated by using virtual crack closure technique(VCCT), finally the fracture toughness parameters satisfying thecriterion of equal KI are obtained. The results show that the errors range between the calculated results and standard fracture toughness value of silicon nitride is from -6.58% to -3.74%.So the test results of Berkovich indentation fracture toughness model are relatively accurate and reliable,and the validity of VCCT is verified. This work can provide technical means for the quality evaluation and parameter optimization of ceramic materials.

Key words: VCCT; Berkovich indenter; ceramic materials; fracture toughness; finite element analysis