Fracture Strength of Silicon Nitride under Biaxial Stresses

Fracture strength of silicon nitride was studied under biaxial stress states. Multiaxial fracture distribution functions by several fracture criteria were employed to analyze tension/torsion, compression/torsion test. The most appropriate criterion was Shetty's empirical equation (parameter c=1.4) and the modefied G criterion (parameter β=0.9). The fracture strength of a disk for a spin test was estimated by the equivalent normal stress of Shetty's empirical equation and the modified G criterion. Good agreement between the experimental data and the estimated values were obtained.