Small fatigue crack propagation in Si3N 4 at high temperature
Miyashita Yukio; Zainuddin Bin Sajuri; Zhu Shijie; Mutoh Yoshiharu
Abstract:Behaviors of fatigue crack propagation in Si3N 4 at 1300 deg. in air were investigated. The results of fatigue tests showed that a cyclic fatigue crack initiated from a precrack introduced by the indentation method when the precrack was above 150mm in length, but from inherent flaws when the length of precrack was below 150mm. The fatigue process at 1300 deg. was predominantly time dependent in the present testing condition. The crack growth rate for short crack was higher than that for long through thickness crack. Difference of crack growth behavior between short and long cracks will certainly result from difference in stress shielding effect due to bridging. Key Words:cyclic fatigue, small crack, crack propagation, high temperature, silicon nitride