Si₃N₄の繰返し混合モード荷重下でのき裂伝ぱ挙動

抄録

Fracture behavior of Si₃N₄ ceramic was investigated under cyclic mode I/mode II mixed-mode loading in various environments. The crack propagation rate was higher than that for cyclic mode I loading, and it was higher in water than in nitrogen gas. The fretting and hydration reaction seemed more active than those for cyclic mode I loading, and therfore even if the stress shielding effects by particle bridging and wedging exist, those effects were easily decreased, and the effective stress intensity factor range ΔK_tip was increased. When the debris was accumlated by the fretting between the crack surfaces, the substantial effective stress intensity factor for mode II was increased. Therefore, it was suggested that in the case that K_I was decreased by the particle bridging and K_II was increased by the fretting the fracture morphology became transgranular fracture rather than interglanular fracture.