セラミックスの繰返し疲労強度の簡便評価法

抄録

A simple method to evaluate cyclic fatigue strength in ceramics was proposed using load range, ΔP-increasing procedure and applied for silicon nitride. The proposed method enabled to obtain statistical property of cyclic fatigue strength by much less number of specimens compared to that required in the conventional procedure of statistical fatigue tests. The ΔP-increasing condition was expressed by initial value of maximum stress, σ_{max, 1,} and increasing rate of maximum stress, dσ_max/dN. These parameters influenced the maximum stress at failure, σ_{max, f}, which could be approximated by two-parameter Weibull distribution. P-S-N curve was estimated by two Weibull distributions under different ΔP-increasing conditions based on the assumption of crack growth law and of linear cumulative damage law. The estimated P-S-N curves were independent of the assumptions and agreed with the experimental data obtained under ΔP-constant condition at the higher stress level, while it was conservative under lower stress level.