セラミックスの疲労寿命に及ぼす保証試験の影響

概要

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Cyclic fatigue behavior of silicon nitride was investigated at 800℃ in air, and proof tests as a method of improving reliability of fatigue life were carried out at room temperature. Fatigue life distributions for σ_<max>=833 MPa were compared before and after proof testing on a Weibull plot. The truncated fatigue life distribution after proof testing did not coincide with the theoretical curve F_p (N_p), and some fatigue life data after proof testing were shorter than the theoretical minimum life N_<pmin>. F_p (N_p) and N_<pmin> were predicted when no slow crack growth occurred during proof testing. A statistical method was developed to predict actual truncated fatigue life distribution F_p'(N_f) and minimum life N_<fmin> after proof testing. The predicted curve was consistent with the experimental life data, and N_<fmin>≈0.27N_<pmin>. From the minimum life N_<fmin> predicted by our method, the influence of proof testing on fatigue life was estimated in terms of the degradation of truncation strength due to slow crack growth during proof testing. It was found that the truncation strength was ≈0.94σ_p, where σ_p is proof stress.
社団法人日本機械学会の論文
1994-03-25