各種人工微小欠陥の相互干渉効果が疲労限界に及ぼす影響の√<area>パラメータモデルによる評価

概要

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The fatigue limit of metals containing various small defects can be evaluated by the √<area> parameter model.The model is constructed with two parameters:a geometrical parameter (√<area>) and Vickers hardness Hv of marix.In order to demonstrate the validity of the √<area> parameter model,it is experimentally shown that the fatigue limits of hard steel specimens (Hv=510) having an initial crack,a two-hole defect connected with fatigue crack and one hole defact with the same value of √<area> are approximately identical in spite of their bug deffernce in stress concentration factor.In the next step,the method of evaluating the mutual interaction effect of small defacts is proposed on the basis if the fatigue test results and three-dimensional numerical stress analysis of crack interaction.Finally,the method is aplied to evaluate the mutual interaction effect of spheroidal graphite in a nodular cast iron.The lower bound of scatter in fatigue limit (σ<wl>) is obtained by using the fatigue limit perdiction equation with the expected maximum size of graphite (√<area>_<max>).The expected value of √<area>_<max> in a large number of specimens can be estimated by estimated by statistics of extreme values.In order to redict an accurate σ<wl>,the value of √<area>_<max> must be estimated by considering the mutual interaction effct of spheroidal grahite.Otherwise,the prediction becomes unconservative.
社団法人日本材料学会の論文
1993-10-15