直流竜位差法による疲労き裂伝ぱ速度の統計的実験と確率モデルの検討(<小特集>信頼性工学)

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By using the fatigue crack growth test system developed in the previous study, Statistical data of fatigue crack growth rate da/dN in 2024-T3 aluminum alloy were obtained. Eighteen specimens were tested. In the test system used, the crack length was measured using the DC electrical potential method and preciseload control was madeusingamicro computer. Thus, Scatter intesting conditiorlS and laborneeded were decreased as compared with the previous test by the presetau thorsin which the crack length was measure dusing atravell gmicroscope. From an alyses of the experimental data, the coefficient of variation η<ΔN>, of the number of stresscycles for crack growth from a givenvalue of a to a+Δa (△a=0.1mm) was found to benearly constant in dependent of a. This implies that m in Paris' law da/dN=C (△K)^m canberegarded tobedeterministicin the present data. Then, the composite variability mode lasas to chasticmodel of d a/dN proposed previously by the presentauthors was examined using the present data. In this model, Cistreated as arand on variable in volving the inter-specimen variability and the intra-Specimen variability, where as m is treated as deterministic. From comparison of them odel with the data, the inter-Specime Variability was found to be considerably smaller in the present data than in the previous data. This seems to be due to the decrease of scatter in testing conditions. Furthermore, the correlation distanceδof the intra-specimen variability of C was found much smaller in the present data than in the previous data. The value of δestimated from the present data was of the order of a grain size. This suggest that the intra speciman variability of C occurs from grain to grain.
社団法人日本材料学会の論文
1991-03-15

直流竜位差法による疲労き裂伝ぱ速度の統計的実験と確率モデルの検討(<小特集>信頼性工学)

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