7-3黄銅のアンモニアふん囲気中での応力腐食割れ過程中の表面応力変化およびき裂の成長挙動

概要

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Thin plate specimens of annealed 7-3 brass were subjected to gaseous ammonia under the loading conditions of constant displacement of tension, and constant of bending and equi-biaxial bending. The followings are the summary of the results obtained : (1) The time to crack nucleation, defined as the time when the applied stress fell down 3% of the initial value, was found to become shorter in the order of equi-biaxial bending, tension, and bending tests. The ratio of crack growth period to total life was 0.35 in the case of tension and 0.20〜0.24 in the case of bending. In the bending test under the stress level of 4 kg/mm^2, the specimen did not fracture although cracks were nucleated. (2) The surface stress measured by X-rays was found to decrease markedly with the nucleation of plural cracks. At the time ratio t/t_f of 0.7, the mean span between adjacent cracks became nearly equal to the mean crack length and the stress on the specimen surface vanished. X-ray measurement of the surface stress was proposed in the present study to be a possible non-destructive method for monitoring the progress of damage due to stress corrosion cracking.
1977-03-15