匍匐限の迅速測定法に就て (I)

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Being judged from literatures and the author's experience, the elongation ε is represented by the experimental formula ε=cl^n in the first stage of creep which continues at least 1000 hrs. at 500℃ or below, and in the second stage the velocity of creep is approximately constant. So the velocity at the end of the first stage, approximately equal to the velocity in the second stage, is calculated from the formu'a ν′=nε′/t′, where t′ is the time interval of the first stage and ε′ the total elongation of creep of the first stage ; and ε′ is obtained by the logε-logt straight line extrapolated through tl e first stage. It was pointed out that the creep strength is more precisely inferred from the velocity ν′ calculated as above than from the mean velocity of the short duration ν^^-, for ν′ varies considerably even if ν^^- is constant, according to the variation of n with the material, the testing temperature or the stress applied. In applying the present discussion, the author investigated the effect of various heat treatments on Cr-Mo steel by the extrapolating method abovementioned, showing that the normalized and tempered specimen has greater creep strength than the quenched and tempered one.
社団法人日本鉄鋼協会の論文
1943-04-25