COD仮説による脆性破壊発生特性の研究

概要

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The effects of rype of loading (bending and tensile), notch acuity and specimen size on critical COD value defined as a criterion for brittle crack initiation are studied experimentally and discussed based on Dugdale-Barenblatt model.The followings are obtained conclusively : (1) Critical COD value is independent of type of loading, provided that material used and test temperature are the same. (2) Notch acuity has a certain effect on critical COD. When notch radius is less than 0.1mm, however, the effect is so slight that it is practically sufficient to use a machine notched specimen instead of fatigue cracked one.(3) Critical COD value is independent of specimen size. Consequently, with Dugdale-Barenblatt model, fracture stress of large specimen can be predicted from COD test on small specimen. It is confirmed that measured and predicted fracture stresses almost coincide.(4) Judging from above test results, COD hypothesis is an excellent fracture criterion under the large scale yielding condition.