J_iの寸法効果とJ_<IC>試験条件に関する研究

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In this paper, we investigated effects which thickness and width of the test specimen give on J_i, J at the initiation of a stable crack growth. Also, taking into account the test results, we estimated quantitatively the size-limitations of J_<IC> test by the finite element method. We obtained conclusions as follows. (1) From the experimental results about the size-effects on J_i ; i) a) Effect of width (or ligament length) of the test specimen on J_i are proved to be contrary to that of thickness. b) CTODi, Crack Opening Displacement (CTOD) at the initiation of the stable crack growth, is proved to be independent of thickness of the test specimen. And the dependence of CTODi on width (or ligament length) is caused by an en-or of the formula to calculate CTOD. Because, according to CTOD difined and described in this paper, CTODi is regarded as a material constant. ii) Its' found that temperature-dependent curves of J_c J on the initiation of the cleavage fracture, and J_i are shift extremly by the size-effects. Therefore, we should take into account that J_<IC< which is estimated from small test specimens is occasionally not appropriate. (2) From the results of finite element method i) The existing size-limitations of J_<IC> test which are described as B, b ⪈ 25J_<IC>/_<flow> are invalid, so we cannot estimate the true J_<IC> which is independent of size of the test specimen. The invalidness is caused by the reason why J_i can agree with the true J_<IC> owing to the mixed effects of thickness and width of the test specimen. ii) The size-limitations of J_<IC> test which are taken into account material characteristics are formulized of the plane-strain condition. iii) Its' found that we can make use of the size-limitations of this paper as a sufficiently condition when using the standard test specimen which thickness is equal to the width.
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J_iの寸法効果とJ_<IC>試験条件に関する研究

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