制御圧延材のセパレーションと破壊じん性

概要

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Facture mechanics tests have been made on high strength, controlled rolled steel in a wide temperature range. Fracture toughness, fatigue fracture toughness and separation intiation properties have been investigated in detail by using compact tension and three points bending specimens. The main conclusions obtained are as follows: (1) A new separation index I,e, separation depth index (S. D. I), was proposed, and this index was shown to be a good parameter because of its sensitivity to plastic constraint and temperature. (2) The test material was found to indicate singular ductile-brittle transition behaviour. The J integral at the transition temperature was about 0.02 Mj/m^2, which is about two figures smaller then that of ordinary weldable structural steel. (3) The singular ductile-brittle transition behaviour of the controlled rolled steel is caused by the rapid decrease of plastic constraint ahead of the notch which results from the initiation of separation.
1985-04-15