ESSO試験片におけるぜい性き裂伝ぱ過程および停止時の応力拡大係数(<小特集>X線材料強度小特集)

概要

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The X-ray fractography was applied to the full thickness, ESSO specimens made of a 250 mm thick steel for nuclear reactor presssure vessels SA533B Cl. 1 to study the phenomena of brittle crack propagation and arrest. The stress intensity factor K_I^<dyn> obtained through the half value breadth of the X-ray diffraction intensity curve from the fracture surface increased strongly as the crack propagated except in the very early stage in which K_I^<dyn> decreased significantly. It had an upper limit around the half of the crack propagation length before the first arrest, decreased thereafter and then gradually increased with oscillations until the crack was finally arrested. While the crack propagated at a nearly constant velocity, K_I^<dyn> increased monotonically. When the crack velocity decreased sharply, the increase in K_I^<dyn> discontinued and oscillations started. The relation between the stress intensity factor at crack arrest K_I^<dyn>(Arrest) and temperature did not depend upon the testing method. The stress intensity factor at crack arrest K_<ca> which was obtained by the static analysis of the ESSO test tended to underestimate the crack arrest toughness.
1982-03-15