SEDL / STP / STP924-EB / STP23216S

Critical Behavior of Nonpropagating Crack in Steel

Kunio, T
Professor, associate professor, and graduate student, Keio University, Yokohama,

Yamada, K
Professor, associate professor, and graduate student, Keio University, Yokohama,

Kim, MG
Professor, associate professor, and graduate student, Keio University, Yokohama,

Pages: 10    Published: Jan 1988

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Abstract

A study has been made on the critical condition for the nonpropagation of a crack in Stage II growth at the endurance limit of pearlitic steel with special emphasis on the closure behavior of the crack.

It is found from fatigue experiments and measurements of crack opening displacement that a tip of the nonpropagating crack (NPC) is closed at the stress level of the endurance limit. It is also found that the tip of the NPC opens again under the original endurance limit when the NPC is vacuum-annealed. Therefore, it turns out that the crack which has propagated in Stage II growth stops its propagation by the closure effect resulting mainly from the local residual compressive stress at the crack tip.

Further experimental evidence implies that not only the crack closure due to residual compressive stress (plasticity induced), but also the closure associated with the oxidation during the reduced crack propagation, is responsible for the existence of NPC at the endurance limit.