摘要
Many experimental investigations have previously been performed and recentlydone on different shipbuilding structural steels where the specimens size and crack depth/specimenwidth (a/W) were varied. A series of interesting results have been gained. It is worthwhile to havea review on the effect of a/W ratio on fracture toughness, and further theoretical analysis isnecessary. In this paper, experimental work in elastic-plastic fracture mechanics (EPFM) wasdiscussed. Tests had been carried out on 10 kinds of strength steels. Results showed that J_i andδ_i. values increased with decreasing a/W when a/W【0.3 for three-point bend specimens and thatshallow crack specimens which have less constrained flow field give markedly higher values oftoughness than deeply notched specimens. However, for a/W】0.3, the toughness was found to beindependent of a/W. Slip line field analysis shows that for shallow cracks, the hydrostatic stressis lower than that from standard deeply cracked bend specimen which develops a high level of cracktip constraint, provides a lower bound estimate of toughness, and will ensure an unduly conservativeapproach when applied to structure defects especially if initiation values of COD / J-integral areused.
