A review of the effect of a/W ratio on fracture toughness (Ⅰ)—experimental investigation in EPFM |
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摘 要: |
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关 键 词: | 断裂韧度 COD 浅裂纹 a/W率 EPFM |
收稿时间: | 8 December 2004 |
A review of the effect of <Emphasis Type="Italic">a/W</Emphasis> ratio on fracture toughness (I) —Experimental investigation in EPFM |
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Authors: | Li Qing-fen Jin Guo Wang Yan-bo |
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Institution: | (1) School of Mechanical and Electrical Engineering, Harbin Engineering University, 150001 Harbin, China |
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Abstract: | Many experimental investigations have previously been performed and recently done on different shipbuilding structural steels
where the specimens size and crack depth/specimen width (a/W) were varied. A series of interesting results have been gained. It is worthwhile to have a review on the effect of a/W ratio on fracture toughness, and further theoretical analysis is necessary. In this paper, experimental work in elasticplastic
fracture mechanics (EPFM) was discussed. Tests had been carried out on 10 kinds of strength steels. Results showed that J
i
and δ1 values increased with decreasing a/W when a/W<0.3 for three-point bend specimens and that shallow crack specimens which have less constrained flow field give markedly
higher values of toughness than deeply notched specimens. However, for a/W>0.3, the toughness was found to be independent of a/W. Slip line field analysis shows that for shallow cracks, the hydrostatic stress is lower than that from standard deeply cracked
bend specimen which develops a high level of crack tip constraint, provides a lower bound estimate of toughness, and will
ensure an unduly conservative approach when applied to structure defects especially if initiation values of COD/J-integral are used. |
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Keywords: | fracture toughness COD J-integral a/W ratio shallow crack |
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