Studies on A533B-1 ferritic pressure vessel steel have indicated that both strength under-matching and overmatching of materials modifies crack growth resistance curves compared with the relevant base-line materials. If the analysis procedures for homogenous materials are applied to test results then strength over-matching causes an apparent elevation of the J-R curve, and under-matching a lowering of the J-R curve. These differences in observed behaviour are reduced if the appropriate strength mis-match plastic eta factors are used in the determination of the experimental J-integral values.
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