ORAL REFERENCE: 040OR EXPERIMENTAL STUDY ON THE EFFECT OF PLASTIC CONSTRAINT ON DUCTIAL TEARING

The effect of plastic constraint on the initiation of ductile tears in four different alloy steels has been experimentally studied by measuring the crack opening displacement and J- integral at initiation in three-point bend specimens with deep and shallow notches in this paper. Experimental results of seven groups of different strength alloy steels show that bothì and Jì values of ductile tear from the shallow crack specimens which have less constraint flow field are significantly higher than deeply notched specimens. Slip- line- field analysis shows that, for shallow crack, 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, will ensure an unduly conservative approach when applied to structural defects, especially if initiation values of COD and J-integral are used