EFFECT OF FLAW DIMENSIONS ON DUCTILE FRACTURE BEHAVIOR OF NON-ALIGNED MULTIPLE FLAWS IN A PLATE

The fitness-for-service codes require the characterization of nonaligned multiple flaws for flaw evaluation, which is performed using a flaw proximity rule. Worldwide, almost all such codes provide their own proximity rule, often with unclear technical bases of the application of proximity rule to ductile or fully plastic fracture. In particular, the effect of flaw dimensions of multiple surface flaws on fully plastic fracture of non-aligned multiple flaws had not been clear. To clarify the effect of the difference of part through-wall and through-wall flaws on the behavior of fully plastic fracture, the fracture tests of flat plate specimens with non-aligned multiple part through-wall flaws were conducted. When the flaw depth a was shallow with 0.4 in ratio of a to thickness t, the maximum load P-max occurred at penetration of multiple flaws and the effect of vertical distance of non-aligned multiple flaws H on P-max was not so significant. However, when flaw depth was deep with 0.8 in a/t, P-max occurred after penetration of flaws and the effect of H on P-max could be seen clearly. It was judged that the through-wall flaw tests were appropriate for discussion of the effect of H on Pmax and the alignment rule Of multiple flaws. In addition, in order to clarify the appropriate length parameter to estimate Pmax of test specimens with dissimilar non-aligned through-wall multiple flaws, the fracture tests of plate specimens were also conducted. The effect of different flaw length on Pmax was discussed with maximum, minimum and averages of dissimilar non-aligned multiple flaw lengths. Experimental results showed that the maximum length would be an appropriate length parameter to estimate P-max, when the non-aligned multiple through-wall flaws were dissimilar.