Fracture Toughness in the Transition Regime for A533B-1 Steel: The Effect of Specimen Sidegrooving

Abstract

This report describes the results of an experimental test program to investigate the influence of specimen sidegrooving on the cleavage fracture toughness of A533B-1 steel. The work represents a companion study to a previous investigation into the effects of specimen size on the cleavage fracture toughness of the same A533B-1 plate material. Compact specimens were prepared in two sizes (12.5 and 25 mm thick) in the 0, 20 or 50% sidegrooved conditions. A total of 160 tests were performed in the transition regime with a minimum of 29 specimens being tested for each specimen size and depth of sidegrooving. Variations in cleavage fracture toughness were characterized using exponential curve fits to data across a temperature range and arithmetic mean values calculated at discrete test temperatures. The results show that sidegrooving has the effect of decreasing the mean level of cleavage toughness in the upper transition regime (high mean K levels) and increasing it in the lower transition regime (low mean K levels). These results are explained in terms of the competing effects of increased specimen constraint and reduced net thickness in sidegrooved specimens. Reduced resistance to ductile tearing in sidegrooved specimens is also shown to be a contributing factor to decreased toughness levels in the upper transition regime.