Development of cleavage fracture toughness locus considering constraint effects

In this paper, the higher order terms in the crack tip stress fields are investigated macroscopically for more realistic assessment of structural material behaviors. For reactor pressure vessel material of A533B ferritic steel, effects of crack size and temperature have been evaluated using 3-point SENB specimens through a series of finite element analyses, tensile tests and fracture toughness tests. The T-stress, Q-parameter andq-parameter as well as theK andj-integral are calculated and mutual relationships are investigated also. Based on the evaluation, it has proven that the effect of crack size from standard length (a/W=0.53) to shallow length(a/W=0.11) is remarkable whilst the effect of temperature from - 20°C to-60°C is negligible. Finally, the cleavage fracture toughness loci as a function of the promising Q-parameter orq-parameter are developed using specific test results as well as finite element analysis results, which can be applicable for structural integrity evaluation considering con-straint effects.