Comparison of some indirect measures of crack arrest

Indirect measures determined in tests like drop weight NDT have been applied for evaluating the crack arrest fracture toughness of steels besides the KIa measured in standard plain-strain crack arrest tests. A correlation is proposed here between the transition temperatures of a crack arrest force measured on normal Charpy specimens in instrumented impact tests and a KIa level measured on full-size specimens. The 4 kN crack arrest force, determined from the crack arrest force and temperature dependence of various steels, was shown to give a good correlation in respect to the KIa = 100 MPa√m. The correlation was validated for some steels on which the crack initiation and crack arrest fracture toughness vs. temperature values differed sufficiently from each other. The transition temperatures for the 4 kN crack arrest force were also found to correlate well with the NDT temperatures measured by drop weight tests on different steels, but only a poor correlation was found between the 4 kN crack arrest force and the 41 J absorbed energy transition temperatures measured by instrumented Charpy tests, indicating the different nature of these tests. The neutron fluence dependence of the 4 kN transition temperature was determined for one Cr-Mo-V reactor pressure vessel steel and an estimate of the fluence dependence of KIa was obtained. It was also shown that the same master curve definition derived for the crack initiation fracture toughness KJc is applicable also for the crack arrest fracture toughness KIa