Correlations Between <i>K</i>Ic and Charpy V-Notch Test Results in the Transition-Temperature Range

Charpy V-notch (CVN) impact-test results are used widely in various toughness specifications even though the energy absorption values cannot be related directly to structural design. Conversely, KIc, the plane-strain stress-intensity factor at onset of unstable crack growth, can be related to structural design, but KIc test results usually are not used in toughness specifications. To the designer, however, KIc values are more useful than CVN values. An investigation, therefore, was conducted to determine whether correlations could be developed between KIc and CVN test results in the transition-temperature range to assist both the materials engineer and the structural designer. The results showed that various correlations do exist between KIc and CVN test results in the transition-temperature range. Static KIc values were correlated with the energy absorptions determined with slow-bend fatigue-cracked CVN specimens, and dynamic KIc values were correlated with the energy absorptions determined with dynamic fatigue-cracked CVN specimens. Empirical correlations also were developed between the results of slow-bend KIc tests and the results of standard CVN impact tests for the transition-temperature region as well as the upper-shelf region. Furthermore, the results show that slow-bend and impact CVN data can be used to predict the effects of dynamic loading on KIc values. In general, the results of this investigation have shown that correlations between KIc and CVN test results do exist, and that these correlations can be used to estimate KIc values as well as the effect of loading rate on KIc from CVN test results.