Abstract
In order to resolve reported discrepancies between the results of four-point bend tests and uniaxial constant load tests on UNS S31603 in sour environments, a series of systematic tests has been conducted to compare the two test methodologies under carefully controlled conditions. It was demonstrated conclusively that tests performed in uniaxial tension at constant load are inherently more severe than tests performed in constant displacement four-point bending due to the presence of low-temperature creep in the former. The enhanced susceptibility to stress corrosion cracking is attributed to the presence of additional tensile plastic strain in specimens that have undergone low-temperature creep. Tests performed in uniaxial tension were also found to be more severe than those performed in four-point bend even when dynamic strain was eliminated by performing them at constant displacement. A key observation is that no load relaxation due to low-temperature creep occurs during the four-point test. The results emphasize the need to take into consideration factors such as the level of tensile plastic strain in service when selecting the appropriate test method for a given application.
