Specimen-size dependency and modelling of energy evolution during high-temperature low-cycle fatigue of pressure vessel steel

High-temperature low-cycle fatigue testing was conducted on pressure vessel steel using standard and miniature specimen sizes and the fatigue toughness required for macrocrack propagation was investigated. A definite specimen-size dependency was observed for both the threshold cumulative plastic strain energy and cycles required for macrocrack propagation, which was explained to be influenced by geometric conditions. An analytical modelling prediction was developed that accounted for specimen-size dependency and was successfully applied to predict fatigue toughness to macrocrack propagation.

► Fatigue toughness to macrocrack propagation studied through different specimen sizes.
► Specimen-size dependency found for cumulative plastic strain energy parameter.
► Size dependency due to geometric differences on plastic strain energy absorbed by material and defects.
► Modelling prediction removing size dependency developed to predict fatigue toughness.