Small punch tests to estimate the mechanical properties of steels for steam power plant : II. Fracture toughness

Accurate measurements of the fracture appearance transition temperature and fracture toughness KIC are greatly desired for engineering in steam power plant, especially from the standpoint of life extension. The current toughness of materials at critical locations is a key characteristic necessary for the remaining life analysis. For this purpose, small punch test techniques using miniature-sized specimens have been investigated on header components. Linear relationships, obtained between mechanical characteristics determined from small punch tests and from Charpy tests, have been used to estimate the fracture appearance transition temperature. Energy based and fracture stress formulations have been applied to estimate the fracture toughness in the upper- and lower-shelf regimes on a class of low alloy steels.