Strain Limit of Pressure Vessel Steels

To prevent from the local failure of pressure vessels due to excessive plastic deformation,the strain limit of pressure vessel steels was studied.The measurement methods and analysis approaches of the ductile fracture strains were studied.Based on tensile tests of notched bar specimens,the relationship between stress triaxiality factor and fracture strain was established for three typical Chinese pressure vessel steels including 16MnR,Q235 and 0Cr18Ni9.The test results were compared with the strain limit condition in ASME Ⅷ-2 2007.It is shown that the strain limit criterion of ASME is suitable for carbon steels but not suitable for austenitic stainless steels in Chinese pressure vessel steels.To improve the calculation accuracy for fracture strain of materials and to establish the strain limit condition for Chinese pressure vessel steels,a lot of further studies on testing and analysis are expected.