Multiaxial Creep Deformation and Prediction of Residual Creep Life Time for Heat-Resistant Ferritic Steel

摘要

Ductile materials often exhibit brittle manner under some multiaxial stress fields. However, testing apparatuses, procedures and specimens for multiaxial stress tests seem to be much more complicated comparing with those for uniaxial ones. Circumferentially notched bars show multiaxiality of stress in the vicinity of the notch root. A series of creep tests for a heat-resistant ferritic steel, 2.25Cr-1Mo employed as a ductile material were conducted to investigate the transition from ductile fractures to brittle ones for notched specimens. This transition is shown at longer creep lives. A unique and simple technique to predict the residual creep life time of notched specimens is proposed; When the ductility of materials at fracture keeps constant, only a measurement of deformation rate at a time interval can help to estimate the residual creep life time.