Finite element analysis of uniaxial and multiaxial state of stress on creep rupture behaviour of 2.25Cr-1Mo steel

Effect of multiaxial state of stress on creep rupture behaviour of 2.25Cr-1Mo steel has been investigated. Multiaxial state of stress during creep test has been introduced by incorporating two different circumferential U-notches in the uniaxial creep specimen. Creep tests on both plain and notched specimens were carried out at 873 K over a stress range of 90-210 MPa. The creep rupture life of the material was found to increase in presence of the notch with the consequent decrease in creep rupture ductility. The increase in rupture life was found to be more for relatively sharper notch. Finite element analysis coupled with continuum damage mechanics was carried out to understand the creep damage evolution during uniaxial and multiaxial creep exposures. The predicted uniaxial creep deformation and rupture life of the material were in good agreement with the experimental results. The creep rupture life of the notched specimen has been predicted and was found to be controlled predominantly by von-Mises stress. The creep damage in this steel under multiaxial state of stress was predominantly in the form of microstructural degradation with some evidences of intergranular creep cavitation especially at lower stresses.