THEORETICAL-MODEL OF CREEP FRACTURE UNDER TRIAXIAL STATE OF STRESS

Application of a theoretical model of creep damage and creep rupture of metals is presented in this paper. The constitutive equations derived in this model account for the stiffness and strength reduction of the material due to damage growth and make it possible to determine the rupture time for a multi-axial state of stress. The theoretical predictions were compared with the experimental results obtained for tri-axially loaded samples of Nimonic 80A, aluminium alloy and copper. To this end the tri-axial experimental data available in the literature for a Bridgman notched bar and for tri-axial cruciform specimens were used. A good agreement between theory and experiment was observed particularly for the most decisive test of equal tri-axial tension.