Dependence of creep deformation behavior in the root of notch on creep rupture life

Abstract

The object of the investigation was to examine the dependence of creep strain in root of notch on the creep rupture life for the round bar with the circumferential V-notch during the short-time creep at high temperature. In the long-time creep under the low stress, it is possible to estimate the stress and strain distributions of notch root only from the creep deformation. However, it is necessary to sufficiently consider the plastic deformation under the creep of the load of the relatively high stress, since elastic, plastic and creep deformation are dependent on each other. In this study, the tensile creep rupture tests of the circumferential 60° V-notched bar for a type SUS 304 stainless steel were carried out at 873K in the air, and in order to discussed the deformation at the notch root under short-time creep in the laboratory, elasticity, plasticity and creep analysis were carried out using a finite element method (FEM). The elongation of the notch groove was measured under creep test and compared with the results of FEM analysis using the plastic and creep constitutive equations which were determined from the tension test and the tensile creep testing of smooth specimen. A considerably good agreement is obtained between the numerically computed and the experimentally observed plastic and creep deformation behaviors of the notched bars under constant loading, and the conclusion was got like that the mean creep strain rate between the edges of the V-shaped notch governs creep deformation and rupture under highly constrained deformation in tri-axial states of stress. © 2012 The Japan Society of Mechanical Engineers.