Detailed three-dimensional analysis of side-grooved compact tension specimens under creep loading

Abstract

The three-dimensional (3D) effect on the stress field near the crack tip under creep loading has been investigated via detailed finite-element analyses on side-grooved compact tension (CT) specimens with various thicknesses. The mechanical properties used in the model are typical of those for a 9%Cr steel at 550°C and a Norton creep exponent of 10 was applied. Plane strain and 3D analyses for the CT specimens without side grooves were also performed and the differences in stress distributions in the three analysis conditions are discussed in relation to the creep J-integral C*. The value of C* was found to decrease with increasing thickness and to decrease significantly because of the enhanced constraint effect of the side grooves. With increasing thickness, the stress state in the central region is close to that under plane strain conditions, irrespective of the existence of the side groove. Stress triaxiality, however, is distributed more uniformly along thickness in the side-grooved specimen than in the specimen without side grooves. The C* values of the side-grooved specimens are similar across the full range of thickness studied: no strong effect of thickness was observed.