STUDY ON CONSTRAINT EFFECT AND CREEP CRACK INITIATION OF PLATE CONTAINING ELLIPTICAL EMBEDDED CRACKS

In this study, a plate structure containing elliptical embedded cracks loaded under high temperature is studied. The constraint effect and creep crack initiation of the plate con-taining embedded cracks are discussed by using the finite element method based on the creep ductility exhaustion model. It is indicated that the highest constraint level or the load-independent parameter Q* is observed at the endpoint of the ellipse major axis of an elliptical embedded crack, and the constraint levels increase with crack length or depth, which represents a worse condition for the structure, such as higher stress concentration and greater danger of failure for a larger crack depth ratio a/t or crack length ratio a/c. Moreover, under the creep condition, the embedded crack with a larger a/t, a/c or loadings is accompanied with a higher crack driving force, which can accelerate creep damage, creep cracking initiation (CCI) and shorten the creep crack initiation (CCI) time. Additionally, an empirical prediction equation and engineering approach to the constraint parameter and the CCI time for elliptical embedded cracks are proposed, and the engineering approach to the CCI time is validated.