AN INNOVATIVE ROBUST METHOD FOR CREEP LIFE ASSESSMENTS OF COMPONENTS CONTAINING STRESS CONCENTRATORS UNDER PRIMARY PLUS SECONDARY PLUS TERTIARY CREEP

摘要

In calculating creep life of components using analytical and/or numerical methods, it is a common practice to ignore the primary and tertiary creep regions and assume the material deforms according to the power law secondary creep alone. This may lead to non-conservative results that contain significant error. A robust and simple method, coined UNSW-CLl method, for creep life assessments of components with complex geometry that may contain a stress concentration region is described. UNSW-CLl method models the effect of primary plus secondary plus tertiary creep deformation. The paper reasons that the UNSW-CLl method is easy to use because it requires the following input data only that are readily available: 1. the geometry, dimensions and loading of the component. 2. the elastic stress concentration factor. 3. creep material data. 4. the creep rupture time for the plain component excluding the stress concentration region (for example, in case of a vessel-nozzle joint, excluding the nozzle-vessel intersection so that the component may be considered as a plain vessel). Such a simple method is particularly appropriate for online life assessments.