Development of procedures for the assessment of defects at elevated temperature

Abstract

Within the CEGB a comprehensive assessment document which gives advice on structural assessments at elevated temperature is being prepared. A part of the document which has already been drafted is that dealing with the treatment of defects under creep loadings. This is the high temperature counterpart of the CEGB's low temperature defect assessment procedure, commonly known as R6. The high temperature procedure is described and the materials data and calculations required to perform an assessment are discussed. It is shown that simplified calculations based on reference stress techniques can be used and these require only a knowledge of the limit load and the stress intensity factor of the defective component. Thus, if an R6 assessment of a defective component can be performed, then so can an elevated temperature assessment provided the relevant materials data are available. The next stage in the description of structures with defects is the treatment of cyclic loading where crack extension can occur by combinations of fatigue and creep. It has been found that the approach which has been developed for creep loading can be extended without great difficulty; the approach which is being adopted for thin-shell structures is indicated.