Simplified J-estimations based on the Engineering Treatment Model for homogeneous and mismatched structures

This paper presents simplified J-estimation equations for defective homogeneous and strength mismatched structures, based on the Engineering Treatment Model (ETM). For homogeneous structures, two modifications are made to the existing ETM J-estimation equations; firstly a modification of the contained yielding solutions, and secondly modification of J-estimation equations for materials exhibiting Lueders strain. Based on the proposed J-estimation equations for homogeneous structures, J-estimation equations for welded structures with strength mismatch are proposed. The proposed J-estimation equations for both homogeneous and mismatched structures are then compared with selected elastic-plastic finite element results. The comparisons show excellent agreement and so provide confidence in the use of the proposed J-estimation equations for defect assessment. Finally, comparison with another simplified method, the R6 method, is discussed.