A modified engineering critical assessment method for deeply-embedded cracks in metallic pipelines subjected to large plastic strain

摘要

The results of three-dimensional finite element analyses indicate that the normalized J-integral values of surface cracks are almost 3 times higher than those of deeply-embedded cracks, provided the sizes of the surface and deeply-embedded cracks are the same. In this paper, we introduce a factor F, which serves as an adjustment factor to reduce the degree of conservatism. The results show that F is the function of the non-dimensional deeply-embedded crack height (2a(e)/t), since F is markedly affected by 2a(e)/t. Furthermore, after introducing the factor F, the crack tip constraint of the deeply-embedded cracks is found to be lower than that of the surface cracks, which gives a further conservatism in using the factor F for assessment of embedded cracks. (C) 2017 Elsevier Ltd. All rights reserved.