An engineering approach to safety assessment for non- J-controlled crack growth

Abstract

The J ̃ 1 -integral has been proposed as a new fracture parameter for non- J-controlled crack growth in previous studies. In this paper, the J ̃ 1 -integral is investigated to assess the safety of structures with defects. The estimation formula for the J ̃ 1 -integral is presented to calculate the crack driving force by referring to the engineering estimation expression of the J-integral. The material resistance curves J R− Δa and J ̃ 1R − Δa , of A533B material, are obtained by tests and nonlinear finite element analyses. The J ̃ 1 -integral failure criterion for non- J-controlled crack growth is assumed in the paper according to the crack driving force and the material resistance curves. The method of admissible stress curve, i.e. the stress-crack length curve, is developed to simplify the conventional engineering assessment procedure by following the failure criterion for non- J-controlled crack growth. A new engineering safety assessment approach is proposed to assess the ductile fracture instability of flawed structures for non- J-controlled crack growth by the method of an admissible stress curve. Two examples for the compact tension configuration and the cylinder with a surface crack under internal pressure are examined by using the new engineering assessment approach. The new engineering safety assessment approach obviously simplifies the conventional engineering assessment procedure. By comparing with the tests, the results from these two examples show that this new engineering safety assessment approach for non- J-controlled crack growth gives a reliable prediction for the ultimate load capacity of flawed structures.