Leak‐before‐break Conditions of Plates and Pipes Under High Fatigue Stresses

The leak‐before‐break(LBB) behaviour of a structural component under high fatigue stress, low‐cycle fatigue conditions is an important problem in nuclear power plants, liquid nitrogen gas tankers and chemical plants. This paper is an experimental study to clarify the crack shape at penetration, crack opening behaviour after penetration and the LBB condition for plate specimens and pipe specimens. The fatigue load which realizes the LBB condition, P F LBB' is based on a net‐stress criterion. It is found that P F LBB is dependent only on the initial crack length a 0 . Furthermore, it is shown that the crack opening displacement V at the centre of a penetrated crack can be derived using the gross stress, σ G' and the front surface crack length, a s' together with the back surface crack length, a b .