Quantification of pipe-end restraint effects on J and COD for circumferential through-wall cracked pipes in tension

Abstract

This paper provides analytical equations to quantify the effect of the pipe-end rotation restraint effect on elastic and elastic–plastic J and COD for circumferential through-wall cracked pipes in axial tension. Analytical equations to relate the bending moment in the cracked section and axial tension are derived using displacement and rotation compatibility equations. It is found that negative (crack-closing) bending moment in the cracked section is generated due to end restraint, which is proportional to axial tension due to internal pressure. The method to calculate J and COD for restrained pipe is proposed using the equivalent combined tension and bending moment without end restraint. The Proposed equations are used to predict bending moments in the cracked section, which are then compared with elastic and elastic–plastic FE results for various parametric conditions (such as the axial tension magnitude, crack location, crack length, strain hardening exponent), showing good agreement. FE J and COD from restrained pipes are also compared with the proposed method, showing good agreement.