Fracture assessment of seam and seamless steel pipes by application of the ring-shaped bending specimens

Abstract

The topic of this work is analysis of fracture behaviour and resistance of the thin-walled seamless and seam steel pipes, through application of the recently proposed ring-shaped specimen (PRNB - Pipe Ring Notched Bend). The main loading of these pipes in exploitation is internal pressure, which is why axial defects present a significant threat to their integrity and work safety. The ring-shaped specimen geometry is fairly simple to fabricate from a new or exploited pipeline and the specimens have the same thermo-mechanical treatment, assembly conditions, etc. as the actual structure. Experimental-numerical procedure is applied for prediction of the fracture behaviour; this included material characterisation, testing of ring specimens by bending, as well as micromechanical analysis of ductile fracture. In experimental testing, the deformation of the specimens is monitored by using the stereometric measurement system. Numerical analysis is performed in software package Simulia Abaqus, including the application of the micromechanical Complete Gurson model (CGM). The results obtained in this study, along with some previously published results, lead to conclusion that PRNB specimen is a good option for testing of fracture resistance of cylindrical elements such as pipes.