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

• Published in: Theoretical and applied fracture mechanics 2019-10, Vol.103, p.102302, Article 102302
• Main Authors: Musrati, Walid, Medjo, Bojan, Gubeljak, Nenad, Štefane, Primož, Veljić, Darko, Sedmak, Aleksandar, Rakin, Marko
• Format: Article
• Language: English
• Subjects: Complete Gurson model; Computer simulation; Ductile fracture; Finite element method; Fracture toughness; Internal pressure; Micromechanical analysis; Numerical analysis; Seam and seamless steel pipes; Specimen geometry; Steel pipes; Stress concentrator; Thermomechanical treatment
• ISSN: 0167-8442; 1872-7638
• DOI: 10.1016/j.tafmec.2019.102302

•Fracture resistance of seam and seamless thin-walled pipes is examined.•Recently proposed specimens applied: Pipe-ring notched bending (PRNB).•Notch produced by electrical discharge machining (R = 0.25 mm) as stress concentrator.•Experimental testing and micromechanical modelling (CGM model).•Influence of specimen geometry and heterogeneity (seam/base metal) is assessed. 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.