Modelling of Fracture Toughness of X80 Pipeline Steels in DTB Transition Region Involving the Effect of Temperature and Crack Growth

• Published in: Metals (Basel ) Vol. 10; no. 1; p. 28
• Main Authors: Xu, Jie, Song, Wei, Cheng, Wenfeng, Chu, Lingyu, Gao, Hanlin, Li, Pengpeng, Berto, Filippo
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.01.2020
• Subjects: coarse-grained heat affected zone (cghaz); Computer simulation; Cooling; Crack opening displacement; Crack propagation; Crack tips; Ductile fracture; Ductile-brittle transition; finite element analysis (fea); Finite element method; Fracture mechanics; Fracture toughness; Geometry; High strength low alloy steels; Mathematical models; Metal fatigue; Pipelines; Simulation; Steel; Stress-strain curves; Structural steels; Temperature; Temperature dependence; Temperature effects; Tensile strength; Thermal simulation; weld thermal simulation; x80 pipeline steels; Yield stress
• ISSN: 2075-4701; 2075-4701
• DOI: 10.3390/met10010028

This work presents an investigation of the effects of temperature and crack growth on cleavage fracture toughness for weld thermal simulated X80 pipeline steels in the ductile-to-brittle transition (DBT) regime. A great bulk of fracture toughness (crack tip opening displacement—CTOD) tests and numerical simulations are carried out by deep-cracked single-edge-notched bending (SENB) and shallow-cracked single-edge-notched tension (SENT) specimens at various temperatures (−90 °C, −60 °C, −30 °C, and 0 °C). Three-dimensional (3D) finite element (FE) models of tested specimens have been employed to obtain computational data. The results show that temperature exerts only a slight effect on the material hardening behavior, which indicates the crack tip constraint (as denoted by Q-parameter) is less dependent on the temperature. The measured CTOD-values give considerable scatter but confirm well-established trends of increasing toughness with increasing temperature and reducing constraint. Crack growth and 3D effect exhibited significant influences on CTOD-CMOD relations at higher temperatures, −30 °C and 0 °C for the SENT specimen.