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

• Main Authors: Jie Xu, Wei Song, Wenfeng Cheng, Lingyu Chu, Hanlin Gao, Pengpeng Li, Filippo Berto
• Format: Article
• Language: English
• Published: MDPI AG 2019-12-01
• Series: Metals
• Subjects: fracture toughness; coarse-grained heat affected zone (cghaz); x80 pipeline steels; weld thermal simulation; finite element analysis (fea)
• Online Access: https://www.mdpi.com/2075-4701/10/1/28

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.