Ductile fracture of Q460 steel: Effects of stress triaxiality and Lode angle

• Published in: Journal of constructional steel research Vol. 123; pp. 1 - 17
• Main Authors: Li, Wenchao, Liao, Fangfang, Zhou, Tianhua, Askes, Harm
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.08.2016
• Subjects: Ductile fracture; Fracture mechanics; Fracturing; High strength steels; Lode angle parameter; Mathematical models; Q460 high strength structural steel; Scanning electron microscope; Shear; Stress triaxiality; Stresses; Structural steels; Triaxiality; Lode angle parameter; Ductile fracture; Q460 high strength structural steel; Scanning electron microscope; Stress triaxiality
• ISSN: 0143-974X; 1873-5983
• DOI: 10.1016/j.jcsr.2016.04.018

The ductile fracture characteristics of Chinese Q460 high strength structural steel under quasi-static condition were studied by using mechanical tests of four types of notched specimens. The influence of stress state on fracture mechanism of the material was investigated by observing the fracture surfaces of all test specimens using the Scanning Electron Microscope. Meanwhile, corresponding numerical simulations were conducted to collect the critical stress and strain at notch for all test specimens. The effects of stress triaxiality and Lode angle parameter, which were found to be the key parameters governing the ductile fracture of metallic material in many studies, on fracture strain of the Q460 structural steel were investigated. The analysis results show that different fracture mechanisms were observed in different stress triaxiality regions. At high stress triaxialities, Q460 steel exhibits a typical mechanism of “void nucleation, growth and coalescence”. When stress triaxiality equals to zero, a shear fracture mechanism was observed. At low stress triaxiality values, fracture develops as a combination of shear and void growth modes. In addition, the ductility of Q460 structural steel under pure shear or plane strain is lower than that under axisymmetric tension, especially at low stress triaxiality. •The notch has an “embrittling and strengthening” effect on Q460 structural steel.•The stress triaxiality controls the ductility and fracture mechanism of the steel.•The ductility of Q460 steel is different under different Lode angle parameter.•The results can be used to calibrate micromechanical fracture models for Q460 steel.