Characterization of ductile fracture criterion for API X80 pipeline steel based on a phenomenological approach

Abstract Steel pipelines for oil/gas transportation might be subjected to large plastic strain under extreme loading conditions, which will lead to localized fracture. The damage mechanics model is a promising tool to perform most of the assessment analysis and evaluation at the simulation level. In this paper, a micro-based Gurson-Tvergarrd-Needleman (GTN) model and two recently proposed uncoupled fracture criteria, modified Mohr-Coulomb (MMC) criterion and extended Rice-Tracey (ERT) criterion are evaluated using API X80 steel. A comprehensive experimental study including five different notched specimens covering a wide range of stress triaxiality and lode dependence is conducted. Corresponding finite element models are established. A phenomenon-based hybrid numerical-experimental calibration method is used to determine the fracture parameter for these three models. Then the calibrated parameters are validated through notched tensile tests and compact tension (CT) tests. It is shown that the presented fracture criteria are in a good capability to characterize the ductile fracture behaviors of API X80 pipeline steel.