Parameter Calibrations of Micromechanics-Based Fracture Models of Q345 Steel

• 1、Department of Building Engineering, Tongji University

Abstract：Micromechanics-based facture models can be used to predict ductile fracture in steel structures. The stress modified critical strain (SMCS) model and the void growth model (VGM) are suitable to predict fracture initiation under monotonic loading, while the corresponding degraded significant plastic strain (DSPS) model and the cyclic void growth model (CVGM) are fit for fracture prediction under ultra low cycle fatigue loading. SMCS and VGM models include parameters α and η respectively, which indicate the material toughness. DSPS and CVGM models include not only parameters α and η, but also degraded parameters that reflect the damage effect of cyclic loading. In addition, characteristic length is involved in all the models. In order to calibrate the parameters in these models for the largely used Q345 steel in China, material tests, scanning electron microscope tests and finite element analyses were conducted. The test specimens were made from base metal, deposit metal and heat affected zone of Q345 steel to investigate crack initiation in welded connections. The results of this paper can be applied to predict ductile fracture in welded steel connections.

Keywords： Fracture Micromechanical model Parameter calibration