Strain aging effect on micro-fracture behavior of Q355 steel and its welds

Abstract

Static strain aging has significant effects on the mechanical behavior of steel materials and should be considered in the failure prediction of partially damaged welded steel connections. Micromechanical fracture models have been demonstrated to predict ductile fracture initiation in welded steel connections. This study investigates and updates the micromechanical fracture prediction model of structural steel and its weld metal affected by static strain aging. Q355B structural steel base metal, heat-affected zone (HAZ), and weld metal are adopted to manufacture 60 smooth round bar (SRB) and 126 notched round bar (NRB) specimens affected by different levels of static strain aging effect. The mechanical properties and true stress-strain curves affected by static strain aging are obtained for numerical analysis by conducting uniaxial tensile tests on the SRB specimens. The characteristic length and fracture toughness parameters of the micromechanical fracture prediction models are calibrated using uniaxial tensile tests and finite element analysis (FEA) of the NRB specimens. The applicability of the updated micromechanical fracture models to the three materials affected by strain aging is verified by introducing the calibrated micromechanical fracture models as fracture criteria into the user subroutine USDFLD in the ABAQUS FEA software. This study contributes to the ductile fracture analysis of partially damaged welded steel connections affected by strain aging using micromechanical fracture models.