STUDY ON MICROMECHANICAL FRACTURE MODELS OF STRUCTURAL STEEL AND ITS WELDS

Abstract

Steel structures have been widely used in constructions due to their advantages of lightweight, high strength, short construction time and high recycling and reuse potential. Fracture failure in steel structures should be prevented to avoid collapse of the whole structures. Micromechanical fracture models can capture the fracture initiation mechanisms and therefore can be used to predict ductile fractures in steel. Twelve smooth round bars were carried out to obtain the material properties and 36 notched round bars were tested to calibrate the parameters of stress modified critical strain (SMCS) model and the void growth model (VGM) for structural steels (Q235B and Q345B) and the corresponding welds. Specimens were extracted from the base metal, the weld metal and the heat affected zone (HAZ) to investigate fracture behaviour in different parts of the welded joint. Scanning electron microscope (SEM) measurements were taken and finite element models were developed to calibrate the models. The test results and calibrated parameters are reported. Moreover, the calibrated models are applied to analyses the fracture behaviour of welded joints and their accuracy are validated. The calibrated and validated models can be used for further numerical fracture analysis in welded steel structures.