Damage Parameters Identification And Joints Application Of Q345B Steel Based On GTN Model

A large number of engineering examples and experimental research results show that most of the steel structure engineering accidents are caused by the fracture of steel in a certain part.Therefore,to solve the safety problem of complex steel structures,the fracture damage mechanism of the engineering structure must be studied from the perspective of building steels.Therefore,to solve the safety problem of complex steel structures,we must study the fracture damage mechanism of engineering structures from the perspective of building steel meso.The meso damage model of GTN is used to analyze the initiation,growth and polymerization process of micro holes and micro cracks from the meso level of materials.It is one of the constitutive models widely applied in meso damage field to link the damage evolution process at meso level with the macroscopical mechanical properties.At present,the domestic GTN meso structure damage damage model of construction project based on the results is not much,so this paper based on GTN damage model,the damage parameter of Q345B steel with GTN model to identify the construction,identification of the Q345B steel fatigue damage parameter GTN model is applied to study damage to steel joints.Since the construction of Q345B steel were carried out three kinds of smooth and notched round bar specimen uniaxial tensile test,a smooth round bar specimen for basic mechanical properties of Q345B steel under uniaxial tensile test,three kinds of notched round bar specimen uniaxial tensile test to obtain load displacement curves for steel Q345B damage recognition the parameters of the GTN model based on the foundation;followed by a smooth and notched round bar specimen fracture surface SEM experiment in scanning electron microscope photos can be seen on the fracture surface has many homogeneous dimples,and can find the obvious holes phenomenon,the scanning electron microscopic observation demonstrated that the GTN model is reasonable in simulation of ductile metals the damage and fracture of materials at the same time,smooth and notch difference between test rod fracture surface is compared to determine the characteristic length,provides a finite element model of grid division encryption area Basis?Using GTN meso damage model simulates three notched round bar specimen uniaxial tensile test,found notched round bar specimen of finite element model of crack initiation point is located in the center of symmetry,and along the fault for external expansion;analyzes the influence curve of displacement volume fraction of damage parameters in GTN model of load finite element model;comparison test and finite element results,fitted with Q345B steel GTN damage model parameters;found that the fracture surface of the test pieces in the notched round bar,triaxial stress on the crack point maximum,with crack propagation decreases gradually,and the round bar specimen gap is bigger,the corresponding position of stress three the shaft is smaller.According to the relevant literature and processing of Q345B steel plate shear specimens,and tensile tests were carried out,obtaining the load displacement curves,using the GTN model for shear plate finite element simulation,with the damage zone stress three axis of the lower degree,the corresponding position of the void nucleation rate decreases after nucleation and growth in the number of points more slowly,should three axis force of nucleation at the minimum position after the volume fraction or even stop the growth,displacement and load breaking point shear plate load finite element simulation of the displacement curve is far greater than the experimental results,this paper analysis the GTN model ignores the influence of shear fracture,the GTN model is not suitable for three axis force under low degree.The identification of the Q345B steel base material damage parameters and welding application material damage parameters to identify the relevant literature based on Q345B in steel tubular joints damage fracture prediction,obtain the evolution process and the results of finite element analysis of steel structure GTN model based on intersecting joint damage,and compared with the test results,to verify this kind of injury the applicability of the model in the prediction of construction in damage and fracture.Through this study,shows that the GTN model can simulate tensile test of T type tubular joints,that has a certain accuracy of the GTN model in the study of tubular joints damage fracture,fracture prediction can be carried out using GTN node model,has some reference value and significance to the actual project.