| Earthquake action is characterized by large strain and ultra-low cycle.The deformation of steel structure under earthquake load is greater than the yield strain,so in this case,the steel structure members or nodes are prone to fracture and damage.In recent years,many scholars have conducted in-depth studies on the fracture mechanism of steel structures,from traditional fracture mechanics to local fracture theory based on micro-fracture mechanism,and have proposed micro-fracture models with different application ranges,but many models are only applicable to a single stress state or loading The conditions are not suitable for fracture prediction of steel structures under seismic loads.The SWDM model is suitable for the common high-stress triaxiality of fracture in engineering,and the influence of the Lode angle parameter is introduced to make the model more accurate in fracture prediction under plane stress.The form of hyperbolic sine function can be used for fracture prediction under cyclic loading However,the model does not consider the influence of the reverse strain of the loading history on cyclic fracture,so that it may still have the same limitation of the CVGM model,that is,the fracture index is 0 after several cycles,and it cannot accurately adapt to the non-proportional loading conditions.Therefore,this paper introduces the influence of loading history on the basis of the SWDM model and proposes the SWDM-Pro model.This article mainly includes the following aspects:(1)Introduce the derivation process of the SWDM-Pro model,select the appropriate steel circulation constitutive,use the finite element software ABAQUS user subroutine VUMAT for material properties to compile the constitutive and fracture model of the material,used to steel The whole process of loading and fracture is verified and simulated.(2)Use Q420 B steel weldment series materials(base metal,deposit metal and heat affected zone)to design material plate specimens,circumferential notched test specimens and flat notched specimens to provide different stress states to calibrate the SWDM-Pro model fracture parameters.The data of the material plate test piece is used to calibrate the basic data of the steel material and the cyclic constitutive parameters.The data of the monotonic tensile fracture specimens are used to calibrate the relevant parameters of the stress state of the model.The data of the cyclic loading fracture specimens calibrate the cycle fracture parameters,using s user subroutine program to verify the accuracy of the model.The results show that the steel constitutive used in this paper can accurately simulate the hysteretic performance of steel under cyclic loading,and the new SWDM-Pro model can more accurately simulate the whole process of steel fracture.(3)Use the existing Q235 B,Q345B,Q390 B,Q460D sample data to uniformly calibrate the SWDM-Pro model parameters,verify the accuracy and applicability of the model,and provide the model’s recommended parameters for different steels.Finally,user subroutine program is applied to the beam-column joint to predict the fracture of the steel structure node to verify the application effect of the SWDM-Pro model proposed in this paper to the actual engineering node.The results show that the new SWDM-Pro model has good accuracy for the fracture prediction of different steel materials,and the model can be applied to the fracture prediction of actual engineering nodes. |
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