Research On The Fracture Behavior Of Weld Mental Based On Micromechanical Damage Models

Recently,many studies in the field of fracture mechanics have shown that in addition to the stress triaxiality,the Lode angle is an important parameter affecting the plastic flow and ductile failure of metallic materials.So,in recent years there have been many research findings around Lode angle,deviatoric stress invariant and low stress triaxiality.But at the present stage in the study of the weld metal fracture properties,it is impossible to simulate the ductile fracture under the condition of deviatoric stress and low stress triaxial accurately with the SMCS,VGM,DSPS,CVGM models in general use,which consider only the relationship between the triaxial stress level,equivalent plastic strain and stress state.Therefore,this paper designs different kinds of fracture specimens which are suitable for studying high,medium and low stress triaxial and deviatoric stress states,then conducts the uniaxial tensile test and the ultra-low-cycle fatigue fracture performance test.Subsequently the fracture properties of the weld metal were studied by multidimensional such as the stress triaxiality,Roth angle parameter and the Lode parameter L.The main contents are as follows:(1)Five kinds of specimens corresponding to different stress states were designed,including smooth round bar specimens,cylindrical notched specimens,groove plate specimen,rectangular notched specimens,and inclination notched specimen.Then,this paper conduct series of uniaxial tensile and ultra-low-cycle fatigue fracture performance test,analyze the load-displacement curves of uniaxial tensile and fatigue loading specimens,determine the fracture displacement and the number of fracture rings which error analysist is carried out simultaneously.(2)The Swift-Voce of uniaxial tension model and the Chaboche of combined enhancement model are calibrated.The simulation of each type of specimen is performed using Abaqus finite element software,which can accurately simulate the load-displacement curves of this batch of weld metal under uniaxial tension and fatigue load.The broken position of test and simulation can also be similar.(3)The LOU,VGM,SWDM fracture models for fracture prediction of uniaxial tensile tests and the CLOU,CVGM,and SWDM fracture models for fracture prediction of fatigue tests are calibrated by the historical data of finite element simulation.And the model expressions are applied into the UVARM user subprograms to perform fracture prediction simulations on the uniaxial tensile and fatigue loading tests of the weld metal.The damage accumulation process of different models and the error of the fracture displacement and the number of fracture are analyzed to discuss the advantages and disadvantages of each model in different stress states.