| Welding technology is widely used in the fields of bridges,buildings,machinery and other industries.The components made of welding have the advantages of good connection performance,large structural stiffness and good integrity.In the construction of the bridge,the welding process is commonly used in the connection of steel to make a stable and reliable node.However,the process of welding is a complex process of physical and chemical change,accompanied by a transient and huge energy conversion.The temperature of the welding component will increase sharply,which makes the yield limit of some regions deform.When the region is cooled,it will play a role in the surrounding area to ensure that the deformation is coordinated,and the residual stress is produced inside the welding component.The residual stress will have a certain influence on the mechanical properties of the bridge members,which can cause the bridge safety problems when it is serious.Therefore,it is necessary to study the influence of welding residual stress on the mechanical properties of bridge steel truss joints,so as to take some protective measures to weaken or eliminate this influence.In this paper,the principle of welding process,the heat source used in the welding process and the heat conduction law of heat are described.At the same time,the equation of temperature field is introduced,which is the foundation of the finite element simulation of the temperature field coupled with the stress and strain field in the welding process.Then this paper describes the process of numerical simulation of the welding process by using the large-purpose finite element software ANSYS.In the simulation,the indirect method is used,that is,the temperature field is calculated first,then the results of the temperature field are introduced into the model,and the stress and strain field is calculated.This article selects the typical truss node K steel box discussed in the finite element simulation of temperature field,combined with the specific manual welding process parameters,control variable method is used to change the material physical parameters were studied.In the selection of heat sources,the selection and welding process are similar to the gaussian distribution heat flow function.In the calculation of welding heatsource displacement,the finite element APDL programming is used to realize the movement of the heat source position.Through the study on the welding temperature field distribution found in the early stage of the cooling,the temperature field in the core temperature drops quickly,when the core temperature down to about 200 ℃,the cooling process stable,when the cooling time after 3600 s basic close to room temperature,can be thought of as welded components with air convection coefficient is zero.Then based on the temperature field was used as a result,the analysis of the welding seam of the changing law of stress field during cooling,the cooling process,the extreme stress of the weld position showed a trend of increase gradually,eventually in the K node of weld residual stress of the acute Angle of up to 223 mpa.Further,according to the welding residual stress analysis results of K type node,the residual stress effect on the ultimate bearing capacity of the K type node,the results show that when the local stress exceed the yield stress as the ultimate bearing capacity for determining boundaries,the residual stress of welds had a greater influence on the ultimate load coefficient,maximum effect reached 60%;When the ultimate bearing capacity of the k-type node is determined,the residual stress field of the single welding seam has little influence on the overall ultimate bearing capacity.Type at the same time,in order to accurately simulate the K node in the ultimate bearing capacity of practical engineering structures,this paper proposes a fine beam element and three-dimensional entity unit coupling analysis method,can be more accurate to obtain K node outside load level. |
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