Research On Friction Stir Welding Of Metro Floor Based On Numerical Simulation

Friction Stir Welding(FSW),as a new welding technology,has been widely used in modern rail transit manufacturing due to its advantages of environmental protection and small welding induced deformation.Aluminum alloy floor as a large structure which requires high planeness in Metro components,often produced by metal inert gas welding(MIG)in traditional production.Due to its low production efficiency and large deformation,in recent years,FSW has been gradually used to manufacture aluminium alloy floor.Although FSW has some advantages over traditional arc welding in deformation control,there is still a local non-uniform heating process in the welding process,which brings about the problem of welding induced deformation.How to further optimize the process to control welding deformation more effectively has become a top priority in production.Based on the numerical simulation method,this paper studies the deformation law in subway aluminum alloy floor production and the optimization scheme of welding process oriented to deformation control.The work provides theoretical and technical support for the deformation control of this type of floor by using friction stir welding.Firstly,the local and global finite element models of friction stir welding of 6005A-T6 aluminum alloy subway floor are established.Based on the mathematical model of combined heat source,a three-dimensional thermo-elastic-plastic finite element analysis of typical floor structures is carried out by sequential thermo-mechanical coupling method.The results are extracted and the shrinkage strain is calculated.Then the elastic-plastic calculation of the whole aluminum alloy model of Metro is carried out by using the shrinkage strain method,and the welding deformation of the Metro floor structure are obtained.Then we compared the numerical simulation and the actual measurement results.The results show that the trend of welding deformation calculated by simulation is basically consistent with that measured.The maximum error between simulation and actual measurement is 0.5mm,which proves the accuracy of the method and model used in this paper,and lays a foundation for the Process Optimization Oriented to deformation control.From the point of view of engineering application and realization of optimal deformation control,five welding sequence and loading position schemes for FSW welding of subway floor are developed.By analyzing and comparing the deformation results of different schemes,the influence of welding sequence and fixture location on the final welding deformation was explored.On this basis,a deformation control scheme for simultaneous welding of double stirring joints is proposed,and the welding situation is simulated and analyzed.Generally speaking,the welding deformation can be effectively controlled by symmetrically arranging the welding sequence and setting certain constraints near the welding seam.