Research On Friction Stir Welding Of Metro Side Wall Based On Numerical Simulation

Friction stir welding(FSW)technology with its advantages of environmental protection and great quality welded joints,is widely used in the rail transit industry.In the process of welding,the problem of welding deformation is inevitable.Therefore,how to optimize the welding parameters to control the welding induced deformation effectively becomes an extremely key issue in the production.This paper predicted the deformation of metro side wall by employing numerical simulation method,and optimized the welding process.Based on sequential thermodynamic coupling method,FSW finite element models of 5mm and 3mm thick friction stir welding(FSW)6082-T6 aluminum alloy sheet were established.Their FSW processes under different welding parameter working condition were simulated respectively.The results show that,the temperature decreased with the increase of welding speed and increased with the increase of mixed head rotation speed.The transverse residual stress is unimodal distribution,and longitudinal residual stress has large fluctuation in both ends of the weld bead.The effects of welding speed on residual stress was more obvious than mixed head rotation speed.The whole deformation trend to a reversed saddle,longitudinal deformation is convex and transverse residual stress is concave.The welding induce deformation decreased with the increase of welding speed and increased with the increase of mixing head rotation speed.Based on shrinkage strain method,a FSW model of 6005A-T6 aluminum alloy metro sidewall was established and simulated.Firstly,a three-dimensional thermal-elastic-plastic finite simulation of the local sidewall structure was carried out by using combined equivalent heat source and sequential thermodynamic coupling method.And then,according to the result of the local model,the shrinkage strain was extracted and obtained.The deformation of full-scale metro sidewall was calculated by using shrinkage strain method.Comparing with simulated results and experimental measurement results,they have the same distribution trend.The maximum error between simulated deformation and experimental distortion is within 20%.According to practical experience and theoretical basis,various welding sequence and structure size schemes are designed.According to analysis and comparation of the deformation results of each program,the thesis explored the influence of welding sequence and the profiles on the final welding induced deformation and obtained optimal sequence and profile of the aluminum alloy section.