Numerical Simulation Research On Friction Stir Welding Of7075Aluminumalloy

The welded joint obtained through friction stir welding has the characteristics ofsmall deformation, high strength etc. So friction stir welding can be widely used inaeronautical and aerospace industry, ship building industry, Auto manufacturing, etc.However, friction stir welding is a complex plastic deformation process with highnonlinearity under coupled effects with multi-factors. To understand the changeregularity of temperature field, material flow, etc. in friction stir welding and reveal themechanism of welding parameters on temperature and migration of the weld materialshave become the key problems urgent to be solved. Therefore, the investigation on theabove mentioned key problems has been carried out by using FEM (Finite ElementMethod) combined with theoretical analysis, this is very significant in theoreticalfoundation extending and practical guidance.Based on software ABAQUS, this paper establishes the three dimensional coupledthermal-mechanical finite element model of friction stir welding by using the tool withconical and inclination angle, and then verified that the model is reliable. It is found thatthe maximums of equivalent strain and the flow of the material are all on the uppersurface of the workpiece where contact with the edge of the shoulder, but after a timethey are almost not changed in the welding process. We can also found that the plasticstrain area locates in the welded region behind the tool, but the material flow mainlydistributes around the tool, and the region is narrow.The temperature field and the influence mechanism of welding parameters on it areinvestigated systematically. It is found that:(1) temperature field distributessymmetrically along the center line of the weld，and temperature is higher behind thetool.(2) The temperature of the materials near the tool increases with the much greaterrevolving speed, and then it keeps almost constant, but when the materials have adistance with the tool, the temperature of them in front of the tool and on advancing sideof the workpiece increases with increasing rotational speeds, and the opposite effect isobserved behind the tool and on retreating side of the workpiece; and (3) the increasesof welding speeds lead to a bigger affecting region of temperature, but the temperatureof the materials near the tool is not affected basically, and the temperature of the materials in front of the tool has an opposite change trend with the welding speeds, butthe temperature of the materials behind the tool increases with increasing weldingspeeds.The materials migration and the influence mechanism welding parameters on it arestudied deeply. It is shown that (1) the metals in front of the tool and from advancingside of the workpiece both have the best flowability(migration amount is the largest) inhorizontal and thickness direction, the second place is taken by the retreating side, andthe poorest flowability of the materials is behind the tool;(2) all materials fromretreating side of the workpiece are forced to move upwards, but the materials fromadvancing side of the workpiece flow and mix violently, the top metals move downwardand the materials at the bottom move upward;(3) with the reducing of weld speed orincreasing of rotation speed, whether it is from advancing or retreating side of theworkpiece, the flowability of top metals increases a lot, so it is beneficial to obtainwelded joint of good performance.