| Refill friction stir spot welding(FSSW) is a solid spot welding technique which is suitable for the connection of light alloy, which has the advantages of excellent performance, beautiful appearance, energy conservation, environmental protection and so on, so it has wide application prospects in the fields of lightweight design. In order to promote the application of refill FSSW technology in the field of industry and promote the development of lightweight, the refill FSSW equipment was researched and developed based on the principle of refill FSSW, and the process experiment on 6061 aluminum alloy was carried out in this study.The process of refill FSSW was analyzed, and the main technological parameters were determined. According to the function of the refill FSSW tool, the material of the tool was selected and the size of the tool was determined. It was obtained that the maximum plunge force required for the equipment is 20 k N by the the plunge force measurement experiment. And according to the maximum friction theory, the maximum torque to be supplied by the equipment is 45 N ?m, and the pressing force is 20 k N. The design parameters of the refill FSSW equipment were determined, which laid the foundation for the design of the equipment.According to the motion characteristics of each component of the refill FSSW equipment, the design scheme and the design route of the mechanical structure were established. The coaxial motion of the sleeve and the pin was realized by using the hollow ball screw and the hollow direct drive servo motor. By using modular design idea, the design of the mechanical structure of the refill FSSW equipment was completed. The 3D model of the equipment was established by using Solid Works software, and all the processing drawings were drawn, the processing of the related parts and the overall assembly of the equipment were completed.Through analysing the control object and combining with the process of the refill FSSW, the control requirements were proposed. By comparing the current mainstream controller, the PLC and touch screen were used as the controller, and the control system scheme was established. According to the control system scheme, the hardware of the control system was designed, and the electric control cabinet was built up. The design of control system program and man-machine interface was finished.The refill FSSW equipment was tested and it was found that the equipment met the design requirements. The welding experiments of 6061 aluminum alloy, AZ91 magnesium alloy and brass were carried out, and the solder joints with good appearance were obtained. In view of the 6061 aluminum alloy, the forming and microstructure of the refill FSSW joint were studied. It was found that the cross section of the joint is like a "basin", and there are Hook and connection zone in the joint. According to the grain size, the joint can be divided into stir zone, thermo machanically affected zone and heat affected zone. The influence of process parameters on the tensile shear properties of the joints was studied. It was found that with the increases of the tool rotation speed, plunging depth, and the plunging/refilling speed, the tensile shear failure load of the joint firstly increased and then decreased. The optimization of process parameters on 2mm thick 6061-T6 aluminum alloy was carried out by response surface methodology. The optimized tensile shear failure load of 7934 N can be obtained at the tool rotation speed of 1506 rpm, the plunging depth of 2.46 mm, and the plunging/refilling speed of 60.84mm/min. |
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