Abstract
Aiming at the softening problem of 7075 superhard aluminium welded joints such as hot cracks and gas holes in traditional fusion welding process, a dynamic robust control model based on the relationship between friction stir welding process parameters and welded joint strength is established. According to the non-linear relationship between global motion estimation and welded strength parameters, a dynamic robust control model of stirring needle motion is established, and the physical parameters such as elongation after fracture, tensile strength and hardness are calculated. A robust dynamic evolutionary optimization model of welding process parameters is established in the future to realize real-time optimization control of process parameters. On the basis of global motion control, the electric power output of the friction stir welding main motor is predicted according to the required line energy input of the stirring needle motion characteristics, and the real-time optimal control method of the motor electric power based on the expected thermal energy input of the welding process is established. A series of strength tests of welded joints based on the model show that the predicted results of the model can meet the needs of engineering and have practical value in engineering.
Highlights
7075 series aluminum alloy is widely used in aerospace, military, vehicle and other fields due to its high strength
The traditional riveting process has the advantages of easy operation and high tensile strength in high-strength aluminum alloy welding [1]–[3]
By using friction stir welding as solid phase welding, the problem of joint softening such as pores and hot cracks in the welding process caused by TIG or laser welding process can be well solved [4]–[6]
Summary
7075 series aluminum alloy is widely used in aerospace, military, vehicle and other fields due to its high strength. Aiming at the metal plastic flow and its thermodynamic nonlinear characteristics during high-hardness aluminum alloy welding process are studied. Liu: Global Robust Control Model of Friction Stir Welding of Aluminum Alloy flow of the weld metal and the nonlinear process of cooling is studied, and the dynamic optimization control of the welding process is implemented. According to the temperature of the test piece, the plasticizing flow of the weld metal and the change of the grain size of the dynamic recrystallization, the stirring needle is motion compensated. Aiming at the line energy input control problem in the welding process, the main motor power robust estimation model is established to determine the optimal motor energy output power prediction value to ensure that the required input thermal power meets the global motion control requirements during the online energy control period. The strength test of welded joints shows that the prediction results of the model can meet the engineering needs and have practical value
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