Feasibility And Fatigue Performance Of Aluminum Alloy Clinching-resistance Spot Welding Hybrid Process Connection Joint

In the automotive and aerospace sectors,aluminum alloys are being used more and more widely due to their light weight and high material properties.But there are still some problems with the connection of aluminum alloys.The clinching-resistance spot welding hybrid process connection technology is a new type of connection method for thin plate materials.The connection principle is based on the clinching connection and then performing resistance spot welding on the clinched joints.In this paper,Al5052 aluminum-magnesium alloy is used as the main research object.The connection test of Al5052 aluminum-magnesium alloy is carried out by clinching-resistance spot welding composite connection technology.The optimal process parameters of resistance spot welding hybrid process connection are determined by orthogonal test,from statics and dynamics.Fatigue properties are analyzed in terms of mechanical properties and failure mechanisms,providing a new connection method for aluminum alloy sheet joints.Al5052 aluminum-magnesium alloy and Al1420 aluminum-lithium alloy were selected as test materials.Feasibility connection test of the same/different material combination by clinching-resistance spot welding hybrid process connection technology.The formability,joint strength and failure mechanism of the joint were examined by non-destructive testing,static testing and micro-fracture scanning of the hybrid process connection joint.Tests show that the clinching-resistance spot welding hybrid process connection technology can realize the connection of aluminum alloy,and the Al5052 joint has the best formability and mechanical properties.The Al5052 aluminum-magnesium alloy material combination was selected,and the orthogonal experimental design method was used to explore the optimal process parameters of the joint resistance spot welding connection.By designing orthogonal table,orthogonal test analysis,load-displacement curve analysis,range and variance analysis,the optimal process parameters of resistance spot welding of Al5052 aluminum-magnesium alloy clinching-resistance spot welding hybrid process connection joint are as follows: welding current 26 k A,power time 160 ms,electrode pressure 0.3MPa.The conclusion is consistent with the verification test.The order of the resistance spot welding parameters from high to low is: electrode pressure,welding current,power time.Dynamic fatigue test using Al5052 aluminum-magnesium alloy clinching-resistance spot welding hybrid process connection joint.Taking the clinched joint and the resistance spot welded joint as the control group,the fatigue life of the three sets of joints under different cyclic loads was obtained.Using the three-parameter power function method to fit the fatigue life curve of the joint and analyze its characteristics.The fatigue properties of Al5052 aluminum-magnesium alloy clinching-resistance spot welding hybrid process connection joint were analyzed from macroscopic and microscopic perspectives.The characteristics of fatigue fracture of composite joints,fatigue failure process,failure mode,crack source generation and its extension were investigated by SEM scanning electron microscope.The results show that for the Al5052 aluminum-magnesium alloy material,the fatigue performance of the clinching-resistance spot welding hybrid process connection joint is better than that of the resistance spot welded joint.The failure mode is the failure of the lower plate fracture,and the fatigue crack source is generated in the middle of the joint bottom.Moreover,the static mechanical properties of the clinching-resistance spot welding hybrid process connection joint are better than those of the clinching joint.