Study On Formability Of Aluminum Alloy Based On Acoustic Emission And Digital Image Processing

Because aluminum alloy plate has the advantages of light weight,high strength,good corrosion resistance,easy forming and so on,it has been widely used in the architecture,automobile manufacturing,packaging transportation and aerospace industry.The failure process of aluminum alloy is the transformation from dislocation movement to formation,extension and fracture of cracks.AE can record and reflect the change of plastic deformation and micro crack generation and propagation of aluminum alloy sheet.Digital speckle correlation method is a kind of method which can accurately measure the full strain of metal.This paper researches on strain characteristics at different times and the characteristics of acoustic emission combining with digital speckle correlation method,AMARIS 3D Strain Testing System and Acoustic Emission Testing System and Aluminum Alloy uniaxial tension and rigid punch bulging test.The main contents and conclusions of this dissertation are:(1)Based on the Digital speckle correlation method,the strain field of uniaxial tensile process was obtained by using AMARIS optical strain measurement system.Combining with uniaxial tensile strain field,the deformation and failure mechanism of aluminum alloy during tensile process is analyzed.The strain field of necking instability up to fracture process is deeply researched.It's found that the necking instability occurs in the deformation concentrated part of the specimen,and the crack propagates along the deformation concentrated position until it breaks down.(2)The uniaxial tensile test was carried out on the aluminum alloy specimens of different sizes,and the acoustic emission signals were obtained by the acoustic emission testing system.Applying characteristic parameter,waveform and frequency spectrum analysis three methods to analyze the AE signal characteristic of the uniaxial tension throughout the process,and the mechanism of acoustic emission generated in the process of forming Aluminum Alloy combined with Aluminum Alloy tensile strain field,(3)Combined with the deformation failure mechanism and acoustic emission mechanism of aluminum alloy during tensile process,the characteristics of strain field and acoustic emission signal in the process of rigid punch bulging is analyzed,in order to determine the forming limit state.Based on the AMARIS strain diagram,the ultimate strain point can be obtained t.It provides a feasible method for determine the limit state of sheet forming,and comparing with AMARIS digital image method,this method is more reliable in safety design.