Theory And Numerical Analysis Of AA5083 Tube HGMF Process

The subject comes from the project(51305386) supported by National Young Science Foundation of China which name is "Technology and theoretical research on lightweight alloy tubes with hot granules medium pressure forming process".Hot Solid Granule Medium Forming Technology(HGMF Technology) adopted heat-resistant solid granule medium to substitute liquid or gas of existing soft mold sheet thermoforming process to form light alloy sheet. Granules medium enjoys many advantages, which provides a new method to solve the difficulty of the forming of light alloy tubes and sheets at room temperature, such as withstanding high pressure and high temperature, filling well, sealing easily, loading simply, etc. Research and development of this process has a wide application prospect, so this process can provide a new technology and method for thermoforming of light alloy tubes that with high strength, low ductility, high-deformation, complex cross-section, high dimensional accuracy and high surface quality requirements.In this paper, the 5-series aluminium alloy tube is taken as the research object, and the solid granules is regarded as the bearing medium, the theoretical analysis and the numerical formulation for the HGMF process on AA5083 sheet are conducted. Firstly, the mechanical property test and research on AA5083 tube and welding tube are conducted through the unidirectional tensile test of thermal-state sheet and the circumferential tensile of thermal-state tube. The true strain-stress curves of AA5083 under different temperatures and strain rate conditions are obtained, and mathematical descriptions for the constitutive relation are provided; the effects of temperature and strain rates on some material property parameters, such as yield ratio, ductility and normal anisotropy, are studied; the characters and causes of tube fracture are analyzed by observing the appearance of fracture. Meanwhile, the volume compression test, side pressure coefficient test and pressure-transfer test on thermal-state solid granules are adapted to analyze the mechanical property and pressure-transfer law of non-mental thermotolerant solid granule medium. The volume compressibility and side pressure stress curves of granules with different diameters are measured in different temperature; the impacts of those factors, such as: temperature, load, boundary conditions of bearing the medium, etc., on the pressure-transfer performance of solid granule medium are studied; based on FEM, the simulation model of solid granule medium is founded, and the comparison between this model and test is conducted. Based on the material performance tests of AA5083 and solid granule medium, the numerical simulation model for HGMF technology on AA5083 is established by the application of FEM software---ABAQUES, the impacts of the geometric condition and technical parameters of tube forming on the influence rule of tube forming property are studied, and during the forming process, some bulging characteristics, such as: the variation of contour, the distribution law of wall-thickness, the forming tendency of fracture, etc., whose forming mechanisms are analyzed, which provide data support for the further exploration and practical application of HGFM technology on light alloy tube.