Research On Viscous Warm Pressure Forming Of Magnesium Alloy

The plasticity of magnesium alloys generally is quite poor at room temperature due to the hexagonal crystal packed crystal structure. So it is difficult for magnesium alloys to form the sheet metals with high quality and complicated shape. In this paper, based on the existing viscous pressure forming technology and combination of the performance and characteristic of magnesium alloy at high temperature, the formability of magnesium alloy can be improved through the viscous warm pressure forming. So the application of viscous pressure forming is extended.Firstly, the temperature range of thermal stability and compression performance of methyl vinyl silicone rubber as viscous medium have been tested through the thermal compression experiment of viscous medium; the rheological property of viscous medium has been analyzed through the thermal flowability experiment of viscous medium. At the same time, during the thermal stability temperature range of viscous medium, the warm uniaxial tensile tests of AZ31 B magnesium alloy have been conducted then the influence of temperature and tensile speed on the mechanical properties of magnesium alloy is analyzed.Secondly, the warm couple deformation rule of viscous medium and AZ31 B magnesium alloy has been researched through the finite element simulations and experiments of AZ31 B magnesium alloy viscous warm pressure bulging. And the velocity variation and pressure stress distribution of viscous medium and the equivalent strain distribution of magnesium alloy at different temperatures have been observed. Then the best temperature and process parameters have been ascertained.Thirdly, based on the bulging rule of different ellipticity die, the influence of part complexity on the formability of viscous warm pressure forming of AZ31 B magnesium alloy has been analyzed. So the section shape, the thickness reduction rate, the radial strain of sheet and the pressure distribution of viscous medium with different ellipticity have been obtained. At the same time, the forming limit diagram(FLD) of viscous warm pressure bulging of AZ31 B magnesium alloy has been obtained through measurement of limit forming specimens.Finally, based on the combination of stress-state analysis at the center area of bulging specimen with the ellipticity die and the Cockafk-Latham fracture criterion, the damage model of viscous warm pressure bulging with ellipticity has been established to predict the limit dome heights of specimens with different ellipticity. Prediction results have been combined with the experimental results of viscous warm pressure bulging with different ellipticity die. The comparison shows the accuracy of damage model.