Study On Deformation Behavior Of AZ31 Magnesium Alloy Tube In Hydroforming Process At Elevated Temperature

With the development of micro-electromechanical system(MEMS),micro-components made of microtubes are studied in many industries.Considering the density similar to human skeleton and excellent biocompatibility,medical instruments made of magnesium tubes have been widely used in medical treatments.In order to produce micro-components with complex shapes and avoid machining and welding,the hydroforming process has been studied extensively in recent years.The mechanical properties of magnesium alloys are affected greatly by temperature,for example,the yield strength of magnesium alloys decreases with the increase of temperature,thus the formability is improved remarkably.In this paper.the deformation behavior of magnesium alloy in hydroforming process at elevated temperature was studied.Considering the liquid medium such as hydraulic oil is flammable at high temperature,an equipment of hydroforming process at elevated temperature with gas medium was designed,and the deformation behavior of tubes made of AZ31 magnesium alloy in hydroforming process at elevated temperature was investigated by finite element modelling(FEM)and plastic forming theory respectively.The contents of this paper are as follows:(1)In order to extend the application of hydroforming process,an equipment of hydroforming process at elevated temperature with gas medium was designed at the account of hot-working and plastic forming.(2)In order to obtain the deformation behavior and the distribution of stress and strain in tubes made of AZ31 magnesium alloy,the numerical simulation of hydroforming process was conducted by ANSYS/LS-dyna,and the orthogonal experimental method was used to optimize the loading path of hydroforming process.The deformation behavior of tubes was obtained by analyzing the distribution of stress and strain,the flow volume of mass ratio at different areas,the variation of wall thickness,the main deformation parameters,the plane plastic stress locus diagram respectively.(3)The calculation method of stress and wall thickness at any point is obtained by analyzing the stress and wall thickness in different areas of tubes in hydroforming process considering plastic theory and method of difference.Compared with the experimental data of hydroforming process,the calculation results of T-shape tube are verified.