Research On Magnesium Alloy Special Shaped Part Of SGMF Based On GTN Model

Magnesium alloy has the characteristics of low plasticity and difficulty in forming at room temperature.Compared with the traditional rigid punch forming,granules medium of sheet metal solid granules medium forming(abbreviation SGMF)have the advantages of good fluidity,easy sealing and high temperature resistance,and the sheet forming performance is improved.Therefore,the development of the SGMF in the complex cross-section of magnesium alloy at high temperature is of great significance to the expanding of magnesium alloy application.The forming process of sheet metal is a gradual accumulation of internal damage process.Therefore,the process parameters can be optimized by the analysis of the sheet damage behavior during the forming process.GTN(Gruson-Tvergaard-Needleman)damage model links the macroscopic tensile process of the material with the internal damage evolution process,and the fracture behavior of the material can be analyzed and predicted.The introduction of GTN model into numerical simulation has a guiding significance for the subsequent experiment and production.The true stress-strain curves of magnesium alloy are obtained by uniaxial tensile test of magnesium alloy.The fracture and necking of the specimens are analyzed by scanning electron microscopy(SEM),and the true stress and strain curves are applied to the uniaxial tensile model established by ABAQUS finite element software based on GTN model.The parameters required by the GTN damage model are determined by the finite element inverse method and the image analysis method.The experiments of measuring the friction coefficient between the magnesium alloy sheet and the mold,magnesium alloy sheet and granules are carried out,which provides a reference for the numerical simulation to set the contact condition.Based on the GTN damage model,the SGMF finite element model of magnesium alloy special shaped part is established.The influence of friction coefficient and blank holder gap on the damage evolution of parts is analyzed by finite element method.The rupture region of the workpiece during forming process is predicted and the optimum process parameters of the SGMF of magnesium alloy special shaped part are determined.The forming process of special shaped part is studied according to experiment,and the experiment results and simulation results are compared.It is shown that t he rupture position of the test part coincides with the rupture region predicted by SGMF finite element model of magnesium alloy special shaped part based on GTN damage model,and wall thickness variation trend of test part is identical with simulation.The correctness of the established numerical model in this paper is verified.