Research On Pressure Distribution Characteristics Of Sheet Metal Viscous Pressure Forming

In the sheet metal forming process,the interaction between the sheet metal and the forming tool directly determines the forming effect of the sheet metal.However,the contact surface between the sheet metal and the forming tool is a closed interface during the deformation process,so the interaction between the sheet metal and the forming tool can not be tracked and measured through the sensing elements,thus the current research is limited to theoretical analysis and finite element simulation.It is necessary to explore the direct measurement method of the interface interaction between the sheet metal and the forming tool in the forming process,which is helpful to obtain the true deformation load on various areas of the sheet metal,and to analyze the deformation state of the sheet metal and the distribution of the forming pressure field.In this paper,viscous pressure forming is taken as the research object,and the interaction between sheet metal and viscous medium is studied by direct measurement method.The non-uniform pressure field in viscous pressure forming is the main factor to improve sheet metal formability,however the distribution of non-uniform pressure field during the forming process is mainly studied by indirect method at present.In this paper,a new method of pressure measurement for sheet metal viscous pressure forming by Prescale is proposed,which is originally used for interface pressure measurement.The distribution of forming pressure on the interface between the medium and the sheet metal in the process of viscous pressure forming is measured intuitively.By comparing the experimental data with finite element numerical simulation results,the general law of non-uniform pressure distribution in viscous pressure forming process is obtained.Firstly,the experiments of viscous pressure bulging was carried out to confirm the feasibility of pressure measuring by using Prescale.Combined with plunger stroke-test force curve,the model of Prescale used for measuring forming pressure was determined,and a series of tests were carried out to determine the optimum shape and size of Prescale.Then the non-uniform pressure distribution in the process of viscous free bulging and viscous die bulging were studied,and the pressure distribution in different experimental conditions was measured and analyzed by using suitable types of Prescale.The influence of the bulging height,the molecular weight of the viscous medium,the loading speed and the orders of fitting mold cavity on the distribution of wall thicknessand pressure field of forming parts was obtained.The results showed that the forming pressure decreases from the center to the edge of sheet metal in viscous free bulging.With the increase of bulging height or loading speed,the pressure field between sheet metal and viscous medium increases,and the distribution of non-uniform pressure becomes more obvious.On the other hand,the distribution of the non-uniform pressure field in viscous die bulging is directly related to the orders of fitting mold cavity.The earlier the fitting order is,the higher the pressure is.Finally,the numerical simulation of viscous pressure forming process was carried out by using ANSYS/LS-DYNA finite element simulation software.And the simulation results were compared with the experimental results to summarize the distribution characteristics of non-uniform pressure field in viscous pressure forming.