Study On The Hydroforming Of Pet Film Based On Experiment And Finite Element Simulation

At present,the method of metal mold forming is the most common way of forming PET films in the IMD(In-Mould-Decoration)processes.However,the forming of IMD films used this method can be very challenging due to shallower forming depth,uneven film thickness distribution,and obvious die marks on the surfaces of the forming films.Through searching a lot of references,it could be found that the pressure bulging method could solve the above-mentioned problems out of the metal mold forming use.Based on the application characteristics of different pressure bulging media,the hydraulic bulging was chose to perform experiments.In this study,the characteristics and regularity of PET film deformation were explored under different forming parameter conditions.In this paper,the characteristics and influencing factors of sheet metal pressure bulging were investigated,and then designed a set of pre-test bench and verified the feasibility of hydraulic bulging by the pre-experiment.According to the problems from the pre-experiment,a secondary test bench was built up.The method uses a single variable to design the experimental plan and analyzes the different process parameters,gets some important results.In freely hydraulic bulging of PET films,the results show that the diaphragm region is easy to burst and the burst zone’s thickness is about 0.08 mm as the pressure increases in the intermediate portion forming process.Compared with the pressure load method,loading rate and BHF loading have greater impacts on forming.Through the hydraulic bulge of box shape forming process,the results show that the thinnest area occurs in the bottom corner of the die area when the film forming,and it usually bursts in the bottom corner of the die area.In a fitting mold structure,the die fillet is bigger and more conducive to the film forming.The blank area is too large or too small to have serious impact on the performance of the membrane forming.Based on the PET material,the digital material model was selected.The stress-strain curves of the PET films were obtained by an uniaxial tensile test at room temperature.And the material model parameters were obtained by fitting the curves.The free pressure bulging and boxes pieces box shape pressure forming finite simulation models of PET films by the uniaxial tension test verification.From the numerical simulation of the diaphragm by the hydraulic bulging,the stress,thickness varies under different process parameters.From the simulation and experimental results,the analysis shows that PET material parameters can fit the PET film performance...