Three-dimensional simulation of thermoforming process and its comparison with experiments

Three-dimensional solid element analysis and the membrane approximated anal ysis employing the hyperelastic material model have been developed for the simulation of the thermoforming process. For the free inflation test of a r ectangular sheet, these two analyses showed the same behavior when the shee t thickness was thin, and they deviated more and more as the sheet thicknes s increased. In this research, we made a guideline for the accuracy range o f sheet thickness for the membrane analysis to be applied. The simulations were performed for both vacuum forming and the plug-assisted forming proces s. To compare the simulation results with experiments, laboratory scale the rmoforming experiments were performed with acrylonitrile-butadiene-styrene (ABS). The material parameters of the hyperelastic model were obtained by u ni-directional hot tensile tests, and the thickness distributions obtained from experiments corresponded well with the numerical results. Non-isotherm al analysis that took into account the sheet temperature distribution measu red directly from the experiments was also performed. It was found that the non-isothermal analysis greatly improved the predictability of the numeric al simulation, and it is important to take into account the sheet temperatu re distribution for a more reliable simulation of the thermoforming process .