Analyses and measurements on bending performance of gas-assisted injectionmolded parts

Numerical simulation and experimental measurements were carried out to asse ss the bending behavior of gas-assisted injection-molded parts. Polystyrene plate parts of different thicknesses, designed with various channel geomet ries, were gas-assisted injection molded. Part flexible strength was measur ed by a bending test. It was found that part stiffness basically increases linearly with the inertia moment of the plate. Gas channel design, introduc ing an additional moment of inertia determined by the geometry of the chann el section and the hollowed core, resulted in structural reinforcement of t he part. An analysis algorithm based on DKT/VRT elements superimposed with beam elements, representing gas channels of various section geometries, was developed to evaluate part bending behavior. An equivalent diameter was as signed to the beam element so that both the original gas channel and the ci rcular beam had the same moment of inertia. The results from this 2.5-dimen sional model were also verified with three-dimensional analyses using the A NSYS program. The present simulations show reasonable accuracy upon compari son to bending tests and predictions from ANSYS. This investigation indicat es that it is possible to use the same CAE finite-element mesh modeled for process simulation when performing part structure and warpage analyses, res ulting in high computational efficiency. (C) 1999 John Wiley & Sons, Inc.