Three-dimensional modeling of the stress evolution in injection molded parts based on a known melt pressure field

To obtain the initial conditions for ejection analysis of an injection molded part, a numerical simulation of the stress evolution in the material during injection molding is required. This topic, described in the literature only modestly for the full three-dimensional geometry, is addressed here by proposing an approach simple enough to be implemented in a general purpose solid mechanics simulation code. This feature makes it especially suitable with respect to the analysis of ejection, where custom code development might present hindering amount of additional work. As temperature and pressure field evolutions are obtainable through a computational fluid dynamics analysis, they are taken as input data in the stress analysis. The novelty of the approach is in the treatment of the melt region, where explicit tracking of the melt-solid interface is substituted by imposing the known pressure field in the melt region. The validity of the approach is experimentally tested by analyzing shrinkage and mass of moldings, as well as partial cavity pressure evolution at different packing pressure settings.