Evaluation of the Predictive Capacity of Viscosity Models in Polymer Melt Filling Simulations

The increase in computational power in the last years has favored application of simulation strategies to forming operations, especially injection molding. The successful numerical predictions require appropriate material modeling, so that an erroneous choice of a rheological model can considerably compromise the simulation, resulting in high expenses with rework and re-planning. Therefore, in addition to obtaining a good experience in injection processing, design engineers must have knowledge of mathematical models. Within this framework, the present study aims to evaluate the predictive capacity of several well-known viscosity models for thermoplastic injection process by comparing numerical results with experimental data for an ABS polymer. The numerical solution approximated the generalized Hele-Shaw model using the Moldflow® software. The numerical-experimental comparative tests were performed for the filling phase, from which the shape of the polymer flow front, mass filling fraction and time efficiency at different filling stages were addressed. The results show that substantial differences arise when a mistaken rheological model is adopted, and the importance of the temperature, shear rate and pressure in the numerical predictions.