Prediction of residual stresses in injection moulded parts

For automotive plastic parts, mostly used for interior assemblies, there is a clear demand of an increased accuracy of the simulation model. One crucial input for the simulation model is the correct material data. Based on test data, it is known that the dynamic material properties of a plastic part can differ significantly from the material data given in the data sheet (which is based on a specimen). One assumption to explain the difference is the residual stresses caused by the injection moulding process. A methodology has been developed to simulate the injection moulding process in Moldex3D and how the results can be used in other FEA structure analysis software. In this work, the focus has been to use the results from the injection moulding simulation in Abaqus within a parallel project. To prepare for continuous analysis after the injection moulding simulation, a comparison between shell and solid elements was performed to evaluate the difference between the two models. In addition, since the number of elements through the thickness is important in injection moulding simulation, an investigation with 3, 5 and 7 elements through the thickness has been done. The process parameters are crucial for the appearance and property for the final product. In order to determine how the process parameters influence the residual stress, only one parameter is changed at the time.