Some Analytical Analysis Of Flow And Heat Transfer Behavior In Injection Molding

Injection molding is the main processing method in batch production of 3D exact complex plastic part. It produces more than one third of all plastic product. Injection molding is a complex procedure of flow and heat transfer, as the melt's procedure of flow and heat transfer in the filling system and cavity are very complex. Though numerical method makes much progress in the analysis of velocity field, temperature field and pressure field in injection molding, numerical simulation lacks exact descriptions of variety of physics fields in molding procedure are very short in the numerical simulation. Hence, realizing the analytical analysis of flow and heat transfer problems in injection molding becomes an effective method by which variety of physics fields in molding procedure are realized and understand in detail.Therefore, to realize the scientific understanding of injection molding procedure, detailed analysis for the classical flow and heat transfer problems in filling process of injection molding is made based on the analytical thinking.Firstly, for the flow and heat transfer problems of feeding system, based on Ellis model and governing equations in One-dimensional cavity, analytic calculation the variation of pressure field, flow rate and temperature in changes with different process conditions. Meanwhile, the effects of the heat conduction, thermal diffusion and shear heating thermal convection on flow and heat transfer behavior were investigated.Secondly, for the injection molding of regular-sized plastic parts with microstructure is a specific flow and heat transfer problem with multi-scale geometric structure. A hybrid method combined numerical simulation and analytical solution was used to analyze the flow behavior of this multi-scale geometric structure. Finite element/finite difference method was carried out to simulating the filling processing in macro cavity, and the profile of pressure at entry of microstructure is obtained. Meanwhile, an analytical model is formulated to correlate the injection distance in the microstructure with entrance pressure, micro geometric dimensions, flow rates and material properties.Lastly, in connection with the temperature profiles of forming process, similar solutions with differential equations theory was used to analysis the effects of the thermal convection, heat conduction between the melt and the wall, viscous heat consumption on temperature profiles. And then, discussion the effects of different process parameters on the temperature field in thickness direction.This thesis is supported by the National Natural Science Foundation (10872186).