Li Dequn

Three-dimensional finite element method for the filling simulation of injection molding

With the development of molding techniques, molded parts have more complex and larger geometry with nonuniform thickness. In this case, the velocity and the variation of parameters in the gapwise direction are considerable and cannot be neglected. A three-dimensional (3D) simulation model can predict the filling process more accurately than a 2.5D model based on the Hele–Shaw approximation. This paper gives a mathematical model and numeric method based on 3D model to perform more accurate simulations of a fully flow. The model employs an equal-order velocity–pressure interpolation method. The relation between velocity and pressure is obtained from the discretized momentum equations in order to derive the pressure equation. A 3D control volume scheme is used to track the flow front. During calculating the temperature field, the influence of convection items in three directions is considered. The software based on this 3D model can calculate the pressure field, velocity field and temperature field in filling process. The validity of the model has been tested through the analysis of the flow in cavities.

Modeling and simulation of heat transfer for glass bulb mold

Abstract Cooling system design in glass bulb pressing operation can greatly affect the productivity and the quality of the final product. The concept of cyclic-averaged steady temperature field is proposed in modeling. Heat transfer in the mold region is considered to be a cyclic-steady three-dimensional conduction; heat transfer within the glass melt region is treated as a transient, one-dimensional conduction; heat exchange between the cooling system surface and coolant is treated as a steady heat convection. A hybrid model consisting of a three-dimensional boundary element method for the mold region and a finite-difference method with a variable mesh for the melt region is used for numerical simulation. Compared with the experimental data, the numerical model developed here is computationally efficient and sufficiently accurate.

Numerical prediction of process-induced residual stresses in glass bulb panel

A numerical simulation model for predicting residual stresses which arise during the solidification process of pressed glass bulb panel was developed. The solidification of a molten layer of glass between cooled parallel plates was used to model the mechanics of the buildup of residual stresses in the forming process. A thermorheologically simple thermoviscoelastic model was assumed for the material. The finite element method employed was based on the theory of shells as an assembly of flat elements. This approach calculates residual stresses layer by layer like a truly three-dimensional calculation, which is well suited for thin pressed products of complex shape. An experimental comparison was employed to verify the proposed models and methods.