Numerical algorithms for injection molding based on Giesekus viscoelastic model

doi:10.19491/j.issn.1001-9278.2023.09.009

Abstract

Abstract:

The calculation of viscoelastic flow is one of the challenges in the injection molding flow analysis. With regard to the viscoelastic characteristics and taking into account the inertia effect， a viscoelastic theoretical model for the melt flow in injection molding was developed based on the Giesekus constitutive model. The viscoelastic equation was integrated into a partial differential equation containing transient， convection and source terms， and the discretization method of the viscoelastic equation was proposed on the basis of the finite volume method. Taking a reference from the discrete elastic viscous stress splitting （DEVSS） in the finite element framework， a discrete splitting algorithm （FVM⁃DEVSS） based on the finite volume method was proposed， and a computational procedure for three⁃dimensional viscoelastic flow was developed. The validity of this algorithm was verified using the classically fully developed shrinkage flow at a shrinkage ratio of 4∶1. Then， the melt flow front， gate pressure and fusion line position were correctly predicted through combing with the mold filling flow experiments. The photoelastic experimental results proved the validity of the method again in the present study. The results indicated that the developed viscoelastic algorithm could effectively express the effect of melt viscosity and elasticity on the flow pressure and accurately predict the position of a fusion line and the formation process when two melt fonts met together. In addition， the flow⁃induced stress during the melt filling process could be calculated effectively and accurately through the developed viscoelastic algorithm.

Key words: Giesekus model, flow?induced stress, finite volume method, injection molding

CLC Number:

TQ320.66⁺2

HUA Shaozhen, CAO Wei. Numerical algorithms for injection molding based on Giesekus viscoelastic model[J]. China Plastics, 2023, 37(9): 57-63.

Figures/Tables 8

Fig.1. Numerical results of half 4∶1 planar contraction flow

Fig.2. Geometry and dimension of the runner and cavity

Fig.3. Experimental and umerical results at different filling time

Fig.4. Comparison of gating pressure in three cases

Fig.5. Geometry and dimension of rectangular cavity with hole

Fig.6. Numerical simulation of filling

Fig.7. Forming of weld line ：（a） numerical results；（b） experimental results

Fig.8. Comparison of numerical simulation and experimental results of flow⁃induced stresses ：（a） Birefringence experimental results［29］；（b） Numerical simulation results

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