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Research Papers

Three-Dimensional Viscoelastic Simulation for Injection/Compression Molding Based on Arbitrary Lagrangian Eulerian Description

[+] Author and Article Information
Wei Cao, Shaozhen Hua, Shixun Zhang, Yaming Wang, Haimei Li, Chuntai Liu, Changyu Shen

National Engineering Research Center of
Mold and Die,
Zhengzhou University,
Zhengzhou, Henan 450002, China

Tao Wang

Beijing Institute of Aeronautical Materials,
Beijing 100095, China

Contributed by the Design Engineering Division of ASME for publication in the JOURNAL OF COMPUTATIONAL AND NONLINEAR DYNAMICS. Manuscript received May 23, 2015; final manuscript received December 27, 2015; published online February 3, 2016. Assoc. Editor: Zdravko Terze.

J. Comput. Nonlinear Dynam 11(5), 051004 (Feb 03, 2016) (8 pages) Paper No: CND-15-1139; doi: 10.1115/1.4032384 History: Received May 23, 2015; Revised December 27, 2015

Different from conventional injection molding (CIM), injection/compression molding (ICM) evolves boundary variation in gapwise direction. In order to describe melt flow characteristics in ICM correctly, a new material derivative based on arbitrary Lagrangian Eulerian (ALE) description was introduced to modify the material derivatives in the governing and constitutive equations. To avoid large amount of calculation and weak stability of integral numerical method, an iterative approach employing twofold iterations was proposed to decouple the interdependence between velocity, stress, and temperature. The initial values of material parameters in constitutive equations were obtained or fitted by rheological experiments. The ICM experiments for an iso-thick and a var-thick rectangular panel were carried out to validate the proposed method and find the special characteristics of ICM. In addition, the photoelastic tests on a quarter of spherical part processed by ICM were conducted to identify the relationship between residual flow-induced stress distributions and flow fields. Both simulations and experiments show that the pressure profile displays a plateau during compression, temperature decreases with time according to exponential law, large flow-induced stress originates in thick transitional region, flow start, and flow end areas, and gravity has significant effect on meltfront for thick part ICM. The good agreement between experiments and simulations indicates that the current method can properly describe the flow characteristics of ICM.

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Figures

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Fig. 1

Diagram of a point transformation in ALE scheme

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Fig. 2

Diagram of polymer melt flow during compression

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Fig. 3

Mixed finite elements used in this study with (a) P2(10) element: four vertices + six edge midpoints, (b) P1(4) element: four vertices in which •—value of u,T and ×—value of p, τ

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Fig. 4

Diagram of the dimension of the studied parts: (a) iso-thick part and (b) var-thick part. O—sensor location and ◀—polymer entrance.

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Fig. 5

Simulated meltfronts of iso-thick panel at times: (a) 3 s, (b) 5 s, (c) 7 s, and (d) 9 s

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Fig. 6

Measured pressures of sensors 2 and 4 change with time during iso-thick part ICM

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Fig. 7

Simulated meltfronts of var-thick panel at times: (a) 3 s, (b) 5 s, (c) 8 s, and (d) 10 s

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Fig. 8

Measured sensors' pressures of iso-thick panel injection molding with injection velocity (for screw): 60 mm/s, filling/packing switch: 30 mm, packing pressure: 80 MPa, and melt temperature: 300 °C

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Fig. 9

Comparison between the measured and simulated sensors' pressures of (a) iso-thick panel and (b) var-thick panel during filling and compressing stages. − (thick and discrete line) represents experimental data and − (thin and smooth line) denotes the simulated data.

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Fig. 10

Comparison between the measured and simulated sensors' temperatures of (a) iso-thick panel and (b) var-thick panel during filling and compressing stages. − (thick and discrete line) represents experimental data and − (thin and smooth line) denotes the simulated data.

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Fig. 11

Dimension of one-quarter of spherical part

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Fig. 12

Comparison between the simulated (a) first normal stress difference and (b) photoelasticpictures

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