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Analysis of the packing stage of a viscoelastic melt
Author(s) -
Nguyen Ky T.,
Kamal Musa R.
Publication year - 1993
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760331103
Subject(s) - materials science , shrinkage , mold , viscoelasticity , composite material , residual stress , isothermal process , finite element method , planar , work (physics) , stage (stratigraphy) , mechanics , mechanical engineering , structural engineering , thermodynamics , paleontology , physics , computer graphics (images) , biology , computer science , engineering
The packing stage starts at the end of mold filling. During this stage, additional material is forced into the mold to compensate for the shrinkage during subse‐quent cooling. Underpacking results in molded parts with dimensional variation. Overpacking causes flash at the parting lines, stick during ejection, and excess residual stresses resulting in warpage. The packing stage is thus extremely important in the determination of the final quality of the product. Despite its importance, analysis of the packing stage has been relatively ignored, particularly the viscoelastic effect. In this work, the analysis of the isothermal packing stage is presented for a Maxwell fluid. A set of governing equations is derived for a two‐dimensional mold and solved using the Galerkin finite element method. In addition to the distribution of velocity and pressure, the model predicts the stresses in the planar direction, which could be used for subsequent calculation of the residual stresses.