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Dimensional Stability and Residual Stresses
Prediction and control of shrinkage, warpage, and residual stresses are difficult generic problems associated with the use of plastics. This chapter presents three simple models of increasing complexity to explain the mechanics of the plastic part shaping processes. It addresses dimensional stability and residual stresses in amorphous materials. A highly idealized model for the molding process, in which there are no temperature gradients in the solidifying melt, does not account for cooling rate and fill‐time, or cycle time, effects. Molten layer solidification model developed for predicting the effect of time‐varying temperature and pressure histories on part shrinkage predicts a linear dependence of shrinkage on an effective pressure. Viscoelastic solidification model provides insights into how the packing‐pressure history affects shrinkage. The chapter also addresses questions of the type: Is it necessary to apply the packing pressure till the part has solidified? During which phase of the molding cycle is the packing pressure most effective in reducing shrinkage?
Dimensional Stability and Residual Stresses
Prediction and control of shrinkage, warpage, and residual stresses are difficult generic problems associated with the use of plastics. This chapter presents three simple models of increasing complexity to explain the mechanics of the plastic part shaping processes. It addresses dimensional stability and residual stresses in amorphous materials. A highly idealized model for the molding process, in which there are no temperature gradients in the solidifying melt, does not account for cooling rate and fill‐time, or cycle time, effects. Molten layer solidification model developed for predicting the effect of time‐varying temperature and pressure histories on part shrinkage predicts a linear dependence of shrinkage on an effective pressure. Viscoelastic solidification model provides insights into how the packing‐pressure history affects shrinkage. The chapter also addresses questions of the type: Is it necessary to apply the packing pressure till the part has solidified? During which phase of the molding cycle is the packing pressure most effective in reducing shrinkage?
Dimensional Stability and Residual Stresses
Stokes, Vijay K. (author)
Introduction to Plastics Engineering ; 555-614
2020-05-11
60 pages
Article/Chapter (Book)
Electronic Resource
English
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