Accession Number : ADA303564

Title :   Compressive Flow of Viscoelastic Materials.

Descriptive Note : Doctoral thesis,

Corporate Author : DELAWARE UNIV NEWARK CENTER FOR COMPOSITE MATERIALS

Personal Author(s) : Lee, Seung J.

PDF Url : ADA303564

Report Date : JUN 1982

Pagination or Media Count : 209

Abstract : The compressive flow of viscoelastic materials between two parallel flat disks under a constant load has been investigated analytically, numerically, and experimentally. This process simulates a number of compression molding and lubrication experiments; the purpose of our study was to assess the effects of fluid viscoelasticity and of temperature gradients in these applications. A dimensionless group has been found very useful for determining the flow regimes when there exists a substantial transverse viscosity gradient in the fluid charge, such as in the nonisothermal compression molding processes. Compressive flow of linear viscoelastic materials has been analyzed analytically. It shows that the squeezing motion becomes oscillatory when the ratio of the Deborah number to the Reynolds number is larger than a critical value, and that the linear viscoelastic materials are squeezed faster than the corresponding Newtonian cases. Compressive flow of various non-linear model fluids has also been analyzed numerically. The Maxwell fluid behaves much like linear viscoelastic materials, except under extraordinarily high loading conditions. But, the Johnson-Segalman model and the Marrucci structural model show that slower squeezing may arise after the initial rapid transient under moderate loading conditions. This slower squeezing must be due to the special features of these models, which the Maxwell model does not exhibit, such as stress overshoot in the transient flows. Experimentally two different observations have been made. A silicone polymer shows the oscillatory and the faster squeezing, which is predictable by the Maxwell type of model fluid. (MM)

Descriptors :   *VISCOELASTICITY, *COMPRESSIBLE FLOW, *LUBRICATION, *MOLDING TECHNIQUES, POLYMERS, PROCESSING, LOADS(FORCES), TEMPERATURE GRADIENTS, LINEARITY, PARALLEL ORIENTATION, VISCOUS FLOW, VISCOSITY, REYNOLDS NUMBER, SILICONES, COMPRESSIVE PROPERTIES, COMPRESSION MOLDING.

Subject Categories : Lubricants and Hydraulic Fluids
      Hydraulic and Pneumatic Equipment
      Mfg & Industrial Eng & Control of Product Sys
      Fluid Mechanics
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE