Now showing items 4-23 of 50

    • Degradation in Cone-Plate Rheometry 

      Giacomin, A. Jeffrey; Gilbert, Peter H. (2018-07)
      We analyze quantitatively the oxidative degradation of a sample in a cone-plate rheometer, as oxygen diffuses inward, radially, from the free boundary. We examine rheometer error mitigation by means of nitrogen blanketing, ...
    • Degradation in Parallel-Disk Rheometry 

      Giacomin, A. Jeffrey; Pasquino, R.; Saengow, Chaimongkol; Gilbert, Peter H. (2018-08)
      We analyze quantitatively the oxidative degradation of a sample in a parallel-disk rheometer, as oxygen diffuses inward, radially, from the free boundary. We examine rheometer error mitigation by means of nitrogen blanketing, ...
    • Die Drool and Polymer Degradation 

      Hoy, Geoffrey S.; Giacomin, A. Jeffrey; Gilbert, Peter H. (2015-06-24)
      Die drool is an operational problem associated with polymer extrusion. Extrudate collects outside of the die, necessitating periodic disruptions for cleaning. There exists some debate as to the mechanism that produces ...
    • Elastomers in Large-Amplitude Oscillatory Uniaxial Extension Revisited 

      Dessi, Claudia; Vlassopoulos, Dimitris; Giacomin, A. Jeffrey; Saengow, Chaimongkol (2017-07)
      In this work, we subject elastomers to a fixed pre-stretch in uniaxial extension, ε p , upon which a large-amplitude, ε 0 , oscillatory uniaxial extensional (LAOE) deformation is superposed. We find that if both ε p and ε ...
    • Elastomers in Oscillatory Uniaxial Extension 

      Dessi, Claudia; Vlassopoulos, Dimitris; Giacomin, A. Jeffrey; Saengow, Chaimongkol (2016-02)
      In this work, we subject elastomers to a fixed pre-stretch in uniaxial extension, ε p , upon which a large-amplitude, ε 0 , oscillatory uniaxial extensional (LAOE) deformation is superposed. We find that if both ε p and ε ...
    • Ethermodynamic Instability of Polymeric Liquids in Large-Amplitude Oscillatory Shear Flow from Corotational Maxwell Fluid 

      Saengow, Chaimongkol; Giacomin, A. Jeffrey (2018-04)
      When polymeric liquids are subjected to oscillatory shear flow, if the amplitude of the shear rate is high enough, the shear stress response will become aperiodic. This has been variously attributed to fracture, common ...
    • Exact Analytical Interconversion between Durometer Hardness Scales 

      Gilbert, Peter H.; Giacomin, A. Jeffrey (2017-02)
      Previous work has related Young’s modulus to durometer hardness for any standardized scale. In this paper, we build on this work to solve explicitly and exactly for the hardness in any one standardized durometer hardness ...
    • Exact Analytical Solution for Large-Amplitude Oscillatory Shear Flow 

      Saengow, Chaimongkol; Giacomin, A. Jeffrey; Kolitawong, Chanyut (2015-03-16)
      When polymeric liquids undergo large-amplitude shearing oscillations, the shear stress responds as a Fourier series, the higher harmonics of which are caused by fluid nonlinearity. Previous work on large-amplitude oscillatory ...
    • Exact Analytical Solution for Large-Amplitude Oscillatory Shear Flow from Oldroyd 8-Constant Framework: Shear Stress 

      Saengow, Chaimongkol; Giacomin, A. Jeffrey; Kolitawong, Chanyut (2017-01)
      The Oldroyd 8-constant model is a continuum framework containing, as special cases, many important constitutive equations for elastic liquids. When polymeric liquids undergo large-amplitude oscillatory shear flow, the shear ...
    • Exact Coefficients for Rigid Dumbbell Suspensions for Steady Shear Flow Material Function Expansions 

      Piette, Jourdain H.; Jbara, Layal; Saengow, Chaimongkol; Giacomin, A. Jeffrey (2008-07)
      From kinetic molecular theory, we can attribute the elasticity of polymeric liquids to macromolecular orientation. For a suspension of rigid dumbbells, subject to a particular flow field, we must first solve the diffusion ...
    • Exact Solutions for Oscillatory Shear Sweep Behaviors of Complex Fluids from the Oldroyd 8-constant Framework 

      Saengow, Chaimongkol; Giacomin, A. Jeffrey (2017-05)
      Large-amplitude oscillatory shear flow (LAOS) is a popular for studying the nonlinear physics of complex fluids. Specifically, the strain rate sweep (also called the strain sweep) is used routinely to identify the onset ...
    • Exact-solution for Cone-plate Viscometry 

      Giacomin, A. Jeffrey; Gilbert, Peter H. (2017-08)
      The viscosity of a Newtonian fluid is often measured by confining the fluid to the gap between a rotating cone that is perpendicular to a fixed disk. We call this experiment cone-plate viscometry. When the cone angle ...
    • Extruding Plastic Pipe From Eccentric Dies 

      Saengow, Chaimongkol; Giacomin, A. Jeffrey; Kolitawong, Chanyut (2015-05-25)
      To solidify plastic pipe, the pipe is transported through a long cooling chamber. Inside this chamber, inside the pipe, the plastic remains molten, and this inner surface solidifies last. The flow due to the self-weight ...
    • Fluid Elasticity in Plastic Pipe Extrusion: Loads on Die Barrel 

      Saengow, Chaimongkol; Giacomin, A. Jeffrey (2017-07)
      In large thick plastic pipe extrusion, the residence in the cooling chamber is long, and the melt inside the pipe sags under its own weight, causing the product to thicken on the bottom (and to thin on the top). To compensate ...
    • Fourier Decomposition of Polymer Orientation in Large-Amplitude Oscillatory Shear Flow 

      Giacomin, A. Jeffrey; Gilbert, Peter H.; Schmalzer, Andrew M. (2015-03-17)
      In our previous work, we explored the dynamics of a dilute suspension of rigid dumbbells as a model for polymeric liquids in large-amplitude oscillatory shear flow, a flow experiment that has gained a significant following ...
    • Hydrodynamic Interaction for Rigid Dumbbell Suspensions in Steady Shear Flow 

      Piette, Jourdain H.; Saengow, Chaimongkol; Giacomin, A. Jeffrey (2018-12)
      From kinetic molecular theory, we can attribute the rheological behaviors of polymeric liquids to macromolecular orientation. The simplest model to capture the orientation of macromolecules is the rigid dumbbell. For a ...
    • Knuckle Formation From Melt Elasticity in Plastic Pipe Extrusion 

      Saengow, Chaimongkol; Giacomin, A. Jeffrey; Kolitawong, Chanyut (2016-07)
      When plastic pipe is solidified, it proceeds through a long cooling chamber. Inside the chamber, inside the extrudate, the plastic is molten, and this inner surface solidifies last. Sag then happens inside this cooling ...
    • Large-Amplitude Oscillatory Shear: Comparing Parallel-Disk with Cone-Plate Flow 

      Giacomin, A. Jeffrey; Gilbert, Peter H.; Merger, Dimitri; Wilhelm, Manfred (2014-09-30)
      We compare the ratio of the amplitudes of the third to the first harmonic of the torque, |T3|/|T1|, measured in rotational parallel-disk flow, with the ratio of the corresponding harmonics of the shear stress, |T3|/|T1|, ...
    • Macromolecular Origins of Fifth Shear-Stress Harmonic in Large-Amplitude Oscillatory Shear Flow 

      Jbara, Layal M.; Gilbert, Peter H.; Giacomin, A. Jeffrey (2016-08)
      This study examines the simplest relevant molecular model of a polymeric liquid in large-amplitude oscillatory shear (LAOS) flow: the suspension of rigid dumbbells in a Newtonian solvent. For such suspensions, the viscoelastic ...
    • Macromolecular Tumbling and Wobbling in Large-Amplitude Oscillatory Shear Flow 

      Jbara, Layal M.; Giacomin, A. Jeffrey (2018-11)
      For a suspension of rigid dumbbells, in any simple shear flow, we recently solved for the diffusion equation for the orientation distribution function by a power series expansion in the shear rate magnitude. In this paper, ...