Flexibility of three differential constitutive models evaluated by large amplitude oscillatory shear and Fourier transform rheology

Pivokonský, Radek; Filip, Petr; Zelenková, Jana

doi:10.1016/j.polymer.2016.09.014

Cited by 3 publications

(2 citation statements)

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“…For both ways of parameters optimization, the values of the “anisotropic” parameter α in the Giesekus model attained values exceeding 0.5. However, as discussed in Bird et al [38] and Schleiniger and Weinacht [39], the values of the parameter α exceeding 0.5 (α ∈ (0.5,1]) result in unphysical predictions as also documented in [27].…”

Section: Resultsmentioning

confidence: 82%

“…The suitability of modeling the rheological data within a non-linear viscoelastic region (covered by the LAOS measurements) for individual empirical [7,15] and differential constitutive equations [15,16,17,18,19,20,21,22,23,24,25,26,27] has recently attracted attention. Naturally, these analyses are subject to used polymeric materials and to applied forces to which material is exposed (characterized by strain and frequency).…”

Section: Introductionmentioning

confidence: 99%

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Two Ways to Examine Differential Constitutive Equations: Initiated on Steady or Initiated on Unsteady (LAOS) Shear Characteristics

2017

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The exponential Phan–Tien and Tanner (PTT), Giesekus, Leonov, and modified extended Pom–Pom (mXPP) differential constitutive models are evaluated in two ways: with regard to steady shear characteristics and with regard to large amplitude oscillatory shear characteristics of a solution of poly(ethylene oxide) in dimethyl sulfoxide. Efficiency of the models with nonlinear parameters optimized with respect to steady shear measurements is evaluated by their ability to describe large amplitude oscillatory shear (LAOS) characteristics. The reciprocal problem is also analyzed: The nonlinear parameters are optimized with respect to the LAOS measurements, and the models are confronted with the steady shear characteristics. In this case, optimization is based on the LAOS measurements and equal emphasis is placed on both real and imaginary parts of the stress amplitude. The results show that the chosen models are not adequately able to fit the LAOS characteristics if the optimization of nonlinear parameters is based on steady shear measurements. It follows that the optimization of nonlinear parameters is much more responsible if it is carried out with respect to the LAOS data. In this case, when the optimized parameters are used for a description of steady shear characteristics, efficiency of the individual models as documented differs.

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Section: Resultsmentioning

confidence: 82%