scholarly journals Theoretical rheological models for olive oil

2020 ◽  
Vol 2 (3) ◽  
pp. 122-127
Author(s):  
Ioana Stanciu
Keyword(s):  
Shear Rate ◽  
Olive Oil ◽  
Dynamic Viscosity ◽  
Exponential Dependence ◽  
Rheological Models ◽  
Shear Rates ◽  
Constant Shear ◽  
Exponential Decline ◽  
Increasing Temperature ◽  
Constant Shear Rate

This paper proposes new rheological models for olive oil. The purpose of this study was to find an exponential  dependence between temperature and dynamic viscosity of olive oil, using one equation. Equation constants lnη0, A1 and t1 were determined by fitting exponential. The olive oil have investigated using a Haake VT 550 Viscotester developing shear rates ranging between 3 and 120 s-1 and measuring viscosities from 104 to 106 mPa·s when the HV1 viscosity sensor is used. Olive oil dynamic viscosity decreases with increasing temperature at constant shear rate.  Plotting the ln dynamic viscosity depending on temperature shows an exponential decline.

Shear Flow and Large Amplitude Oscillation Shear Study of Solutions of Aggregating Micellar Casein Particles

2008 ◽  
Vol 18 (2) ◽  
pp. 23050-1-23050-7 ◽  
Author(s):  
Anne Pitkowski ◽  
Taco Nicolai ◽  
Dominique Durand
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Shear Flow ◽  
Heating Temperature ◽  
Constant Shear ◽  
Micellar Casein ◽  
Large Amplitude Oscillation ◽  
Increasing Temperature ◽  
Small Shear ◽  
Constant Shear Rate

Abstract Small micellar casein particles were formed in aqueous solutions of native casein after addition of polyphosphate. These so-called submicelles aggregated and gelled with a rate that increased with increasing temperature. The evolution of the viscosity during this process was determined at constant shear rate or shear stress. When applying a small shear stress the viscosity increased strongly until the shear rate became immeasurably slow, but when the applied shear stress exceeded a critical value (σc) the aggregates broke up and the viscosity reached a maximum. At longer times the viscosity decreased rapidly at first, followed by a very slow decrease. σc was independent of the shear rate and heating temperature, but increased strongly with increasing casein concentration. At constant shear rate the stress remained close to σc, but fluctuated irregularly. After cessation of shear flow, gels were formed rapidly. Oscillation shear measurements for σ > σc showed a strongly non-linear response at the time of maximum viscosity.

Influence of Fillers on the Viscosity Properties of One-Pack Polyurethane Sealants

2021 ◽  
Vol 410 ◽  
pp. 605-610
Author(s):  
Kseniya A. Timakova ◽  
Yuriy T. Panov ◽  
Evgeniy A. Timakov
Keyword(s):  
Shear Rate ◽  
Dynamic Viscosity ◽  
Sharp Increase ◽  
Sharp Decrease ◽  
Shear Forces ◽  
Complex Orientation ◽  
Developed Surface ◽  
Mineral Fillers ◽  
Constant Shear Rate ◽  
Shape Of Particles

The paper investigates the effect of fillers on the viscosity properties of one-pack polyurethane sealants. It is noted that with the introduction of such mineral fillers as Mikarb, Midol, MTD2 chalk and aluminum hydroxide, the dynamic viscosity of the composition increases uniformly, while when filled with chemically precipitated Calofort SV chalk and MT-GShM talc, an abnormally sharp increase in viscosity is observed. Such an increase in viscosity for Calofort SV is explained by a highly developed surface, in contrast to other fillers. Talc is characterized by a plate-like shape of particles, which leads to a complex orientation of talc particles in the composition and shear difficulties.It was found that a sealant filled with chemically precipitated chalk has more than 100 pts. wt.(parts by weight), per 100 pts. wt. of the prepolymer under the influence of shear forces (at a constant shear rate) during the first 10 minutes of exposure, a sharp decrease in viscosity is observed, which is characteristic of thixotropic compositions, reaching a constant value after 5-10 minutes. After 10 minutes, the thixotropy of the sealant is restored. Talc does not impart thixotropic properties to the sealant composition.

scholarly journals Computer aided optimisation of a constant shear-rate micro-channel contraction

2009 ◽  
Vol 50 ◽  
pp. 1004
Author(s):  
Simon Higgins ◽  
Gregory J Sheard ◽  
Andreas Fouras ◽  
Kerry Hourigan
Keyword(s):  
Shear Rate ◽  
Micro Channel ◽  
Constant Shear ◽  
Computer Aided ◽  
Constant Shear Rate

Plastic Deformation Kinetics of 95.5Sn4Cu0.5Ag Solder Joints

1995 ◽  
Vol 117 (2) ◽  
pp. 100-104 ◽  
Author(s):  
Z. Guo ◽  
Yi-Hsin Pao ◽  
H. Conrad
Keyword(s):  
Plastic Deformation ◽  
Shear Stress ◽  
Shear Rate ◽  
Solder Joints ◽  
Deformation Kinetics ◽  
Constant Shear ◽  
Controlling Mechanism ◽  
Deformation Equation ◽  
Kinetics Of ◽  
Constant Shear Rate

The plastic deformation kinetics of 95.5Sn4Cu0.5Ag solder joints were determined in monotonic loading shear over the temperature range of 25°–150°C using three types of tests: (a) constant shear rate, (b) constant shear stress (creep), and (c) differential tests (changes in shear rate or temperature during an otherwise isothermal constant shear rate test). The deformation kinetics were evaluated in terms of the Dorn high temperature plastic deformation equation γ˙p=A(μb/kT)D(b/d)P(τ/μ)n where γ˙p is the shear rate, μ the shear modulus, b the Burgers vector, D the appropriate diffusion coefficient, d the grain size and τ the shear stress. A, p, and n are constants whose values depend on the rate controlling mechanism. It was found that n increased with stress from ~4 at 2 MPa to ~20 at 25 MPa, relatively independent of temperature. The activation ΔH was determined to be 21.1 ± 2 kcal/mole. The constant A, however, decreased with temperature from a value of ~1018 at 25°C to ~1010 at 150°C. The values of n and ΔH suggest that dislocation glide and climb is the rate controlling mechanism and hence that p ≈ 0. It is speculated that the large decrease in A with temperature may be the result of an effect on the microstructure.

scholarly journals Aging, Rejuvenation and Thixotropy in Complex Fluids: Time-dependence of the Viscosity at Rest and under Constant Shear Rate or Shear Stress

2008 ◽  
Vol 18 (5) ◽  
pp. 53298-1-53298-13
Author(s):  
Daniel Quemada
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Volume Fraction ◽  
Complex Fluids ◽  
Transient Behaviour ◽  
Volume Fractions ◽  
Constant Shear ◽  
Constant Shear Stress ◽  
Constant Shear Rate ◽  
Viscosity Changes

Abstract Complex fluids exhibit time-dependent changes in viscosity that have been ascribed to both thixotropy and aging. However, there is no consensus for which phenomenon is the origin of which changes. A novel thixotropic model is defined that incorporates aging. Conditions under which viscosity changes are due to thixotropy and aging are unambiguously defined. Viscosity changes in a complex fluid during a period of rest after destructuring exhibit a bifurcation at a critical volume fraction ϕc2. For volume fractions less than ϕc2 the viscosity remains finite in the limit t →∞. For volume fractions above critical the viscosity grows without limit, so aging occurs at rest. At constant shear rate there is no bifurcation, whereas under constant shear stress the model predicts a new bifurcation in the viscosity at a critical stress σB, identical to the yield stress σy observed under steady conditions. The divergence of the viscosity for σ≤σB is best defined as aging. However, for σ > σB, where the viscosity remains finite, it seems preferable to use the concepts of restructuring and destructuring, rather than aging and rejuvenation. Nevertheless, when a stress σA(≤σB) is applied during aging, slower aging is predicted and discussed as true rejuvenation. Plastic behaviour is predicted under steady conditions when σ > σB. The Herschel-Bulkley model fits the flow curve for stresses close to σB, whereas the Bingham model gives a better fit for σ >> σB. Finally, the model’s predictions are shown to be consistent with experimental data from the literature for the transient behaviour of laponite gels.

Viscometric Performance Evaluation Of Oil With Respect To Shear Rate, Temperature And Shearing Time

2011 ◽  
Author(s):  
E. G. Goh ◽  
C. S. Kow ◽  
W. B. Wan Nik
Keyword(s):  
Fourier Series ◽  
Shear Rate ◽  
Rheological Models ◽  
Specific Temperature ◽  
The Difference ◽  
Temperature Shear ◽  
Relationship Of ◽  
The Relationship ◽  
Historical Treatment ◽  
Constant Shear Rate

Dalam kajian ini, kami menilai kelakuan asas minyak mineral (Mobil Extra 2T) yang dikenakan tekanan daripada keadaan pegun ke 1900 1/s keterikan pada masa keterikan yang berlainan (60, 300 dan 900 s) dan dikekalkan pada 1900 1/s keterikan di antara 30 dan 60 s, dan kemudiannya dengan pengurangan keterikan sehingga keadaan pegun pada masa keterikan 60, 300 dan 900 s. Proses ini diulangi daripada 40 ke 100°C dengan peningkatan suhu 20°C. Pengukuran kelikatan dilakukan dengan ThermoHaake (Rheometer model RS600) dan pengawal suhu (Haake – Phoenix model C1 35P). Kegagalan persamaan reologi dalam permodelan hubungan kelikatan–keterikan dikenalpasti dan persamaan alternative iaitu siri Fourier dicadang sebagai pengganti dengan nilai R2 bersamaan 0.99. Integrasi siri Fourier daripada 0 ke 1900 1/s telah dilakukan pada lengkung peningkatan dan penurunan keterikan. Keputusan menunjukkan lesapan–keterikan ( τL ) boleh diwakili dengan perbezaan nilai integrasi di antara lengkung peningkatan dan penurunan keterikan, pada satu suhu dan masa keterikan. Kaedah ini dicadangkan untuk menilai prestasi minyak pada pemerolehan semula kelikatan selepas dikenakan keterikan. Kata kunci: Kelikatan; suhu; keterikan; persamaan reologi; siri Fourier In this study, we evaluate the fundamental behaviour of mineral oil (Mobil Extra 2T) that was stressed from stagnant condition to a shear rate of 1900 1/s in different shearing time (60, 300 and 900 s), remained at constant shear rate of 1900 1/s between 30 to 60 s, and continued by decreasing shear rate to stagnant condition at specific shearing time of 60, 300 and 900 s. This process was repeated from 40 to 100°C with an interval of 20°C. Viscosity measurement was carried out by ThermoHaake (Rheometer model RS600) and temperature control (Haake – Phoenix model C1 35P). Failure of rheological models in modeling the relationship of viscosityshear rate was demonstrated and alternative model i.e. Fourier series was proposed as a substitution with a high R–squared value of 0.99. Integration of Fourier series from 0 to 1900 1/s was carried out on increasing and decreasing shear rate–generated curves. Results showed a consistent trend of lost–shear stress ( τL ), represented by the difference of integration value of increasing and decreasing shear rate–generated curves, at specific temperature and shearing time. This method is proposed to evaluate the performance of oil on viscosity recovery after historical treatment of shear rate. Key words: Viscosity; temperature; shear rate; rheological models; Fourier series

Shear induced periodic structure changes in concentrated alumina suspensions at constant shear rate monitored by FBRM

2004 ◽  
Vol 44 (3) ◽  
pp. 313-318 ◽  
Author(s):  
Frank Bagusat ◽  
Bodo B�hme ◽  
Peter Schiller ◽  
Hans-J�rg M�gel
Keyword(s):  
Shear Rate ◽  
Periodic Structure ◽  
Constant Shear ◽  
Structure Changes ◽  
Constant Shear Rate ◽  
Alumina Suspensions
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