Parameters Of Rheological Model Research Articles

Strain-dependent behaviour of cold recycled material mixtures in cyclic compression tests

The purpose of the study is to evaluate strain-dependent behaviour of Cold Recycled Material (CRM) mixtures using three frameworks typically applied for Hot Mix Asphalt (HMA): linear viscoelastic (LVE) limits; non-linearity directions; changes in rheological model parameters. To this aim, the complex modulus of three CRM mixtures with different bitumen-to-cement ratio (0.2, 0.6 and 1.8) was measured in cyclic compression mode, at increasing level of axial deformation (from 35 to 195 μstrain) and at three temperatures (4, 20 and 40 °C). CRM mixtures showed strong strain dependent behaviour, which does not fully comply with the LVE hypothesis. LVE limit framework is applicable, but strain limits for CRM are different from HMA. Linearity direction framework does not give unique trend, hence it is not applicable in the same way as it was developed for HMA. The most promising framework for further analysis is the change in rheological model parameters, but it requires high number of performed tests.

Calibration of Thixotropic and Viscoelastic Shear-Thinning Fluids Using Pipe Rheometer Measurements

Some non-Newtonian fluids have time-dependent rheological properties like a shear stress that depends on the shear history or a stress overshoot that is a function of the resting time, when fluid movement is started. The rheological properties of such complex fluids may not stay constant while they are used in an industrial process, and it is therefore desirable to measure these properties frequently and with a simple and robust device like a pipe rheometer. This paper investigated how the time-dependent rheological properties of a thixotropic and viscoelastic shear-thinning fluid can be extracted from differential pressure measurements obtained at different flowrates along a circular pipe section. The method consists in modeling the flow of a thixotropic version of a Quemada fluid and solving the inverse problem in order to find the model parameters using the measurements made in steady-state conditions. Also, a Maxwell linear viscoelastic model was used to reproduce the stress overshoot observed when starting circulation after a resting period. The pipe rheometer was designed to have the proper features necessary to exhibit the thixotropic and viscoelastic effects that were needed to calibrate the rheological model parameters. The accuracy of rheological measurements depends on understanding the effects that can influence the observations and on a proper design that takes advantage of these side effects instead of attempting to eliminate them.

Material characterization of EN AC-Al Si12CuNiMg alloy in stress relaxation and creep conditions

Al–Cu–Mg alloys are widely used in various applications, especially engine components, where it is subjected to elevated temperatures during operation. Prolonged exposure of these components to elevated temperatures gradually leads to creep and relaxation phenomena. This study aims to investigate the effects of temperature on stress relaxation and creep behavior of the aluminum-silicon alloy EN AC-Al Si12CuNiMg. Furthermore, this study evaluates the effect of temperature on the rheological model parameters of this alloy. Experimental tests were conducted to investigate the stress relaxation and creep behavior of this alloy at different temperatures of 150°C, 250°C, and 350°C. The rheological model parameters were then determined from the obtained experimental data. The Standard Linear Solid Model (SLSM) was used to fit the stress relaxation and creep curves obtained from the experiment. Overall, the results indicate that increasing temperature significantly affects the stress relaxation and creep behavior of the investigated alloy, with higher temperatures leading to increased relaxation and creep rates. Additionally, the rheological model parameters of the alloy were found to vary with temperature.

Data-driven rheological characterization of stress buildup and relaxation in thermal greases

Thermal greases, often used as thermal interface materials, are complex paste-like mixtures composed of a base polymer in which dense metallic (or ceramic) filler particles are dispersed to improve the heat transfer properties of the material. They have complex rheological properties that impact the performance of the thermal interface material over its lifetime. We perform rheological experiments on thermal greases and observe both stress relaxation and stress buildup regimes. This time-dependent rheological behavior of such complex fluid-like materials is not captured by steady shear-thinning models often used to describe these materials. We find that thixo-elasto-visco-plastic (TEVP) and nonlinear-elasto-visco-plastic (NEVP) constitutive models characterize the observed stress relaxation and buildup regimes, respectively. Specifically, we use the models within a data-driven approach based on physics-informed neural networks (PINNs). PINNs are used to solve the inverse problem of determining the rheological model parameters from the dynamic response in experiments. These training data are generated by startup flow experiments at different (constant) shear rates using a shear rheometer. We validate the “learned” models by comparing their predicted shear stress evolution to experiments under shear rates not used in the training datasets. We further validate the learned TEVP model by solving a forward problem numerically to determine the shear stress evolution for an input step-strain profile. Meanwhile, the NEVP model is further validated by comparison to a steady Herschel–Bulkley fit of the material’s flow curve.

Secondary consolidation characteristics of organic soil modified by bio-enzyme based on the Gibson model

In order to study the secondary consolidation characteristics of organic soil improved by bio-enzyme, the secondary consolidation test was carried out. First, the Gibson rheological model parameters were fitted according to the experimental results. Then, the relationship between rheological model parameters, Ca/Cc value, secondary consolidation coefficient Ca, and load was analyzed for different ratios of bio-enzyme. The results showed that: 1) the rheological model parameters were negatively correlated with the ratios of bio-enzyme and positively correlated with the load value. The rheological model parameters E1 (Kelvin elastic modulus) and η (Kelvin viscosity coefficient) reached the maximum value when the ratio of bio-enzyme was 0.01%. 2) The secondary consolidation coefficient was related to the load and showed a certain law. At 100 kPa, the secondary consolidation coefficient of samples reached the peak. When it was less than 200 kPa, the secondary consolidation coefficient changed obviously with the increase in load. When the load was greater than 200 kPa, the variation trend of the secondary consolidation coefficient tended to be gentle with the increase in load and finally tended to be constant. With the increase in load, the secondary consolidation coefficient Ca finally approached to a stable value. 3) The value of Ca/Cc of improved organic soil varied from 0.042 to 0.1 under various loads. In this article, the secondary consolidation characteristics of organic soil modified by bio-enzyme were studied. The secondary consolidation strain can be predicted by the established rheological model parameter equations.

Adjoint-based sensitivity analysis of viscoelastic fluids at a low deborah number

This work performs an adjoint-based sensitivity analysis of a viscoelastic fluid flow around a cylinder in a confined channel. The viscoelastic behavior of the fluid is modeled by the Oldroyd-B constitutive equation and the quantity of interest of the flow is set to the resistance of the cylinder. A set of continuous adjoint governing equations is formulated to quantify the local sensitivities of rheological model parameters on the drag of the cylinder. The adjoint equations are solved together with the original resistance prediction problem, at the Deborah number 0.5. Final outcomes are the field resistance-sensitivity maps for the Oldroyd-B model parameters that imply the local relative importance of different underlying physical mechanisms reflected in the model parameters. In particular, the sensitivity map of relaxation parameter distinguishes two opposing effects of fluid elasticity to resistance of the cylinder depending on the location. While the fluid elasticity near the top and bottom surfaces reduces the resistance, it works adversely near the front and back surfaces. The example illustrates how adjoint-based sensitivity analysis can be utilized for developing effective flow control strategies in many applications working with viscoelastic fluids.

Magnesium Bromide as Novel High-Density Packer Fluid in Oilfield Applications

Abstract The rheology of a packer fluid (PF) is the most crucial aspect prompting the efficacious well completion effectiveness. In the drilling industry, a high-density, solid-free, low viscosity, and alkaline pH packer fluid is a big advancement and requirement. Here, we develop a magnesium bromide as an effective solid-free, high-density packer fluid (HDPF) for oilfield applications. We believe that investigating the rheological parameters such as shear stress, yield point, plastic and apparent viscosity, and gel strength 10 s and 10 min at a varying temperature of 84–192 °F is essential for optimizing the rheological performance. In order to enhance the completion efficiency, our work is more focused on overcoming the rheological and density limitations of existing traditional packer fluid. Our results show that the packer fluid has a low value of plastic viscosity (1.95–7.05 cP) and also exhibits a high density of 13.41 lb/gal, a specific gravity of 1.61. We have reported the pH at the alkaline region (pH 7.14) with solid-free. Here, we have investigated the Bingham plastic rheological model and Herschel Bulkley model parameters with experimental rheological data, and it is adaptive to novel packer fluid to predict the rheological parameters. Conspicuously, the rheological models, along with data analysis, have enormous possibilities in envisaging real-time quantification of shear stress and viscosity to enable the user to monitor and evaluate a suitable packer fluid in oilfield applications.

Modeling nonequilibrium thermoviscoelastic material behaviors of glass in nonisothermal glass molding

AbstractNonisothermal glass molding (NGM) is developed aiming to satisfy the fabrication of complex and precision optical elements at high production volumes. The technology, however, was encountered by the high form deviation of manufactured glass optics. During the nonisothermal compression molding, glass undergoes a rapid temperature change making it a transition from equilibrium to nonequilibrium nature of matter. Owing to this characteristic, viscoelastic material behaviors of glass depend on not only temperature but also thermal history. Understanding the nature of nonequilibrium thermoviscoelasticity, the central importance to control the final shape and optical characteristics of the manufactured glass optics is the focus of this research. First, this study presents preliminary experimental investigations indicating the difference in viscoelastic deformation responses under the equilibrated and nonequilibrated glass specimens. In the following, modeling the temperature‐dependent viscoelasticity over a wide temperature range in glass transition region is described, where temperature is directly coupled in each parameter of a rheological constitutive model. This concept allows us to bypass the thermorheologically simple assumption used to tolerate the description of thermoviscoelastic responses in most of the earlier works. Finally, we propose a modeling method that incorporates temperature and thermal history into the rheological model parameters, each of which is described by employing the Mauro–Allan–Potuzak viscosity equation. Viscoelastic experiments were carried out to validate the model. The results show that the time‐dependent responses varying with temperature are well predicted in both equilibrium and nonequilibrium regimes of glass‐forming systems. The benefit of this research is that a unique material model is entirely applicable for numerical studies of various hot forming processes such as annealing when glass undergoes pure thermal loads, as well as precision glass molding and NGM when glass is deformed by fully coupled thermal–mechanical loads under either its equilibrium or nonequilibrium state of materials, respectively.

Quasi‐Newtonian Approach determination of velocity profile for the fully developed axial power law fluid flow in concentric annuli

AbstractThe Quasi‐Newtonian Approach has been developed for the closed‐form analytical solution of isothermic, inelastic, and steady‐state fully developed axial power law fluid flow in a concentric annuli. This approach is developed to eliminate the need to solve the two flow regions separately in the rheological flow problems. Using the approximate definition shear deformation distribution of power law rheological model, an analytical expression, which permits direct evaluation of the velocity distribution profiles, volumetric flow rate, and pressure drop in concentric annuli is derived. It is shown that all developed equations are applicable for both Newtonian and non‐Newtonian flows in concentric annuli, and these can be applied for a wider range of rheological parameters of the power law rheological model. Final analytical equations can easily be used in all theoretical and practical applications of the power law flow problems in annuli that are encountered in several interdisciplinary fields without using tables, graphs, and tedious numerical calculations. Theoretically obtained, fully developed velocity profiles are compared with the experimental results taken from the relevant literature.

The effect of cassava and wheat starches complexation with selected fatty acids on their functional properties

The aim of the study was to evaluate the impact of selected fatty acids: palmitic, stearic or oleic on functional properties of cassava and wheat starches. Effectiveness of complexation procedure was evaluated by determination of complexing index, lipids content and fatty acid composition. Native starches and their complexes with fatty acids were analyzed for water binding capacity and solubility in water, in vitro digestibility, pasting characteristic and rheological properties. On the basis of the obtained results it was found that values of complexing index values for both starches complexed with oleic acid were remarkably higher than those determined in palmitic or stearic counterparts. Starches complexation with fatty acids resulted in a significant increase in the percentage share of used fatty acid in total fatty acid composition. Presence of oleic acid in cassava starch significantly limited its water binding capacity and solubility in water. Complexation with all fatty acids used in the study resulted in an increase in final viscosity and rheological stability of cassava starch pastes. Wheat starch complexes with fatty acids were characterised by higher pasting temperatures as compared to non-complexed counterpart, with the greatest effect observed for starch–oleic acid complex. In most cases complexation of starches with fatty acids contribute to an increase in contents of resistant starch fraction. Analysis of rheological model parameters revealed that procedure of oleic acid complexation increased by twice the values of consistency coefficient, and significantly decreased flow index of both wheat and cassava starches.

Precise Method to Estimate the Herschel-Bulkley Parameters from Pipe Rheometer Measurements

Accurate characterization of the rheological behavior of non-Newtonian fluids is critical in a wide range of industries as it governs process efficiency, safety, and end-product quality. When the rheological behavior of fluid may vary substantially over a relatively short period of time, it is desirable to measure its viscous properties on a more continuous basis than relying on spot measurements made with a viscometer on a few samples. An attractive solution for inline rheological measurements is to measure pressure gradients while circulating fluid at different bulk velocities in a circular pipe. Yet, extracting the rheological model parameters may be challenging as measurement uncertainty may influence the precision of the model fitting. In this paper, we present a method to calibrate the Herschel-Bulkley rheological model to a series of differential pressure measurements made at variable bulk velocities using a combination of physics-based equations and nonlinear optimization. Experimental validation of the method is conducted on non-Newtonian shear-thinning fluid based on aqueous solutions of polymers and the results are compared to those obtained with a scientific rheometer. It is found that using a physics-based method to estimate the parameters contributes to reducing prediction errors, especially at low flow rates. With the tested polymeric fluid, the proportion difference between the estimated Herschel-Bulkley parameters and those obtained using the scientific rheometer are −24% for the yield stress, 0.26% for the consistency index, and 0.30% for the flow behavior index. Finally, the computation requires limited resources, and the algorithm can be implemented on low-power devices such as an embedded single-board computer or a mobile device.

Structure-rheology elucidation of human blood via SPP framework and TEVP modeling

Recent work modeling the rheological behavior of human blood indicates that it has all the hallmark features of a complex material, including shear-thinning, viscoelastic behavior, a yield stress, and thixotropy. After decades of modeling steady state blood data, and the development of simple steady state models, like the Casson and Herschel-Bulkley the advancement and evolution of blood modeling to incorporate more thixo-elasto-visco-plastic (TEVP) features to accurately capture transient flow has renewed interest. With recently collected steady state and oscillatory shear flow rheological data from a DHR-3 using human blood, we show modeling efforts with a contemporary thixo-elasto-visco-plastic (TEVP) model. Best fit rheological model parameters are used to determine values for normal, healthy blood and corroborate correlations from literature. Series of physical processes (SPP) analysis is incorporated to illustrate how mechanical properties are tied to the transient, evolving microstructure of human blood and physiological parameters. Using LAOS data predictions of the structure parameter, λ is compared, and correlated with the transient elastic modulus, G t ′ .

The Master‐Curve Band considering Measurement and Modeling Uncertainty for Bituminous Materials

This paper proposes using the master‐curve band (MCB) to incorporate the unavoidable measurement errors and modeling uncertainty into the bitumen master‐curve construction. In general, the rheological property of bitumen within the linear viscoelastic region is characterized by the master curve of modulus and/or phase angle, provided that the bitumen complies with the time‐temperature superposition principle (TTSP). However, the master‐curve construction is essentially a mathematical fitting process regardless of whether or not the original data is perfect enough to fit. For this reason, the MCB was introduced to consider the uncertainty information instead of a single master curve. Rheological data of four kinds of bitumen including unaged and aged bitumen were used to construct the MCBs. The results indicated that the generalized sigmoidal model showed the widest master‐curve band, followed by Christensen‐Anderson‐Marasteanu (CAM) and CAM (Gg) models. The width of MCB was a useful tool to identify the sensitivity of bitumen to rheological models. The sensitivity of bitumen to rheological models is associated with the number of active parameters in rheological models and model parameters’ confidence intervals. The construction of an MCB was beneficial to select the rheological models. Accordingly, the CAM (Gg) model is proved to be the best to analyze the aging effects.

Impact of rheological model on numerical simulation of low-pressure powder injection moulding

ABSTRACT The aim of this study is to quantify the impact of different rheological models on the accuracy of LPIM numerical simulation. Two different feedstocks were formulated, and rheological profiles were characterised using a rotational rheometer from which the parameters of different rheological models were extracted and then implemented in an Autodesk Moldflow package. Mould filling patterns into a rectangular shape mould cavity were simulated, and then validated using real-scale injections. Depending on the feedstock rheological behaviour, models are not always well adapted to predict the mixture viscosity over the entire shear rate range. Because injections were performed at constant volumetric flow, all the rheological models were successfully used to predict the injected length. However, the simulated pressure through the mould cavity was only accurately simulated using the second-order or matrix models since these viscosity models were able to adequately capture the feedstock behaviour in the shear rate range representing the injections.

The Historical Earthworks of the Warsaw Citadel

In this study, we analyzed the methods and technologies used for constructing earthworks and military engineering in the latter period before the industrial revolution in Poland. The research object, the Warsaw Citadel, is a source of knowledge about military heritage from the aspect of conservation and protection of specific engineering achievements, which were dictated by early Russian geopolitical doctrine. Within the framework of the ongoing project of material heritage protection and popularization of history, the fortress has been transformed into a modern museum building. The new symbolic message of architecture was redefined, leaving behind the gloomy dominance elements in the scenery of the nearby city. In this study, reception tests of ground anchors were used for analysis. They were treated as a tool to determine the heterogeneity of fortification of historical earthworks. In the presented calculation procedure, limitations in the availability of geotechnical tests were overcome. Geological terrain layout and embankment excavation technology significantly impacted their quality and reliability. Currently, the embankments are slashed with anchored retaining walls. Ground anchors were used at short distances and were tested according to the national standard procedures. The results of the load tests are based on the physical properties of the subsoil, the conditions of contact with the supporting elements of the anchors, and the material properties. The soil interaction with the anchors is described using a rheological model, the constants of which were obtained using a fractional derivative model. The spatial variability of the rheological model parameters is presented using theoretical semivariograms matching the empirical data. The semivariograms explain the spatial correlation of the tested constants of the rheological model of the substrate with the anchors. The results of non-destructive testing were influenced by factors such as time and consolidation processes. The obtained results allowed us to directly draw conclusions about the repetitiveness of embankment features and indirectly about the quality of their construction.

Effects of test levels on creep and relaxation characteristic parameters of stem for rice seedlings grown in plastic cell tray

Creep and relaxation characteristics of stem for rice seedlings grown in plastic cell tray were studied by static tensile testing, in order to determine the relationship between characteristic parameters (rheological model parameters, stress components and strain components) and test levels (stress levels and strain levels). Rice seedling stem specimen used in the test was 40 mm in length. And the applied test values for the creep and relaxation test ranged from 1.0-3.0 MPa and 1.5%-3.5%, respectively, each for 5 levels. The results indicated that elastic modulus in the creep and relaxation model was not affected by test levels. However, except that viscosity coefficient ηkv was a constant and ηm1 decreased with the increase of test levels, other viscosity coefficient and rheological time nonlinearly increased as the test levels increased. And strain components in the creep model and stress components in the relaxation model significantly increased as the test levels increased. Keywords: model parameters, rheological property, stress relaxation, creep property, rice seedling stem, plastic cell tray DOI: 10.25165/j.ijabe.20201304.5673 Citation: Xiao J Q, Ma R J, Chen Y. Effects of test levels on creep and relaxation characteristics parameters of stem for rice seedling grown in plastic cell tray. Int J Agric & Biol Eng, 2020; 13(4): 19–28.

Effects of test levels on creep and relaxation characteristic parameters of stem for rice seedlings grown in plastic cell tray

Creep and relaxation characteristics of stem for rice seedlings grown in plastic cell tray were studied by static tensile testing, in order to determine the relationship between characteristic parameters (rheological model parameters, stress components and strain components) and test levels (stress levels and strain levels). Rice seedling stem specimen used in the test was 40 mm in length. And the applied test values for the creep and relaxation test ranged from 1.0-3.0 MPa and 1.5%-3.5%, respectively, each for 5 levels. The results indicated that elastic modulus in the creep and relaxation model was not affected by test levels. However, except that viscosity coefficient ηkv was a constant and ηm1 decreased with the increase of test levels, other viscosity coefficient and rheological time nonlinearly increased as the test levels increased. And strain components in the creep model and stress components in the relaxation model significantly increased as the test levels increased. Keywords: model parameters, rheological property, stress relaxation, creep property, rice seedling stem, plastic cell tray DOI: 10.25165/j.ijabe.20201304.5673 Citation: Xiao J Q, Ma R J, Chen Y. Effects of test levels on creep and relaxation characteristics parameters of stem for rice seedling grown in plastic cell tray. Int J Agric & Biol Eng, 2020; 13(4): 19–28.

Simulation of generalized Newtonian fluids with the Smoothed Particle Hydrodynamics method

AbstractIn this paper we examine Direct Numerical Simulation DNS of single phase non‐Newtonian fluids described by a generalized Newtonian rheology. Non‐Newtonian flow including large deformations and free surface flow could be observed in a wide range of industrial and environmental applications. For that reason, we choose the Lagrangian Smoothed Particle Hydrodynamics (SPH) as a simulation tool. The non‐Newtonian solver is implemented into the general purpose particle framework HOOMD‐blue [1,2], which allows for massive parallel CPU and GPU simulations. Numerical accuracy of the model is demonstrated by simulating confined Poiseuille flow between parallel plates. The validation has been done for a wide variety of shear strain–shear stress ratios where also the effect of the solid‐fluid interface boundary condition is examined. Furthermore, a comparison with the experimental results for the broken dam problem [3] showed good accuracy of the free‐surface flow prediction. Additionally, we have investigated a slump test (Abrams cone [4]), a relatively simple but in practice often performed experiment for non‐Newtonian yield‐stress fluids. Finally, we have investigated in further detail the cone diameter, height, flow time, the final shape and the influence of the rheological model parameters as well as the boundary conditions related to the stationary cone configuration.

Biopolymer Drill-in Fluid Performance for Different Rheological Models using Statistical Characterisation

Appropriate selection of rheological models is important for hydraulic calculations of pressure loss prediction and hole cleaning efficiency of drilling fluids. Power law, Bingham-Plastic and Herschel-Bulkley models are the conventional fluid models used in the oilfield. However, there are other models that have been proposed in literature which are under/or not utilized in the petroleum industry. The primary objective of this paper is to recommend a rheological model that best-fits the rheological behaviour of xanthan gum-based biopolymer drill-in fluids for hydraulic evaluations. Ten rheological models were evaluated in this study. These rheological models have been posed deterministically and due to the unrealistic nature have been replaced by statistical models, by adding an error (disturbance) term and making suitable assumptions about them. Rheological model parameters were estimated by least-square regression method. Models like Sisko and modified Sisko which are not conventional models in oil industry gave a good fit. Modified Sisko model which is a four parameter rheological model was selected as the best-fit model since it produced the least residual mean square of 0.61 Ibf2/100ft4. There is 95% certainty that the true best-fit curve lies within the confidence band of this function of interest. Keywords: Biopolymer; Least-Square Regression; Residual Mean Squares; Rheologram

Influence of chemical additives for warm mix asphalts on the short-term ageing of a plain bitumen

Over the last years, the use of warm mix asphalt (WMA) in asphalt industry allows important reductions in production and compaction temperatures guarantying relevant environmental benefits. However, the most proper laboratory procedure for short-term ageing of WMAs must still be defined. This study aims at evaluating the effect of temperature and chemical additives on bitumen short-term ageing. For this purpose, a 70/100 pen-grade bitumen and two chemical additives were investigated in terms of conventional (penetration, softening point), viscosity and rheological tests, as well as FTIR-ATR analysis. As expected, binders aged at lower temperatures show reduced oxidation as compared to those aged at higher temperatures, implying a lower oxidative hardening. In general, aged binders containing the chemical additives show a reduction of the effect of ageing, or anti-ageing effect. Moreover, the rheological model parameters of the binders present good correlations with penetration values and softening point temperatures, as well as with the chemical parameters determined by FTIR-ATR.