Linear Viscoelastic Properties Research Articles

Investigating linear viscoelastic response of cylindrical and prismoidal bituminous mixtures subjected to torsion using dynamic shear rheometer

This study investigates the influence of specimen geometry on the linear viscoelastic (LVE) properties of bituminous mixtures in torsion using a dynamic shear rheometer. Cylindrical and prismoidal specimens with identical material constituents and volumetric properties are prepared using a shear box compactor. Amplitude sweep tests show that LVE limits decrease with increasing temperature, with prismoidal specimens exhibiting higher LVE limits. The frequency-dependent response and relaxation characteristics are analysed through isothermal and master curve analysis. The results show that prismoidal specimens have a higher shear modulus, relaxation modulus, and longer relaxation times than cylindrical samples. The impact of specimen geometry becomes more significant at higher temperatures and lower reduced frequencies. The study demonstrates the inadequacy of correction factors for addressing geometry-based stresses in prismoidal bituminous mixture specimens. The results show the necessity to relook into ASTM D7552 ((2022). Standard test method for determining the complex shear modulus (G*) of bituminous mixtures using dynamic shear rheometer. ASTM International) for computing the linear viscoelastic properties of bituminous mixtures.

Studying the effect of bimodality on the linear viscoelastic properties of LLDPE/UHMWPE blends and determining their MWD from rheology

Studying the effect of bimodality on the linear viscoelastic properties of LLDPE/UHMWPE blends and determining their MWD from rheology

Conditions for a microfluidic creep experiment for microparticles using a cross-slot extensional flow device.

The micromechanical measurement field has struggled to establish repeatable techniques because the deforming stresses can be difficult to model. A recent numerical study [Lu et al., J. Fluid Mech. 962, A26 (2023)] showed that viscoelastic capsules flowing through a cross-slot can achieve a quasi-steady strain near the extensional flow stagnation point that is equal to the equilibrium static strain, thereby implying that the capsule's elastic behavior can be captured in continuous device operation. However, no experimental microfluidic cross-slot studies have reported quasi-steady strains for suspended cells or particles to our knowledge. Here, we demonstrate experimentally the conditions necessary for the cross-slot microfluidic device to replicate a uniaxial creep test at the microscale and at relatively high throughput. By using large dimension cross-slots relative to the microparticle diameter, our cross-slot implementation creates an extensional flow region that is large enough for agarose hydrogel microparticles to achieve a strain plateau while dwelling near the stagnation point. This strain plateau will be key for accurately and precisely measuring viscoelastic properties of small microscale biological objects. We propose an analytical mechanical model to extract linear viscoelastic mechanical properties from observed particle strain histories. Particle image velocimetry measurements of the unperturbed velocity field is used to estimate where in the device particles experienced extensional flow and where the mechanical model might be applied to extract mechanical property measurements. Finally, we provide recommendations for applying the cross-slot microscale creep experiment to other biomaterials and criteria to identify particles that likely achieved a quasi-steady strain state.

Nonequilibrium theory of the linear viscoelasticity of glass and gel forming liquids

We propose a first-principles theoretical approach for the description of the aging of the linear viscoelastic properties of a colloidal liquid after a sudden quench into a dynamically arrested (glass or gel) state. Specifically, we couple a general expression for the time-evolving shear-stress relaxation function G(τ;t), written in terms of the non-equilibrium structure factor S(k;t) and intermediate scattering function F(k,τ;t), with the equations that determine S(k;t) and F(k,τ;t), provided by the non-equilibrium self-consistent generalized Langevin equation theory. In this manner, we obtain a closed theoretical scheme that directly connects interparticle forces with experimentally accessible rheological properties of nonequilibrium amorphous states of matter. The predictive capability of the resulting theoretical formalism is illustrated here with its concrete application to the Weeks–Chandler–Andersen model of a soft-sphere fluid.

Role of sulfated GAGs in shear mechanical properties of human and porcine cornea

Role of sulfated GAGs in shear mechanical properties of human and porcine cornea

The energy consumption characteristics of a new type of energy dissipating vibration-damping fastener

To address the issue of inadequate energy dissipation capacity in current vibration-damping fasteners, this study examined the impact of stiffness and damping factor of vibration-damping fasteners on the vibration attenuation rate of rails, based on the theoretical model of a periodic double-layer support system. An intrinsic manganese–copper (Mn–Cu) damping alloy model was established, and the parameters for the Prony analysis and PRF model were determined to accurately define the hyperelastic and linear viscoelastic properties of the damping alloy in the finite element simulation software. A new type of energy dissipating vibration-damping fastener (NEDF) was designed based on these criteria and practical operational conditions. Static and dynamic stiffness simulation calculations were performed to examine the vibration isolation ability of NEDF, which was then installed in a rail system to conduct hammering tests, aiming to investigate its energy dissipation characteristics. The results indicated that NEDF exhibited a high damping factor and maintained significant vibration isolation capacity, notably enhancing the vibration attenuation rate of the rails and improving energy dissipation capacity.

Molecular Model for Linear Viscoelastic Properties of Entangled Polymer Networks.

A molecular Kuhn-scale model is presented for the stress relaxation dynamics of entangled polymer networks. The governing equation of the model is given by the general form of the linearized Langevin equation. Based on the fluctuation-dissipation theorem, the stress relaxation modulus is derived using the normal mode representation. The entanglements are introduced as additional entropic springs connecting internal beads of the network strands. The validity of the model is assessed by comparing predicted stress relaxation modulus and viscoelastic storage and loss moduli with the estimates from molecular dynamics (MD) simulations, using the same computer models. A finite element procedure is proposed and used to assemble the network connectivity matrix, and its numerically solved eigenvalues are used to predict the linear stress relaxation dynamics. Both perfect (fully polymerized stoichiometric) and imperfect networks with different soluble and dangling structures and loops are studied using mapped Kuhn-scale network models with up to several dozen thousand Kuhn segments. It is shown that for the overlapping ranges of times and frequencies, the model predictions and MD estimates agree well.

Influence of Polymer Concentration on the Viscous and (Linear and Non-Linear) Viscoelastic Properties of Hydrolyzed Polyacrylamide Systems in Bulk Shear Field and Porous Media.

Enhanced oil recovery (EOR) methods are generally employed in depleted reservoirs to increase the recovery factor beyond that of water flooding. Polymer flooding is one of the major EOR methods. EOR polymer solutions (especially the synthetic ones characterized by flexible chains) that flow through porous media are not only subjected to shearing forces but also extensional deformation, and therefore, they exhibit not only Newtonian and shear thinning behavior but also shear thickening behavior at a certain porous media shear rate/velocity. Shear rheometry has been widely used to characterize the rheological properties of EOR polymer systems. This paper aims to investigate the effect of the polymers' concentrations, ranging from 25 ppm to 2500 ppm, on the viscous, linear, and non-linear viscoelastic properties of hydrolyzed polyacrylamide (HPAM) in shear field and porous media. The results observed indicate that viscous properties such as Newtonian viscosity increase monotonically with the increase in concentration in both fields. However, linear viscoelastic properties, such as shear characteristic time, were absent for concentrations not critical in both shear rheometry and porous media. Beyond the critical association concentration (CAC), the modified shear thinning index decreases in terms of concentration in both fields, signifying their intensified thinning. At those concentrations higher than CAC, the viscoelastic onset rate remains constant in both fields. In both fields, the shear thickening index, a strict non-linear viscoelastic property, initially increases with concentration and then decreases with concentration, signifying that the polymer chains do not stretch significantly at higher concentrations. Also, another general observation is that the rheological properties of the polymer solutions in both porous media and shear rheometry only follow a similar trend if the concentration is higher than the CAC. At concentrations less than the CAC, the shear and porous media onset rates follow different trends, possibly due to the higher inertial effect in the rheometer.

Evolution of local relaxed states and the modeling of viscoelastic fluids

We introduce a class of continuum mechanical models aimed at describing the behavior of viscoelastic fluids by incorporating concepts originated in the theory of solid plasticity. Within this class, even a simple model with constant material parameters is able to qualitatively reproduce a number of experimental observations in both simple shear and extensional flows, including linear viscoelastic properties, the rate dependence of steady-state material functions, the stress overshoot in incipient shear flows, and the difference in shear and extensional rheological curves. Furthermore, by allowing the relaxation time of the model to depend on the total strain, we can reproduce some experimental observations of the non-attainability of steady flows in uniaxial extension and link this to a concept of polymeric jamming or effective solidification. Remarkably, this modeling framework helps in understanding the interplay between different mechanisms that may compete in determining the rheology of non-Newtonian materials.

The effect of starch types on extensional, linear and nonlinear rheological properties of starch cracker dough

The effect of starch types on extensional, linear and nonlinear rheological properties of starch cracker dough

Mechanistic Pavement Modeling of Typical Brazilian Pavements: Cohesive Zone Fracture Modeling and Continuum Damage Modeling

Pavement performance evaluation with respect to fatigue cracking has seen a major shift toward more rigorous mechanistic models that can capture the complex damage response of the mixtures more accurately. This study utilized two mechanistic methods (cohesive zone [CZ]-based fracture modeling and continuum damage [CD] modeling) to study the cracking behavior of asphalt mixtures and subsequently predict the damage-associated performance of pavements. A Superpave mixture designed for Brazilian highway conditions was selected to evaluate the two modeling approaches for the performance of the mixture when utilized as a surface course within typical Brazilian highway pavements. The mixture was first evaluated for its linear viscoelastic properties, and then the damage characteristics of the mixture were obtained through two different experiments: the semi-circular bending (SCB) beam test and the cyclic fatigue (CF) test. The SCB tests performed at different loading rates were used to obtain the model parameters of the nonlinear viscoelastic CZ model with a Gaussian damage evolution criterion, while the CF tests were performed at different strain amplitudes, and the mixture-specific damage characteristic curve and the fatigue failure criterion were obtained using the simplified-viscoelastic continuum damage model. From a design perspective, three pavement structures that varied in geometry (pavement layer thickness) and underlying layer properties were selected while retaining the same asphalt mixture. The three pavement scenarios were evaluated for the fatigue cracking performance from each of the mechanistic modeling methods. The results indicate that both methods rank the performance of the pavement structures in a similar manner, while the damage initiation and progression were seen to be different because of the different mechanics in modeling cracks.

Switchable microscale stress response of actin-vimentin composites emerges from scale-dependent interactions.

The mechanical properties of the mammalian cell regulate many cellular functions and are largely dictated by the cytoskeleton, a composite network of protein filaments, including actin, microtubules, and intermediate filaments. Interactions between these distinct filaments give rise to emergent mechanical properties that are difficult to generate synthetically, and recent studies have made great strides in advancing our understanding of the mechanical interplay between actin and microtubule filaments. While intermediate filaments play critical roles in the stress response of cells, their effect on the rheological properties of the composite cytoskeleton remains poorly understood. Here, we use optical tweezers microrheology to measure the linear viscoelastic properties and nonlinear stress response of composites of actin and vimentin with varying molar ratios of actin to vimentin. We reveal a surprising, nearly opposite effect of actin-vimentin network mechanics compared to single-component networks in the linear versus nonlinear regimes. Namely, the linear elastic plateau modulus and zero-shear viscosity are markedly reduced in composites compared to single-component networks of actin or vimentin, whereas the initial response force and stiffness are maximized in composites versus single-component networks in the nonlinear regime. While these emergent trends are indicative of distinct interactions between actin and vimentin, nonlinear stiffening and longtime stress response appear to both be dictated primarily by actin, at odds with previous bulk rheology studies. We demonstrate that these complex, scale-dependent effects arise from the varied contributions of network density, filament stiffness, non-specific interactions, and poroelasticity to the mechanical response at different spatiotemporal scales. Cells may harness this complex behavior to facilitate distinct stress responses at different scales and in response to different stimuli to allow for their hallmark multifunctionality.

Asphalt binder modified with high density polyethylene: 2S2P1D rheological modelling and damage characterization

ABSTRACT The new needs in the paving industry have led to the intensification of the use of modified binders, and the use of plastics (non-biodegradable waste) can be an ally in facing both environmental and technical challenges. This study evaluated the feasibility of modifying a conventional asphalt binder with high density polyethylene (HDPE) at contents of 1, 3 and 5% for performance improvement, using rheological and performance tests. The linear viscoelastic properties were obtained by the temperature-frequency sweep test, and for the first time the 2S2P1D rheological model was used to describe these data for an HDPE-modified binder. Resistance to permanent deformation and fatigue was verified by the Multiple Stress Creep Recovery (MSCR) and Linear Amplitude Sweep (LAS) tests, respectively. The Fatigue Factor of Binder was obtained at 3 levels of strain for the first time for this material. HDPE made the material stiffer and more elastic observed by the coefficients of the 2S2P1D model. The modification resulted in better performance regarding permanent deformation and in general had an impact of less than 10% on the fatigue life of the material. Thus, it is possible to state that HDPE can be incorporated into the asphalt binder without harming its performance.

Linking Chemical Structure to the Linear and Nonlinear Properties of Asphalt Binders

The study described in this paper aims to establish the relationship between the chemical composition and rheological properties of asphalt binders in both the linear viscoelastic (LVE) and nonlinear viscoelastic (NLVE) domains. Two asphalt binders with different penetration grades were subjected to four distinct aging treatments of varying severity, resulting in changes in their chemical fingerprints. Chemical characteristics of the asphalt binders were analyzed using thin-layer chromatography (TLC), Fourier Transform infrared spectroscopy (FTIR), and gel permeation chromatography (GPC). Frequency sweep tests were conducted to evaluate the LVE behavior of the asphalt binders, while multiple stress creep recovery (MSCR) tests were employed to assess their NLVE properties. With regard to the LVE properties, rheological index ( R) and zero shear viscosity (ZSV) derived from the Christensen-Anderson-Marasteanu (CAM) model exhibited high correlations with FTIR and molecular weight distribution (MWD) parameters. Additionally, the polydispersity index (PDI) displayed a stronger correlation with LVE-based parameters. Findings from the MSCR tests revealed that the sensitivity of the percentage recovery ( %R) to chemical composition, as opposed to nonrecoverable creep compliance ( Jnr), can be largely attributed to the degree of nonlinearity. Furthermore, it was observed that lower molecular weight molecules exert a greater influence on %R in the nonlinear domain. Finally, it was found that Jnrslope is a more reliable parameter than Jnrdiff for assessing the effects of chemical makeup on stress and temperature sensitivity.

Self-Cross-Linking Latex Pressure-Sensitive Adhesives: Preparation and Investigation on Adhesion, Linear Viscoelastic, and Nonlinear Large-Strain Properties

Self-Cross-Linking Latex Pressure-Sensitive Adhesives: Preparation and Investigation on Adhesion, Linear Viscoelastic, and Nonlinear Large-Strain Properties

Viscoelastic characterization of the mucus from the skin of loach (II) using linear viscoelastic property

ABSTRACT A structuralized Rivlin-Sawyers model with inhomogeneous shear-rate effect on the component of relaxation spectrum was proposed here to express the viscoelastic property of loach mucus. The linear viscoelastic property of the mucus was obtained using the experimental frequency sweep data at small strain, and the viscosity in the shear-rate decreasing region with 0.0631 s−1 as the maximum shear rate was fitted by the model with inhomogeneous shear-rate effect. Both the predictions of the steady viscosity curves with four maximum shear rates, i.e., 0.004 s−1, 0.01 s−1, 0.1 s−1, and 1 s−1, and that of the transient shear viscosity in the step rate experiment at 0.1 s−1 show reasonable characterization of the model on the viscoelasticity of the loach skin mucus.

Performance Assessment of High Reclaimed Asphalt Pavement Asphalt Mixtures with Recycling Agents

The increased use of reclaimed asphalt pavement (RAP) in asphalt mixtures has promoted the use of recycling agents (RAs) to mitigate the effect of oxidized materials on the performance of asphalt mixtures. This laboratory-based study assesses the linear viscoelastic (LVE), cracking resistance, and permanent deformation properties of recycled asphalt mixtures containing RAs. The dosage levels used for this study were determined based on the manufacturer’s recommendation to restore the blended binder system’s low-temperature performance grade (PGL) to −22°C. The study found that blending a performance grade (PG) 64-22 virgin binder with RAs in high RAP mixtures can yield a comparable LVE response to high RAP mixtures designed using a softer binder (PG 58-28). Moreover, the study revealed that the cracking performance of high RAP mixtures could be improved without jeopardizing the rutting potential of the material by using RAs at dosage levels selected to yield a blended binder PGL of −22°C.

Evaluating the Fatigue-Cracking Resistance of North Dakota’s Asphalt Mixtures

Fatigue cracking is a critical pavement distress caused by extreme environmental conditions and heavy repeated cyclic loading. Performance-based design methods that use mechanistic models focus on material performance properties, creating an opportunity to use engineered and recycled materials such as reclaimed asphalt pavement (RAP). The primary goal of this study was to use the simplified viscoelastic continuum damage (S-VECD) model to assess the fatigue behavior of North Dakota’s asphalt mixtures. Eight mixtures typically used in North Dakota were sampled and underwent | E*| testing to determine their linear viscoelastic (LVE) properties. The S-VECD tests were conducted on the same mixtures to determine their damage characteristics. The outputs from the two tests were exported to the FlexMATTM software to obtain their damage characteristic curves, DR failure criterion parameters, and Sapp-index values. CT-index values for the same mixtures were obtained from the North Dakota Department of Transportation (NDDOT). The results revealed that the mixture used for HWY 52, which does not contain RAP, was least susceptible to fatigue cracking. The mixture used for HWY 6, which contains the highest RAP content (25%), had the lowest fatigue resistance, revealing RAP’s stiffening effect on asphalt mixtures. The mixture used for HWY 1, which used the performance grade (PG) 58S-34 binder, had the second-highest fatigue-cracking resistance despite containing 15% RAP, indicating that binder grade affects an asphalt mixture’s fatigue behavior. A relatively low correlation was observed between the CT-index and Sapp-index.

Relationship between the poly(glycerol adipate) prepolymers chain microstructure and linear viscoelastic properties of the elastomers

Relationship between the poly(glycerol adipate) prepolymers chain microstructure and linear viscoelastic properties of the elastomers

Influence of Specimen Geometries on the Viscoelastic Properties of Bituminous Mixtures in Torsion

A standard test method for determining the linear viscoelastic properties of bituminous mixtures in torsion prescribes the use of a dynamic shear rheometer. The method uses a prismoidal specimen (rectangular cross section) sliced from a Superpave gyratory compacted sample. However, the geometry utilized in the standard is a non-axisymmetric cross section, which leads to the development of warping stress when the specimen is tested in torsion using a dynamic shear rheometer. On the other hand, axisymmetric geometry, such as cylinder (circular cross section), does not warp when subjected to torsion. This study investigates the influence of the two specimen geometries, namely prismoidal and cylindrical, on the linear viscoelastic properties of bituminous mixtures in torsion. The specimens are obtained from a bituminous mixture with a nominal maximum aggregate size of 13.2 mm, and statistical analysis is carried out to determine whether the material constitution in the specimen geometries is identical. A frequency sweep experiment is conducted at 10, 20, and 30°C with a constant strain amplitude of 0.001% in the frequency range of 0.01 Hz to 20 Hz. The absolute shear modulus of the prismoidal specimens is found to be higher than that of cylindrical specimens because of warping stresses in prismoidal specimens. It was seen that the effect of warping stress is greater at higher temperatures and lower frequencies. Correction factors are used to correct the absolute shear modulus of prismoidal specimens. These findings highlight the importance of considering correction factors for warping when characterizing prismoidal bituminous mixtures in torsion.