Viscous Response Research Articles

State-of-the-art Review of Springback Behavior of Polymers

The spring-in and spring-back behavior of polymers is intricate and influenced by various process parameters and mechanisms, including interply slip, anisotropic thermal expansion, and crystallization, all of which can lead to residual stresses. Composite materials made of metal and polymer are being investigated by researchers as a promising alternative to monometallic materials due to their superior properties. However, the number of studies related to metal/polymer/metal laminates on the same topics is relatively limited. A comprehensive review study was carried out with a focus on research works that were conducted with the consideration of different process parameters, such as radius of die and punch, friction, and force applied by blank holder, in order to observe their impact on the springback behavior of polymers. Springback on polymer components depends on the accuracy of appropriate materials and the consideration of appropriate experimental strategies. However, due to their viscoelastic properties, polymers demonstrate distinctive springback behavior. Furthermore, when subjected to deformation, polymers experience a combination of elastic and viscous responses, resulting in immediate elastic recovery and time-dependent viscoelastic relaxation. This intricate behavior presents difficulties in precisely forecasting and managing springback. To enhance the control and optimization of springback in polymer-based manufacturing processes, it is essential to improve the understanding of polymer behavior under diverse loading conditions and to refine simulation techniques accordingly. This review focuses on springback prediction models specific to polymers.

Filled elastomers sliding over smooth obstacles: Experiments and modeling in large deformations

The objective of this paper is to shed light on the mechanical response of filled elastomers in sliding contact. Compared to situations encountered by tires in breaking conditions, the study only considers smooth obstacles in order to analyse the contribution of finite deformations and of the complex viscosity of filled elastomers without facing all the complexity of surface roughness. For this purpose, a new experiment is introduced that allows to measure the friction on the surface of a filled elastomer that is subjected to large local deformation through a cyclic contact loading applied by sliding indenters. The setup uses smooth spherical indenters sliding on the material of interest within a temperature controlled water tank. The relevance of adhesion forces is reduced by using Teflon as a dry lubricant and Sinnozon as a surfactant. To analyze the experimental results, full-field simulations of the experiments are carried out within the setting of finite viscoelastodynamics by making use of two types of viscoelastic constitutive models for the filled elastomer: (i) a classical viscoelastic model combining a Mooney–Rivlin equilibrium elasticity and Maxwell branches with constant viscosities and (ii) an internal-variable-based viscoelastic model that was introduced in (Kumar and Lopez-Pamies, Comptes Rendus Mecanique 344, 102-112) for unfilled elastomers and that is extended herein to account for the more complex viscous response of filled elastomers.

Chirality and odd mechanics in active columnar phases.

Chiral active materials display odd dynamical effects in both their elastic and viscous responses. We show that the most symmetric mesophase with 2D odd elasticity in three dimensions is chiral, polar, and columnar, with 2D translational order in the plane perpendicular to the columns and no elastic restoring force for their relative sliding. We derive its hydrodynamic equations from those of a chiral active variant of model H. The most striking prediction of the odd dynamics is two distinct types of column oscillation whose frequencies do not vanish at zero wavenumber. In addition, activity leads to a buckling instability coming from the generic force-dipole active stress analogous to the mechanical Helfrich-Hurault instability in passive materials, while the chiral torque-dipole active stress fundamentally modifies the instability by the selection of helical column undulations.

Three-dimensional cellular structures for viscous and thermal energy control in acoustic and thermoacoustic applications

The multi-scale asymptotic method provides a separate description of the viscous and thermal response functions governing acoustic waves propagation through porous materials. However, these response functions are inherently interdependent for simple porous structures such as slits or tubes – their determination being directly influenced by the microstructural features of the geometry. This study aims to identify, characterize, and realize a microgeometry providing the ability to independently modify the viscous and thermal behaviours. A relative autonomy in the control of these phenomena would make it possible to regulate energy conversion processes within the structure, which can be either dissipative (e.g., sound absorption) or generative (e.g., thermoacoustic gain). Among the various microgeometries, cellular solids made by an assembly of cells with solid edges or faces, packed together so that they fill space, emerge as promising candidates for achieving such a goal. Within the interconnected cells (pores), the viscous losses are governed by the aperture sizes of the faces (throat section). On the other hand, the thermal exchanges are closely related to the interface between the fluid and the solid and consequently to the dimensions of the cells. The identified microstructure is a typical Kelvin cell-based geometry, modified to account for manufacturing constraints, and characterized by faces with well-defined opening ratio and thickness. This work presents a model, experimentally validated, to predict the transport parameters of such cellular solids. It provides a valuable tool for designing microstructures having the attributes to independently tune thermal and viscous effects for specific application requirements.

Modified and generalized single-element Maxwell viscoelastic model.

In this Letter, the single-element Maxwell model is generalized with respect to the wave vector and extended with a correction function that measures the reduced viscous response. This model has only two free parameters and avoids the attenuation-frequency locking present in the original model. Through molecular simulations it is shown that the model satisfactory predicts the transverse dynamics of the binary Lennard-Jones system at different temperatures, as well as water and toluene at ambient conditions. The correction function shows that the viscous response is significantly reduced compared to the predictions of the original Maxwell model and that there exists a characteristic length scale of minimum dissipation.

Impact of temperature on ophthalmic viscosurgical devices and clinical implications: a pilot study.

To evaluate how temperature affects the rheology of common ophthalmic viscosurgical devices (OVDs) and clinical implications. Tennent Institute of Ophthalmology, Glasgow, with Department of Mechanical and Aerospace Engineering, and Advanced Materials Research Laboratory, University of Strathclyde, Glasgow, United Kingdom. Laboratory pilot study. The viscous and elastic responses of 3 OVDs (Eyefill-SC/Eyefill-C/Eyefill-HD) were measured using rotational and extensional rheometers at clinically relevant temperatures (5°C, 25°C, 37°C). Thermal properties were evaluated using differential scanning calorimetry and laser-flash analysis. The OVDs tested exhibited viscoelastic properties and shear-thinning behavior. Apparent viscosities and relaxation time were higher at lower temperatures. The Eyefill-C and Eyefill-SC exhibited predominantly viscous character at low frequencies with a transition to predominantly elastic behavior at high frequencies. An increase in temperature led to a decrease in relaxation time under shear and extension. At low frequencies, Eyefill-C and Eyefill-SC moduli increase with decreasing temperatures. Eyefill-HD at 25°C and 37°C displays 2 crossover points, with the storage modulus dominating at low and high frequencies indicating a predominantly elastic behavior. Thermal property analysis revealed Eyefill-C had the lowest thermal conductivity. This pilot study confirms our clinical experience that OVD properties are affected by low temperatures, with increased viscosities at low shear rates and higher relaxation times. Cold OVD can cause greater resistance to initiation of intraocular lens (IOL) injection system forces (compared with warmer OVD). Excessively forced injection using cold OVD could contribute to inadvertent cannula detachment if incorrectly assembled, or uncontrolled IOL release leading to avoidable injury.

The interplay between soy proteins and dietary fiber in determining the structure and texture of high moisture extrudates

The (joint) contribution of soy proteins and dietary fibers (DFs) in determining the structure and texture of high moisture extrudates remains largely unclear. Blends of soy protein isolate (SPI) and a soy DF-enriched fraction (SDF) were prepared in different ratios, and their bulk rheology and water mobility distribution when hydrated to 60% moisture were related to the structure, texture, and protein extractability of high moisture extrudates prepared at the same moisture level. Increasing the DF proportion in hydrated SPI-SDF blends resulted in higher storage and loss moduli in linear region. In the non-linear region, however, higher DF levels resulted in more viscous behavior. The mobility of weakly interacting water protons decreased in samples with more DF. High moisture extrudates made from SPI had a layered microstructure consisting of V-shaped lamellae. Extrudates prepared from a blend containing 25% DF had more fibrous appearance with thin, branched protein-rich lamellae. Extrudates containing 52% DF exhibited a macrostructure without the presence of distinct layers or fibers and lacked a continuous protein network in their microstructure. The contribution of disulfide bonds to sustaining the protein network increased in extrudates containing more DF. Extrudates containing more DFs had lower cutting strengths and anisotropic indices. Strong negative correlations were found between the phase angle (obtained at 95 °C) in the non-linear region of the hydrated blends (indicating the relative importance of the viscous response) and the cutting strength of the extrudates in both longitudinal (R = −0.759) and perpendicular (R = −0.883) directions to the flow. In conclusion, the ratio of soy protein to DF had a significant impact on the characteristics of high moisture extrudates, which were associated with alterations in rheological properties, water mobility distribution and protein extractability.

Laser speckle rheological microscopy reveals wideband viscoelastic spectra of biological tissues.

Viscoelastic transformation of tissue drives aberrant cellular functions and is an early biomarker of disease pathogenesis. Tissues scale a range of viscoelastic moduli, from biofluids to bone. Moreover, viscoelastic behavior is governed by the frequency at which tissue is probed, yielding distinct viscous and elastic responses modulated over a wide frequency band. Existing tools do not quantify wideband viscoelastic spectra in tissues, leaving a vast knowledge gap. We present wideband laser speckle rheological microscopy (WB-SHEAR) that reveals elastic and viscous response over sub-megahertz frequencies previously not investigated in tissue. WB-SHEAR uses an optical, noncontact approach to quantify wideband viscoelastic spectra in specimens spanning a range of moduli from low-viscosity fibrin to highly elastic bone. Via laser scanning, micromechanical imaging is enabled to access wideband viscoelastic spectra in heterogeneous tumor specimens with high spatial resolution (25 micrometers). The ability to interrogate the viscoelastic landscape of diverse biospecimens could transform our understanding of mechanobiological processes in various diseases.

New insights into MHD squeezing flows of reacting-radiating Maxwell nanofluids via Wakif's–Buongiorno point of view

AbstractThis work presents a computational investigation of a squeezing nanofluid flow under the influence of thermal radiation, magnetohydrodynamics (MHD), and chemical process in a constrained parallel-wall geometry. In this study, the non-Newtonian behavior of a rate-type (Maxwell) nanofluid is captured by rheological expressions that serve as the foundation for the flow formulation. This kind of thinking makes it possible to simulate the intricate nanofluid behavior that incorporates the elastic and viscous responses, which are useful in a variety of situations related to nanofluid dynamics, rheology, and materials science. Additionally, the transport equations are modeled properly using Wakif's–Buongiorno nanofluid model. The equations reflecting the dynamics of the nanofluid and heat-mass transport are developed based on admissible physical assumptions, such as the negligible viscous dissipation as well as the lower magnetic Reynolds number. After that, several similarity variables are introduced in these equations to get the dimensionless formulation form. Akbari–Ganji's method is used to carry out extensive computational simulations. Our results show that the increased squeezing parameters lead to larger horizontal and vertical velocities. On the other hand, the temperature showed a reverse relationship with the increasing squeezing parameters and exhibiting a cooling impact.

Analysis of time‐dependent mechanical behavior of polyethylene

AbstractNew data analysis based on a spring‐dashpot model is developed to provide very close simulation of stress variation in polyethylene (PE) when subjected to a multi‐relaxation (MR) test. The model consists of a quasi‐static branch and two (long‐ and short‐term) viscous branches. The study shows that viscous stresses applied to the two dashpots and the model parameters can be quantified as functions of displacement (stroke) by simulating closely the stress variation in relaxation. Using these parameters, influences of stress triaxiality and material grade on PE's stress response at relaxation stages are examined, and along with experimental data at the loading stages, spring constants in the two viscous branches are determined. The results indicate that among three PE grades, spring constants and their trend of variation are similar in the long‐term viscous branch, but not in the short‐term counterpart. The results also show that by decreasing specimen gauge length 10 times to increase stress triaxiality, spring constants in the two viscous branches become closer to each other. The work concludes that the new data analysis can determine all parameters in the model, which can then be considered to quantify the role of the viscous stress response for PE's load‐carrying performance.Highlights Use a simple model to simulate complex, multiple relaxation behaviors of PE. Determine all model parameter values to characterize PE's relaxation behavior. Illustrate the effect of stress triaxiality on PE's viscous stress response. Show the similarity and difference of the viscous stress response among 3 PEs.

Development of an asphalt mixture with polymer incorporation modified by industrial graphene nanoplatelets for high-performance to rutting

ABSTRACT This study aimed to develop a high-performance asphalt mixture resistant to rutting through modification with industrial-scale graphene nanoplatelets (industrial GNPs). To achieve this objective, industrial GNPs were incorporated into an SBS-modified asphalt binder at concentrations of 2%, 4%, 6%, 8%, and 10% by mass of the asphalt binder. The aim was to select a design content to enhance the rutting performance of the resulting asphalt mixture. The nanomaterial content selection criterion was based on apparent viscosity results and rheological parameters (MSCR). Two asphalt mixtures were produced after determining the nanomaterial content: a reference mixture and another modified by the selected content (2.64% of industrial GNPs). The mechanical performance was assessed through resistance to rutting tests on French Orniéurer equipment and, in a secondary character, the fatigue resistance under four-point bending. The results showed better rheological behaviour of the modified composites than of the original binder, decreasing the viscous response at high temperatures and thus reducing the non-recoverable deformations. The resistance to rutting of the modified mixture exceeded that of the reference mixture by 19% (mean rut for 30,000 cycles) without significant damage to the fatigue life, proving the high rutting performance of the alternative asphalt mixture.

Development of 3D printed tissue-mimicking materials: Combining fiber reinforcement and fluid content for improved surgical rehearsal

The prevalence of medical errors during surgical procedures has led to a higher emphasis on improving surgical outcomes, by improving surgical planning and training. Anatomical models have become valuable tools for pre-operative planning and current 3D printed models strive to better match real soft biological tissues. This study aimed to develop novel 3D printed material composites with controllable mechanical properties that mimic soft tissue. Concepts of microstructuring, fiber reinforcement and fluid infill in extrusion-based 3D printing are combined to design tunable materials towards target tissues of porcine muscle and liver. Material characterization was performed in triangular wave cyclic experiments under uniaxial tension with increasing displacements. Hereby, initial EI and final EII elastic moduli were evaluated. Further, the viscous response was characterized by the dissipated energy ratio UD and suture retention strength (SRS) was determined by single tensile pull-out tests Elastic moduli of printed materials were successfully tuned to 510 ± 10 kPa, closely resembling porcine muscle with 580 ± 150 kPa. The dissipated energy ratio UD of the silicone was increased from 0.09 ± 0.01 to 0.46 ± 0.17 by addition of gyroid infill and viscous fluid. Suture retention strength (SRS) for porcine liver tissue was 1.64 ± 0.42 N, while that of 3D printed silicone showed a mean SRS of 5.1 ± 0.6 N. Although the exact properties of porcine muscle and liver tissue require finer tuning, this study established techniques for refinement of 3D printed tissue-mimicking materials, ultimately enabling more accurate models for surgical rehearsal.

Accurate visualization colorectal cancer by monitoring viscosity variations with a novel mitochondria-targeted fluorescent probe

Colorectal cancer (CRC) is one of the most prevalent malignant tumors worldwide, exhibiting high morbidity and mortality. Lack of efficient tools for early diagnosis and surgical resection guidance of CRC have been a serious threat to the long-term survival rate of the CRC patients. Recent studies have shown that relative higher viscosity was presented in tumor cells compared to that in normal cells, leading to viscosity as a potential biomarker for CRC. Herein, we reported the development of a series of novel viscosity-sensitive and mitochondria-specific fluorescent probes (HTB, HTI, and HTP) for CRC detection. Among them, HTB showed high sensitivity, minimal background interference, low cytotoxicity, and significant viscous response capability, making it an ideal tool for distinguishing colorectal tumor cells from normal cells. Importantly, we have successfully utilized HTB to visualize in a CRC-cells-derived xenograft (CDX) model, enriching its medical imaging capacity, which laid a foundation for further clinical translational application.

Hall and viscous dissipation effects on mixed convective MHD heat absorbing flow due to an impulsively moving vertical porous plate with ramped surface temperature and concentration

AbstractThe current investigation is purported on viscous heating dissipation and Hall consequences on mixed convection magneto‐hydrodynamic heat captivating fluid transmitting from an impulsively starting vertical porous plate with ramp surface temperature and concentration in the existence of chemical reaction and radiation. The dimensional flow dominating partial differential equations is translated into a non‐dimensional partial differential form by adopting appropriate variables and parameters. A finite element approach is driven to simplify the resulting dimensionless nonlinear linked partial differential equations with initial and boundary stipulates. The after‐effects of flow commanding parameters on the velocity components, temperature and concentration are broadly analysed graphically, whereas both primary and secondary shear stresses, heat and mass transferral rates close to the surface area of the plate are discussed in tables. The ultimate results of this research revealed that viscous heating dissipation, Hall current, and thermal and mass buoyancy responses intensify both velocity components, whereas the efficacy of magnetic fields and radiation degrade both velocity components. The temperature distribution devalues with increasing heat absorption and Prandtl number, but a contrary impulse was noted with viscous heating dissipation. Likewise, concentration distribution expands with time progress but decays with chemical reaction parameters. A comparative analysis among the current results and certain research studies in the literature manifests the results’ precision and correctness.

A constitutive model considering creep damage of wood

AbstractThe serviceability of wooden structures involves multiphysical phenomena, notably the interactions among creep, plasticity, and damage. The influence of creep on the initialization of the damage and on its growth and spread can be adjusted by an additional alpha parameter in order to take into account the coupled effect between creep and damage more properly. We integrate an orthotropic viscoelastic model, based on the generalized Kelvin chain, with an orthotropic damage model, capturing both the immediate nonlinear elastic–plastic–damage response and the time-dependent viscous response of timber. The combination of these material models is important to obtain a realistic description of wood behavior, because the timber shows an immediate nonlinear elastic–plastic–damage response, but also the time-dependent viscous response. In this paper, we algorithmize, implement, and validate the concept of ‘creep damage’, a phenomenon observed in wooden structures. Benchmark tests reveal two distinct patterns of damage in beech wood, immediate postload damage that evolves over time and damage that occurs and spreads during the loading period.

Experimental characterization and constitutive modeling of thermoplastic polyurethane under complex uniaxial loading

This paper presents the testing and constitutive modeling of a Thermoplastic Polyurethane (TPU) compound used in commercial applications. The tested specimens were extracted directly from a TPU sphere used in check valves through water-jet cutting. The tests included tensile and compression tests under complex uniaxial loading protocols to capture different nonlinear phenomena, such as stress softening, hysteresis, relaxation, creep, and rate dependence. The material is modeled assuming a nonlinear elastic equilibrium path that may exhibit stress softening (i.e., Mullins effect), and a hysteretic viscoplastic response that presents rate dependence at three different time scales. To achieve this constitutive behavior, a Parallel Rheological Framework model is used. The nonlinear elastic equilibrium path is modeled using the generalized Yeoh hyperelastic model. The stress softening of the equilibrium path is modeled using the Ogden-Roxburgh damage model on the deviatoric response. The hysteretic viscous response is further split into three viscoplastic chains to represent time dependence at three different time scales in a decoupled way. Each viscoplastic chain is modeled using the Bergstrom-Boyce model with its standard evolution law of the creep strain. The model parameters were found using a stochastic optimization scheme to simultaneously fit all the considered tests. The outstanding agreement between the model and the experimental data across a wide range of loading scenarios provides additional insight into the time-dependent behavior and deformation mechanism of TPUs. Moreover, it shows that the mechanical behavior of these materials can be represented by decoupling the nonlinear viscoplastic behavior in different time scales.

A viscoplastic constitutive model for plastic silts and clays for static slope stability applications

A viscoplastic model for representing plastic silts and clays in geotechnical static slope stability applications is presented. The PM4SiltR model builds on the stress ratio-controlled, critical state-based, bounding surface plasticity model PM4Silt and is coded as a dynamic link library for use in the finite difference program FLAC 8.1. PM4SiltR incorporates strain rate-dependent shear strength, stress relaxation, and creep using a consistency approach combined with an internal strain rate and auto-decay process. The model does not include a cap, and as such cannot simulate strain rate-dependent consolidation under increasing overburden stress. Six parameters control the viscous response for PM4SiltR while the parameters controlling the nonviscous components of the response are the same as for PM4Silt. Single element simulations are presented to illustrate the influence of viscoplasticity on the constitutive response in direct simple shear loading and undrained creep. Single element responses are shown to be consistent with observed experimental results. Simulations of a hypothetical tailings dam constructed using the upstream method are performed to illustrate use of PM4SiltR at field scale. Results of field scale simulations show PM4SiltR can model undrained creep and progressive failure leading to delayed slope instability after relatively minor changes in loading conditions at field scale.

Elastoviscoplasticity intensifies the unstable flows through a micro-contraction geometry

This study focuses on the two-dimensional numerical investigation of complex fluid flows through a micro-contraction geometry in the creeping flow regime, specifically examining elastoviscoplastic (EVP) fluids. These fluids exhibit a combination of viscous, elastic, and plastic behaviors. The governing equations, including mass and momentum, are solved using a finite volume method-based discretization technique. Saramito’s constitutive model is utilized to accurately represent the viscous, elastic, and plastic responses of the EVP fluid. The present results demonstrate significant differences in flow dynamics, such as vortex dynamics and transitions between flow regimes (e.g., steady to unsteady), when compared to simple Newtonian and non-Newtonian viscoelastic (VE) or viscoplastic (VP) fluids. This study reveals that when the yield strain (ϵy) exceeds a critical value, approximately ranging from 0.79 to 0.89, the flow transits from a steady to an unsteady state for the EVP fluids. Importantly, the present study shows that EVP fluids exhibit intensified chaotic flow dynamics and increased instability compared to VE and VP fluids under similar flow conditions. However, the presence of shear-thinning behavior in EVP fluids suppresses this instability. The analysis of local velocity fields and flow deformation in this study highlights the impact on the stretching of fluid microstructure and elastic stresses, which ultimately contribute to the origin of this intensified unstable flow condition for EVP fluids. The finding from this study holds significant potential for enhancing heat or mass transfer rates and mixing efficiency in micro-scale systems, where the prevailing steady and laminar flow conditions often hinder these transport processes.

Degradation during Mixing of Silica-Reinforced Natural Rubber Compounds.

The optimal mixing conditions for silica-filled NR compounds dictate the need to proceed at a high temperature, i.e., 150 °C, to achieve a sufficient degree of silanization. On the other hand, natural rubber is prone to degradation due to mechanical shear and thermal effects during mixing, particularly at long exposure times. The present work investigates NR rubber degradation during mixing in relation to prolonged silanization times. The Mooney viscosity and stress relaxation rates, bound rubber content, storage modulus (G'), and delta δ were investigated to indicate the changes in the elastic/viscous responses of NR molecules related to rubber degradation, molecular chain modifications, and premature crosslinking/interaction. In Gum NR (unfilled), an increase in the viscous response with increasing mixing times indicates a major chain scission that causes a decreased molecular weight and risen chain mobility. For silica-filled NR, an initial decrease in the Mooney viscosity with increasing silanization time is attributed to the chain scission first, but thereafter the effect of the degradation is counterbalanced by a sufficient silanization/coupling reaction which leads to leveling off of the viscous response. Finally, the higher viscous response due to degradation leads to the deterioration of the mechanical properties and rolling resistance performance of tire treads made from such silica-filled NR, particularly when the silanization time exceeds 495 s.

Melting heat effect in MHD flow of maxwell fluid with zero mass flux

This study delves into the investigation of Maxwell fluid flow across a sheet with a particular effort on the melting heat and zero mass flux at the boundary. A Maxwell fluid, characterized by both viscous and elastic responses, plays a pivotal role in various industrial and biological applications. The mathematical model describing Maxwell fluid flow is represented using non-linear momentum and energy equations, incorporating MHD. Similarity transformation is used to change from partial differential equation to ordinary differential equation. The introduction of a phase change term in the energy equation accounts for the melting heat effect at the boundary. The BVP4C solver using MATLAB is hired to numerically answer the system of equations, enabling the determination of the steady-state solution. The solution of this investigation offers valuable insights into the interplay between viscoelasticity and melting heat effects on various flow characteristics, including velocity and temperature profiles. The practical significance of this research is evident in polymer processing, food processing, and materials engineering, where the understanding of Maxwell fluids and their interaction with melting boundaries is essential for process optimization and product quality. So far in the literature survey no one have considered Melting heat effect along with Maxwell fluid. The conclusion for this study is that Melting heat effect increases velocity profile and decreases the temperature profile. This is the main conclusion of this research.