Simultaneous Characterization of Relaxation, Creep, Dissipation, and Hysteresis by Fractional-Order Constitutive Models

We considered relaxation, creep, dissipation, and hysteresis resulting from a six-parameter fractional constitutive model and its particular cases. The storage modulus, loss modulus, and loss factor, as well as their characteristics based on the thermodynamic requirements, were investigated. It was proved that for the fractional Maxwell model, the storage modulus increases monotonically, while the loss modulus has symmetrical peaks for its curve against the logarithmic scale log(ω), and for the fractional Zener model, the storage modulus monotonically increases while the loss modulus and the loss factor have symmetrical peaks for their curves against the logarithmic scale log(ω). The peak values and corresponding stationary points were analytically given. The relaxation modulus and the creep compliance for the six-parameter fractional constitutive model were given in terms of the Mittag–Leffler functions. Finally, the stress–strain hysteresis loops were simulated by making use of the derived creep compliance for the fractional Zener model. These results show that the fractional constitutive models could characterize the relaxation, creep, dissipation, and hysteresis phenomena of viscoelastic bodies, and fractional orders α and β could be used to model real-world physical properties well.

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Effect of Ultraviolet-A (UV-A) and Ultraviolet-C (UV-C) Light on Mechanical Properties of Oyster Mushrooms during Growth

Journal of Biophysics ◽

10.1155/2014/687028 ◽

2014 ◽

Vol 2014 ◽

pp. 1-6 ◽

Cited By ~ 3

Author(s):

Tindibale L. Edward ◽

M. S. K. Kirui ◽

Josiah O. Omolo ◽

Richard G. Ngumbu ◽

Peter M. Odhiambo

Keyword(s):

Mechanical Properties ◽

Storage Modulus ◽

Loss Factor ◽

Loss Modulus ◽

Control Sample ◽

Ultraviolet A ◽

Significant Difference ◽

Ultraviolet C ◽

Oyster Mushrooms ◽

Uv C

This study investigated the effects of ultraviolet-A (UV-A) and ultraviolet-C (UV-C) light on the mechanical properties in oyster mushrooms during the growth. Experiments were carried out with irradiation of the mushrooms with UV-A (365 nm) and UV-C (254 nm) light during growth. The exposure time ranged from 10 minutes to 60 minutes at intervals of 10 minutes and irradiation was done for three days. The samples for experimental studies were cut into cylindrical shapes of diameter 12.50 mm and thickness 3.00 mm. The storage modulus, loss modulus, and loss factor of the irradiated samples and control samples were determined for both UV bands and there was a significant difference between the storage modulus, loss modulus, and loss factor of the irradiated samples by both UV bands with reference to the control sample, P<0.05. UV-C light irradiated samples had higher loss modulus and loss factor but low storage modulus as temperature increased from 35 to 100°C with respect to the control sample while UV-A light irradiated samples had lower loss modulus, low loss factor, and higher storage modulus than UV-C irradiated samples.

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Fabrication and Characterization of Isotropic and Anisotropic Magnetorheological Elastomers, Based on Silicone Rubber and Carbonyl Iron Microparticles

Polymers ◽

10.3390/polym10121343 ◽

2018 ◽

Vol 10 (12) ◽

pp. 1343 ◽

Cited By ~ 13

Author(s):

Jesús Puente-Córdova ◽

M. Reyes-Melo ◽

Luis Palacios-Pineda ◽

Imperio Martínez-Perales ◽

Oscar Martínez-Romero ◽

...

Keyword(s):

Experimental Data ◽

Silicone Rubber ◽

Carbonyl Iron ◽

Loss Modulus ◽

Rubber Matrix ◽

Zener Model ◽

Magnetorheological Elastomers ◽

In Series ◽

Fractional Zener Model

This article focuses on studying the rheological behavior of isotropic and anisotropic magnetorheological elastomers (MREs), made of carbonyl iron microparticles dispersed into a silicone–rubber matrix by considering 20 and 30 wt % of microparticles. Sample sets were prepared for each composition, with and without the application of an external magnetic field. Experimental measurements of the material rheology behavior were carried out by a shear oscillatory rheometer at constant temperature, to determine both the shear storage modulus (G′) and shear loss modulus (G′′) for all characterized samples. Then, experimental data collected from the isotropic and the anisotropic material samples were used to plot the Cole-Cole diagrams to quantify the interfacial adhesion between carbonyl iron microparticles and the silicone-rubber matrix. Furthermore, the Fractional Zener Model (FZM) with two spring-pots in series is used for quantitative analysis of collected experimental data.

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Quasi-static and dynamic nanomechanical characterization of PMMA/ZnO nanocomposite thick films synthesized by ultrasonication and spin-coating

Polymers and Polymer Composites ◽

10.1177/0967391121998484 ◽

2021 ◽

pp. 096739112199848

Author(s):

B Krishna ◽

A Chaturvedi ◽

Neelam Mishra ◽

K Das

Keyword(s):

Storage Modulus ◽

Spin Coating ◽

Loss Factor ◽

Loss Modulus ◽

Polymer Nanocomposite ◽

Mechanical Analysis ◽

Nanocomposite Films ◽

Nanomechanical Property ◽

Indentation Hardness ◽

Indentation Modulus

Polymer nanocomposite films, comprising of polymethylmethacrylate (PMMA) as the matrix and zinc oxide (ZnO) nanoparticles as reinforcement, have been prepared using ultrasonication and spin-coating techniques, with ZnO content up to 20 wt.%. The effect of the processing on the microstructure and nanomechanical properties have been investigated. The nanocomposite film thickness is found to vary from 2.4 ± 0.2 µm for pristine PMMA to 33.1 ± 0.5 µm for PMMA/20 wt.% ZnO nanocomposite. Quasi-static nanoindentation showed that the indentation modulus varied from 4.68 ± 0.07 GPa for pristine PMMA to 5.04 ± 0.14 GPa for PMMA/20 wt.% ZnO nanocomposite, while the indentation hardness varied from 275.94 ± 5.67 MPa to 292.39 ± 10.88 MPa in the same range. However, the highest indentation modulus and the highest hardness are exhibited by PMMA/10 wt.% ZnO nanocomposite. Scanning electron microscopy of the synthesized films provided the evidence behind such variation in material properties. In addition, the experimentally obtained elastic moduli were compared with values predicted by using Eshelby-Mori-Tanaka micromechanics. Nanoindenter-based dynamic mechanical analysis of the PMMA nanocomposite thin films revealed the variation of storage modulus, loss modulus and loss factor of the films in the frequency range of 10 Hz to 201.5 Hz. For all PMMA/ZnO nanocomposites, the storage modulus is found to increase monotonically from 10 Hz to ∼100 Hz, beyond which the values reached a plateau. The loss modulus and loss factor for all PMMA/ZnO nanocomposites are found to decrease with increasing frequency. These results form an essential step toward establishing process-structure-nanomechanical property relationships for PMMA/ZnO nanocomposite films.

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Influence of κ-Carrageenan, Modified Starch and Inulin Addition on Rheological and Sensory Properties of Non-fat and Non-added Sugar Dairy Dessert

Current Nutrition & Food Science ◽

10.2174/1573401315666190301152645 ◽

2020 ◽

Vol 16 (4) ◽

pp. 462-469

Author(s):

Zhaleh Sheidaei ◽

Bahareh Sarmadi ◽

Seyede M. Hosseini ◽

Fardin Javanmardi ◽

Kianoush Khosravi-Darani ◽

...

Keyword(s):

Storage Modulus ◽

Loss Modulus ◽

Viscoelastic Behavior ◽

Textural Properties ◽

Complex Viscosity ◽

Sensory Properties ◽

Modified Starch ◽

Consumer Health ◽

Added Sugar ◽

Textural Parameters

Background: The high amounts of fat, sugar and calorie existing in dairy desserts can lead to increase the risk of health problems. Therefore, the development of functional and dietary forms of these products can help the consumer health. Objective: This study aims to investigate the effects of κ-carrageenan, modified starch and inulin addition on rheological and sensory properties of non-fat and non-added sugar dairy dessert. Methods: In order to determine the viscoelastic behavior of samples, oscillatory test was carried out and the values of storage modulus (G′), loss modulus (G″), loss angle tangent (tan δ) and complex viscosity (η*) were measured. TPA test was used for analysis of the desserts’ texture and textural parameters of samples containing different concentrations of carrageenan, starch and inulin were calculated. Results: All treatments showed a viscoelastic gel structure with the storage modulus higher than the loss modulus values. Increasing amounts of κ-carrageenan and modified starch caused an increase in G′ and G″ as well as η* and a decrease in tan δ. Also, firmness and cohesiveness were enhanced. The trained panelists gave the highest score to the treatment with 0.1% κ-carrageenan, 2.5% starch and 5.5% inulin (sucralose as constant = 0.25%) and this sample was the best treatment with desirable attributes for the production of non-fat and non-added sugar dairy dessert. Conclusion: It can be concluded that the concentration of κ-carrageenan and starch strongly influenced the rheological and textural properties of dairy desserts, whereas the inulin content had little effect on these attributes.

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Wave propagation dynamics in a fractional Zener model with stochastic excitation

Fractional Calculus and Applied Analysis ◽

10.1515/fca-2020-0079 ◽

2020 ◽

Vol 23 (6) ◽

pp. 1570-1604

Author(s):

Teodor Atanacković ◽

Stevan Pilipović ◽

Dora Seleši

Keyword(s):

Wave Propagation ◽

Constitutive Equation ◽

Equations Of Motion ◽

Weak Form ◽

Stochastic Excitation ◽

Expansion Theorem ◽

Zener Model ◽

Dissipation Inequality ◽

Regularity Properties ◽

Fractional Zener Model

Abstract Equations of motion for a Zener model describing a viscoelastic rod are investigated and conditions ensuring the existence, uniqueness and regularity properties of solutions are obtained. Restrictions on the coefficients in the constitutive equation are determined by a weak form of the dissipation inequality. Various stochastic processes related to the Karhunen-Loéve expansion theorem are presented as a model for random perturbances. Results show that displacement disturbances propagate with an infinite speed. Some corrections of already published results for a non-stochastic model are also provided.

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Mechanical Consequences of Dynamically Loaded NiTi Wires under Typical Actuator Conditions in Rehabilitation and Neuroscience

Journal of Functional Biomaterials ◽

10.3390/jfb12010004 ◽

2021 ◽

Vol 12 (1) ◽

pp. 4

Author(s):

Umut D. Çakmak ◽

Zoltán Major ◽

Michael Fischlschweiger

Keyword(s):

Shape Memory Alloy ◽

Shape Memory ◽

Storage Modulus ◽

Loss Factor ◽

Empirical Relation ◽

Material Behavior ◽

Chemical Compositions ◽

Loading Frequency ◽

Frequency Dependency ◽

Controlled Conditions

In the field of rehabilitation and neuroscience, shape memory alloys play a crucial role as lightweight actuators. Devices are exploiting the shape memory effect by transforming heat into mechanical work. In rehabilitation applications, dynamic loading of the respective device occurs, which in turn influences the mechanical consequences of the phase transforming alloy. Hence in this work, dynamic thermomechanical material behavior of temperature-triggered phase transforming NiTi shape memory alloy (SMA) wires with different chemical compositions and geometries was experimentally investigated. Storage modulus and mechanical loss factor of NiTi alloys at different temperatures and loading frequencies were analyzed under force-controlled conditions. Counterintuitive storage modulus- and loss factor-dependent trends regarding the loading frequency dependency of the mechanical properties on the materials’ composition and geometry were, hence, obtained. It was revealed that loss factors showed a pronounced loading frequency dependency, whereas the storage modulus was not affected. It was shown that force-controlled conditions led to a lower storage modulus than expected. Furthermore, it turned out that a simple empirical relation could capture the characteristic temperature dependency of the storage modulus, which is an important input relation for modeling the rehabilitation device behavior under different dynamic and temperature loading conditions, taking directly into account the material behavior of the shape memory alloy.

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Calibration of Finn Model and UBCSAND Model for Simplified Liquefaction Analysis Procedures

Applied Sciences ◽

10.3390/app11115283 ◽

2021 ◽

Vol 11 (11) ◽

pp. 5283

Author(s):

Jui-Ching Chou ◽

Hsueh-Tusng Yang ◽

Der-Guey Lin

Keyword(s):

Numerical Simulation ◽

Constitutive Model ◽

Structural Damage ◽

Simulation Analysis ◽

Constitutive Models ◽

Soil Liquefaction ◽

Analysis Procedure ◽

Liquefaction Resistance ◽

Simplified Procedure ◽

Liquefaction Analysis

Soil-liquefaction-related hazards can damage structures or lead to an extensive loss of life and property. Therefore, the stability and safety of structures against soil liquefaction are essential for evaluation in earthquake design. In practice, the simplified liquefaction analysis procedure associated with numerical simulation analysis is the most used approach for evaluating the behavior of structures or the effectiveness of mitigation plans. First, the occurrence of soil liquefaction is evaluated using the simplified procedure. If soil liquefaction occurs, the resulting structural damage or the following mitigation plan is evaluated using the numerical simulation analysis. Rational and comparable evaluation results between the simplified liquefaction analysis procedure and the numerical simulation analysis are achieved by ensuring that the liquefaction constitutive model used in the numerical simulation has a consistent liquefaction resistance with the simplified liquefaction analysis procedure. In this study, two frequently used liquefaction constitutive models (Finn model and UBCSAND model) were calibrated by fitting the liquefaction triggering curves of most used simplified liquefaction analysis procedures (NCEER, HBF, JRA96, and T-Y procedures) in Taiwan via FLAC program. In addition, the responses of two calibrated models were compared and discussed to provide guidelines for selecting an appropriate liquefaction constitutive model in future projects.

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Rheological and Textural Properties of Apple Pectin-Based Composite Formula with Xanthan Gum Modification for Preparation of Thickened Matrices with Dysphagia-Friendly Potential

Polymers ◽

10.3390/polym13060873 ◽

2021 ◽

Vol 13 (6) ◽

pp. 873

Author(s):

Huaiwen Yang ◽

Chai-Chun Tsai ◽

Jung-Shiun Jiang ◽

Chi-Chung Hua

Keyword(s):

Storage Modulus ◽

Water Consumption ◽

Xanthan Gum ◽

Loss Modulus ◽

Textural Properties ◽

Apple Pectin ◽

Composite Matrix ◽

Low Concentrations ◽

Composite Formula

Modifying the consistency of a given edible fluid matrix by incorporating food thickeners is a common nursing remedy for individuals with dysphagia when adequate water consumption is a concern. As apple pectin (AP) offers nutraceutical benefits, properly formulated apple pectin (AP)-based thickeners featuring xanthan gum (XG) can be superior candidates for preparation of dysphagia-friendly matrices (DFMs). Our recruited DFMs exhibit fluid-like behavior (loss modulus > storage modulus, G” > G’) at lower AP concentrations (2 and 5%, w/w); they turn into weak/critical gels (G’ ≈ G”) as the concentration becomes higher (9%). In contrast, XG-DFMs display gel-like attributes with G’ > G”, even at rather low concentrations (<1%) and become more resistant to sugar, Na+, and Ca2+ modifications. The composite matrix of AP1.8XG0.2 (constraint at 2%) exhibits a confined viscosity of 278 ± 11.7 mPa∙s, which is considered a DFM, in comparison to only AP- or XG-thickened ones. The hardness measurements of XG0.6 and AP1.2XG0.8 are 288.33 ± 7.506 and 302.00 ± 9.849 N/m2, respectively, which potentially represent a promising formulation base for future applications with DFMs; these textural values are not significantly different from a commercially available product (p > 0.05) for dysphagia nursing administrations.

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Constitutive Modeling for Flow Stress Behavior of Nimonic 80A Superalloy During Hot Deformation Process

High Temperature Materials and Processes ◽

10.1515/htmp-2014-0204 ◽

2016 ◽

Vol 35 (3) ◽

pp. 327-336 ◽

Cited By ~ 2

Author(s):

Sendong Gu ◽

Liwen Zhang ◽

Chi Zhang ◽

Wenfei Shen

Keyword(s):

Flow Stress ◽

Constitutive Model ◽

Hot Deformation ◽

Critical Strain ◽

Volume Fraction ◽

Constitutive Models ◽

Avrami Equation ◽

Peak Strain ◽

Compression Tests ◽

Nimonic 80A

AbstractThe hot deformation characteristics of nickel-based alloy Nimonic 80A were investigated by isothermal compression tests conducted in the temperature range of 1,000–1,200°C and the strain rate range of 0.01—5 s–1on a Gleeble-1500 thermomechanical simulator. In order to establish the constitutive models for dynamic recrystallization (DRX) behavior and flow stress of Nimonic 80A, the material constantsα,nand DRX activation energyQin the constitutive models were calculated by the regression analysis of the experimental data. The dependences of initial stress, saturation stress, steady-state stress, dynamic recovery (DRV) parameter, peak strain, critical strain and DRX grain size on deformation parameters were obtained. Then, the Avrami equation including the critical strain for DRX and the peak strain as a function of strain was established to describe the DRX volume fraction. Finally, the constitutive model for flow stress of Nimonic 80A was developed in DRV region and DRX region, respectively. The flow stress values predicted by the constitutive model are in good agreement with the experimental ones, which indicates that the constitutive model can give an accurate estimate for the flow stress of Nimonic 80A under the deformation conditions.

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