scholarly journals Modeling the Viscoelastic Behavior of Quartz and Clay Minerals in Shale by Nanoindentation Creep Tests

Geofluids ◽  
2022 ◽  
Vol 2022 ◽  
pp. 1-16
Author(s):  
Jianfeng Wang ◽  
Yuke Liu ◽  
Chao Yang ◽  
Wenmin Jiang ◽  
Yun Li ◽  
...  
Keyword(s):  
Clay Minerals ◽  
Peak Load ◽  
Viscoelastic Behavior ◽  
Optical Microscope ◽  
Viscoelastic Deformation ◽  
Creep Tests ◽  
Viscoelastic Models ◽  
Small Peak ◽  
Viscoelastic Parameters ◽  
Regression Parameters

The viscoelastic behavior of minerals in shales is important in predicting the macroscale creep behavior of heterogeneous bulk shale. In this study, in situ indentation measurements of two major constitutive minerals (i.e., quartz and clay) in Longmaxi Formation shale from the Sichuan Basin, South China, were conducted using a nanoindentation technique and high-resolution optical microscope. Firstly, quartz and clay minerals were identified under an optical microscope based on their morphology, surface features, reflection characteristics, particle shapes, and indentation responses. Three viscoelastic models (i.e., three-element Voigt, Burger’s, and two-dashpot Kelvin models) were then used to fit the creep data for both minerals. Finally, the effects of peak load on the viscoelastic behavior of quartz and clay minerals were investigated. Our results show that the sizes of the residual imprints on clay minerals were larger than that of quartz for a specific peak load. Moreover, the initial creep rates and depths in clay minerals were higher than those in quartz. However, the creep rates of quartz and clay minerals displayed similar trends, which were independent of peak load. In addition, all three viscoelastic models produced good fits to the experimental data. However, due to the poor fit in the initial holding stage of the three-element Voigt model and instability of the two-dashpot Kelvin model, Burger’s model is best in obtaining the regression parameters. The regression results indicate that the viscoelastic parameters obtained by these models are associated with peak load, and that a relatively small peak load is more reliable for the determination of viscoelastic parameters. Furthermore, the regression values for the viscoelastic parameters of clay minerals were lower than those of quartz and the bulk shale, suggesting the former facilitates the viscoelastic deformation of shale. Our study provides a better understanding of the nanoscale viscoelastic properties of shale, which can be used to predict the time-dependent deformation of shale.

scholarly journals Creep Modelling of Rootstock during Holding in Watermelon Grafting

Agriculture ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1266
Author(s):  
Kang Wu ◽  
Jianzhong Lou ◽  
Chen Li ◽  
Wei Luo ◽  
Congcong Li ◽  
...  
Keyword(s):  
Creep Deformation ◽  
Viscoelastic Model ◽  
Mechanical Damage ◽  
Viscoelastic Behavior ◽  
Damage Mechanism ◽  
Deformation Characteristics ◽  
Mechanical Compression ◽  
Creep Tests ◽  
Viscoelastic Parameters ◽  
Test Velocity

The fragile structure of a rootstock predisposes the stem to mechanical damage during grafting. Thus, it is necessary to take into account the rootstock’s rheological properties under mechanical compression when designing a clamping mechanism. This study focused on cucurbit, a typical rootstock for watermelon grafting. Firstly, we adopted a four-element Burgers model to analyze viscoelastic behavior and deformation characteristics of the rootstock, then conducted creep tests to obtain the parameters of the viscoelastic model. Next, we developed a model for the rootstock during holding based on viscoelastic parameters, loading force and contact time. Moreover, we evaluated the effect of various loading forces and test velocities on creep deformation to reveal the least damage on the rootstock. Results showed that the influence of loading force on the creep deformation was greater than test velocity. Finally, the holding test indicated that the clamping mechanism with silicone rubber can effectively prevent the damage to the stem. Specifically, the loading force should be controlled below 4 N to reduce the associated damage. Taken together, our findings provide a theoretical basis for analyzing the holding damage mechanism during watermelon grafting.

Identification of Nonlinear Viscoelastic Models of Flexible Polyurethane Foam From Uniaxial Compression Data

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
Yousof Azizi ◽  
Patricia Davies ◽  
Anil K. Bajaj
Keyword(s):  
Uniaxial Compression ◽  
Viscoelastic Model ◽  
Viscoelastic Behavior ◽  
Model Parameters ◽  
Viscoelastic Models ◽  
Nonlinear Viscoelastic ◽  
Compression Data ◽  
Computationally Intensive ◽  
Nonlinear Viscoelastic Model ◽  
Flexible Polyurethane

Flexible polyethylene foam is used in many engineering applications. It exhibits nonlinear and viscoelastic behavior which makes it difficult to model. To date, several models have been developed to characterize the complex behavior of foams. These attempts include the computationally intensive microstructural models to continuum models that capture the macroscale behavior of the foam materials. In this research, a nonlinear viscoelastic model, which is an extension to previously developed models, is proposed and its ability to capture foam response in uniaxial compression is investigated. It is hypothesized that total stress can be decomposed into the sum of a nonlinear elastic component, modeled by a higher-order polynomial, and a nonlinear hereditary type viscoelastic component. System identification procedures were developed to estimate the model parameters using uniaxial cyclic compression data from experiments conducted at six different rates. The estimated model parameters for individual tests were used to develop a model with parameters that are a function of strain rates. The parameter estimation technique was modified to also develop a comprehensive model which captures the uniaxial behavior of all six tests. The performance of this model was compared to that of other nonlinear viscoelastic models.

Viscoelastic Models for Ligaments and Tendons

1994 ◽  
Vol 47 (6S) ◽  
pp. S282-S286 ◽  
Author(s):  
S. L.-Y. Woo ◽  
G. A. Johnson ◽  
R. E. Levine ◽  
K. R. Rajagopal
Keyword(s):  
Constitutive Modeling ◽  
Finite Strain ◽  
Experimental Studies ◽  
Viscoelastic Behavior ◽  
Microstructural Change ◽  
Viscoelastic Models ◽  
Dependent Behavior ◽  
Recent Approach ◽  
Single Integral ◽  
Strain Model

Ligaments and tendons serve a variety of important functions in the human body. Many experimental studies have focused on understanding their mechanical behavior, mathematical modeling has also contributed important information. This paper presents a brief review of viscoelastic models that have been proposed to describe the nonlinear and time-dependent behavior of ligaments and tendons. Specific attention is devoted to quasi-linear viscoelasticity (QLV) and to our most recent approach, the single integral finite strain model (SIFS) which incorporates constitutive modeling of microstructural change. An example is given in which the SIFS model is used to describe the viscoelastic behavior of a human patellar tendon.

Finite deformation and fractional order viscoelasticity of an auxetic foam

2022 ◽  
pp. 1045389X2110643
Author(s):  
Eugenia Stanisauskis ◽  
Paul Miles ◽  
William Oates
Keyword(s):  
Fractional Order ◽  
Finite Deformation ◽  
Viscoelastic Behavior ◽  
Integer Order ◽  
Relaxation Effects ◽  
Viscoelastic Parameters ◽  
Rate Dependent ◽  
Improve Model ◽  
Model Predictions ◽  
And Performance

Auxetic foams exhibit novel mechanical properties due to their unique microstructure for improved energy-absorption and cavity expansion applications that have fascinated the scientific community since their inception. Given the advancements in material processing and performance of polymer open cell auxetic foams, there is a strong desire to fully understand the nonlinear rate-dependent deformation of these materials. The influence of nonlinear compressibility is introduced here along with relaxation effects to improve model predictions for different stretch rates and finite deformation regimes. The viscoelastic behavior of the material is analyzed by comparing fractional order and integer order calculus models. All results are statistically validated using maximum entropy methods to obtain Bayesian posterior densities for the hyperelastic, auxetic, and viscoelastic parameters. It is shown that fractional order viscoelasticity provides [Formula: see text]–[Formula: see text] improvement in prediction over integer order viscoelastic models when the model is calibrated at higher stretch rates where viscoelasticity is more significant.

Viscoelastic Properties of Soft Tissue by Discrete Model Characterization

1968 ◽  
Vol 90 (2) ◽  
pp. 239-247 ◽  
Author(s):  
C. E. Jamison ◽  
R. D. Marangoni ◽  
A. A. Glaser
Keyword(s):  
Experimental Technique ◽  
Human Body ◽  
Biological Tissues ◽  
Viscoelastic Models ◽  
Pig Skin ◽  
Viscoelastic Parameters ◽  
Body Tissues ◽  
Mathematical Equations ◽  
Viscoelastic Modeling ◽  
Injury Research

In order to study the response of the human body to acceleration and force, it is necessary to be able to relate force to deformation in various body tissues. Problems wherein this becomes essential include aerospace travel, crash injury research, and shock/vibration environments produced by mechanical systems. Since the tissues within the human body are viscoelastic in nature, it is important to apply proper viscoelastic relations when investigating the mechanics of deformation. This paper discusses on experimental technique for obtaining discrete viscoelastic models of soft biological tissues. The application of this experimental technique, using guinea pig skin as an example, is presented along with numerical results for the various viscoelastic parameters. A discussion of discrete viscoelastic modeling and the necessary mathematical equations for relating deformation to force is also included.

scholarly journals Flutter and Divergence Instability of Axially-Moving Nanoplates Resting on a Viscoelastic Foundation

2019 ◽  
Vol 9 (6) ◽  
pp. 1097 ◽  
Author(s):  
Jingbo Duan ◽  
Dapeng Zhang ◽  
Wenjie Wang
Keyword(s):  
Graphene Nanosheets ◽  
Viscoelastic Behavior ◽  
Nonlocal Elasticity Theory ◽  
Small Scale ◽  
Complex Frequency ◽  
Viscoelastic Foundation ◽  
Viscoelastic Parameters ◽  
Axial Forces ◽  
Divergence Instability ◽  
Axially Moving

Moving nanosystems often rest on a medium exhibiting viscoelastic behavior in engineering applications. The moving velocity and viscoelastic parameters of the medium usually have an interacting impact on the mechanical properties of nanostructures. This paper investigates the dynamic stability of an axially-moving nanoplate resting on a viscoelastic foundation based on the nonlocal elasticity theory. Firstly, the governing partial equations subject to appropriate boundary conditions are derived through utilizing the Hamilton’s principle with the axial velocity, viscoelastic foundation, nonlocal effect and biaxial loadings taken into consideration. Subsequently, the characteristic equation describing the dynamic characteristics is obtained by employing the Galerkin strip distributed transfer function method. Then, complex frequency curves for the nanoplate are displayed graphically and the effects of viscoelastic foundation parameters, small-scale parameters and axial forces on divergence instability and coupled-mode flutter are analyzed, which show that these parameters play a crucial role in affecting nanostructural instability. The presented results benefit the designation of axially-moving graphene nanosheets or other plate-like nanostructures resting on a viscoelastic foundation.

scholarly journals Identification and Frequency Dependence of Viscoelastic Parameters during Dynamic Creep Tests on Selected Pome Fruits

2019 ◽  
Vol 1 (3) ◽  
pp. 324-331 ◽  
Author(s):  
Csaba Farkas ◽  
László Fenyvesi ◽  
Károly Petróczki
Keyword(s):  
Viscoelastic Model ◽  
Model Parameters ◽  
Variable Load ◽  
Pome Fruit ◽  
Creep Tests ◽  
Viscoelastic Parameters ◽  
Wide Range ◽  
Dynamic Creep ◽  
Pome Fruits ◽  
Compressive Loads

In this paper, a novel control-loop concept is presented to investigate the viscoelastic properties of different pome fruits. Repeated mechanical effects are one of the most important risk factors during the postharvest procedures, so our work aimed to expand knowledge in the field. The actual investigations involved Golden Delicious apples and Packham pears. The developed model is based on the Poynting–Thomson body and, during the validating dynamic creep tests, different repeated compressive loads were applied. The examined frequencies were chosen from the most common components of the frequency distribution during the transportation process; the given range is responsible for the highest volume of fruit damage and the most extensive losses. The identified mathematical system determines the viscoelastic model parameters with the best fit to the measured creep data. The model properties of the tested fruit textures are compared in six different frequency setups, with the inspected pome species showing different elastic and viscous responses for the adjusted load conditions. The custom testing device with variable load functions and the proposed solution allow system identification with a wide range of setup possibilities. The resulted viscoelastic parameters can be used for further failure analysis and for the comparison of different pome fruit materials.

scholarly journals Prediction of creep behavior of laminated woven fabric with adhesive interlining under low stress in the bias direction

2016 ◽  
Vol 87 (3) ◽  
pp. 285-295 ◽  
Author(s):  
Masayuki Takatera ◽  
Ken Ishizawa ◽  
KyoungOk Kim
Keyword(s):  
Creep Strain ◽  
Creep Behavior ◽  
Viscoelastic Model ◽  
Element Model ◽  
Woven Fabric ◽  
Creep Model ◽  
Creep Tests ◽  
Viscoelastic Models ◽  
Experimental Creep ◽  
The Face

The effect of adhesive interlining on the creep behavior of a woven fabric in the bias direction was investigated. Three-element viscoelastic models were used to approximate the creep behavior of a face fabric and adhesive interlining. The creep model of a laminated fabric comprised a six-element model in which two three-element models are connected in parallel with the three-element model. Creep tests were carried out using face fabrics, adhesive interlinings, and their laminated fabrics without and with bonding adhesive interlining by hanging samples in the 45° bias direction under their own weight for 7 days. Creep strains of face fabrics bonded with adhesive interlining were found to be weaker than those of the face fabrics. The creep behavior for the face and interlining fabrics could be approximated using the three-element viscoelastic model with appropriate parameters. The experimental creep behavior of a laminated fabric without bonding was similar to the theoretical behavior. However, the experimental creep of laminated fabrics with bonding interlining was less than the calculated creep, owing to the increase in stiffness due to the adhesive. By revising the six-element model with the strains just after hanging and for 2 days, it was possible to predict the creep strain over 7 days.

Linking Internal Dissipation Mechanisms to the Effective Complex Viscoelastic Moduli of Ferroelectrics

2016 ◽  
Vol 84 (2) ◽  
Author(s):  
Charles S. Wojnar ◽  
Dennis M. Kochmann
Keyword(s):  
Microstructure Evolution ◽  
Domain Switching ◽  
Constitutive Models ◽  
Viscoelastic Behavior ◽  
Maxwell Model ◽  
Hysteretic Behavior ◽  
Ferroelectric Ceramics ◽  
Internal Variables ◽  
Viscoelastic Parameters ◽  
Generalized Maxwell Model

Microstructural mechanisms such as domain switching in ferroelectric ceramics dissipate energy, the nature, and extent of which are of significant interest for two reasons. First, dissipative internal processes lead to hysteretic behavior at the macroscale (e.g., the hysteresis of polarization versus electric field in ferroelectrics). Second, mechanisms of internal friction determine the viscoelastic behavior of the material under small-amplitude vibrations. Although experimental techniques and constitutive models exist for both phenomena, there is a strong disconnect and, in particular, no advantageous strategy to link both for improved physics-based kinetic models for multifunctional rheological materials. Here, we present a theoretical approach that relates inelastic constitutive models to frequency-dependent viscoelastic parameters by linearizing the kinetic relations for the internal variables. This enables us to gain qualitative and quantitative experimental validation of the kinetics of internal processes for both quasistatic microstructure evolution and high-frequency damping. We first present the simple example of the generalized Maxwell model and then proceed to the case of ferroelectric ceramics for which we predict the viscoelastic response during domain switching and compare to experimental data. This strategy identifies the relations between microstructural kinetics and viscoelastic properties. The approach is general in that it can be applied to other rheological materials with microstructure evolution.

Identification of Nonlinear Viscoelastic Models of Flexible Polyurethane Foam From Uniaxial Compression Data

2012 ◽  
Author(s):  
Yousof Azizi ◽  
Patricia Davies ◽  
Anil K. Bajaj
Keyword(s):  
Uniaxial Compression ◽  
Viscoelastic Model ◽  
Viscoelastic Behavior ◽  
Model Parameters ◽  
Viscoelastic Models ◽  
Nonlinear Viscoelastic ◽  
Compression Data ◽  
Computationally Intensive ◽  
Nonlinear Viscoelastic Model ◽  
Flexible Polyurethane

Flexible polyethylene foam, which is used in many engineering applications, exhibits nonlinear and viscoelastic behavior. To date, several models have been proposed to characterize the complex behavior of foams from the computationally intensive microstructural models to continuum models that capture the macroscale behavior of the foam materials. A nonlinear viscoelastic model, which is an extension of previously developed models, is proposed and its ability to capture foam response in uniaxial compression is investigated. It is assumed in the model that total stress is decomposed into the sum of a nonlinear elastic component, which is modeled by a higher order polynomial, and a nonlinear hereditary type viscoelastic component. System identification procedures are developed to estimate the model parameters using uniaxial compression data from experiments conducted at different rates. The performance of this model is compared to that of other nonlinear viscoelastic models.

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