Constitutive Modeling for Design and Control of Magnetostrictive Galfenol Devices

A dynamic, nonlinear model for magnetic induction and strain response of cubic magnetostrictive materials to 3-D dynamic magnetic fields and 3-D stresses is developed. Dynamic eddy current losses and inertial stresses are modeled by coupling Maxwell’s equations to Newton’s second law through a nonlinear constitutive model. The constitutive model is derived from continuum thermodynamics.

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Constitutive Modeling for Design and Control of Magnetostrictive Galfenol Devices

Advances in Science and Technology - Smart Materials & Micro/Nanosystems ◽

10.4028/3-908158-11-7.13 ◽

2008 ◽

pp. 13-18

Author(s):

Marcelo J. Dapino ◽

Phillip G. Evans

Keyword(s):

Constitutive Modeling ◽

And Control ◽

Magnetostrictive Galfenol

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Nonlinear Constitutive Model of Soil-bentonite Based on Triaxial Tests along Different Stress Paths

Canadian Geotechnical Journal ◽

10.1139/cgj-2020-0158 ◽

2020 ◽

Author(s):

Pengcheng Ma ◽

Han Ke ◽

Xing Tong ◽

Yun Min Chen

Keyword(s):

Constitutive Model ◽

Test Data ◽

Nonlinear Model ◽

Large Scale ◽

Triaxial Tests ◽

Silty Clay ◽

Cutoff Wall ◽

Model Framework ◽

Nonlinear Constitutive Model ◽

Modified Cam Clay

To investigate the constitutive behavior of soil-bentonite, which is commonly used as the backfill of cutoff walls, a series of triaxial tests were conducted along different stress paths. The tested soil-bentonite comprises 5% Wyoming bentonite and 95% silty clay excavated from a landfill site located in Jiangsu Province, China. Some mechanical properties of the soil-bentonite, including the compression characteristic, shearing characteristic, and coupled deformation of mean and deviatoric stress, were discussed based on the test data. Then, a nonlinear constitutive model was developed under the axisymmetric condition based on a modified hypoelastic model framework. All six independent parameters included in the model were calibrated according to the test data. The mechanical behaviors that the triaxial tests revealed can be fully reflected by the nonlinear model; therefore, it can reasonably describe the stress-strain behaviors of the soil-bentonite in triaxial tests of this study and another literature. Compared with the Modified Cam-Clay model, the prediction effect for the shear strain of the nonlinear model is better. According to a large-scale in-situ test employing a soil-bentonite cutoff wall, the actual stress paths of soil-bentonite are basically included in the application scope of the nonlinear model, preliminarily indicating its applicability for practical engineering projects.

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Advanced Constitutive Modeling of the Thixotropic Elasto-Visco-Plastic Behavior of Blood: Steady-State Blood Flow in Microtubes

Materials ◽

10.3390/ma14020367 ◽

2021 ◽

Vol 14 (2) ◽

pp. 367

Author(s):

Konstantinos Giannokostas ◽

Yannis Dimakopoulos ◽

Andreas Anayiotos ◽

John Tsamopoulos

Keyword(s):

Blood Flow ◽

Steady State ◽

Constitutive Model ◽

Blood Plasma ◽

Constitutive Modeling ◽

Flow Direction ◽

Momentum Balance ◽

Plastic Behavior ◽

Flow Investigation ◽

The Impact

The present work focuses on the in-silico investigation of the steady-state blood flow in straight microtubes, incorporating advanced constitutive modeling for human blood and blood plasma. The blood constitutive model accounts for the interplay between thixotropy and elasto-visco-plasticity via a scalar variable that describes the level of the local blood structure at any instance. The constitutive model is enhanced by the non-Newtonian modeling of the plasma phase, which features bulk viscoelasticity. Incorporating microcirculation phenomena such as the cell-free layer (CFL) formation or the Fåhraeus and the Fåhraeus-Lindqvist effects is an indispensable part of the blood flow investigation. The coupling between them and the momentum balance is achieved through correlations based on experimental observations. Notably, we propose a new simplified form for the dependence of the apparent viscosity on the hematocrit that predicts the CFL thickness correctly. Our investigation focuses on the impact of the microtube diameter and the pressure-gradient on velocity profiles, normal and shear viscoelastic stresses, and thixotropic properties. We demonstrate the microstructural configuration of blood in steady-state conditions, revealing that blood is highly aggregated in narrow tubes, promoting a flat velocity profile. Additionally, the proper accounting of the CFL thickness shows that for narrow microtubes, the reduction of discharged hematocrit is significant, which in some cases is up to 70%. At high pressure-gradients, the plasmatic proteins in both regions are extended in the flow direction, developing large axial normal stresses, which are more significant in the core region. We also provide normal stress predictions at both the blood/plasma interface (INS) and the tube wall (WNS), which are difficult to measure experimentally. Both decrease with the tube radius; however, they exhibit significant differences in magnitude and type of variation. INS varies linearly from 4.5 to 2 Pa, while WNS exhibits an exponential decrease taking values from 50 mPa to zero.

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A nonlinear strain-rate dependent constitutive model for uncured rubber materials under large deformation

Journal of Mechanics ◽

10.1093/jom/ufaa015 ◽

2020 ◽

Vol 37 ◽

pp. 118-125

Author(s):

Weihua Zhou ◽

Changqing Fang ◽

Huifeng Tan ◽

Huiyu Sun

Keyword(s):

Constitutive Model ◽

Large Deformation ◽

Mechanical Response ◽

Uniaxial Tensile ◽

Hysteresis Phenomenon ◽

Mechanical Behaviors ◽

Nonlinear Constitutive Model ◽

Rate Dependent ◽

Parallel Networks ◽

Non Gaussian

Abstract Uncured rubber possesses remarkable hyperelastic and viscoelastic properties while it undergoes large deformation; therefore, it has wide application prospects and attracts great research interests from academia and industry. In this paper, a nonlinear constitutive model with two parallel networks is developed to describe the mechanical response of uncured rubber. The constitutive model is incorporated with the Eying model to describe the hysteresis phenomenon and viscous flow criterion, and the hyperelastic properties under large deformation are captured by a non-Gaussian chain molecular network model. Based on the model, the mechanical behaviors of hyperelasticity, viscoelasticity and hysteresis under different strain rates are investigated. Furthermore, the constitutive model is employed to estimate uniaxial tensile, cyclic loading–unloading and multistep tensile relaxation mechanical behaviors of uncured rubber, and the prediction results show good agreement with the test data. The nonlinear mechanical constitutive model provides an efficient method for predicting the mechanical response of uncured rubber materials.

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