Experimental Determination of Layer-Specific Hyperelastic Parameters of Human Descending Thoracic Aortas

2019 ◽  
Author(s):  
Isabella Bozzo ◽  
Marco Amabili ◽  
Prabakaran Balasubramanian ◽  
Ivan Breslavsky ◽  
Giovanni Ferrari
Keyword(s):  
Storage Modulus ◽  
Thoracic Aorta ◽  
Loss Tangent ◽  
Viscoelastic Model ◽  
Viscoelastic Behavior ◽  
Axial Direction ◽  
Maxwell Model ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Descending Thoracic Aorta

Abstract Heart disease is the second leading cause of death in Canada resulting in $20.9 billion annual healthcare expenditures [1,2]. Understanding the mechanics of the human descending thoracic aorta is fundamental for comprehending the development of pathologies and improving surgical prostheses. This study presents hyperelastic and viscoelastic material characterizations of the human descending thoracic aorta from twelve different donors, with a mean age of 49.4 years. The specimens were dissected into the three constituent layers: intima, media and adventitia. Evaluating the layer-specific opening angles led to the computation of the circumferential residual stresses. Uniaxial tensile tests of each layer, in both the circumferential and axial direction, were used to model the hyperelastic behavior according to the Gasser-Ogden-Holzapfel model (GOH). The storage modulus and loss tangent for the layers were obtained from uniaxial harmonic excitations at varied frequencies, to model the viscoelastic behavior with the generalized Maxwell model. The results showed a positive correlation between age and stiffness for all layers, both axially and circumferentially. Similar loss tangent values were found across the three layers. A large increase in the storage modulus from static to dynamic experiments further corroborates the importance of a viscoelastic model of the aorta, rather than solely hyperelastic.

Nonlinear Dynamic Viscoelastic Model for Osteoarthritic Cartilage Indentation Force

2011 ◽  
Author(s):  
A. Vidal-Lesso ◽  
E. Ledesma-Orozco ◽  
R. Lesso-Arroyo ◽  
L. Daza-Benitez
Keyword(s):  
Mechanical Properties ◽  
Soft Tissues ◽  
Mechanical Response ◽  
Viscoelastic Model ◽  
Viscoelastic Behavior ◽  
Indentation Test ◽  
Maxwell Model ◽  
Relaxation Curve ◽  
Geometrical Parameters ◽  
Osteoarthritic Cartilage

Biomechanical properties and dynamic response of soft tissues as articular cartilage remains issues for attention. Currently, linear isotropic models are still used for cartilage analysis in spite of its viscoelastic nature. Therefore, the aim of this study was to propose a nonlinear viscoelastic model for cartilage indentation that combines the geometrical parameters and velocity of the indentation test with the thickness of the sample as well as the mechanical properties of the tissue changing over time due to its viscoelastic behavior. Parameters of the indentation test and mechanical properties as a function of time were performed in Laplace space where the constitutive equation for viscoelasticity and the convolution theorem was applied in addition with the Maxwell model and Hayes et al. model for instantaneous elastic modulus. Results of the models were compared with experimental data of indentation tests on osteoarthritic cartilage of a unicompartmental osteoarthritis cases. The models showed a strong fit for the axial indentation nonlinear force in the loading curve (R2 = 0.992) and a good fit for unloading (R2 = 0.987), while an acceptable fit was observed in the relaxation curve (R2 = 0.967). These models may be used to study the mechanical response of osteoarthritic cartilage to several dynamical and geometrical test conditions.

A Nonlinear Anisotropic Viscoelastic Model for the Tensile Behavior of the Corneal Stroma

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
T. D. Nguyen ◽  
R. E. Jones ◽  
B. L. Boyce
Keyword(s):  
Soft Tissues ◽  
Viscoelastic Model ◽  
Corneal Stroma ◽  
Viscoelastic Behavior ◽  
Cyclic Stress ◽  
Uniaxial Tensile ◽  
Nonlinear Creep ◽  
Stress Strain ◽  
Highly Nonlinear ◽  
Tensile Strip

Tensile strip experiments of bovine corneas have shown that the tissue exhibits a nonlinear rate-dependent stress-strain response and a highly nonlinear creep response that depends on the applied hold stress. In this paper, we present a constitutive model for the finite deformation, anisotropic, nonlinear viscoelastic behavior of the corneal stroma. The model formulates the elastic and viscous response of the stroma as the average of the elastic and viscous response of the individual lamellae weighted by a probability density function of the preferred in-plane lamellar orientations. The result is a microstructure-based model that incorporates the viscoelastic properties of the matrix and lamellae and the lamellar architecture in the response of the stroma. In addition, the model includes a fully nonlinear description of the viscoelastic response of the lamellar(fiber) level. This is in contrast to previous microstructure-based models of fibrous soft tissues, which relied on quasilinear viscoelastic formulations of the fiber viscoelasticity. Simulations of recent tensile strip experiments show that the model is able to predict, well within the bounds of experimental error and natural variations, the cyclic stress-strain behavior and nonlinear creep behavior observed in uniaxial tensile experiments of excised strips of bovine cornea.

Mechanical properties of Precontraint 1202 S2 based on uniaxial tensile and creep tests

2016 ◽  
Vol 36 (4) ◽  
pp. 254-270 ◽  
Author(s):  
Andrzej Ambroziak ◽  
Paweł Kłosowski
Keyword(s):  
Mechanical Properties ◽  
Polyvinyl Chloride ◽  
Viscoelastic Model ◽  
Tensile Tests ◽  
Woven Fabric ◽  
Uniaxial Tensile ◽  
Creep Tests ◽  
Linear Elastic ◽  
Coated Fabric ◽  
Long Time

The purpose of the paper is the estimation of the polyvinyl chloride – polyester-coated fabric (Precontraint 1202 S2) mechanical properties under uniaxial tensile tests as well as short- and long-time creep tests. The uniaxial tests are the basis of non-linear elastic description while the creep tests are used for the evaluation of the stiffness parameters in time and for the identification of the standard viscoelastic model. The paper also includes a short survey of literature concerning the coated woven fabric description.

Viscoelastic Damping Effect on Brake Squeal Noise

2009 ◽  
Author(s):  
Gael Chevallier ◽  
Franck Renaud ◽  
Jean-Luc Dion
Keyword(s):  
Degrees Of Freedom ◽  
Viscoelastic Model ◽  
Viscoelastic Behavior ◽  
Maxwell Model ◽  
Element Model ◽  
Brake Squeal ◽  
Generalized Maxwell Model ◽  
Space Formulation ◽  
Damping Materials ◽  
Squeal Noise

Brake squeal remains a widespread cause for discomfort in automobiles. Manufacturers overcome this problem by adding damping materials in their systems. The purpose of this work is to take into account the damping in the modeling. As the materials exhibit a viscoelastic behavior, the authors chose to model the damping with the Generalized Maxwell model. Moreover, the authors have tested their method on a detailed Finite Element-model of a brake system. To compute the complex poles of the model, the authors have established a state-space formulation of the viscoelastic model with a new assumption that allows one to reduce the number of states. Making the computation on the whole model is rather difficult due to the number of Degrees Of Freedom, the model is thus reduced on a basis constituted with the eigenvectors of the undamped model. Several results are also presented and discussed as the observed phenomena are rather different from the results obtained with undamped systems.

scholarly journals Comparison of Pavement Layers Responses with Considering Different Models for Asphalt Concrete Viscoelastic Properties

2013 ◽  
Vol 21 (2) ◽  
pp. 15-20 ◽  
Author(s):  
Mehdi Koohmishi
Keyword(s):  
Asphalt Concrete ◽  
Structural Model ◽  
Viscoelastic Model ◽  
Viscoelastic Behavior ◽  
Maxwell Model ◽  
Elastic Behavior ◽  
Linear Elastic ◽  
Concrete Layer ◽  
Linear Viscoelastic Behavior ◽  
Linear Viscoelastic

Abstract In this paper, a comparison between pavement responses is performed by considering two different models for the linear viscoelastic behavior of an asphalt concrete layer. Two models, the Maxwell model and the Kelvin-Voigt model, are generalized. The former is used in ABAQUS and the latter in KENLAYER. As a preliminary step, an appropriate structural model for a flexible pavement structure is developed in ABAQUS by considering linear elastic behavior for all the layers. According to this model, when the depth of a structural model is equal to 6 meters, there is a good agreement between the ABAQUS and KENLAYER results. In this model, the thickness of the pavement is equal to 30 centimeters, and the thickness of the subgrade is equal to 5.7 meters. Then, the viscoelastic behavior is considered for the asphalt concrete layer, and the results from KENLAYER and ABAQUS are compared with each other. The results indicate that the type of viscoelastic model applied to an asphalt concrete layer has a significant effect on the prediction of pavement responses and, logically, the predicted performance of a pavement.

Parameter Identification Methods for Generalized Maxwell Models: Engineering Approach for Small-Strain Viscoelasticity

2010 ◽  
Vol 659 ◽  
pp. 379-384 ◽  
Author(s):  
Gábor Bódai ◽  
Tibor Goda
Keyword(s):  
Parameter Identification ◽  
Maxwell Model ◽  
Small Strain ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Compression Tests ◽  
Identification Methods ◽  
Generalized Maxwell Model ◽  
Limited Frequency

The present paper surveys briefly the parameter identification methods widely used in case of generalized Maxwell-model. Beside those basing on dynamical-mechanical thermal analysis (DMTA) and stress relaxation measurement authors have presented a technique using simple tensile tests. The latter can be effectively used by combining it with the genetic algorithm of Matlab for parameter identification in a limited frequency/time domain. The proposed method can be generalized easily for example for shear and compression tests too. After comparing it with other existing methods author make a proposal for the strain rate of the uniaxial tensile test.

scholarly journals Hyperelastic and Viscoelastic Properties of Brain Tissue in Tension

2012 ◽  
Author(s):  
Badar Rashid ◽  
Michel Destrade ◽  
Michael D. Gilchrist
Keyword(s):  
Finite Element ◽  
Brain Tissue ◽  
Brain Injuries ◽  
Diffuse Axonal Injury ◽  
Viscoelastic Behavior ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Strain Rates ◽  
Average Rise

Mechanical characterization of brain tissue at high loading velocities is particularly important for modelling Traumatic Brain Injury (TBI). During severe impact conditions, brain tissue experiences a mixture of compression, tension and shear. Diffuse axonal injury (DAI) occurs in animals and humans when the strains and strain rates exceed 10% and 10/s, respectively. Knowing the mechanical properties of brain tissue at these strains and strain rates is thus of particular importance, as they can be used in finite element simulations to predict the occurrence of brain injuries under different impact conditions. In this research, uniaxial tensile tests at strain rates of 30, 60 and 90/s up to 30% strain and stress relaxation tests in tension at various strain magnitudes (10%–60%) with an average rise time of 24 ms were performed. The brain tissue showed a stiffer response with increasing strain rates, showing that hyperelastic models are not adequate and that viscoelastic models are required. Specifically, the tensile engineering stress at 30% strain was 3.1 ± 0.49 kPa, 4.3 ± 0.86 kPa, 6.5 ± 0.76 kPa (mean ± SD) at strain rates of 30, 60 and 90/s, respectively. The Prony parameters were estimated from the relaxation data. Numerical simulations were performed using a one-term Ogden model to analyze hyperelastic and viscoelastic behavior of brain tissue up to 30% strain. The material parameters obtained in this study will help to develop biofidelic human brain finite element models, which subsequently can be used to predict brain injuries under impact conditions.

FINITE ELEMENT SIMULATION OF BIOFILM VISCOELASTIC BEHAVIOR UNDER VARIOUS LOADINGS

2018 ◽  
Vol 18 (05) ◽  
pp. 1850056 ◽  
Author(s):  
XIAOLING WANG ◽  
KAI ZHAO ◽  
HUI ZHAO
Keyword(s):  
Finite Element ◽  
Viscoelastic Model ◽  
Viscoelastic Behavior ◽  
Maxwell Model ◽  
Theoretical Models ◽  
Rate Dependent ◽  
Air Interface ◽  
Linear Viscoelastic Theory ◽  
Solid Liquid Interface ◽  
Solid Liquid

Experiments showed that biofilms exhibit viscoelasticity under both displacement and stress loadings, irrespective of pellicles at liquid–air interface or biofilms at solid–liquid interface. However, the general theoretical models are lacking inuniformly and quantitatively describing biofilms’ viscoelastic behavior under various loading conditions. We use the linear viscoelastic theory — Generalized Maxwell model to describe the viscoelastic mechanical properties of biofilms, and study the responses of biofilms under different loadings, including various strain/stress loading rates and cyclic loadings, by finite element method. The results can capture the typical viscoelastic characteristics of biofilms, such as creep, hysteresis, energy dissipation and loading rate-dependent behavior. Our work provides a simple viscoelastic model not only for bacterial biofilms but also for other biological materials.

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