Energy-based constitutive modelling of local material properties of canine aortas

This study aims at determining the in vitro anisotropic mechanical behaviour of canine aortic tissue. We specifically focused on spatial variations of these properties along the axis of the vessel. We performed uniaxial stretch tests on canine aortic samples in both circumferential and longitudinal directions, as well as histological examinations to derive the tissue's fibre orientations. We subsequently characterized a constitutive model that incorporates both phenomenological and structural elements to account for macroscopic and microstructural behaviour of the tissue. We showed the two fibre families were oriented at similar angles with respect to the aorta's axis. We also found significant changes in mechanical behaviour of the tissue as a function of axial position from proximal to distal direction: the fibres become more aligned with the aortic axis from 46° to 30°. Also, the linear shear modulus of media decreased as we moved distally along the aortic axis from 139 to 64 kPa. These changes derived from the parameters in the nonlinear constitutive model agreed well with the changes in tissue structure. In addition, we showed that isotropic contribution, carried by elastic lamellae, to the total stress induced in the tissue decreases at higher stretch ratios, whereas anisotropic stress, carried by collagen fibres, increases. The constitutive models can be readily used to design computational models of tissue deformation during physiological loading cycles. The findings of this study extend the understanding of local mechanical properties that could lead to region-specific diagnostics and treatment of arterial diseases.

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Constitutive Model for Concrete: An Overview

Current World Environment ◽

10.12944/cwe.10.special-issue1.94 ◽

2015 ◽

Vol 10 (Special-Issue1) ◽

pp. 782-788 ◽

Cited By ~ 2

Author(s):

Mehdi Shekarbeigi ◽

Hasan Sharafi

Keyword(s):

Constitutive Model ◽

Damage Mechanics ◽

Constitutive Models ◽

Continuum Damage Mechanics ◽

Constitutive Modelling ◽

Continuum Damage ◽

Endochronic Theory ◽

Small Deformations

In the last three decades, the constitutive modelling of concrete evolved considerably. This paper describes various developments in this field based on different approaches such anelasticity, plasticity, continuum damage mechanics, plastic fracturing, endochronic theory, microplane models, etc. In this article the material is assumed to undergo small deformations. Only time independent constitutive models and the issues related to their implementation are discussed

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A Constitutive Model for Rock Joints under Cyclic Loading

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.243-249.2211 ◽

2011 ◽

Vol 243-249 ◽

pp. 2211-2215

Author(s):

Dong Mei Yang ◽

Xiang Bo Qiu

Keyword(s):

Constitutive Model ◽

Mechanical Behaviour ◽

Rock Joint ◽

Joint Stiffness ◽

Constitutive Models ◽

Jointed Rock ◽

Rock Joints ◽

Cyclic Loads ◽

Loaded Rock ◽

Good Agreement

Cyclic loads are commonly encountered in geotechnical engineering; however most constitutive models do not account for the effect that such loads can have on the mechanical behaviour of soils and rocks. This work is concerned with the behaviour of jointed rock and, as the overall mechanical behaviour of jointed rock is usually dominated by the mechanical behaviour of the joints, it is focused on the behaviour of rock joints under cyclic loads. In particular, an extension of the existed constitutive model for cyclically loaded rock joints is presented. Variations of rock joint stiffness in both the normal and the shear directions of loading due to surface degradation are taken into account. The degradation of asperities of first and second order is considered, while a new relation is proposed for the joint stiffness in the normal direction during unloading. Numerical simulation results show good agreement of model predictions with existing experimental results.

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Machine learning based multiscale calibration of mesoscopic constitutive models for composite materials: application to brain white matter

Computational Mechanics ◽

10.1007/s00466-021-02009-1 ◽

2021 ◽

Author(s):

Duncan Field ◽

Yanis Ammouche ◽

José-Maria Peña ◽

Antoine Jérusalem

Keyword(s):

Machine Learning ◽

Composite Materials ◽

White Matter ◽

Constitutive Model ◽

Constitutive Models ◽

Constitutive Modelling ◽

Model Parameters ◽

Brain White Matter ◽

Specific Loading ◽

Spatially Varying

AbstractA modular pipeline for improving the constitutive modelling of composite materials is proposed.The method is leveraged here for the development of subject-specific spatially-varying brain white matter mechanical properties. For this application, white matter microstructural information is extracted from diffusion magnetic resonance imaging (dMRI) scans, and used to generate hundreds of representative volume elements (RVEs) with randomly distributed fibre properties. By automatically running finite element analyses on these RVEs, stress-strain curves corresponding to multiple RVE-specific loading cases are produced. A mesoscopic constitutive model homogenising the RVEs’ behaviour is then calibrated for each RVE, producing a library of calibrated parameters against each set of RVE microstructural characteristics. Finally, a machine learning layer is implemented to predict the constitutive model parameters directly from any new microstructure. The results show that the methodology can predict calibrated mesoscopic material properties with high accuracy. More generally, the overall framework allows for the efficient simulation of the spatially-varying mechanical behaviour of composite materials when experimentally measured location-specific fibre geometrical characteristics are provided.

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Preliminary Study on the Deformation of Yuxi Basin under Gravity Action by Nonlinear Finite Element Simulation

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.170-173.1097 ◽

2012 ◽

Vol 170-173 ◽

pp. 1097-1106

Author(s):

Tie Fei Li ◽

Xue Liang Chen ◽

Meng Tan Gao

Keyword(s):

Constitutive Model ◽

Great Influence ◽

Constitutive Models ◽

Secondary Development ◽

Modified Model ◽

Nonlinear Constitutive Model ◽

Element Simulation ◽

Calculation Results ◽

Nonlinear Elastic ◽

Nonlinear Finite Element Simulation

Abstract. A secondary development of the ADINA software for Duncan-Chang E-B nonlinear elastic constitutive model was conducted in this paper, and the veracity of calculation results was verified. To contrast linear constitutive model and Duncan-Chang nonlinear constitutive model, the deformation of YuXi basin profile model under gravity action was calculated by both of the constitutive models. The results show that the subsidence in the linear results is about 12% larger than the nonlinear results, and the nonlinear model has advantages in parameter choosing. Meanwhile, a modified model of YuXi basin which depends on the latest data from our recent work in YuXi area was built to compare with the original model, the calculation results show that the changes in the basin basement structure and basin depth have great influence on the distribution and maximums of the deformation results, when the changes in the internal structure and sequence influence relatively little.

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Parametric Investigation of Mooney-Rivlin Material Constants on Silicone Biocomposite

Materials Science Forum ◽

10.4028/www.scientific.net/msf.882.51 ◽

2017 ◽

Vol 882 ◽

pp. 51-55 ◽

Cited By ~ 1

Author(s):

Siti Humairah Kamarul Bahrain ◽

Jamaluddin Mahmud

Keyword(s):

Mechanical Properties ◽

Constitutive Model ◽

Future Study ◽

Mechanical Behaviour ◽

Constitutive Models ◽

Material Constant ◽

High Tendency ◽

Material Constants ◽

Hyperelastic Materials ◽

Linear Behaviour

Hyperelastic materials are unique materials that have high tendency to stretch and its highly non-linear behaviour is commonly investigated using hyperelastic constitutive models. The aim of this paper is to investigate the sensitivity of Mooney-Rivlin material constants; C1 and C2 values in order to observe the behavior and pattern of the stress-stretch graph for silicone-kenaf composite. There were no previous studies done in regards to assess the mechanical behaviour of the stress-stretch curve for silicone-kenaf biocomposite by varying the Mooney-Rivlin material constants. The material constant, C1 and C2 are varied into few cases and the patterns of stress-stretch curves are studied. It was found that variations of C1 and C2 material constants could contribute differently on the mechanical properties of silicone-kenaf composite. Thus, the results and findings of this study could be further enhanced by future study to gain deeper understanding on the hyperelastic materials behaviour and Mooney-Rivlin hyperelastic constitutive model.

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Effects of Joint Congruency on the Response of a Tension-Compression Nonlinear Constitutive Model for Cartilage

ASME 2008 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2008-192897 ◽

2008 ◽

Author(s):

Benjamin J. Ellis ◽

Gerard A. Ateshian ◽

Andrew E. Anderson ◽

Clare Canal ◽

Steve A. Maas ◽

...

Keyword(s):

Constitutive Model ◽

Solid Phase ◽

Constitutive Models ◽

Incompressible Material ◽

Material Behavior ◽

Nonlinear Material ◽

Similar Response ◽

Joint Congruency ◽

Nonlinear Constitutive Model ◽

Rate Dependent

Articular cartilage exhibits inhomogeneous, rate-dependent and tension-compression (TC) nonlinear material properties. It is a biphasic material (solid and fluid phases) and its solid phase is stiffer in tension than compression [1]. Despite this complex material behavior, elastic, incompressible material models can be used to predict the short-time loading response of cartilage [2]. To our knowledge, the use of an anisotropic incompressible material to represent cartilage in a finite element (FE) joint model has not been investigated and thus the importance of the TC nonlinearity in the analysis of 3D articular contact models is limited [3]. We have been investigating a TC nonlinear incompressible constitutive model to represent hip cartilage. The objective of this study was to assess the influence of TC nonlinearity on FE predictions of stress and strain as a function of congruency between two spherical cartilage layers. It was hypothesized that the TC nonlinear and neo-Hookean constitutive models would yield a similar response when the cartilage layers were nearly congruent, but as the congruency of the cartilage layers decreased the predicted response from the two materials would be different.

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A 3-D Constitutive Model for Finite Element Analyses of Agarose with a Range of Gel Concentrations

10.1101/2020.07.25.221317 ◽

2020 ◽

Author(s):

Xiaogang Wang ◽

Ronald K. June ◽

David M. Pierce

Keyword(s):

Finite Element ◽

Constitutive Model ◽

Finite Element Modeling ◽

Computational Models ◽

Model Parameters ◽

Optimization Approach ◽

Widespread Application ◽

Element Modeling ◽

High Stiffness

AbstractHydrogels have seen widespread application across biomedical sciences and there is considerable interest in using hydrogels, including agarose, for creating in vitro three-dimensional environments to grow cells and study mechanobiology and mechanotransduction. Recent advances in the preparation of agarose gels enable successful encapsulation of viable cells at gel concentrations as high as 5%. Agarose with a range of gel concentrations can thus serve as an experimental model mimicking changes in the 3-D microenvironment of cells during disease progression and can facilitate experiments aimed at probing the corresponding mechanobiology, e.g. the evolving mechanobiology of chondrocytes during the progression of osteoarthritis. Importantly, whether stresses (forces) or strains (displacement) drive mechanobiology and mechanotransduction is currently unknown. We can use experiments to quantify mechanical properties of hydrogels, and imaging to estimate microstructure and even strains; however, only computational models can estimate intra-gel stresses in cell-seeded agarose constructs because the required in vitro experiments are currently impossible. Finite element modeling is well-established for (computational) mechanical analyses, but accurate constitutive models for modeling the 3-D mechanical environments of cells within high-stiffness agarose are currently unavailable. In this study we aimed to establish a 3-D constitutive model of high-stiffness agarose with a range of gel concentrations. We applied a multi-step, physics-based optimization approach to separately fit subsets of model parameters and help achieve robust convergence. Our constitutive model, fitted to experimental data on progressive stress-relaxations, was able to predict reaction forces determined from independent experiments on cyclical loading. Our model has broad applications in finite element modeling aimed at interpreting mechanical experiments on agarose specimens seeded with cells, particularly in predicting distributions of intra-gel stresses. Our model and fitted parameters enable more accurate finite element simulations of high-stiffness agarose constructs, and thus better understanding of experiments aimed at mechanobiology, mechanotransduction, or other applications in tissue engineering.

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Enhanced Piezoelectric Fibered Extracellular Matrix to Promote Cardiomyocyte Maturation and Tissue Formation: A 3D Computational Model

Biology ◽

10.3390/biology10020135 ◽

2021 ◽

Vol 10 (2) ◽

pp. 135

Author(s):

Pau Urdeitx ◽

Mohamed H. Doweidar

Keyword(s):

Extracellular Matrix ◽

Cell Migration ◽

Computational Models ◽

Cell Junctions ◽

Tissue Formation ◽

Cardiac Muscle Cells ◽

Cell Processes ◽

Electrical Stimuli ◽

Cell Cell

Mechanical and electrical stimuli play a key role in tissue formation, guiding cell processes such as cell migration, differentiation, maturation, and apoptosis. Monitoring and controlling these stimuli on in vitro experiments is not straightforward due to the coupling of these different stimuli. In addition, active and reciprocal cell–cell and cell–extracellular matrix interactions are essential to be considered during formation of complex tissue such as myocardial tissue. In this sense, computational models can offer new perspectives and key information on the cell microenvironment. Thus, we present a new computational 3D model, based on the Finite Element Method, where a complex extracellular matrix with piezoelectric properties interacts with cardiac muscle cells during the first steps of tissue formation. This model includes collective behavior and cell processes such as cell migration, maturation, differentiation, proliferation, and apoptosis. The model has employed to study the initial stages of in vitro cardiac aggregate formation, considering cell–cell junctions, under different extracellular matrix configurations. Three different cases have been purposed to evaluate cell behavior in fibered, mechanically stimulated fibered, and mechanically stimulated piezoelectric fibered extra-cellular matrix. In this last case, the cells are guided by the coupling of mechanical and electrical stimuli. Accordingly, the obtained results show the formation of more elongated groups and enhancement in cell proliferation.

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Study of biaxial mechanical properties of the passive pig heart: material characterisation and categorisation of regional differences

International Journal of Mechanical and Materials Engineering ◽

10.1186/s40712-021-00128-4 ◽

2021 ◽

Vol 16 (1) ◽

Author(s):

Fulufhelo Nemavhola

Keyword(s):

Mechanical Properties ◽

Constitutive Model ◽

Computational Models ◽

Heart Diseases ◽

Interventricular Septum ◽

Model Material ◽

Biaxial Test ◽

Material Behaviour ◽

Material Parameters ◽

Biaxial Tests

AbstractRegional mechanics of the heart is vital in the development of accurate computational models for the pursuit of relevant therapies. Challenges related to heart dysfunctioning are the most important sources of mortality in the world. For example, myocardial infarction (MI) is the foremost killer in sub-Saharan African countries. Mechanical characterisation plays an important role in achieving accurate material behaviour. Material behaviour and constitutive modelling are essential for accurate development of computational models. The biaxial test data was utilised to generated Fung constitutive model material parameters of specific region of the pig myocardium. Also, Choi-Vito constitutive model material parameters were also determined in various myocardia regions. In most cases previously, the mechanical properties of the heart myocardium were assumed to be homogeneous. Most of the computational models developed have assumed that the all three heart regions exhibit similar mechanical properties. Hence, the main objective of this paper is to determine the mechanical material properties of healthy porcine myocardium in three regions, namely left ventricle (LV), mid-wall/interventricular septum (MDW) and right ventricle (RV). The biomechanical properties of the pig heart RV, LV and MDW were characterised using biaxial testing. The biaxial tests show the pig heart myocardium behaves non-linearly, heterogeneously and anisotropically. In this study, it was shown that RV, LV and MDW may exhibit slightly different mechanical properties. Material parameters of two selected constitutive models here may be helpful in regional tissue mechanics, especially for the understanding of various heart diseases and development of new therapies.

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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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