scholarly journals An Investigation of Uniaxial Mechanical Properties of Excised Sheep Heart Muscle Fibre – Fitting of Different Hyperelastic Constitutive Models

2021 ◽  
Author(s):  
Fulufhelo Nemavhola ◽  
Harry M Ngwangwa ◽  
Thanyani Pandelani
Keyword(s):  
Experimental Data ◽  
Soft Tissues ◽  
Constitutive Models ◽  
Finite Element Models ◽  
Predictive Capability ◽  
Material Parameters ◽  
Linear Finite Element ◽  
Fitting Algorithm ◽  
Testing Data

Abstract : This paper presents the investigation of biomechanical behaviour of sheep heart fibre using uniaxial tests in various samples. Non-linear Finite Element models (FEA) that are utilised in understanding mechanisms of different diseases may not be developed without the accurate material properties. This paper presents uniaxial mechanical testing data of the sheep heart fibre. The mechanical uniaxial data of the heart fibre was then used in fitting four constitutive models including the Fung model, Polynomial (Anisotropic), Holzapfel (2005) model, Holzapfel (2000) model and the Four-fibre Family model. Even though the constitutive models for soft tissues including heart myocardium have been presented over several decades, there is still a need for accurate material parameters from reliable hyperelastic constitutive models. Therefore, the aim of this research paper is to select five hyperelastic constitutive models and fit experimental data in the uniaxial experimental data of the sheep heart fibre. A fitting algorithm was made used to optimally fitting and determination of the material parameters based on selected hyperelastic constitutive model. In this study, the evaluation index (EI) was used to measure the performance and capability of each selected anisotropic hyperelatic model. It was observed that the best predictive capability of the mechanical behaviour of sheep heart fibre the Polynomial (anisotropic) model has the EI of 100 and this means that it is the best performance when compared to all the other models.

Interpretation of Experimental Data is Substantial for Constitutive Characterization of Arterial Tissue

2021 ◽  
Author(s):  
Ondrej Lisický ◽  
Anna Hrubanová ◽  
Jiri Bursa
Keyword(s):  
Experimental Data ◽  
Soft Tissues ◽  
Constitutive Models ◽  
Uniaxial Stress ◽  
Mechanical Tests ◽  
Data Sets ◽  
Stress Strain ◽  
Rigorous Approach ◽  
Carotid Wall

Abstract The paper aims at evaluation of mechanical tests of soft tissues and creation of their representative stress-strain responses and respective constitutive models. Interpretation of sets of experimental results depends highly on the approach to the data analysis. Their common representation through mean and standard deviation may be misleading and give non-realistic results. In the paper, raw data of 7 studies consisting of 11 experimental data sets (concerning carotid wall and atheroma tissues) are re-analysed to show the importance of their rigorous analysis. The sets of individual uniaxial stress-strain curves are evaluated using three different protocols: stress-based, stretch-based and constant-based, and the population-representative response is created by their mean or median values. Except for nearly linear responses, there are substantial differences between the resulting curves, being mostly the highest for constant-based evaluation. But also the stretch-based evaluation may change the character of the response significantly. Finally, medians of the stress-based responses are recommended as the most rigorous approach for arterial and other soft tissues with significant strain stiffening.

Material Identification On Thin Shells Using the Virtual Fields Method, Demonstrated On the Human Eardrum

2021 ◽  
Author(s):  
Felipe Pires ◽  
Stephane Avril ◽  
Pieter Livens ◽  
Julio A. Cordioli ◽  
Joris Dirckx
Keyword(s):  
Experimental Data ◽  
Outer Surface ◽  
Plate Theory ◽  
Measurement Data ◽  
Total Strain ◽  
Virtual Fields Method ◽  
Material Parameters ◽  
Membrane Strain

Abstract Characterization of material parameters from experimental data remains challenging, especially on biological structures. One of such techniques allowing for the inverse determination of material parameters from measurement data is the Virtual Fields Method (VFM). However, application of the VFM on general structures of complicated shape has not yet been extensively investigated. In this paper, we extend the framework of the VFM method to thin curved solids in 3D, commonly denoted shells. Our method is then used to estimate theYoung's modulus and hysteretic damping of the human eardrum. By utilizing Kirchhoff plate theory, we assume that the behavior of the shell varies linearly through the thickness. The total strain of the shell can then be separated in a bending and membrane strain. This in turn allowed for an application of the VFM based only on data of the outer surface of the shell. We validated our method on simulated and experimental data of a human eardrum made to vibrate at certain frequencies. It was shown that the identified material properties were accurately determined based only on data from the outer surface and are in agreement with literature. Additionally, we observed that neither the bending nor the membrane strain in an human eardrum can be neglected and both contribute significantly to the total strain found experimentally.

Emulating the Interfacial Kinematics of CNS White Matter With Finite Element Techniques

2011 ◽  
Author(s):  
Yi Pan ◽  
Assimina A. Pelegri ◽  
David I. Shreiber
Keyword(s):  
Finite Element ◽  
White Matter ◽  
Soft Tissues ◽  
Axonal Injury ◽  
Mechanical Strain ◽  
Finite Element Models ◽  
Correct Determination ◽  
The Central Nervous System ◽  
Primary Trauma

Axonal injury represents a critical target for TBI and SCI prevention and treatment. Mechanical strain has been identified as the proximal cause of axonal injury, while secondary ischaemic and excitotoxic insults associated with the primary trauma potentially exacerbate the structural and functional damage. Many studies have been attempted to identify the states of stress and strain in white matter using animal and finite element models. These material models employed in finite element simulations of the central nervous system (CNS) of soft tissues heavily depend on phenomenological representations. The accuracy of these simulations depends not only on correct determination of the material properties but also on precise depiction of the tissues’ microstructure.

On the determination of material parameters for internal variable thermoelastic–viscoplastic constitutive models

2007 ◽  
Vol 23 (8) ◽  
pp. 1349-1379 ◽  
Author(s):  
A. Andrade-Campos ◽  
S. Thuillier ◽  
P. Pilvin ◽  
F. Teixeira-Dias
Keyword(s):  
Constitutive Models ◽  
Internal Variable ◽  
Material Parameters

Microstructurally Motivated Constitutive Models for Mouse Arteries

2009 ◽  
Author(s):  
Laura Hansen ◽  
William Wan ◽  
Rudolph Gleason
Keyword(s):  
Vascular Remodeling ◽  
Carotid Arteries ◽  
Constitutive Models ◽  
Axial Loading ◽  
Local Environment ◽  
Stress And Strain ◽  
Biaxial Testing ◽  
Material Parameters ◽  
Local Stresses ◽  
Testing Data

Vascular remodeling occurs as cells sense changes in their mechanical environment. Thus, quantifying the cells’ local environment in terms of stress and strain distributions is an important aspect in studies of vascular remodeling. Knowledge of the constitutive behavior of vessel will allow the local stresses and strains to be calculated given applied loads and geometry. The goal of this study is to determine material parameters for several constitutive models by fitting biaxial testing data from mouse carotid arteries cultured under different axial loading conditions [1].

Determination of Material Parameters of Concrete for Non-Linear Modeling

2013 ◽  
Vol 651 ◽  
pp. 321-324 ◽  
Author(s):  
Thomas Zimmermann ◽  
Alfred Strauss ◽  
Katharina Haider
Keyword(s):  
Stochastic Models ◽  
Fracture Process ◽  
Basic Material ◽  
Linear Modeling ◽  
Element Analysis ◽  
Material Parameters ◽  
Linear Finite Element ◽  
Numerical Assessment ◽  
Non Linear

Within this paper an experimental investigation on basic material parameters as well as fracture mechanical properties for different concrete types is presented. In total four different concrete types were investigated. The results of this investigation serve as a basis for further numerical assessment with respect to (a) define suitable stochastic models for the material parameters and (b) to carry out non-linear finite element analysis incorporating the fracture process as well as crack propagation.

scholarly journals Identifiability of Tissue Material Parameters from Uniaxial Tests using Multi-start Optimization

2020 ◽  
Author(s):  
Babak N. Safa ◽  
Michael H. Santare ◽  
C. Ross Ethier ◽  
Dawn M. Elliott
Keyword(s):  
Experimental Data ◽  
Constitutive Model ◽  
Constitutive Models ◽  
Data Fitting ◽  
Tissue Mechanics ◽  
Lateral Strain ◽  
Model Parameters ◽  
Fiber Reinforced ◽  
Material Parameters ◽  
Tissue Material

AbstractDetermining tissue biomechanical material properties from mechanical test data is frequently required in a variety of applications, e.g. tissue engineering. However, the validity of the resulting constitutive model parameters is the subject of debate in the field. Common methods to perform fitting, such as nonlinear least-squares, are known to be subject to several limitations, most notably the uniqueness of the fitting results. Parameter optimization in tissue mechanics often comes down to the “identifiability” or “uniqueness” of constitutive model parameters; however, despite advances in formulating complex constitutive relations and many classic and creative curve-fitting approaches, there is no accessible framework to study the identifiability of tissue material parameters. Our objective was to assess the identifiability of material parameters for established constitutive models of fiber-reinforced soft tissues, biomaterials, and tissue-engineered constructs. To do so, we generated synthetic experimental data by simulating uniaxial tension and compression tests, commonly used in biomechanics. We considered tendon and sclera as example tissues, using constitutive models that describe these fiber-reinforced tissues. We demonstrated that not all of the model parameters of these constitutive models were identifiable from uniaxial mechanical tests, despite achieving virtually identical fits to the stress-stretch response. We further show that when the lateral strain was considered as an additional fitting criterion, more parameters are identifiable, but some remain unidentified. This work provides a practical approach for addressing parameter identifiability in tissue mechanics.Statement of SignificanceData fitting is a powerful technique commonly used to extract tissue material parameters from experimental data, and which thus has applications in tissue biomechanics and engineering. However, the problem of “uniqueness” or “identifiability” of the fit parameters is a significant issue, limiting the fit results’ validity. Here we provide a novel method to evaluate data fitting and assess the uniqueness of results in the tissue mechanics constitutive models. Our results indicate that the uniaxial stress-stretch experimental data are not adequate to identify all the tissue material parameters. This study is of potential interest to a wide range of readers because of its application for the characterization of other engineering materials, while addressing the problem of uniqueness of the fitted results.

Development of Generalized Parameters for Canine Multibody Meniscus Models From Experimental Data

2011 ◽  
Author(s):  
Gavin Paiva ◽  
Trent Guess
Keyword(s):  
Experimental Data ◽  
Soft Tissues ◽  
Biological Tissues ◽  
Finite Element Models ◽  
Santa Ana ◽  
Modeling Techniques ◽  
Flexible Behavior ◽  
Rigid Body Mechanics ◽  
Generalized Parameters ◽  
The Impact

It has been established that in order to accurately model a knee joint a reasonable approximation of the soft tissues present is necessary1. Models which include these soft tissue structures are able to better reproduce joint kinematics, loading, and analyze the impact of damage and pathological joint behavior1. Simulating the behavior of these tissues requires either a detailed understanding of materials properties that can be implemented via finite element models or the production of an empirical model that can be implemented inside other model frameworks2,3. This study explores the application of multibody (MB) modeling techniques in an attempt to capture the flexible behavior of biological tissues inside of a rigid body mechanics software, MD ADAMS (MSC software, Santa Ana, California), by tuning the performance to experimental data using design of experiments (DOE).

scholarly journals A Novel Algorithm for the Determination of Walker Damage in Loaded Disc Springs

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1661
Author(s):  
Max Benedikt Geilen ◽  
Marcus Klein ◽  
Matthias Oechsner
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Finite Element Models ◽  
Material Parameters ◽  
Analytical Formulas ◽  
Stress States ◽  
Disc Spring ◽  
Automated Determination ◽  
Novel Algorithm

In this paper, a novel algorithm for the determination of Walker damage in loaded disc springs is presented. The algorithm takes a 3D-scan of a disc spring, measured residual stresses, material parameters, and spring loads as inputs. It outputs a distribution of Walker damage over the surface area of the input disc spring. As the algorithm allows a fully automated determination of the Walker damage, it can be used by disc spring manufacturers to reduce the working time spent on this task by specialized engineers significantly. Compared to spreadsheet applications using analytical formulas and finite element models using idealized geometry, this approach offers a superior description of the stress states in disc springs.

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