A Comparative Study of Mechanical Properties of Fresh and Elastic-Network Only Proximal Artery Tissues

2007 ◽  
Author(s):  
Philip Kao ◽  
H. Jerry Qi ◽  
Steve Lammers ◽  
Robin Shandas
Keyword(s):  
Mechanical Properties ◽  
Least Squares Method ◽  
Pulmonary Arteries ◽  
Quantitative Comparison ◽  
Uniaxial Deformation ◽  
Elastic Network ◽  
Descending Aorta ◽  
Material Parameters ◽  
Hyperelastic Model ◽  
Left And Right

The contribution of the elastic network to the mechanical behavior of arterial tissues is not well quantified. This paper focuses on the quantification of the behavior of fresh and elastic-network-only (digested) calf arterial tissues in uniaxial deformation using the anisotropic hyperelastic model proposed by Bischoff et al. ([1]). This model characterizes an orthotropic, hyperelastic response, which is well-suited for the modeling of arterial tissues ([2],[3]). For this paper, we attempt to match the material constants associated with the Bischoff-Arruda anisotropic hyperelastic model to our experimental data from arterial tissues including the ascending aortic arch, descending aorta, main, left, and right pulmonary arteries, using a least-squares method. The material parameters obtained from the data fit provide a quantitative comparison of mechanical properties of fresh artery tissues and elastin networks.

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

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.

Comprehensive study on mechanical properties of coated biaxial warp-knitted fabrics

2021 ◽  
pp. 073168442110204
Author(s):  
Bin Yang ◽  
Yingying Shang ◽  
Zeliang Yu ◽  
Minger Wu ◽  
Youji Tao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Failure Modes ◽  
Least Squares Method ◽  
Tensile Tests ◽  
Tensile Creep ◽  
Base Layer ◽  
Sustained Load ◽  
Uniaxial Tensile ◽  
Membrane Structures ◽  
Knitted Fabrics

In recent years, coated fabrics have become the major material used in membrane structures. Due to the special structure of base layer and mechanical properties, coated biaxial warp-knitted fabrics are increasingly applied in pneumatic structures. In this article, the mechanical properties of coated biaxial warp-knitted fabrics are investigated comprehensively. First, off-axial tensile tests are carried out in seven in-plane directions: 0°, 15°, 30°, 45°, 60°, 75°, and 90°. Based on the stress–strain relationship, tensile strengths are obtained and failure modes are studied. The adaptability of Tsai–Hill criterion is analyzed. Then, the uniaxial tensile creep test is performed under 24-h sustained load and the creep elongation is calculated. Besides, tearing strengths in warp and weft directions are obtained by tearing tests. Finally, the biaxial tensile tests under five different load ratios of 1:1, 2:1, 1:2, 1:0, and 0:1 are carried out, and the elastic constants and Poisson’s ratio are calculated using the least squares method based on linear orthotropic assumption. Moreover, biaxial specimens under four load ratios of 3:1, 1:3, 5:1, and 1:5 are further tensile tested to verify the adaptability of linear orthotropic model. These experimental data offer a deeper and comprehensive understanding of mechanical properties of coated biaxial warp-knitted fabrics and could be conveniently adopted in structural design.

A Visco-hyperelastic Model for the Thermo-mechanical Behavior of Polymer Fibers

2010 ◽  
Vol 20 (7) ◽  
pp. 1002-1020 ◽  
Author(s):  
G.P. Potirniche ◽  
A. Pascu ◽  
N. Shoemaker ◽  
P.T. Wang ◽  
M.F. Horstemeyer ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Penetration Resistance ◽  
Polymer Chains ◽  
Polymer Fibers ◽  
Deformation Characteristics ◽  
Uniaxial Deformation ◽  
The Finite Element Method ◽  
Dynamic Event ◽  
Hyperelastic Model ◽  
Strain Rate Hardening

A visco-hyperelastic model for the thermo-mechanical behavior of polymer yarns is presented. The model assumes that the stress in a yarn during uniaxial deformation results from the superposition of strain rate hardening effects and the softening caused by filament damage. The filament damage accounts for the fracture of polymer chains and the failure of inter-chain bonds. The constitutive model was implemented in the finite element method as a 1D rope element, and was applied to the study of nylon 6.6 and Kevlar ® 29 behavior. Numerical simulations of fabrics subjected to ballistic impact were performed, and the model is shown to predict the fabric penetration resistance and the deformation characteristics during the dynamic event.

scholarly journals Ventilation/perfusion mismatch during lung aeration at birth

2014 ◽  
Vol 117 (5) ◽  
pp. 535-543 ◽  
Author(s):  
Justin A. R. Lang ◽  
James T. Pearson ◽  
Arjan B. te Pas ◽  
Megan J. Wallace ◽  
Melissa L. Siew ◽  
...  
Keyword(s):  
Pulmonary Arteries ◽  
Left Lung ◽  
X Ray ◽  
Lung Aeration ◽  
X Ray Imaging ◽  
Iodine Level ◽  
Pulmonary Shunting ◽  
Left And Right ◽  
Near Term ◽  
The Right

At birth, the transition to newborn life is triggered by lung aeration, which stimulates a large increase in pulmonary blood flow (PBF). Current theories predict that the increase in PBF is spatially related to ventilated lung regions as they aerate after birth. Using simultaneous phase-contrast X-ray imaging and angiography we investigated the spatial relationships between lung aeration and the increase in PBF after birth. Six near-term (30-day gestation) rabbits were delivered by caesarean section, intubated and an intravenous catheter inserted, before they were positioned for X-ray imaging. During imaging, iodine was injected before ventilation onset, after ventilation of the right lung only, and after ventilation of both lungs. Unilateral ventilation increased iodine levels entering both left and right pulmonary arteries (PAs) and significantly increased heart rate, iodine ejection per beat, diameters of both left and right PAs, and number of visible vessels in both lungs. Within the 6th intercostal space, the mean gray level (relative measure of iodine level) increased from 68.3 ± 11.6 and 70.3 ± 7.5%·s to 136.3 ± 22.6 and 136.3 ± 23.7%·s in the left and right PAs, respectively. No differences were observed between vessels in the left and right lungs, despite the left lung not initially being ventilated. The increase in PBF at birth is not spatially related to lung aeration allowing a large ventilation/perfusion mismatch, or pulmonary shunting, to occur in the partially aerated lung at birth.

scholarly journals Anisotropic Elastography for Local Passive Properties and Active Contractility of Myocardium from Dynamic Heart Imaging Sequence

2006 ◽  
Vol 2006 ◽  
pp. 1-15 ◽  
Author(s):  
Yi Liu ◽  
Ge Wang ◽  
L. Z. Sun
Keyword(s):  
Mechanical Properties ◽  
Adjoint Method ◽  
Heart Diseases ◽  
Imaging Techniques ◽  
Chamber Pressure ◽  
Cardiac Imaging Techniques ◽  
Dynamic Displacement ◽  
Material Parameters ◽  
Ischemic Region ◽  
Imaging Sequence

Major heart diseases such as ischemia and hypertrophic myocardiopathy are accompanied with significant changes in the passive mechanical properties and active contractility of myocardium. Identification of these changes helps diagnose heart diseases, monitor therapy, and design surgery. A dynamic cardiac elastography (DCE) framework is developed to assess the anisotropic viscoelastic passive properties and active contractility of myocardial tissues, based on the chamber pressure and dynamic displacement measured with cardiac imaging techniques. A dynamic adjoint method is derived to enhance the numerical efficiency and stability of DCE. Model-based simulations are conducted using a numerical left ventricle (LV) phantom with an ischemic region. The passive material parameters of normal and ischemic tissues are identified during LV rapid/reduced filling and artery contraction, and those of active contractility are quantified during isovolumetric contraction and rapid/reduced ejection. It is found that quasistatic simplification in the previous cardiac elastography studies may yield inaccurate material parameters.

Structural-Mechanical Properties of Polyurethane Surface after Carbon Ion Subplantation

2021 ◽  
Vol 887 ◽  
pp. 370-375
Author(s):  
I.A. Morozov ◽  
A.S. Kamenetskikh
Keyword(s):  
Mechanical Properties ◽  
Surface Relief ◽  
Low Energy ◽  
Plasma Modification ◽  
Carbon Ions ◽  
Uniaxial Deformation ◽  
Treatment Regimes ◽  
Subsequent Investigation ◽  
Ion Plasma ◽  
Potential Applications

Ion-plasma modification of polymers has many potential applications, in particular, in the development of biomedical products. Treatment of soft polymers can easily damage the surface; low-energy plasma and subsequent investigation of the structural and mechanical properties of the surface are required. Polyurethane is a widely used block copolymer. Subplantation of carbon ions heterogeneously changes the structural and mechanical properties of the surface (relief, stiffness, thickness of the modified coating), forming a graphene-like nanolayer. Uniaxial deformation of the treated materials in some cases leads to the damage of the surface (local nanocracks, folds). Materials have increased hydrophobicity, good deformability (valid for certain treatment regimes) and can find application in design of products with improved biomedical properties.

Determination of mechanical properties from sharp dynamic indentation

2021 ◽  
pp. 030932472110592
Author(s):  
Bowen Si ◽  
Zhiqiang Li ◽  
Gesheng Xiao ◽  
Xuefeng Shu
Keyword(s):  
Mechanical Properties ◽  
Power Law ◽  
Split Hopkinson Pressure Bar ◽  
Indentation Test ◽  
Hopkinson Pressure Bar ◽  
Dynamic Indentation ◽  
Material Parameters ◽  
Split Hopkinson ◽  
Pressure Bar ◽  
Indentation Response

In this study, a dynamic indentation test method based on the split Hopkinson pressure bar is proposed to obtain the dynamic parameters of Ludwik power law constitutive, namely, Young’s modulus E, strength coefficient K, and strain hardening index n by analyzing dynamic indentation load-indentation depth curve obtained from the theories relating to the Hopkinson pressure bar. The important parameters, namely, loading curvature C and transformation factor [Formula: see text], are invoked to examine the dynamic indentation response results in a wide range of target material parameters. Finite element calculation results are processed through simulation of dynamic indentation response with broad material parameters. Furthermore, the analytical method is used to fit simulation results to obtain the analytical equations for elastic–plastic parameters and curvature parameters for the subsequent analysis. The analytical equation of forward model to predict dynamic indentation response parameter–loading curvature C of a known material is proposed. Then, the elastic–plastic parameters of unknown materials (according to Ludwik power law) are obtained by substituting the dynamic indentation response parameters into an inverse analytical equation under the two types of half-cone angle indenters. The method is verified by other typical materials, which shows that the dynamic indentation test based on the split Hopkinson pressure bar can obtain sufficient conditions to obtain dynamic mechanical properties of target materials.

DYNAMICS OF LEUCINE-RICH REPEAT PROTEINS

2007 ◽  
Vol 02 (03n04) ◽  
pp. 207-219 ◽  
Author(s):  
ANSUMAN LAHIRI ◽  
SOUMALEE BASU
Keyword(s):  
Mechanical Properties ◽  
Ligand Binding ◽  
Dispersion Curve ◽  
Elastic Strip ◽  
Leucine Rich Repeat ◽  
Ribonuclease Inhibitor ◽  
Repeat Number ◽  
Elastic Network ◽  
Repeat Proteins ◽  
Out Of Plane

We have studied the collective dynamics of leucine-rich repeat (LRR) proteins using an elastic network approximation. The slowest mode of the porcine ribonuclease inhibitor (pRI) protein could be visualized as bending fluctuations of a curved elastic strip leading to a planar opening–closing motion of the horseshoe which largely corresponded to the deformation of the protein on ligand binding. The second slowest mode however exhibited a significant out of plane splaying. The distribution of the lowest eigenvalues of different LRR proteins as a function of their repeat number was found to be close to the dispersion curve obtained from pRI whereas that of the leucine-rich variant (LRV) protein showed considerable deviation. The differing mechanical properties of these structurally similar solenoid proteins may have relevance to their function.

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