Biaxial Contractile Mechanics of Common Carotid Arteries of Rabbit

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Keiichi Takamizawa
Keyword(s):  
Mechanical Properties ◽  
Strain Energy Function ◽  
Stretch Ratio ◽  
Constitutive Law ◽  
Passive Condition ◽  
Active Condition ◽  
Residual Strains ◽  
The Subject ◽  
Accurate Stress Analysis ◽  
Common Carotid Arteries

Few multiaxial constitutive laws under the vasoactive condition have been proposed as compared with those under the passive condition. The biaxial isometric properties of vasoactive rabbit arteries were studied, although the constitutive law was not proposed. The purpose of the present study is also to describe the multiaxial active mechanical properties of arteries. A novel strain energy function for the active stress has been proposed. This function is simple and may describe the multiaxial characteristics of constricted vessels. Although this study used mean stress and mean stretch ratio to determine the mechanical properties of vessels, a triaxial constitutive law of constricted vessels may be developed. There remains the subject of residual strains under active condition. If this problem will be solved, the accurate stress analysis under vasoactive conditions is possible.

scholarly journals Diffuse approximation for identification of the mechanical properties of microcapsules

2020 ◽  
pp. 108128652097760
Author(s):  
Carlos Quesada ◽  
Claire Dupont ◽  
Pierre Villon ◽  
Anne-Virginie Salsac
Keyword(s):  
Mechanical Properties ◽  
Active Material ◽  
Liquid Core ◽  
Constitutive Law ◽  
Data Driven ◽  
Membrane Properties ◽  
Mechanical Resistance ◽  
Data Set ◽  
Diffuse Approximation ◽  
Capsule Size

A novel data-driven real-time procedure based on diffuse approximation is proposed to characterize the mechanical behavior of liquid-core microcapsules from their deformed shape and identify the mechanical properties of the submicron-thick membrane that protects the inner core through inverse analysis. The method first involves experimentally acquiring the deformed shape that a given microcapsule takes at steady state when it flows through a microfluidic microchannel of comparable cross-sectional size. From the mid-plane capsule profile, we deduce two characteristic geometric quantities that uniquely characterize the shape taken by the microcapsule under external hydrodynamic stresses. To identify the values of the unknown rigidity of the membrane and of the size of the capsule, we compare the geometric quantities with the values predicted numerically using a fluid-structure-interaction model by solving the three-dimensional capsule-flow interactions. The complete numerical data set is obtained off-line by systematically varying the governing parameters of the problem, i.e. the capsule-to-tube confinement ratio, and the capillary number, which is the ratio of the viscous to elastic forces. We show that diffuse approximation efficiently estimates the unknown mechanical resistance of the capsule membrane. We validate the data-driven procedure by applying it to the geometric and mechanical characterization of ovalbumin microcapsules (diameter of the order of a few tens of microns). As soon as the capsule is sufficiently deformed to exhibit a parachute shape at the rear, the capsule size and surface shear modulus are determined with an accuracy of 0.2% and 2.7%, respectively, as compared with 2–3% and 25% without it, in the best cases (Hu et al. Characterizing the membrane properties of capsules flowing in a square-section microfluidic channel: Effects of the membrane constitutive law. Phys Rev E 2013; 87(6): 063008). Diffuse approximation thus allows the capsule size and membrane elastic resistance to be provided quasi-instantly with very high precision. This opens interesting perspectives for industrial applications that require tight control of the capsule mechanical properties in order to secure their behavior when they transport active material.

MECHANICAL PROPERTIES CHANGE IN THE RAT XENOGRAFT MODEL TREATED BY MESENCHYMAL CELLS CULTURED IN AN HYALURONIC ACID-BASED HYDROGEL

2018 ◽  
Vol 18 (05) ◽  
pp. 1850047
Author(s):  
MUSTAPHA ZIDI ◽  
ERIC ALLAIRE
Keyword(s):  
Mechanical Properties ◽  
Hyaluronic Acid ◽  
Arterial Wall ◽  
Cellular Therapy ◽  
Xenograft Model ◽  
Strain Energy Function ◽  
Aortic Aneurysms ◽  
Large Strains ◽  
Abdominal Aortic ◽  
Wall Stiffness

This study investigated the efficiency of a cellular therapy with mesenchymal stem cells (MSCs) cultured in an hyaluronic acid-based hydrogel on growth of abdominal aortic aneurysms (AAA) obtained in the rat xenograft model. The experimental model was devoted to create an AAA at D14 after grafting of a decellularized abdominal aorta obtained from guinea pigs before being transplanted into rats. At D21, geometrical measurements as radius and length of AAA were performed on untreated ([Formula: see text]) and treated ([Formula: see text]) arteries. When compared to different cases, it was shown that the proposed cellular treatment significantly reduced the expansion of radius and length of AAA. Furthermore, to explore the mechanical properties change of the arterial wall, an inverse finite element method was performed where AAA is represented by an elliptical geometry with varying thicknesses. To identify the material parameters, the AAA tissue was assumed to behave isochoric and isotropic undergoing large strains and described by the Yeoh’s strain energy function. Although limitations exist in this study such as the time of the experimental protocol, the isotropic behavior law of the AAA wall and the axisymmetric geometry of the artery, the results revealed that arterial wall stiffness change and the maximum effective stress decreased during expansion of AAA when cellular treatment is applied.

Effect of temperature on the biaxial mechanics of excised lung parenchyma of the dog

1992 ◽  
Vol 73 (3) ◽  
pp. 1171-1180 ◽  
Author(s):  
J. C. Debes ◽  
Y. C. Fung
Keyword(s):  
Mechanical Properties ◽  
Lung Parenchyma ◽  
Tensile Tests ◽  
Stretch Ratio ◽  
Effect Of Temperature ◽  
Uniaxial Tensile ◽  
Slow Cooling ◽  
Influence Of Temperature On ◽  
Creep And Stress Relaxation ◽  
Tissue Material

The influence of temperature on the mechanical properties of excised saline-filled lung parenchyma of the dog was studied at low lung volume. The motivation of this study was to determine whether lung tissue material without the influence of surface tension undergoes a phase transition in the 20–40 degrees C range, as does synthetic elastin studied by Urry in 1984–1986. Dynamic biaxial and uniaxial tensile tests were done, and strain vs. Lagrangian stress curves were recorded during slow cooling and heating between 40 and 10 degrees C. To emphasize the effects of elastin, strains (defined as stretch ratio minus one) were kept below 30%. A slight decrease in compliance occurred with cooling over the entire temperature range. This effect may be attributed to collagen. It was accompanied by a gradual increase in length as the tissue cooled, an effect that may be attributed to elastin. This process was partially reversible with reheating. However, this effect is in contrast with the sudden drastic change in mechanical properties of synthetic elastin described by Urry. Hysteresis, creep, and stress relaxation were small at these low strains. Possible causes of these effects are discussed.

John Wyrill Christian. 9 April 1926 — 27 February 2001

2008 ◽  
Vol 54 ◽  
pp. 71-94
Author(s):  
George D. W. Smith ◽  
Harshad K. D. H. Bhadeshia
Keyword(s):  
Mechanical Properties ◽  
Phase Transformations ◽  
Materials Science ◽  
Martensitic Transformations ◽  
Metals And Alloys ◽  
The Body ◽  
Physical Metallurgy ◽  
Impurity Effects ◽  
The Subject ◽  
Successive Generations

During a distinguished career, John Wyrill (‘Jack') Christian had a profound impact on the subject of materials science, particularly physical metallurgy. He was recognized as a world authority on martensitic transformations, and laid the foundations forthe modern understanding of this topic. His monumental two–volume work, The theory of phase transformations in metals and alloys , is the classic authoritative treatise on the subject, and remains one of the most important texts ever published in the area of materials science. It redefined the whole field of phase transformations, set new standards of intellectual rigour and comprehensiveness, and inspired successive generations ofscientists to follow in his footsteps. He was also a pioneer in the study of the mechanical properties of metals and alloys, particularly those having the body–centred cubic structure. He and his students played a key role in establishing that the low–temperature mechanical properties ofthis important class of metals are controlled by intrinsic dislocation–lattice interactions and not by impurity effects. He contributed tothe study of many other topics in materials science, including the structure of interfaces, the mechanism of deformation twinning, and the properties of stacking faults. He was the recipient of numerous national and international awards for his work. His researches, which were always characterized by precision and deep physical insight, have stood the test of time.

A summary review of mechanical properties prediction methods for textile reinforced polymer composites

2005 ◽  
Vol 219 (2) ◽  
pp. 91-109 ◽  
Author(s):  
J J Crookston ◽  
A C Long ◽  
I A Jones
Keyword(s):  
Mechanical Properties ◽  
Detailed Analysis ◽  
Polymer Composites ◽  
Numerical Models ◽  
Textile Composites ◽  
Prediction Methods ◽  
Reinforced Polymer ◽  
Mechanical Properties Prediction ◽  
The Subject

The use of textile reinforcements for polymer composite components has become a common practice due to the favourable material costs and labour requirements compared with traditional unidirectional prepreg composites, and the high stiffness and strength compared with the use of randomly orientated reinforcements. As a result, determination of both elastic properties and failure behaviour of textile composites has been the subject of substantial research in recent years. This paper presents a review of some of the analytical and numerical models pertaining to the mechanics of textile composites which have been published in the literature. Particular consideration is given to the suitability of models for the analysis of non-orthogonal weave structures such as those which have been deformed in shear during component manufacture. The intention of the paper is not to provide a detailed analysis of the underlying mathematics of the models discussed, but rather to provide an overview of the work conducted in order to direct further reading.

Human Finger Independence: Limitations due to Passive Mechanical Coupling Versus Active Neuromuscular Control

2004 ◽  
Vol 92 (5) ◽  
pp. 2802-2810 ◽  
Author(s):  
Catherine E. Lang ◽  
Marc H. Schieber
Keyword(s):  
Neuromuscular Control ◽  
The Other ◽  
Passive Condition ◽  
Mechanical Coupling ◽  
Complete Independence ◽  
Active Condition ◽  
Middle Ring ◽  
Human Finger ◽  
Passive Movements ◽  
Flexion And Extension

We studied the extent to which mechanical coupling and neuromuscular control limit finger independence by studying passive and active individuated finger movements in healthy adults. For passive movements, subjects relaxed while each finger was rotated into flexion and extension by a custom-built device. For active movements, subjects moved each finger into flexion and extension while attempting to keep the other, noninstructed fingers still. Active movements were performed through approximately the same joint excursions and at approximately the same speeds as the passive movements. We quantified how mechanical coupling limited finger independence from the passive movements, and quantified how neuromuscular control limited finger independence using an analysis that subtracted the indices obtained in the passive condition from those obtained in the active condition. Finger independence was generally similar during passive and active movements, but showed a trend toward less independence in the middle, ring, and little fingers during active, large-arc movements. Mechanical coupling limited the independence of the index, middle, and ring fingers to the greatest degree, followed by the little finger, and placed only negligible limitations on the independence of the thumb. In contrast, neuromuscular control primarily limited the independence of the ring, and little fingers during large-arc movements, and had minimal effects on the other fingers, especially during small-arc movements. For the movement conditions tested here, mechanical coupling between the fingers appears to be a major factor limiting the complete independence of finger movement.

scholarly journals III.—On Larvæ of Lingula and Pelagodiscus (Discinisca)

1916 ◽  
Vol 51 (1) ◽  
pp. 45-69 ◽  
Author(s):  
J. H. Ashworth
Keyword(s):  
Sea Water ◽  
Rotary Pump ◽  
Water Line ◽  
Run Off ◽  
Large Tank ◽  
Active Condition ◽  
The Subject

The specimens which form the subject of this paper were collected on voyages to and from Australia on board the s.s. Orsova and Otway of the Orient Line. Sea-water was being constantly pumped on each ship, by a rotary pump, from an inlet about 18 feet below the water-line to a large tank on the boat deck, and I was allowed to run off, through a plankton net, as much of the water as I desired in order to collect the organisms contained therein. For this privilege, of which I availed myself to a liberal extent, I beg to thank Captain J. F. Healey and Captain F. S. Symons. The small organisms suffered comparatively little by their passage through the pump and pipes, and were, for the most part, in a living and active condition when examined.

Orthotropic Hyperelasticity in Terms of an Arbitrary Molecular Chain Model

2001 ◽  
Vol 69 (2) ◽  
pp. 198-201 ◽  
Author(s):  
J. E. Bischoff ◽  
E. M. Arruda ◽  
K. Grosh
Keyword(s):  
Constitutive Model ◽  
Strain Energy Function ◽  
Constitutive Law ◽  
Orthotropic Materials ◽  
Chain Model ◽  
Wormlike Chain ◽  
General Terms ◽  
Mechanical Models ◽  
Orthotropic Hyperelasticity ◽  
Wormlike Chain Model

There are many statistical mechanical models of long-chain models, two of which are the freely jointed chain model and the wormlike chain model. A continuum constitutive law for hyperelastic orthotropic materials has recently been developed using the freely jointed chain model as its basis. In this note, the continuum strain energy function is recast in general terms allowing for the incorporation of an arbitrary macromolecular constitutive model. In particular, the orthotropic constitutive model is recast using the wormlike chain model in place of the freely jointed chain model and the effects of this alternation are examined.

Numerical Modelling of FRCM Materials Using Augmented-FEM

2019 ◽  
Vol 817 ◽  
pp. 23-29
Author(s):  
Santi Urso ◽  
Houman A. Hadad ◽  
Chiara Borsellino ◽  
Antonino Recupero ◽  
Qing Da Yang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Test ◽  
Failure Modes ◽  
Elevated Temperatures ◽  
The United States ◽  
Design Guidelines ◽  
Constitutive Law ◽  
Analytical Models ◽  
Fiber Reinforced Polymers ◽  
Fe Model

The use of externally-bonded composite materials for strengthening and rehabilitation of existing structures is among the most popular reinforcement techniques. Technologies, such as Fabric Reinforced Cementitious Matrix (FRCM) have been recently developed to address some of the issues of Fiber Reinforced Polymers (FRP), such as sensitivity to elevated temperatures and UV, impermeability, restricted application in presence of moisture or uneven substrate. For a detailed strengthening design with FRCM composites, the mechanical properties of the materials are required. Analytical models in literature discuss the interaction between the FRCM matrix and fabric using a fracture mechanics approach. These analytical laws were simplified using a trilinear curve in which a constant branch correlated to the friction is added. In the United States, “Acceptance Criteria AC434” includes the test methods to evaluate the mechanical properties of the FRCM through a direct tensile test which uses clevis grips. The material characterization per AC434 is in harmony with ACI 549.4R design guidelines. This study deals with the analysis of FRCM materials using 2D Augmented-Finite Element Method (A-FEM) approach. Constitutive material behaviors were used to implement on A-FE model, which can predict the failure modes of the composite material. The damage of the mortar was described by a trilinear curve, and the number and position of the cracks were fixed preliminarily. The fabric was modelled as a continuum layer attached to the mortar with no-thickness cohesive elements. The cohesive law between fabric and mortar was taken from the literature. The tensile test on the FRCM coupon with one layer of fabric was numerically modeled and compared to the experimental stress-strain curves. Results show that the numerical curves matched the experimental ones and capture the three branches of the FRCM constitutive law as well as the failure mode. This modelling tool will allow researchers to predict the constitutive law of an FRCM mater

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