Simple shearing of soft biological tissues

2010 ◽  
Vol 467 (2127) ◽  
pp. 760-777 ◽  
Author(s):  
Cornelius O. Horgan ◽  
Jeremiah G. Murphy
Keyword(s):  
Simple Shear ◽  
Soft Tissues ◽  
Hydrostatic Stress ◽  
Biological Tissues ◽  
Soft Biological Tissues ◽  
Hyperelastic Materials ◽  
Pressure Term ◽  
Deformation State ◽  
Hydrostatic Stresses

Shearing is induced in soft tissues in numerous physiological settings. The limited experimental data available suggest that a severe strain-stiffening effect occurs in the shear stress when soft biological tissues are subjected to simple shear in certain directions. This occurs at relatively small amounts of shear (when compared with the simple shear of rubbers). This effect is modelled within the framework of nonlinear elasticity by consideration of a class of incompressible anisotropic materials. Owing to the large stresses generated for relatively small amounts of shear, particular care must be exercised in order to maintain a homogeneous deformation state in the bulk of the specimen. The results obtained are relevant to the development of accurate shear test protocols for the determination of constitutive properties of soft tissues. It is also demonstrated that there is a fundamental ambiguity in determining the normal stresses in simple shear when soft tissues are modelled as incompressible hyperelastic materials owing to the arbitrary nature of the hydrostatic pressure term. Two physically well-motivated approaches to determining the pressure are presented here, and the resulting hydrostatic stresses are compared and contrasted. The possible generation of cavitational damage owing to critical hydrostatic stress levels is briefly discussed.

Finite Elastic Deformation for a Class of Soft Biological Tissues

1977 ◽  
Vol 99 (2) ◽  
pp. 98-103
Author(s):  
Han-Chin Wu ◽  
R. Reiss
Keyword(s):  
Energy Function ◽  
Annulus Fibrosus ◽  
Strain Energy ◽  
Soft Tissues ◽  
Broad Class ◽  
Strain Energy Function ◽  
Biological Tissues ◽  
Tension Test ◽  
Soft Biological Tissues ◽  
Precise Form

The stress response of soft biological tissues is investigated theoretically. The treatment follows the approach of Wu and Yao [1] and is now extended for a broad class of soft tissues. The theory accounts for the anisotropy due to the presence of fibers and also allows for the stretching of fibers under load. As an application of the theory, a precise form for the strain energy function is proposed. This form is then shown to describe the mechanical behavior of annulus fibrosus satisfactorily. The constants in the strain energy function have also been approximately determined from only a uniaxial tension test.

A Ternary Solution for Independent Acoustic Impedance and Speed of Sound Matching to Biological Tissues

1982 ◽  
Vol 4 (2) ◽  
pp. 163-170 ◽  
Author(s):  
Jonathan Ophir ◽  
Paul Jaeger
Keyword(s):  
Speed Of Sound ◽  
Acoustic Impedance ◽  
Soft Tissues ◽  
Sound Propagation ◽  
Biological Tissues ◽  
Liquid System ◽  
The Body ◽  
Acoustic Parameters ◽  
Wide Range

In applications requiring a liquid which is acoustically well matched to biological tissues, it is often difficult to find a material which is matched well in terms of both the acoustic impedance and speed of sound propagation in it; changing one parameter invariably affects the other. A three component liquid system is described, which allows independent adjustment of these two acoustic parameters over a wide range. This range encompasses the soft tissues of the body. Results of parameter measurements are presented in the form which allows simple determination of the mixture required to match any combination of acoustic impedance and speed of sound propagation over a given range.

Large Deformation Analysis of Some Soft Biological Tissues

1981 ◽  
Vol 103 (2) ◽  
pp. 73-78 ◽  
Author(s):  
H. Demiray
Keyword(s):  
Soft Tissues ◽  
Biological Tissues ◽  
Deformation Analysis ◽  
Elastic Model ◽  
Soft Biological Tissues ◽  
Large Deformation Analysis ◽  
Vulcanized Rubber ◽  
Nonlinear Stress ◽  
Physiological Structure ◽  
Theoretical Results

Due to physiological structure of most of the soft biological tissues, measurable stresses develop after the specimen has been stretched to many hundreds of percent of its relaxed length. Therefore, the nonlinear stress-strain relations developed for vulcanized rubber cannot be applied to soft tissues, which are constitutionally much more nonlinear than other engineering materials. In this article, using two different elastic models proposed for elastic soft tissues, simple elongation of a cylindrical bar and the inflation of a spherical thick shell, which is deemed to be a model for a left venticle, are studied and the material coefficients characterizing the elastic model are obtained via comparing theoretical results with existing experiments on tissues. Furthermore, the elastic stiffnesses which are very important for physiologists and cardiologists are discussed and the consistency of the result with experiments are indicated.

Constitutive Formulation for Numerical Analysis of Visco-Hyperelastic Damage Phenomena in Soft Biological Tissues

2006 ◽  
Author(s):  
Arturo N. Natali ◽  
Emanuele L. Carniel ◽  
Piero G. Pavan ◽  
Alessio Gasparetto ◽  
Franz G. Sander ◽  
...  
Keyword(s):  
Strain Rate ◽  
Soft Tissues ◽  
Mechanical Response ◽  
Constitutive Models ◽  
Experimental Tests ◽  
Biological Tissues ◽  
Tissue Response ◽  
Time Dependent ◽  
Soft Biological Tissues ◽  
Constitutive Formulation

Soft biological tissues show a strongly non linear and time-dependent mechanical response and undergo large strains under physiological loads. The microstructural arrangement determines specific anisotropic macroscopic properties that must be considered within a constitutive formulation. The characterization of the mechanical behaviour of soft tissues entails the definition of constitutive models capable of accounting for geometric and material non linearity. In the model presented here a hyperelastic anisotropic formulation is adopted as the basis for the development of constitutive models for soft tissues and can be properly arranged for the investigation of viscous and damage phenomena as well to interpret significant aspects pertaining to ordinary and degenerative conditions. Visco-hyperelastic models are used to analyze the time-dependent mechanical response, while elasto-damage models account for the stiffness and strength decrease that can develop under significant loading or degenerative conditions. Experimental testing points out that damage response is affected by the strain rate associated with loading, showing a decrease in the damage limits as the strain rate increases. This phenomena can be investigated by means of a model capable of accounting for damage phenomena in relation to viscous effects. The visco-hyperelastic damage model developed is defined on the basis of a Helmholtz free energy function depending on the strain-damage history. In particular, a specific damage criterion is formulated in order to evaluate the influence of the strain rate on damage. The model can be implemented in a general purpose finite element code. This makes it possible to perform numerical analyses of the mechanical response considering time-dependent effects and damage phenomena. The experimental tests develop investigated tissue response for different strain rate conditions, accounting for stretch situations capable of inducing damage phenomena. The reliability of the formulation is evaluated by a comparison with the results of experimental tests performed on pig periodontal ligament.

scholarly journals Elasticity Imaging of Polymeric Media

2006 ◽  
Vol 129 (2) ◽  
pp. 259-272 ◽  
Author(s):  
Mallika Sridhar ◽  
Jie Liu ◽  
Michael F. Insana
Keyword(s):  
Soft Tissues ◽  
Low Frequency ◽  
Biological Tissues ◽  
Mechanical Stimulus ◽  
Elasticity Imaging ◽  
Soft Biological Tissues ◽  
Viscoelastic Parameters ◽  
Molecular Scale ◽  
Complex Structural ◽  
Creep And Stress Relaxation

Viscoelastic properties of soft tissues and hydropolymers depend on the strength of molecular bonding forces connecting the polymer matrix and surrounding fluids. The basis for diagnostic imaging is that disease processes alter molecular-scale bonding in ways that vary the measurable stiffness and viscosity of the tissues. This paper reviews linear viscoelastic theory as applied to gelatin hydrogels for the purpose of formulating approaches to molecular-scale interpretation of elasticity imaging in soft biological tissues. Comparing measurements acquired under different geometries, we investigate the limitations of viscoelastic parameters acquired under various imaging conditions. Quasi-static (step-and-hold and low-frequency harmonic) stimuli applied to gels during creep and stress relaxation experiments in confined and unconfined geometries reveal continuous, bimodal distributions of respondance times. Within the linear range of responses, gelatin will behave more like a solid or fluid depending on the stimulus magnitude. Gelatin can be described statistically from a few parameters of low-order rheological models that form the basis of viscoelastic imaging. Unbiased estimates of imaging parameters are obtained only if creep data are acquired for greater than twice the highest retardance time constant and any steady-state viscous response has been eliminated. Elastic strain and retardance time images are found to provide the best combination of contrast and signal strength in gelatin. Retardance times indicate average behavior of fast (1–10s) fluid flows and slow (50–400s) matrix restructuring in response to the mechanical stimulus. Insofar as gelatin mimics other polymers, such as soft biological tissues, elasticity imaging can provide unique insights into complex structural and biochemical features of connectives tissues affected by disease.

A Novel Compression Tester for Detecting Anisotropy in Very Soft Biological Tissues

2012 ◽  
Author(s):  
Roy Wang ◽  
Rudolph L. Gleason
Keyword(s):  
Adipose Tissue ◽  
Mechanical Behavior ◽  
Uniaxial Compression ◽  
Material Properties ◽  
Soft Tissues ◽  
Tensile Tests ◽  
Biological Tissues ◽  
Compression Tests ◽  
Anisotropic Behavior ◽  
Soft Biological Tissues

Quantifying the mechanical behavior of very soft tissues (VST) is important when studying responses to injury or designing therapeutic devices; fat, brain, or liver being examples of such tissues. VST can have poor suture retention or clamp holding strength, making tensile tests difficult. As a result, uniaxial compression tests are typically the preferred choice to quantify the mechanical behavior. In these tests, isotropy is generally assumed and measuring the deformation in only one direction is needed if the material is considered incompressible [13]. In this study we present a novel testing apparatus for use on VST under uniaxial compression that can detect anisotropic behavior of the tissue if present. We validate the tester using cardiac adipose tissue and isotropic rubber as the control. Understanding the directional behavior of the tissue is important since anisotropy would require testing in multiple directions to fully characterize the material properties.

scholarly journals Correcting the infrared images of soft biological tissues

2019 ◽  
Vol 55 (1) ◽  
pp. 110-117
Author(s):  
A. P. Ivanov
Keyword(s):  
Soft Tissues ◽  
Thermal Power ◽  
Spherical Shape ◽  
Biological Tissues ◽  
Thermal Source ◽  
Near Surface ◽  
Non Invasive ◽  
Calculation Results ◽  
Heat Transfer Parameter

Non-invasive (remote) thermographic methods based on IR images are being actively implemented. Using the calculation results of the temperature increment that occurs when a pathological source exists in the person’s skin, a number of ways of solving “inverse problems” are proposed. These include the determination of the depth of the thermal source by measuring the mono or polychrome increment of the normalized brightness of the tissue surface at one point; the source depth and heat transfer parameter by measuring the poly or monochrome one of the normalized brightness (or temperature) at two points; the thermal power of the source by measuring the increment of absolute brightness or temperature at one point; the depth of the thermal source and its size in the near-surface layer by measuring the increment of the normalized brightness at two points. In order to solve these problems, the thermophysical and optical properties of the soft tissues of the biological organism are indicated. Analytical solutions are given for describing the temperature and the glow that arises under its influence from the sources of cylindrical and spherical shape.

Automated Estimation of Elastic Material Parameters of a Transversely Isotropic Material Using Asymmetric Indentation and Inverse Finite Element Analysis

2015 ◽  
Author(s):  
Yuan Feng ◽  
Chung-Hao Lee ◽  
Lining Sun ◽  
Ruth J. Okamoto ◽  
Songbai Ji
Keyword(s):  
Finite Element ◽  
Soft Tissues ◽  
Transverse Isotropy ◽  
Transversely Isotropic ◽  
Biological Tissues ◽  
Fiber Reinforced ◽  
Element Analysis ◽  
Soft Biological Tissues ◽  
Tissue Properties ◽  
Brain White Matter

Anisotropy exists in many soft biological tissues. The most common anisotropy is transverse isotropy, which is typical for fiber-reinforced structures, such as the brain white matter, tendon and muscle. Although many methods have been proposed to determine tissue properties, techniques to characterize transversely isotropic materials remain limited. The goal of this study is to investigate the feasibility of asymmetric indentation coupled with numerical optimization based on inverse finite element (FE) simulation to characterize transversely isotropic soft biological tissues. The proposed approach combining indentation and optimization may provide a useful general framework to characterize a variety of fiber-reinforced soft tissues in the future.

A STUDY ON THE EFFECT OF COLLAGEN FIBER ORIENTATION ON MECHANICAL RESPONSE OF SOFT BIOLOGICAL TISSUES

2015 ◽  
Vol 76 (7) ◽  
Author(s):  
Farshid Fathi ◽  
Shahrokh Shahi ◽  
Soheil Mohammadi
Keyword(s):  
Finite Element ◽  
Soft Tissues ◽  
Mechanical Response ◽  
Strain Energy Function ◽  
Soft Materials ◽  
Biological Tissues ◽  
Soft Biological Tissues ◽  
Proposed Model ◽  
The Matrix ◽  
Element Approach

Extensive research has been performed in the past decades to study the behavior of soft biological tissues in order to reduce the need for practical experiments. The applicability of these researches, particularly for skin, ligament, muscles and the heart, brings up its importance in various biological science and technology disciplines such as surgery and medicine. Softness and large deformation govern the behavior of soft materials and prohibit the use of small strains solutions in finite element method.In this work, the focus is set on a strain energy function which has the advantage of accurately representing the behavior of a variety of soft tissues with only a few parameters in a finite element approach. The numerical results are verified with a set of tensile experiments to demonstrate the performance of the proposed model. The parameters include the matrix and collagen bundles and their orientation. Different cases are analyzed and discussed for better prediction of different soft tissue responses.  

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