scholarly journals Functional Grading of a Transversely Isotropic Hyperelastic Model with Applications in Modeling Tricuspid and Mitral Valve Transition Regions

2020 ◽  
Vol 21 (18) ◽  
pp. 6503
Author(s):  
Rajarshi Roy ◽  
Eric Warren ◽  
Yaoyao Xu ◽  
Caleb Yow ◽  
Rama S. Madhurapantula ◽  
...  
Keyword(s):  
Mitral Valve ◽  
Soft Tissues ◽  
Transversely Isotropic ◽  
Biological Tissues ◽  
Functionally Graded ◽  
The Body ◽  
Research Attention ◽  
Graded Material ◽  
Diffraction Imaging ◽  
Tissue Geometry

Surgical simulators and injury-prediction human models require a combination of representative tissue geometry and accurate tissue material properties to predict realistic tool–tissue interaction forces and injury mechanisms, respectively. While biological tissues have been individually characterized, the transition regions between tissues have received limited research attention, potentially resulting in inaccuracies within simulations. In this work, an approach to characterize the transition regions in transversely isotropic (TI) soft tissues using functionally graded material (FGM) modeling is presented. The effect of nonlinearities and multi-regime nature of the TI model on the functional grading process is discussed. The proposed approach has been implemented to characterize the transition regions in the leaflet (LL), chordae tendinae (CT) and the papillary muscle (PM) of porcine tricuspid valve (TV) and mitral valve (MV). The FGM model is informed using high resolution morphological measurements of the collagen fiber orientation and tissue composition in the transition regions, and deformation characteristics predicted by the FGM model are numerically validated to experimental data using X-ray diffraction imaging. The results indicate feasibility of using the FGM approach in modeling soft-tissue transitions and has implications in improving physical representation of tissue deformation throughout the body using a scalable version of the proposed approach.

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.

scholarly journals Tunability of collagen matrix mechanical properties via multiple modes of mineralization

2016 ◽  
Vol 6 (1) ◽  
pp. 20150070 ◽  
Author(s):  
Lester J. Smith ◽  
Alix C. Deymier ◽  
John J. Boyle ◽  
Zhen Li ◽  
Stephen W. Linderman ◽  
...  
Keyword(s):  
Soft Tissues ◽  
Collagen Matrix ◽  
Functionally Graded ◽  
The Body ◽  
Hard Material ◽  
Collagen Scaffolds ◽  
Collagen Matrices ◽  
Mineral Deposition ◽  
Simulated Body Fluids ◽  
Mineralized Collagen

Functionally graded, mineralized collagen tissues exist at soft-to-hard material attachments throughout the body. However, the details of how collagen and hydroxyapatite mineral (HA) interact are not fully understood, hampering efforts to develop tissue-engineered constructs that can assist with repair of injuries at the attachments of soft tissues to bone. In this study, spatial control of mineralization was achieved in collagen matrices using simulated body fluids (SBFs). Based upon previous observations of poor bonding between reconstituted collagen and HA deposited using SBF, we hypothesized that mineralizing collagen in the presence of fetuin (which inhibits surface mineralization) would lead to more mineral deposition within the scaffold and therefore a greater increase in stiffness and toughness compared with collagen mineralized without fetuin. We tested this hypothesis through integrated synthesis, mechanical testing and modelling of graded, mineralized reconstituted collagen constructs. Results supported the hypothesis, and further suggested that mineralization on the interior of reconstituted collagen constructs, as promoted by fetuin, led to superior bonding between HA and collagen. The results provide us guidance for the development of mineralized collagen scaffolds, with implications for bone and tendon-to-bone tissue engineering.

scholarly journals Computational contact mechanics for a medium consisting of functionally graded material coating and orthotropic substrate

2021 ◽  
Vol 4 (4) ◽  
pp. 249-266
Author(s):  
Erdal Öner
Keyword(s):  
Integral Equation ◽  
Singular Integral Equation ◽  
Contact Mechanics ◽  
Singular Integral ◽  
Functionally Graded Material ◽  
Body Force ◽  
Functionally Graded ◽  
The Body ◽  
Flat Punch ◽  
Graded Material

This paper presents a semi-analytical method to investigate the frictionless contact mechanics between a functionally graded material (FGM) coating and an orthotropic substrate when the system is indented by a rigid flat punch. From the bottom, the orthotropic substrate is completely bonded to the rigid foundation. The body force of the orthotropic substrate is ignored in the solution, while the body force of the FGM coating is considered. An exponential function is used to define the smooth variation of the shear modulus and density of the FGM coating, and the variation of Poisson’s ratio is assumed to be negligible. The partial differential equation system for the FGM coating and the orthotropic substrate is solved analytically through Fourier transformations. After applying boundary and interface continuity conditions to the mixed boundary value problem, the contact problem is reduced to a singular integral equation. The Gauss–Chebyshev integration method is then used to convert the singular integral equation into a system of linear equations, which are solved using an appropriate iterative algorithm to calculate the contact stress under the rigid flat punch. The parametric analyses presented here demonstrate the effects of normalized punch length, material inhomogeneity, dimensionless press force, and orthotropic material type on contact stresses at interfaces, critical load factor, and initial separation distance between FGM coating and orthotropic substrate. The developed solution procedures are verified through the comparisons made to the results available in the literature. The solution methodology and numerical results presented in this paper can provide some useful guidelines for improving the design of multibody indentation systems using FGMs and anisotropic materials.

Effect of highly porous bioceramics based on ZrO2 – Y2O3 – CeO2 system on the biological tissues of experimental animals

2020 ◽  
pp. 29-39
Author(s):  
M. V. Kalinina ◽  
◽  
N. Yu. Kovalko ◽  
D. N. Suslov ◽  
Yu. S. Andozhskaia ◽  
...  
Keyword(s):  
Soft Tissues ◽  
Pore Space ◽  
Biological Tissues ◽  
The Body ◽  
Laboratory Animals ◽  
Experimental Animals ◽  
Average Grain Size ◽  
Porous Bioceramics ◽  
Highly Porous

By reverse co-deposition of hydroxides synthesized highly dispersed powder (the average size 8 – 10 nm) of the composition (ZrO2)0.92(Y2О3)0.03(СеО2)0.05, based on it use comprehensive a blowing agent and mechanical activation of the obtained highly porous ceramics (average grain size 60 – 65 nm). The synthesized ceramic material-an implant with an open porosity of 55 % and a pore size of 40 – 800 nm was placed in the body of laboratory animals. The reaction of biological tissues of experimental animals to the introduction of plates made of composite highly porous materials based on t-ZrO2 15 months after their implantation was studied. It is revealed that enhanced revascularization is registered in capsules, and perfusion of tissues is registered in intact zone of ceramics introduction. The possibility of germination of vessels in soft tissues into the available pore space of ceramics is shown. The results obtained in vivo suggest that porous bioceramics based on t-ZrO2 can be used in the production of endoprostheses and implants in such areas of medicine as orthopedics and traumatology.

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.

Additive Manufacturing of Functionally Graded Material Objects: A Review

2018 ◽  
Vol 18 (4) ◽  
Author(s):  
Binbin Zhang ◽  
Prakhar Jaiswal ◽  
Rahul Rai ◽  
Saigopal Nelaturi
Keyword(s):  
Additive Manufacturing ◽  
Functionally Graded ◽  
Graded Materials ◽  
Research Attention ◽  
Complex Shapes ◽  
Spatial Composition ◽  
Graded Material ◽  
Planning Processes ◽  
Key Aspects ◽  
Modeling Representation

Functionally graded materials (FGM) have recently attracted a lot of research attention in the wake of the recent prominence of additive manufacturing (AM) technologies. The continuously varying spatial composition profile of two or more materials affords FGM to possess properties of multiple different materials simultaneously. Emerging AM technologies enable manufacturing complex shapes with customized multifunctional material properties in an additive fashion. In this paper, we focus on providing an overview of research at the intersection of AM techniques and FGM objects. We specifically discuss FGM modeling representation schemes and outline a classification system to classify existing FGM representation methods. We also highlight the key aspects such as the part orientation, slicing, and path planning processes that are essential for fabricating FGM object through the use of multimaterial AM techniques.

Rapid Critical Point Drying of Tissues in a Parr Bomb

1972 ◽  
Vol 30 ◽  
pp. 400-401
Author(s):  
C.A. Baechler ◽  
W. C. Pitchford ◽  
J. M. Riddle ◽  
C.B. Boyd ◽  
H. Kanagawa ◽  
...  
Keyword(s):  
Critical Point ◽  
Critical Pressure ◽  
Soft Tissues ◽  
Biological Tissues ◽  
Critical Temperatures ◽  
Air Drying ◽  
The Past ◽  
Critical Point Drying ◽  
Great Stress ◽  
Infiltration Techniques

Preservation of the topographic ultrastructure of soft biological tissues for examination by scanning electron microscopy has been accomplished in the past by using lengthy epoxy infiltration techniques, or dehydration in ethanol or acetone followed by air drying. Since the former technique requires several days of preparation and the latter technique subjects the tissues to great stress during the phase change encountered during air-drying, an alternate rapid, economical, and reliable method of surface structure preservation was developed. Turnbill and Philpott had used a fluorocarbon for the critical point drying of soft tissues and indicated the advantages of working with fluids having both moderately low critical pressures as well as low critical temperatures. Freon-116 (duPont) which has a critical temperature of 19. 7 C and a critical pressure of 432 psi was used in this study.

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