Multiscale Adaptive Finite Element Computations for Soft Tissue Biomechanics

2007 ◽  
Author(s):  
Triantafyllos Stylianopoulos ◽  
Xiaojuan Luo ◽  
Mark S. Shephard ◽  
Victor H. Barocas
Keyword(s):  
Soft Tissues ◽  
Mechanical Response ◽  
Length Scale ◽  
Adaptive Finite Element ◽  
Mechanical Function ◽  
Collagen Network ◽  
Acceptable Solution ◽  
Soft Tissue Biomechanics ◽  
Network Orientation ◽  
Collagenous Tissues

The mechanical function of soft collagenous tissues is inherently multiscale, with the tissue dimension being in the centimeter length scale and the underlying collagen network being in the micrometer length scale. The strong sensitivity of soft tissues to network orientation and fiber-fiber interactions necessitates the incorporation of both scales in a multiscale methodology [1,2] in order to predict their mechanical response. The computational demands of a multiscale methodology, however, are strenuous and the use of parallel processing and adaptivity are required for succeeding acceptable solution times.

Elucidation of Microstructural Interactions Between Collagen and Non-Fibrillar Matrix in Soft Tissue Using a Coupled Fiber-Matrix Model

2012 ◽  
Author(s):  
Lijuan Zhang ◽  
Spencer P. Lake ◽  
Victor K. Lai ◽  
Victor H. Barocas ◽  
Mark S. Shephard
Keyword(s):  
Soft Tissues ◽  
Mechanical Response ◽  
Tensile Load ◽  
Matrix Composites ◽  
Collagen Network ◽  
Fiber Network ◽  
Matrix Modeling ◽  
Microscale Model ◽  
Fiber Matrix

The mechanical properties of soft connective tissues are governed by their collagen fiber network and surrounding non-fibrillar matrix (e.g., proteoglycans, cells, elastin, etc.). In order to understand how healthy tissues function, and how properties change in injury and disease, it is necessary to quantify the mechanical response of both the collagen network and the non-fibrillar matrix (NFM), as well as the nature of the interaction between these tissue constituents. Using collagen-agarose co-gels as a simple experimental tissue analog system, we have demonstrated how NFM contributes to the mechanical and organizational properties of soft tissues in indentation and tension [1–2]. Furthermore, we used a network-based microscale model to examine how specific NFM properties alter the response of fiber-matrix composites under load [3]. This model fit our experimental data well and provided insight into the role of NFM in tensile mechanics. Since it was constructed according to the conventional approach of superposition of the two constituents (collagen network and NFM), however, the model could not specifically examine local interactions between collagen fibers and the surrounding NFM, which could be critical in assessing tissue damage or cell-matrix interactions. Therefore, we developed and evaluated a fiber-matrix modeling scheme to characterize the microstructural interactions between tissue constituents, as well as to quantify the role of individual tissue components in the behavior of soft tissues under tensile load. For validation, the new model (‘coupled’) was compared to our previous model (‘parallel’) and to experimental co-gel data.

Experimental and Computational Investigation of the Poroviscoelastic Response of Engineered and Native Ligament

2008 ◽  
Author(s):  
Devin T. O’Connor ◽  
Jinjin Ma ◽  
Harish Narayanan ◽  
Krishna R. Garikipati ◽  
Ellen M. Arruda ◽  
...  
Keyword(s):  
Soft Tissue ◽  
Mechanical Characteristics ◽  
Mechanical Response ◽  
Tissue Mechanics ◽  
Soft Tissue Mechanics ◽  
Mechanical Function ◽  
Collagen Gels ◽  
Computational Investigation ◽  
Collagenous Tissues ◽  
Different Levels

Experiments on explanted soft tissue and collagen gels [1], and the theory of soft tissue mechanics [2], indicate that the important mechanisms by which soft collagenous tissues deform and develop stress include elasticity, viscoelasticity and poroelasticity. These contributions to the mechanical response are directly modulated by the content and morphology of collagen, elastin, other molecules such as proteoglycans and glycosaminoglycans, and fluid, which is water. Our engineered collagenous constructs demonstrate histological and mechanical characteristics of native tendon and ligament of different levels of maturity. In order to evaluate whether the constructs have optimal mechanical function for implantation and utility for regenerative medicine, the relation must be established between the content and morphology of collagen and elastin, and the elastic, viscoelastic and poroelastic response of the engineered collagenous constructs at these different developmental levels.

scholarly journals Mechanical plasticity of collagen directs branch elongation in human mammary gland organoids

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
B. Buchmann ◽  
L. K. Engelbrecht ◽  
P. Fernandez ◽  
F. P. Hutterer ◽  
M. K. Raich ◽  
...  
Keyword(s):  
Mechanical Response ◽  
Developmental Process ◽  
Branching Morphogenesis ◽  
Collagen Network ◽  
Mechanical Tension ◽  
Structural Reorganization ◽  
Linear Response Regime ◽  
Human Mammary Gland ◽  
The Matrix ◽  
Tension Generation

AbstractEpithelial branch elongation is a central developmental process during branching morphogenesis in diverse organs. This fundamental growth process into large arborized epithelial networks is accompanied by structural reorganization of the surrounding extracellular matrix (ECM), well beyond its mechanical linear response regime. Here, we report that epithelial ductal elongation within human mammary organoid branches relies on the non-linear and plastic mechanical response of the surrounding collagen. Specifically, we demonstrate that collective back-and-forth motion of cells within the branches generates tension that is strong enough to induce a plastic reorganization of the surrounding collagen network which results in the formation of mechanically stable collagen cages. Such matrix encasing in turn directs further tension generation, branch outgrowth and plastic deformation of the matrix. The identified mechanical tension equilibrium sets a framework to understand how mechanical cues can direct ductal branch elongation.

Dynamic Performance of Neck Protection Devices: Performance Analysis Based on a Simplified Multibody Model of the Human Neck

2012 ◽  
Author(s):  
Massimiliano Gobbi ◽  
Gianpiero Mastinu ◽  
Giorgio Previati ◽  
Ermes Tarallo
Keyword(s):  
Soft Tissues ◽  
Mechanical Response ◽  
Dynamic Performance ◽  
Safety Devices ◽  
Anatomy And Physiology ◽  
Multibody Model ◽  
Impulsive Loads ◽  
Protection Devices ◽  
Safety Systems ◽  
Deformation System

This work is focused on the evaluation of the dynamic performance of different neck protection devices. In order to evaluate the mechanical response of the safety devices, a multibody model of the human neck has been developed in Matlab™ SimMechanics™. The mechanical behavior of the neck is described in the paper and different injury indices are presented and compared. The information about anatomy and physiology of the cervical spine of the neck has been collected from the literature, with particular focus on the mechanism of damage of vertebrae, disks and soft tissues. The multibody model has been validated against experimental data available in the literature concerning impulsive loads representative of crash phenomena. By means of the presented model, some relevant injury indices are computed for an accident involving a motorcyclist. Since the focus has been set on mild injuries of the neck, the simulated crash should cause a high probability of injuries of the neck together with a low probability of damages of the head while wearing a standard helmet. The performance of neck safety devices that link the helmet with the thoracic-shield are evaluated and compared. For sake of clearness, three types of neck safety devices are considered referencing to US patents: an airbag jacket, a 3D cushion wrapping the motorcyclist’s neck, and a “spring and dampers” system. The airbag jacket has been modeled as a high stiffness and low deformation system by considering the airbag in its fully deployed configuration and by neglecting its dynamic performance during inflation phase. The other safety devices have been modeled as lumped parameters spring-damper systems. A sensitivity analysis on the injury indexes has been performed by changing the stiffness and the damping parameters of these safety systems. The injury indexes collected by simulating the different neck safety systems have been compared.

Effects of dynamic indentation on the mechanical response of materials

2008 ◽  
Vol 23 (6) ◽  
pp. 1604-1613 ◽  
Author(s):  
M.J. Cordill ◽  
N.R. Moody ◽  
W.W. Gerberich
Keyword(s):  
Thin Films ◽  
Mechanical Properties ◽  
Mechanical Response ◽  
Length Scale ◽  
Polycrystalline Nickel ◽  
Dynamic Indentation ◽  
Crystalline Materials ◽  
Fused Quartz ◽  
Hardness Values ◽  
Measured Hardness

Dynamic indentation techniques are often used to determine mechanical properties as a function of depth by continuously measuring the stiffness of a material. The dynamics are used by superimposing an oscillation on top of the monotonic loading. Of interest was how the oscillation affects the measured mechanical properties when compared to a quasi-static indent run at the same loading conditions as a dynamic. Single crystals of nickel and NaCl as well as a polycrystalline nickel sample and amorphous fused quartz and polycarbonate have all been studied. With respect to dynamic oscillations, the result is a decrease of the load at the same displacement and thus lower measured hardness values of the ductile crystalline materials. It has also been found that the first 100 nm of displacement are the most affected by the oscillating tip, an important length scale for testing thin films, nanopillars, and nanoparticles.

scholarly journals On the development of instabilities in an annulus and a shell composed of a poro-hyperelastic material

2018 ◽  
Vol 474 (2218) ◽  
pp. 20180239 ◽  
Author(s):  
A. P. S. Selvadurai ◽  
A. P. Suvorov
Keyword(s):  
Soft Tissues ◽  
Mechanical Response ◽  
Numerical Solutions ◽  
Pore Space ◽  
Stability Loss ◽  
Computational Approach ◽  
Hyperelastic Material ◽  
Porous Skeleton ◽  
Internal Pressures

The paper investigates the development of instability in an internally pressurized annulus of a poro-hyperelastic material. The theory of poro-hyperelasticity is proposed as an approach for modelling the mechanical behaviour of highly deformable elastic materials, the pore space of which is saturated with a fluid. The consideration of coupling between the mechanical response of the hyperelastic porous skeleton and the pore fluid is important when applying the developments to soft tissues encountered in biomechanical applications. The paper examines the development of an instability in a poro-hyperelastic annulus subjected to internal pressure. Using a computational approach, numerical solutions are obtained for the internal pressures that promote either short-term or long-term instability in a poro-hyperelastic annulus and a poro-hyperelastic shell. In addition, time-dependent effects of stability loss are examined. The analytical solutions are used to benchmark the accuracy of the computational approach.

A Physically-Based Anisotropic Discrete Fiber Model for Fibrous Soft Tissues

2010 ◽  
Author(s):  
C. Flynn ◽  
M. B. Rubin ◽  
P. M. F. Nielsen
Keyword(s):  
Soft Tissues ◽  
Mechanical Response ◽  
Continuous Distribution ◽  
Collagen Fibers ◽  
Fiber Bundles ◽  
Parameter Study ◽  
Rabbit Skin ◽  
Pig Skin ◽  
Proposed Model ◽  
Physically Based

Physically-based fibrous soft tissue models often consider the tissue to be a collection of fibers with a continuous distribution function to represent their orientations. This study proposes a simple model for the response of fibrous connective tissues in terms of a discrete number of fiber bundles. The proposed model consists of six weighted fiber bundles orientated such that they pass through opposing vertices of an icosahedron. A novel aspect of the proposed model is the use of a simple analytical function to represent the undulation distribution of the collagen fibers. The mechanical response of the elastin fiber is represented by a neo-Hookean hyperelastic equation. A parameter study was performed to analyze the effect of each parameter on the overall response of the model. The proposed model accurately simulated the uniaxial stretching of pig skin with an 8% error-of-fit for stretch ratios up to 1.8. The model also accurately simulated the biaxial stretching of rabbit skin with a 10% error-of-fit for stretch ratios up to 1.9. The stiffness of the collagen fibers determined by the model was about 100 MPa for the rabbit skin and 900 MPa for the pig skin, which are comparable with values reported in the literature. The stiffness of the elastin fibers in the model was about 2 kPa.

scholarly journals The Characteristic Recovery Time as a Novel, Noninvasive Metric for Assessing In Vivo Cartilage Mechanical Function

2020 ◽  
Vol 48 (12) ◽  
pp. 2901-2910 ◽  
Author(s):  
Hattie C. Cutcliffe ◽  
Keithara M. Davis ◽  
Charles E. Spritzer ◽  
Louis DeFrate
Keyword(s):  
Mechanical Property ◽  
Relaxation Time ◽  
Recovery Time ◽  
Mechanical Response ◽  
Ex Vivo ◽  
Cartilage Thickness ◽  
Mechanical Function ◽  
Mechanical State ◽  
T2 Relaxation

AbstractOsteoarthritis (OA) is a disease characterized by the degeneration of cartilage tissue, and is a leading cause of disability in the United States. The clinical diagnosis of OA includes the presence of pain and radiographic imaging findings, which typically do not present until advanced stages of the disease when treatment is difficult. Therefore, identifying new methods of OA detection that are sensitive to earlier pathological changes in cartilage, which may be addressed prior to the development of irreversible OA, is critical for improving OA treatment. A potentially promising avenue for developing early detection methods involves measuring the tissue’s in vivo mechanical response to loading, as changes in mechanical function are commonly observed in ex vivo studies of early OA. However, thus far the mechanical function of cartilage has not been widely assessed in vivo. Therefore, the purpose of this study was to develop a novel methodology that can be used to measure an in vivo mechanical property of cartilage: the characteristic recovery time. Specifically, in this study we quantified the characteristic recovery time of cartilage thickness after exercise in relatively young subjects with asymptomatic cartilage. Additionally, we measured baseline cartilage thickness and T1rho and T2 relaxation times (quantitative MRI) prior to exercise in these subjects to assess whether baseline MRI measures are predictive of the characteristic recovery time, to understand whether or not the characteristic recovery time provides independent information about cartilage’s mechanical state. Our results show that the mean recovery strain response across subjects was well-characterized by an exponential approach with a characteristic time of 25.2 min, similar to literature values of human characteristic times measured ex vivo. Further, we were unable to detect a statistically significant linear relationship between the characteristic recovery time and the baseline metrics measured here (T1rho relaxation time, T2 relaxation time, and cartilage thickness). This might suggest that the characteristic recovery time has the potential to provide additional information about the mechanical state of cartilage not captured by these baseline MRI metrics. Importantly, this study presents a noninvasive methodology for quantifying the characteristic recovery time, an in vivo mechanical property of cartilage. As mechanical response may be indicative of cartilage health, this study underscores the need for future studies investigating the characteristic recovery time and in vivo cartilage mechanical response at various stages of OA.

scholarly journals CAMM Techniques for the Prediction of the Mechanical Properties of Tendons and Ligaments Nanostructures

2005 ◽  
Vol 5 ◽  
pp. 564-570
Author(s):  
Simone Vesentini ◽  
Franco M. Montevecchi ◽  
Alberto Redaelli
Keyword(s):  
Mechanical Properties ◽  
Molecular Modeling ◽  
Connective Tissue ◽  
Soft Tissues ◽  
Collagen Molecule ◽  
Computer Assisted ◽  
Mechanical Function ◽  
Top Down ◽  
Structural Constituent ◽  
Structures And Properties

Theoretical prediction of the mechanical properties of soft tissues usually relies on a top-down approach; that is analysis is gradually refined to observe smaller structures and properties until technical limits are reached. Computer-Assisted Molecular Modeling (CAMM) allows for the reversal of this approach and the performance of bottom-up modeling instead. The wealth of available sequences and structures provides an enormous database for computational efforts to predict structures, simulate docking and folding processes, simulate molecular interactions, and understand them in quantitative energetic terms. Tendons and ligaments can be considered an ideal arena due to their well defined and highly organized architecture which involves not only the main structural constituent, the collagen molecule, but also other important molecular “actors” such as proteoglycans and glycosaminoglycans. In this ideal arena each structure is well organized and recognizable, and using the molecular modeling tool it is possible to evaluate their mutual interactions and to characterize their mechanical function. Knowledge of these relationships can be useful in understanding connective tissue performance as a result of the cooperation and mutual interaction between different biological structures at the nanoscale.

Nonlinear Dynamic Viscoelastic Model for Osteoarthritic Cartilage Indentation Force

2011 ◽  
Author(s):  
A. Vidal-Lesso ◽  
E. Ledesma-Orozco ◽  
R. Lesso-Arroyo ◽  
L. Daza-Benitez
Keyword(s):  
Mechanical Properties ◽  
Soft Tissues ◽  
Mechanical Response ◽  
Viscoelastic Model ◽  
Viscoelastic Behavior ◽  
Indentation Test ◽  
Maxwell Model ◽  
Relaxation Curve ◽  
Geometrical Parameters ◽  
Osteoarthritic Cartilage

Biomechanical properties and dynamic response of soft tissues as articular cartilage remains issues for attention. Currently, linear isotropic models are still used for cartilage analysis in spite of its viscoelastic nature. Therefore, the aim of this study was to propose a nonlinear viscoelastic model for cartilage indentation that combines the geometrical parameters and velocity of the indentation test with the thickness of the sample as well as the mechanical properties of the tissue changing over time due to its viscoelastic behavior. Parameters of the indentation test and mechanical properties as a function of time were performed in Laplace space where the constitutive equation for viscoelasticity and the convolution theorem was applied in addition with the Maxwell model and Hayes et al. model for instantaneous elastic modulus. Results of the models were compared with experimental data of indentation tests on osteoarthritic cartilage of a unicompartmental osteoarthritis cases. The models showed a strong fit for the axial indentation nonlinear force in the loading curve (R2 = 0.992) and a good fit for unloading (R2 = 0.987), while an acceptable fit was observed in the relaxation curve (R2 = 0.967). These models may be used to study the mechanical response of osteoarthritic cartilage to several dynamical and geometrical test conditions.

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