scholarly journals Localization of Viscous Behavior and Shear Energy Dissipation in Articular Cartilage Under Dynamic Shear Loading

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Mark R. Buckley ◽  
Lawrence J. Bonassar ◽  
Itai Cohen
Keyword(s):  
Articular Cartilage ◽  
Energy Dissipation ◽  
Viscoelastic Properties ◽  
Articular Surface ◽  
Critical Role ◽  
Transitional Zone ◽  
Shear Loading ◽  
Confocal Imaging ◽  
Dynamic Shear Modulus ◽  
Dynamic Shear

Though remarkably robust, articular cartilage becomes susceptible to damage at high loading rates, particularly under shear. While several studies have measured the local static and steady-state shear properties of cartilage, it is the local viscoelastic properties that determine the tissue's ability to withstand physiological loading regimens. However, measuring local viscoelastic properties requires overcoming technical challenges that include resolving strain fields in both space and time and accurately calculating their phase offsets. This study combined recently developed high-speed confocal imaging techniques with three approaches for analyzing time- and location-dependent mechanical data to measure the depth-dependent dynamic modulus and phase angles of articular cartilage. For sinusoidal shear at frequencies f = 0.01 to 1 Hz with no strain offset, the dynamic shear modulus |G*| and phase angle δ reached their minimum and maximum values (respectively) approximately 100 μm below the articular surface, resulting in a profound focusing of energy dissipation in this narrow band of tissue that increased with frequency. This region, known as the transitional zone, was previously thought to simply connect surface and deeper tissue regions. Within 250 μm of the articular surface, |G*| increased from 0.32 ± 0.08 to 0.42 ± 0.08 MPa across the five frequencies tested, while δ decreased from 12 deg ± 1 deg to 9.1 deg ± 0.5 deg. Deeper into the tissue, |G*| increased from 1.5 ± 0.4 MPa to 2.1 ± 0.6 MPa and δ decreased from 13 deg ± 1 deg to 5.5 deg ± 0.2 deg. Viscoelastic properties were also strain-dependent, with localized energy dissipation suppressed at higher shear strain offsets. These results suggest a critical role for the transitional zone in dissipating energy, representing a possible shift in our understanding of cartilage mechanical function. Further, they give insight into how focal degeneration and mechanical trauma could lead to sustained damage in this tissue.

Mechanical behaviour of magnetic Silly Putty: Viscoelastic and magnetorheological properties

2015 ◽  
Vol 28 (8) ◽  
pp. 953-960 ◽  
Author(s):  
Nicola Golinelli ◽  
Andrea Spaggiari ◽  
Eugenio Dragoni
Keyword(s):  
Magnetic Field ◽  
Viscoelastic Properties ◽  
Volume Fraction ◽  
Strong Dependence ◽  
Elastic Solid ◽  
Shear Loading ◽  
System Response ◽  
Dynamic Shear ◽  
Static Compression ◽  
Long Time

In this work the mechanical and viscoelastic properties of magnetic Silly Putty are investigated. Silly Putty is a non-Newtonian material whose response depends on the rate at which it is deformed. For a rapid deformation, it behaves as an elastic solid, while over a relatively long time scale, the polymer molecules can be untangled and it flows as a fluid. The purpose of this article is to study the behaviour of this material firstly under a quasi-static compression and shear loading, and secondly under dynamic shear loading. The Silly Putty under study has a volume fraction of ferromagnetic particles. Hence, both quasi-static and dynamic stress are coupled with several strengths of magnetic field in order to assess the influence of the magnetisation on the mechanical and viscoelastic properties of the material. The approach adopted in this work followed the Design of Experiment method so that evaluating the influence of the variables and their interactions on the system response is possible. The results highlight a strong dependence on the deformation rate, while the influence of the magnetic field is weak, especially under dynamic shear tests in which the viscous components are predominant.

scholarly journals Micromechanical Prediction Model of Viscoelastic Properties for Asphalt Mastic Based on Morphologically Representative Pattern Approach

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Zhichen Wang ◽  
Naisheng Guo ◽  
Xu Yang ◽  
Shuang Wang
Keyword(s):  
Shear Modulus ◽  
Prediction Model ◽  
Viscoelastic Properties ◽  
Volume Fraction ◽  
Complex Modulus ◽  
Homogenization Theory ◽  
Dynamic Shear Modulus ◽  
Dynamic Shear ◽  
Low Frequencies ◽  
Asphalt Mastic

This paper is devoted to the introduction of physicochemical, filler size, and distribution effect in micromechanical predictions of the overall viscoelastic properties of asphalt mastic. In order to account for the three effects, the morphologically representative pattern (MRP) approach was employed. The MRP model was improved due to the arduous practical use of equivalent modulus formula solution. Then, a homogeneous morphologically representative model (H-MRP) with the explicit solution was established based on the homogenization theory. Asphalt mastic is regarded as a composite material consisting of filler particles coated structural asphalt and free asphalt considering the physicochemical effect. An additional interphase surrounding particles was introduced in the H-MRP model. Thus, a modified H-MRP model was established. Using the proposed model, a viscoelastic equation was derived to predict the complex modulus and subsequently the dynamic modulus of asphalt mastic based on the elastic-viscoelastic correspondence principle. The dynamic shear rheological tests were conducted to verify the prediction model. The results show that the predicted modulus presents an acceptable precision for asphalt mastic mixed with 10% and 20% fillers volume fraction, as compared to the measured ones. The predicted modulus agrees reasonably well with the measured ones at high frequencies for asphalt mastic mixed with 30% and 40% fillers volume fraction. However, it exhibits underestimated modulus at low frequencies. The reasons for the discrepancy between predicted and measured dynamic shear modulus and the factors affecting the dynamic shear modulus were also explored in the paper.

Osmotic Effects on the Dynamic Shear Properties of Meniscal Fibrocartilage

2008 ◽  
Author(s):  
Patricia H. Ho ◽  
An M. Nguyen ◽  
Marc E. Levenston
Keyword(s):  
Articular Cartilage ◽  
Soft Tissues ◽  
Swelling Pressure ◽  
Dynamic Shear Modulus ◽  
Bathing Solution ◽  
Dynamic Shear ◽  
Shear Moduli ◽  
Meniscal Tissue ◽  
Proteoglycan Degradation ◽  
Tissue Matrix

The meniscus plays an important role in many biomechanical functions of the knee, including shock absorption, load distribution, and joint lubrication. The ability to perform these functions is determined by the interactions of the major tissue constituents (water, proteoglycan, and collagen), although these interactions have not been as thoroughly studied in fibrocartilage as those in other soft tissues. In articular cartilage, electrochemical interactions between negatively charged glycosaminoglycan (GAG) side chains of proteoglycans and the interstitial fluid generate an osmotic swelling pressure that contributes to the compressive stiffness [1], and proteoglycan degradation dramatically decreases compressive and shear moduli [2]. Although the concentration of proteoglycan in the meniscus is substantially lower (<1%) than that in articular cartilage, aggrecan degradation also greatly decreases the compressive and shear moduli of meniscal fibrocartilage [3]. The proteoglycan distribution in meniscal fibrocartilage is macroscopically heterogeneous [4] and is concentrated in the secondary matrix surrounding the circumferential collagen bundles, and the extent to which osmotic interactions explain the influence on fibrocartilage material properties is unknown. Altering the osmotic strength of the bathing solution supplies a means to control osmotic interactions between the GAGs and the environment without degrading the tissue matrix. The objective of this study was to examine the effects of an altered osmotic environment on the dynamic shear modulus of meniscal tissue.

Imaging structural and mechanical properties of articular cartilage using optical polarization tractography

2019 ◽  
Author(s):  
◽  
Mohammadreza Ravanfar
Keyword(s):  
Mechanical Properties ◽  
Articular Cartilage ◽  
Critical Role ◽  
Shear Loading ◽  
Optical Polarization ◽  
Optical Birefringence ◽  
Mechanical Responses ◽  
Collagen Organization ◽  
Radial Zone

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Osteoarthritis (OA) is an extremely common joint disease, which affects more than one-third of all adults in the USA. Although the entire joint compartments are involved, OA is considered as a cartilage disease. Articular cartilage is a thin tissue covering the end of bones in the diarthrodial joints and plays a crucial role in providing a frictionless articulation. In spite of the harsh mechanical environment, cartilage has an amazingly long life due to its unique structure and composition. Cartilage is composed of ~80% water and ~20% solid matrix that mainly consists of collagen fibers and proteoglycans. Collagen degeneration is often an early symptom in OA. Since the fiber structure governs normal functionality in cartilage, the disease progression leads to impaired mechanical functions. Hence, an effective imaging technology that can visualize the collagen organization and its effects on cartilage mechanical properties will help to understand the sophisticated structure-function relationship in cartilage. Polarized light macroscopy (PLM) has been broadly utilized for collagen assessment; however, it requires thin, sectioned samples and thus remains a destructive technology. We introduced a nondestructive alternative to PLM for cartilage imaging using optical polarization tractography (OPT). OPT improved visualization and characterization of the zonal structure in cartilage by calculating the depth-resolved local birefringence and fiber orientation. We demonstrated that parametric imaging can be implemented using multiple complementary tissue contrasts obtained in OPT including surface roughness, birefringence, and fiber dispersion. We showed that parametric OPT imaging provided a morphometric evaluation of collagen damage in human OA cartilage samples. Because OPT can accurately quantify tissue optical birefringence, it can reveal the higher level of complexity in collagen architecture of cartilage. Our multi-incident OPT based biaxial birefringence measurement provided strong evidence of the existence of a leaf-like structure in cartilage. Furthermore, we expanded the capability of OPT technology by developing a method that can simultaneously image the fiber organization and mechanical responses in cartilage. This new method enabled a precise characterization of the zonal structural and mechanical responses to unconfined compressive and directional shear loading. We discovered that the upper part of the radial zone plays a critical role in absorbing compression-induced deformation in cartilage. Young's modulus in cartilage was strongly correlated with the optical birefringence. In the shear test, we found a remarkably higher shear modulus in the radial zone when the sample was sheared along the fibers. In summary, this dissertation research developed new OPT based imaging methods that can fully characterize the collagen organization and its responses during mechanical loading. This new technology has a great potential for nondestructive structural and functional imaging in articular cartilage.

Mechanical Behaviour of Magnetic Silly Putty: Viscoelastic and Magnetorheological Properties

2014 ◽  
Author(s):  
Andrea Spaggiari ◽  
Nicola Golinelli ◽  
Eugenio Dragoni
Keyword(s):  
Magnetic Field ◽  
Viscoelastic Properties ◽  
Volume Fraction ◽  
Strong Dependence ◽  
Elastic Solid ◽  
Shear Loading ◽  
Dynamic Shear ◽  
Static Compression ◽  
Long Time ◽  
Rapid Deformation

In this work the mechanical and viscoelastic properties of the magnetic Silly Putty are investigated. Silly Putty is a non-Newtonian material whose response depends on the rate at which it is deformed. For a rapid deformation it behaves as an elastic solid while over a relatively long time scale stress, the polymer molecules can be untangled and it flows as a fluid. The purpose of this paper is to study the behaviour of this material firstly under a quasi-static compression and shear and secondly under a dynamic shear loading. The Silly Putty under study presents a volume fraction of ferromagnetic particles. Hence, both quasi-static and dynamic stress are coupled with several values of magnetic field in order to assess the influence on the mechanical and viscoelastic properties of magnetic Silly Putty. The approach adopted in this work was based on a Design of Experiment technique so that evaluating the influence of the variables involved and their interactions is possible. The results highlight a strong dependence on the deformation rate while the influence of the magnetic field is weak especially under dynamic shear tests in which the highest deformation are predominant.

scholarly journals Anatomy of the Intermetatarsal Facets of the Fourth and Fifth Metatarsals

2021 ◽  
Vol 6 (1) ◽  
pp. 247301142097570
Author(s):  
Mossub Qatu ◽  
George Borrelli ◽  
Christopher Traynor ◽  
Joseph Weistroffer ◽  
James Jastifer
Keyword(s):  
Articular Cartilage ◽  
Digital Imaging ◽  
Articular Surface ◽  
Implant Design ◽  
Joint Surface ◽  
Fracture Classification ◽  
Articular Damage ◽  
Metatarsal Fracture ◽  
Metatarsal Fractures ◽  
The Mean

Background: The intermetatarsal joint between the fourth and fifth metatarsals (4-5 IM) is important in defining fifth metatarsal fractures. The purpose of the current study was to quantify this joint in order to determine the mean cartilage area, the percentage of the articulation that is cartilage, and to give the clinician data to help understand the joint anatomy as it relates to fifth metatarsal fracture classification. Methods: Twenty cadaver 4-5 IM joints were dissected. Digital images were taken and the articular cartilage was quantified by calibrated digital imaging software. Results: For the lateral fourth proximal intermetatarsal articulation, the mean area of articulation was 188 ± 49 mm2, with 49% of the area composed of articular cartilage. The shape of the articular cartilage had 3 variations: triangular, oval, and square. A triangular variant was the most common (80%, 16 of 20 specimens). For the medial fifth proximal intermetatarsal articulation, the mean area of articulation was 143 ± 30 mm2, with 48% of the joint surface being composed of articular cartilage. The shape of the articular surface was oval or triangular. An oval variant was the most common (75%, 15 of 20 specimens). Conclusion: This study supports the notion that the 4-5 IM joint is not completely articular and has both fibrous and cartilaginous components. Clinical Relevance: The clinical significance of this study is that it quantifies the articular surface area and shape. This information may be useful in understanding fifth metatarsal fracture extension into the articular surface and to inform implant design and also help guide surgeons intraoperatively in order to minimize articular damage.

A Review of the Collagen Orientation in the Articular Cartilage

Cartilage ◽  
2021 ◽  
pp. 194760352098877
Author(s):  
Roy D. Bloebaum ◽  
Andrew S. Wilson ◽  
William N. Martin
Keyword(s):  
Surface Layer ◽  
Articular Cartilage ◽  
Fiber Orientation ◽  
Collagen Fiber ◽  
Articular Surface ◽  
Imaging Techniques ◽  
Collagen Fibers ◽  
Deep Zone ◽  
Collagen Fiber Orientation ◽  
Critical Point Drying

Objective There has been a debate as to the alignment of the collagen fibers. Using a hand lens, Sir William Hunter demonstrated that the collagen fibers ran perpendicular and later aspects were supported by Benninghoff. Despite these 2 historical studies, modern technology has conflicting data on the collagen alignment. Design Ten mature New Zealand rabbits were used to obtain 40 condyle specimens. The specimens were passed through ascending grades of alcohol, subjected to critical point drying (CPD), and viewed in the scanning electron microscope. Specimens revealed splits from the dehydration process. When observing the fibers exposed within the opening of the splits, parallel fibers were observed to run in a radial direction, normal to the surface of the articular cartilage, radiating from the deep zone and arcading as they approach the surface layer. After these observations, the same samples were mechanically fractured and damaged by scalpel. Results The splits in the articular surface created deep fissures, exposing parallel bundles of collagen fibers, radiating from the deep zone and arcading as they approach the surface layer. On higher magnification, individual fibers were observed to run parallel to one another, traversing radially toward the surface of the articular cartilage and arcading. Mechanical fracturing and scalpel damage induced on the same specimens with the splits showed randomly oriented fibers. Conclusion Collagen fiber orientation corroborates aspects of Hunter’s findings and compliments Benninghoff. Investigators must be aware of the limits of their processing and imaging techniques in order to interpret collagen fiber orientation in cartilage.

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