The Asymmetry of Transient Response in Compression Versus Release for Cartilage in Unconfined Compression

2001 ◽  
Vol 123 (5) ◽  
pp. 519-522 ◽  
Author(s):  
L. P. Li ◽  
M. D. Buschmann ◽  
A. Shirazi-Adl
Keyword(s):  
Articular Cartilage ◽  
Large Deformation ◽  
Transient Response ◽  
Tensile Strain ◽  
Hydraulic Permeability ◽  
Compression Tests ◽  
Unconfined Compression ◽  
The Asymmetry

Observations in compression tests of articular cartilage have revealed unequal load increments for compression and release of the same amplitude applied to a disk with an identical previously imposed compression (in equilibrium). The mechanism of this asymmetric transient response is investigated here using a nonlinear fibril-reinforced model. It is found that the asymmetry is predominantly produced by the fibril stiffening with its tensile strain. In addition, allowing the hydraulic permeability to decrease significantly with compressive dilatation of cartilage increases the transient fibril strain, resulting in a stronger asymmetry. Large deformation also enhances the asymmetry as a consequence of stronger fibril stiffening.

Mechanical anisotropy of the human knee articular cartilage in compression

2003 ◽  
Vol 217 (3) ◽  
pp. 215-219 ◽  
Author(s):  
J S Jurvelin ◽  
M D Buschmann ◽  
E B Hunziker
Keyword(s):  
Articular Cartilage ◽  
Poisson’S Ratio ◽  
Articular Surface ◽  
Mechanical Anisotropy ◽  
Poisson's Ratio ◽  
Hydraulic Permeability ◽  
Compression Tests ◽  
Direction Parallel ◽  
Anisotropic Mechanical Properties ◽  
Femoral Groove

Articular cartilage exhibits anisotropic mechanical properties when subjected to tension. However, mechanical anisotropy of mature cartilage in compression is poorly known. In this study, both confined and unconfined compression tests of cylindrical cartilage discs, taken from the adult human patello-femoral groove and cut either perpendicular (normal disc) or parallel (tangential disc) to the articular surface, were utilized to determine possible anisotropy in Young's modulus, E, aggregate modulus, Ha, Poisson's ratio, v and hydraulic permeability, k, of articular cartilage. The results indicated that Ha was significantly higher in the direction parallel to the articular surface as compared with the direction perpendicular to the surface ( Ha = 1.237 ± 0.486 MPa versus Ha = 0.845 ± 0.383 MPa, p = 0.017, n = 10). The values of Poisson's ratio were similar, 0.158 ± 0.148 for normal discs compared with 0.180 ± 0.046 for tangential discs. Analysis using the linear biphasic model revealed that the decrease of permeability during the offset compression of 0–20 per cent was higher ( p = 0.015, n = 10) in normal (from 25.5 × 10− 15 to 1.8 × 10−15 m4/N s) than in tangential (from 12.3 × 10− 15 to 1.3 × 10− 15 m4/N s) discs. Based on the results, it is concluded that the mechanical characteristics of adult femoral groove articular cartilage are anisotropic also during compression. Anisotropy during compression may be essential for normal cartilage function. This property has to be considered when developing advanced theoretical models for cartilage biomechanics.

Unconfined Compression of Articular Cartilage: Nonlinear Behavior and Comparison With a Fibril-Reinforced Biphasic Model

1999 ◽  
Vol 122 (2) ◽  
pp. 189-195 ◽  
Author(s):  
M. Fortin ◽  
J. Soulhat ◽  
A. Shirazi-Adl ◽  
E. B. Hunziker ◽  
M. D. Buschmann
Keyword(s):  
Articular Cartilage ◽  
Mechanical Behavior ◽  
Small Amplitude ◽  
Dynamic Stiffness ◽  
Scaling Law ◽  
Nonlinear Behavior ◽  
Hydraulic Permeability ◽  
Unconfined Compression ◽  
Biphasic Model ◽  
Strain Dependent

Mechanical behavior of articular cartilage was characterized in unconfined compression to delineate regimes of linear and nonlinear behavior, to investigate the ability of a fibril-reinforced biphasic model to describe measurements, and to test the prediction of biphasic and poroelastic models that tissue dimensions alter tissue stiffness through a specific scaling law for time and frequency. Disks of full-thickness adult articular cartilage from bovine humeral heads were subjected to successive applications of small-amplitude ramp compressions cumulating to a 10 percent compression offset where a series of sinusoidal and ramp compression and ramp release displacements were superposed. We found all equilibrium behavior (up to 10 percent axial compression offset) to be linear, while most nonequilibrium behavior was nonlinear, with the exception of small-amplitude ramp compressions applied from the same compression offset. Observed nonlinear behavior included compression-offset-dependent stiffening of the transient response to ramp compression, nonlinear maintenance of compressive stress during release from a prescribed offset, and a nonlinear reduction in dynamic stiffness with increasing amplitudes of sinusoidal compression. The fibril-reinforced biphasic model was able to describe stress relaxation response to ramp compression, including the high ratio of peak to equilibrium load. However, compression offset-dependent stiffening appeared to suggest strain-dependent parameters involving strain-dependent fibril network stiffness and strain-dependent hydraulic permeability. Finally, testing of disks of different diameters and rescaling of the frequency according to the rule prescribed by current biphasic and poroelastic models (rescaling with respect to the sample’s radius squared) reasonably confirmed the validity of that scaling rule. The overall results of this study support several aspects of current theoretical models of articular cartilage mechanical behavior, motivate further experimental characterization, and suggest the inclusion of specific nonlinear behaviors to models. [S0148-0731(00)00702-0]

On the Indentation Testing of Articular Cartilage: Determination of the Effective Poisson’s Ratio Using Two Different-Sized Punches

2008 ◽  
Author(s):  
Eugene T. Kepich ◽  
Roger C. Haut
Keyword(s):  
Articular Cartilage ◽  
Poisson’S Ratio ◽  
Direct Determination ◽  
Collagen Fibers ◽  
Poisson's Ratio ◽  
Compression Tests ◽  
Unconfined Compression ◽  
Collagen Network ◽  
Lateral Expansion

Effective Poisson’s ratio (EPR) of articular cartilage in compression is an important parameter, which is inversely correlated with stiffness of the collagen fibers [1]; and thus, if known, could provide valuable information about integrity of the collagen network in the tissue. Unfortunately, direct determination of the EPR by measuring lateral expansion during unconfined compression tests [2], while being effective, due to it’s destructive nature many times is not desired and/or hard to apply in practice. Optically-determined values of equilibrium EPR for bovine humeral articular cartilage using this method are reported to be in range 0.185±0.0065.

Computational simulation of the multiphasic degeneration of the bone-cartilage unit during osteoarthritis via indentation and unconfined compression tests

2019 ◽  
Vol 233 (9) ◽  
pp. 871-882 ◽  
Author(s):  
Seyed Shayan Sajjadinia ◽  
Mohammad Haghpanahi ◽  
Mohammad Razi
Keyword(s):  
Articular Cartilage ◽  
Subchondral Bone ◽  
Computational Simulation ◽  
Element Model ◽  
Fluid Distribution ◽  
Compression Tests ◽  
Unconfined Compression ◽  
Calcified Cartilage ◽  
Unit Model ◽  
Fluid Fraction

It has been experimentally proposed that the discrete regions of articular cartilage, along with different subchondral bone tissues, known as the bone-cartilage unit, are biomechanically altered during osteoarthritis degeneration. However, a computational framework capturing all of the dominant changes in the multiphasic parameters has not yet been developed. This article proposes a new finite element model of the bone-cartilage unit by combining several validated, nonlinear, depth-dependent, fibril-reinforced, and swelling models, which can computationally simulate the variations in the dominant parameters during osteoarthritis degeneration by indentation and unconfined compression tests. The mentioned dominant parameters include the proteoglycan depletion, collagen fibrillar softening, permeability, and fluid fraction increase for approximately non-advanced osteoarthritis. The results depict the importance of subchondral bone tissues in fluid distribution within the bone-cartilage units by decreasing the fluid permeation and pressure (up to a maximum of 100 kPa) during osteoarthritis, supporting the notion that subchondral bones might play a role in the pathogenesis of osteoarthritis. Furthermore, the osteoarthritis composition-based studies shed light on the significant biomechanical role of the calcified cartilage, which experienced a maximum change of 70 kPa in stress, together with relative load contributions of articular cartilage constituents during osteoarthritis, in which the osmotic pressure bore around 70% of the loads after degeneration. To conclude, the new insights provided by the results reveal the significance of the multiphasic osteoarthritis simulation and demonstrate the functionality of the proposed bone-cartilage unit model.

Brazilian tensile strength test of lightly cemented sand

1995 ◽  
Vol 32 (1) ◽  
pp. 166-171 ◽  
Author(s):  
B.M. Das ◽  
S.C. Yen ◽  
R.N. Dass
Keyword(s):  
Tensile Strength ◽  
Image Analysis ◽  
Tensile Stress ◽  
Tensile Strain ◽  
Optical Image ◽  
Compression Tests ◽  
Unconfined Compression ◽  
Brazilian Tensile Strength ◽  
Cemented Sand ◽  
Strength Tests

Tensile stress – tensile strain relationships for lightly cemented sand specimens obtained by conducting Brazilian tensile strength tests have been presented. The tensile strain measurement was done by using an optical image analysis technique. In addition to the tensile strength tests, some unconfined compression tests on sand specimens with varying cement contents were also performed. Based on the results of the above tests, a nondimensional tensile stress – tensile strain relationship has been presented. Also the variation of the tensile and compressive strength and strain ratios with varying cement contents have been discussed. Key words : lightly cemented sand, optical image analysis, tensile strain, tensile strength, unconfined compression strength.

Comparison of Human Articular Cartilage and Polyvinyl Alcohol Hydrogel as Artificial Cartilage in Microstructure Analysis and Unconfined Compression

2009 ◽  
Vol 87-88 ◽  
pp. 188-193 ◽  
Author(s):  
Feng Li ◽  
Yong Lin Su ◽  
Du Fang Shi ◽  
Cheng Tao Wang
Keyword(s):  
Articular Cartilage ◽  
Polyvinyl Alcohol ◽  
Great Influence ◽  
Microstructure Analysis ◽  
Human Articular Cartilage ◽  
Compression Tests ◽  
Unconfined Compression ◽  
Creep Tests ◽  
Artificial Cartilage ◽  
Pva Hydrogel

Many biomaterials have been developed to replace articular cartilage. One of these materials, polyvinyl alcohol (PVA) hydrogel is proposed to be used as artificial cartilage in joint replacement. To better understand the differences between human articular cartilage and PVA hydrogel, microstructure analysis and unconfined compression were developed. In microstructure analysis, the surface of articular cartilage was smooth and free from any significant morphological features. Some small holes were found in the surface and cross-section of PVA hydrogel. The porous structure of PVA hydrogel was observed clearly by Environmental scanning electron microscopy (ESEM). In unconfined compression tests, the compression modulus of articular cartilage was higher than that of PVA hydrogel. In the creep tests, the strain value of articular cartilage was lower than that of PVA hydrogel all the time. It is indicated that the microstructure of each material has a great influence on their biphasic property which related to their mechanical behavior.

Microstructural changes in soft quick clay at failure

1970 ◽  
Vol 7 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Roland Pusch
Keyword(s):  
Shear Deformation ◽  
Shear Zone ◽  
Residual Strength ◽  
Rigid Bodies ◽  
Compression Tests ◽  
Unconfined Compression ◽  
Shear Forces ◽  
Microstructural Investigation ◽  
Shear Process ◽  
Quick Clay

A series of unconfined compression tests has been made on a marine, quick clay and small specimens were extracted for microstructural investigation. The natural microstructural pattern was characterized by a network of small aggregates connected by links of particles. The links broke down successively at increasing shear deformation and formed domain-like groups of particles. In the macroscopic shear zone the shear forces tended to orient and deform the aggregates.The aggregates behaved as rigid bodies to a certain stress level during the shear process. The concept of residual strength may correspond to the state where the majority of the links have been broken while the aggregates are still intact.

Stabilization of clayey subgrade with waste pumice for road infrastructure

2015 ◽  
Vol 22 (5) ◽  
Author(s):  
Ömür Çimen ◽  
Mehmet Saltan ◽  
S. Nilay Keskin
Keyword(s):  
Mechanical Properties ◽  
Road Construction ◽  
High Plasticity ◽  
Test Results ◽  
Index Properties ◽  
Compression Tests ◽  
Unconfined Compression ◽  
Swelling Potential ◽  
Project Costs ◽  
High Plasticity Clay

AbstractHigh-plasticity clayey subgrade, which is unsuitable for road construction, may sometimes occur along highway routes. In such cases, engineers need to change the route of a highway project, resulting in an increase in road length and project costs. In this study, waste pumice was examined for stabilization of high-plasticity clayey subgrade, which is inappropriate for road construction. For this purpose, the physical and index properties of clay and pumice were determined. Then, the pumice was mixed with high plasticity clay at different ratios by weight. By performing standard Proctor compaction tests on the mixtures, the effects of adding pumice on compaction were also studied. Unconfined compression tests and California bearing ratio (CBR) tests were performed on all pumice-clay mixtures, and the test results and the CBR ratios were compared for each sample, respectively. The results showed that pumice stabilization improved the mechanical properties and reduced the swelling potential of high plasticity clayey subgrade.

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