Nonlinear Tensile Properties of Bovine Articular Cartilage and Their Variation With Age and Depth

2004 ◽  
Vol 126 (2) ◽  
pp. 129-137 ◽  
Author(s):  
Mathieu Charlebois ◽  
Marc D. McKee ◽  
Michael D. Buschmann
Keyword(s):  
Articular Cartilage ◽  
Uniaxial Tension ◽  
Tensile Modulus ◽  
Compressive Properties ◽  
Bovine Articular Cartilage ◽  
Relaxation Period ◽  
Nonlinear Properties ◽  
Tensile Stiffness ◽  
Tension Tests ◽  
Order Of Magnitude

Tensile stiffness of articular cartilage is much greater than its compressive stiffness and plays an essential role even in compressive properties by increasing transient fluid pressures during physiological loading. Recent studies of nonlinear properties of articular cartilage in compression revealed several physiologically pertinent nonlinear behaviors, all of which required that cartilage tensile stiffness increase significantly with stretch. We therefore performed sequences of uniaxial tension tests on fresh bovine articular cartilage slices using a protocol that allowed several hours to attain equilibrium and measured longitudinal and transverse tissue strain. By testing bovine cartilage from different ages (6 months to 6 years) we found that equilibrium and transient tensile modulus increased significantly with maturation and age, from 0 to 15 MPa at equilibrium and from 10 to 28 MPa transiently. Our results indicate that cartilage stiffens with age in a manner similar to other highly hydrated connective tissues, possibly due to age-dependent content of enzymatic and nonenzymatic collagen cross links. The long relaxation period used in our tests (5–10 hours) was necessary in order to attain equilibrium and avoid a very significant overestimation of equilibrium modulus that occurs when much shorter times are used (15–30 minutes). We also found that equilibrium and transient tensile modulus increased nonlinearly when cartilage is stretched from 0 to 10% strain without any previous tare load. Although our results estimate a nonlinear increase in tensile stiffness with stretch that is an order of magnitude lower than that required to predict nonlinear properties in compression, they are in agreement with previous results from other uniaxial tension tests of collagenous materials. We therefore speculate that biaxial tensile moduli may be much higher and thereby more compatible with observed nonlinear compressive properties.

Flow-Independent Viscoelastic Response of Bovine Articular Cartilage Under Dynamic Tensile Loading

2004 ◽  
Author(s):  
Seonghun Park ◽  
Gerard A. Ateshian
Keyword(s):  
Articular Cartilage ◽  
Hysteresis Loop ◽  
Applied Stress ◽  
Mechanical Response ◽  
Tensile Modulus ◽  
Tensile Loading ◽  
Viscoelastic Response ◽  
Bovine Articular Cartilage ◽  
Theoretical Predictions ◽  
Dynamic Tensile Loading

The objective of the current study was to characterize the mechanical response of bovine articular cartilage under dynamic tensile loading. Testing was performed under an applied stress magnitude of 1.3 MPa and frequencies from 10−4 Hz to 10 Hz. The dynamic tensile modulus ranged from 20.1±7.0 MPa at 10−4 Hz to 64.0±9.7 MPa at 10 Hz. The phase angle derived from the area under the stress-strain hysteresis loop changed from 21.4±6.9° at 10−4 Hz to 1.1±0.2° at 10 Hz. Based on earlier theoretical predictions, the observed viscoelastic response in tension may be attributed to the intrinsic viscoelasticity of the collagen-proteoglycan matrix.

Using changes in hydrostatic and osmotic pressure to manipulate metabolic function in chondrocytes

2011 ◽  
Vol 300 (6) ◽  
pp. C1234-C1245 ◽  
Author(s):  
Shuichi Mizuno ◽  
Rei Ogawa
Keyword(s):  
Articular Cartilage ◽  
Osmotic Pressure ◽  
Weight Bearing ◽  
Metabolic Function ◽  
Depth Zone ◽  
Bovine Articular Cartilage ◽  
Sulfated Glycosaminoglycan ◽  
Order Of Magnitude ◽  
Histological Heterogeneity

Articular cartilage has distinct histological depth zones. In each zone, chondrocytes are subject to different hydrostatic (HP) and osmotic pressure (OP) due to weight-bearing and joint-loading. Previous in vitro studies of regeneration and pathophysiology in cartilage have failed to consider the characteristics of histological heterogeneity and the effects of combinations of changes in HP and OP. Thus, we have constructed molecular, biochemical, and histological profiles of anabolic and catabolic molecules produced by chondrocytes from each depth zone isolated from bovine articular cartilage in response to changes in HP and OP. We cultured the chondrocytes with combinations of loading or off-loading of HP at 0–0.5 MPa, 0.5 Hz, and changes in OP of 300–450 mosM over 1 wk, and evaluated mRNA expression and immunohistology of both anabolic and catabolic molecules and amounts of accumulated sulfated glycosaminoglycan. Any changes in HP and OP upregulated mRNA of anabolic and catabolic molecules in surface-, middle-, and deep-zone cells, in descending order of magnitude. Off-loading HP maintained the anabolic and reduced the catabolic mRNA; high OP retained upregulation of catabolic mRNA. These molecular profiles were consistent with immunohistological and biochemical findings. Changes in HP and OP are essential for simulating chondrocyte physiology and useful for manipulating phenotypes.

Mechanical properties of low-density paper

2020 ◽  
Vol 35 (1) ◽  
pp. 61-70
Author(s):  
Na Young Park ◽  
Young Chan Ko ◽  
Lili Melani ◽  
Hyoung Jin Kim
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Structural Change ◽  
Tensile Testing ◽  
Tensile Modulus ◽  
Gauge Length ◽  
Efficiency Factor ◽  
Low Density ◽  
Tensile Stiffness ◽  
Lower Tensile Strength

AbstractFor the mechanical properties of paper, tensile testing has been widely used. Among the tensile properties, the tensile stiffness has been used to determine the softness of low-density paper. The lower tensile stiffness, the greater softness of paper. Because the elastic region may not be clearly defined in a load-elongation curve, it is suggested to use the tensile modulus which is defined as the slope between the two points in the curve. The two points which provide the best correlation with subjective softness evaluation should be selected. Low-density paper has a much lower tensile strength, but much larger elongation at the break. It undergoes a continuous structural change during mechanical testing. The degree of the structural change should depend on tensile conditions such as the sample size, the gauge length, and the rate of elongation. For low-density paper, the tensile modulus and the tensile strength should be independent of each other. The structure efficiency factor (SEF) is defined as a ratio of the tensile strength to the tensile modulus and it may be used a guideline in developing superior low-density paper products.

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