Continuity and Affine Fiber Kinematics in Biaxial Tension of the Supraspinatus Tendon

2011 ◽  
Author(s):  
Spencer E. Szczesny ◽  
John Peloquin ◽  
Sarah Ilkhani-Pour ◽  
Daniel H. Cortes ◽  
Jennifer A. Kadlowec ◽  
...  
Keyword(s):  
Boundary Condition ◽  
Material Properties ◽  
Biaxial Tension ◽  
Supraspinatus Tendon ◽  
Recent Analysis ◽  
Uniaxial Tensile ◽  
Angle Distribution ◽  
Fiber Angle ◽  
Uniaxial Tensile Testing

The human supraspinatus tendon (SST) exhibits strong heterogeneity in fiber alignment and material properties [1,2]. The relationship between fiber angle distribution and material properties has been previously described by a structurally based continuum model [3], which provided new quantitative structure-function relationships to explain the observed SST heterogeneity; however, in some locations and testing directions, the model predictions were not consistent with a continuum assumption [3]. More recent analysis of the change in fiber angle during loading showed that samples with less aligned fibers have less affine kinematics in uniaxial tensile loading [4]. That is, in uniaxial tensile testing, where the transverse edges freely contract, the fiber strain did not match the tissue strain. Because the SST is somewhat transversely constrained by surrounding rotator cuff structures in vivo and has distributed fibers to support multidirectional loading, the freely contracting edges of uniaxial tension may not appropriately constrain the tendon. Therefore, the objective of this study was to evaluate SST stress-strain behavior and affine deformation under biaxial tension. Specifically, if behaving as a continuum, we expected that applying a fixed boundary condition in the transverse direction would produce a higher apparent modulus, a smaller toe-region, and more affine fiber realignment than a free boundary condition.

scholarly journals Cross-linking Electrospun Polydioxanone-Soluble Elastin Blends: Material Characterization

2008 ◽  
Vol 3 (1) ◽  
pp. 155892500800300 ◽  
Author(s):  
Michael J. McClure ◽  
Scott A. Sell ◽  
Catherine P. Barnes ◽  
Whitney C. Bowen ◽  
Gary L. Bowlin
Keyword(s):  
Femoral Artery ◽  
Material Properties ◽  
In Vivo Studies ◽  
Uniaxial Tensile ◽  
Cross Linking ◽  
Materials Testing ◽  
Uniaxial Tensile Testing ◽  
The Cross

The purpose of this study was to establish whether material properties of elastin co-electrospun with polydioxanone (PDO) would change over time in both the uncross-linked state and the cross-linked state. First, uncross-linked scaffolds were placed in phosphate buffered saline (PBS) for three separate time periods: 15 minutes, 1 hour, and 24 hours, and subsequently tested using uniaxial materials testing. Several cross-linking reagents were then investigated to verify their ability to crosslink elastin: 1–ethyl-3–(dimethylaminopropyl)-carbodiimide (EDC), ethylene glycol diglycidyl ether (EGDE), and genipin. Uniaxial tensile testing was performed on scaffolds cross-linked with EDC and genipin, yielding results that warranted further investigation for PDO-elastin blends. Material properties of the cross-linked scaffolds were then found within range of both pig femoral artery and human femoral artery. These results demonstrate PDO-elastin blends could potentially be favorable as vascular grafts, thus warranting future in vitro and in vivo studies.

scholarly journals Biaxial Tensile Testing and Constitutive Modeling of Human Supraspinatus Tendon

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
Spencer E. Szczesny ◽  
John M. Peloquin ◽  
Daniel H. Cortes ◽  
Jennifer A. Kadlowec ◽  
Louis J. Soslowsky ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Collagen Fiber ◽  
Supraspinatus Tendon ◽  
Angle Distribution ◽  
Fiber Angle ◽  
Biaxial Tensile ◽  
Uniaxial Testing ◽  
Biaxial Tensile Testing ◽  
Transverse Stresses ◽  
Fiber Organization

The heterogeneous composition and mechanical properties of the supraspinatus tendon offer an opportunity for studying the structure-function relationships of fibrous musculoskeletal connective tissues. Previous uniaxial testing has demonstrated a correlation between the collagen fiber angle distribution and tendon mechanics in response to tensile loading both parallel and transverse to the tendon longitudinal axis. However, the planar mechanics of the supraspinatus tendon may be more appropriately characterized through biaxial tensile testing, which avoids the limitation of nonphysiologic traction-free boundary conditions present during uniaxial testing. Combined with a structural constitutive model, biaxial testing can help identify the specific structural mechanisms underlying the tendon’s two-dimensional mechanical behavior. Therefore, the objective of this study was to evaluate the contribution of collagen fiber organization to the planar tensile mechanics of the human supraspinatus tendon by fitting biaxial tensile data with a structural constitutive model that incorporates a sample-specific angular distribution of nonlinear fibers. Regional samples were tested under several biaxial boundary conditions while simultaneously measuring the collagen fiber orientations via polarized light imaging. The histograms of fiber angles were fit with a von Mises probability distribution and input into a hyperelastic constitutive model incorporating the contributions of the uncrimped fibers. Samples with a wide fiber angle distribution produced greater transverse stresses than more highly aligned samples. The structural model fit the longitudinal stresses well (median R2 ≥ 0.96) and was validated by successfully predicting the stress response to a mechanical protocol not used for parameter estimation. The transverse stresses were fit less well with greater errors observed for less aligned samples. Sensitivity analyses and relatively affine fiber kinematics suggest that these errors are not due to inaccuracies in measuring the collagen fiber organization. More likely, additional strain energy terms representing fiber-fiber interactions are necessary to provide a closer approximation of the transverse stresses. Nevertheless, this approach demonstrated that the longitudinal tensile mechanics of the supraspinatus tendon are primarily dependent on the moduli, crimp, and angular distribution of its collagen fibers. These results add to the existing knowledge of structure-function relationships in fibrous musculoskeletal tissue, which is valuable for understanding the etiology of degenerative disease, developing effective tissue engineering design strategies, and predicting outcomes of tissue repair.

scholarly journals The influence of sample geometry and size on porcine aortic material properties from uniaxial tensile tests using custom-designed tissue cutters, clamps and molds

PLoS ONE ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. e0244390
Author(s):  
Ming Pei ◽  
Donghua Zou ◽  
Yong Gao ◽  
Jianhua Zhang ◽  
Ping Huang ◽  
...  
Keyword(s):  
Material Properties ◽  
Tensile Testing ◽  
Tensile Tests ◽  
Optimal Choice ◽  
The Other ◽  
Uniaxial Tensile ◽  
Test Results ◽  
Uniaxial Tensile Testing ◽  
Dog Bone ◽  
Weibull Theory

The aim of this study was to identify the influence of specimen geometry and size on the results of aortic uniaxial tensile tests using custom-designed tissue cutters, clamps and molds. Six descending thoracic aortas from pigs were used for rectangular sample tests, in which the circumferential and axial specimens had widths of 6 mm, 8 mm and 10 mm. The other six aortas were used for the dog-bone-shaped sample tests and were punched into circumferential, axial and oblique specimens with widths of 2 mm, 4 mm and 6 mm. We performed uniaxial tensile tests on the specimens and compared the test results. The results showed that mid-sample failure occurred in 85.2% of the dog-bone-shaped specimens and in 11.1% of the rectangular samples, which could be caused by Saint-Venant’s principle. Therefore, rectangular specimens were not suitable for aortic uniaxial tensile testing performed until rupture. The results also showed that the size effect of the aorta conformed to Weibull theory, and dog-bone-shaped specimens with a width of 4 mm were the optimal choice for aortic uniaxial tensile testing performed until rupture.

Instrumented Indentation Testing to Evaluate High-Temperature Material Properties

2011 ◽  
Author(s):  
Chan-Pyoung Park ◽  
Kug-Hwan Kim ◽  
Seung-Kyun Kang ◽  
Won-Je Jo ◽  
Dongil Kwon
Keyword(s):  
High Temperature ◽  
High Temperatures ◽  
Material Properties ◽  
Indentation Test ◽  
Temperature Deformation ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Indentation Testing ◽  
Instrumented Indentation ◽  
Uniaxial Tensile Testing

Mechanical properties must be evaluated at high temperatures to predict high-temperature deformation and fracture behavior, since high-temperature properties differ greatly from those at room temperature. A high-temperature uniaxial tensile test, a representative high-temperature test, is generally used, but it has the limitation of obtaining merely the average material properties. Recently an advanced method for evaluating tensile properties has been developed: the instrumented indentation test (IIT), which simultaneously applies a load and measures displacement. Here we use instrumented indentation testing to evaluate the flow properties (yield strength, ultimate tensile strength, etc.) of heat-resistant steel at high temperature. The contact-area determination algorithm and representative stress-representative strain approach are applied for high temperatures. We compare our experimental results to those of conventional high-temperature uniaxial tensile testing to assess the high-temperature performance of the instumented indentation test.

scholarly journals A Framework for Evaluating Myocardial Stiffness Using 3D-Printed Hearts

2021 ◽  
Author(s):  
Fikunwa Kolawole ◽  
Mathias Peirlinck ◽  
Tyler E. Cork ◽  
Vicky Y. Wang ◽  
Seraina A. Dual ◽  
...  
Keyword(s):  
Constitutive Modeling ◽  
Ground Truth ◽  
Diastolic Filling ◽  
Uniaxial Tensile ◽  
Myocardial Stiffness ◽  
Uniaxial Tensile Testing ◽  
Volume Relationship ◽  
Pressure Volume Relationship ◽  
3D Printed

AbstractMRI-driven computational modeling is increasingly used to simulate in vivo cardiac mechanical behavior and estimate subject-specific myocardial stiffness. However, in vivo validation of these estimates is exceedingly difficult due to the lack of a known ground-truth in vivo myocardial stiffness. We have developed 3D-printed heart phantoms of known myocardium-mimicking stiffness and MRI relaxation properties and incorporated the heart phantoms within a highly controlled MRI-compatible setup to simulate in vivo diastolic filling. The setup enables the acquisition of experimental data needed to evaluate myocardial stiffness using computational constitutive modeling: phantom geometry, loading pressures, boundary conditions, and filling strains. The pressure-volume relationship obtained from the phantom setup was used to calibrate an in silico model of the heart phantom undergoing simulated diastolic filling. The model estimated stiffness was compared with ground-truth stiffness obtained from uniaxial tensile testing. Ultimately, the setup is designed to enable extensive validation of MRI and FEM-based myocardial stiffness estimation frameworks.

Viscoelastic Testing Methodologies for Tissue Engineered Blood Vessels

2005 ◽  
Vol 127 (7) ◽  
pp. 1176-1184 ◽  
Author(s):  
Joseph D. Berglund ◽  
Robert M. Nerem ◽  
Athanassios Sambanis
Keyword(s):  
Blood Vessels ◽  
Mechanical Performance ◽  
Uniaxial Tensile ◽  
Collagen Gels ◽  
Uniaxial Tensile Testing ◽  
Modeling Systems ◽  
Tissue Engineered Blood Vessels ◽  
Linear Viscoelastic

In order to function in vivo, tissue engineered blood vessels (TEBVs) must encumber pulsatile blood flow and withstand hemodynamic pressures for long periods of time. To date TEBV mechanical assessment has typically relied on single time point burst and/or uniaxial tensile testing to gauge the strengths of the constructs. This study extends this analysis to include creep and stepwise stress relaxation viscoelastic testing methodologies. TEBV models exhibiting diverse mechanical behaviors as a result of different architectures ranging from reconstituted collagen gels to hybrid constructs reinforced with either untreated or glutaraldhyde-crosslinked collagen supports were evaluated after 8 and 23 days of in vitro culturing. Data were modeled using three and four-parameter linear viscoelastic mathematical representations and compared to porcine carotid arteries. While glutaraldhyde-treated hybrid TEBVs exhibited the largest overall strengths and toughness, uncrosslinked hybrid samples exhibited time-dependent behaviors most similar to native arteries. These findings emphasize the importance of viscoelastic characterization when evaluating the mechanical performance of TEBVs. Limits of testing methods and modeling systems are presented and discussed.

scholarly journals Simulation of the Effect of Material Properties on Soft Contact Lens On-Eye Power

2019 ◽  
Vol 6 (4) ◽  
pp. 94
Author(s):  
Joshua Moore ◽  
Bernardo T. Lopes ◽  
Ashkan Eliasy ◽  
Brendan Geraghty ◽  
Richard Wu ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Contact Lens ◽  
Material Properties ◽  
Experimental Testing ◽  
Uniaxial Tensile ◽  
Soft Contact ◽  
Silicone Hydrogel ◽  
Soft Contact Lens ◽  
Lens Power

Purpose: To evaluate the variation in the optical power achieved following soft contact lens eye fitting for spherical and cylindrical lenses with differing hydrogel material properties. Methods: Uniaxial tensile tests were performed on four hydrogel materials 77% water-content (w-c) hydrogel, 74% w-c blue silicone hydrogel, 74% w-c clear silicone hydrogel, and 64% w-c clear hydrogel (shortly referred to as H77p0, SiH74p5-blue, SiH74p5-clear, and H64p0-clear), under loading conditions that would be expected in vivo. Finite element models of the cornea and contact lens interaction were generated using spherical and cylindrical lenses with powers varying from −10 to +20 D; overall diameters of either 13.5, 14.0, or 14.5 mm; and with material properties matching those determined through experimental testing. Results: The moduli of elasticity for each of the tested hydrogel materials were 0.195 ± 0.027 MPa, 0.277 ± 0.019 MPa, 0.279 ± 0.01 MPa, and 0.457 ± 0.013 MPa for H77p0, SiH74p5-blue, SiH74p5-clear, and H64p0 respectively. The calculated values of effective power change (EPC) showed strong negative correlations with lens power. This was particularly apparent in the higher end of the lens power spectrum (over +5 D), where each of the materials demonstrated a highly linear reduction in EPC with increased lens power. Conclusions: Soft contact lenses composed of a stiffer hydrogel are far more resilient to changes in EPC across the lower end of the lens power spectrum (−10 to +5 D). Beyond this range, the material choice does not have a significant effect on the EPC.

Influence of post-welding tempering on mechanical behavior of friction welded joints from medium-carbon steels during tensile test

2020 ◽  
pp. 40-49
Author(s):  
A. S. Atamashkin ◽  
E. Yu. Priymak ◽  
N. V. Firsova
Keyword(s):  
Mechanical Behavior ◽  
Welded Joints ◽  
Welded Joint ◽  
Crack Nucleation ◽  
Carbon Steels ◽  
Uniaxial Tensile ◽  
Medium Carbon ◽  
Uniaxial Tensile Testing ◽  
Rotary Friction Welding ◽  
Medium Carbon Steels

The paper presents an analysis of the mechanical behavior of friction samples of welded joints from steels 30G2 (36 Mn 5) and 40 KhN (40Ni Cr 6), made by rotary friction welding (RFW). The influence of various temperature conditions of postweld tempering on the mechanical properties and deformation behavior during uniaxial tensile testing is analyzed. Vulnerabilities where crack nucleation and propagation occurred in specimens with a welded joint were identified. It was found that with this combination of steels, postweld tempering of the welded joint contributes to a decrease in the integral strength characteristics under conditions of static tension along with a significant decrease in the relative longitudinal deformation of the tested samples.

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