scholarly journals Experimental Study of Anisotropic Stress/Strain Relationships of Aortic and Pulmonary Artery Homografts and Synthetic Vascular Grafts

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Yueqian Jia ◽  
Yangyang Qiao ◽  
I. Ricardo Argueta-Morales ◽  
Aung Maung ◽  
Jack Norfleet ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Pulmonary Artery ◽  
True Strain ◽  
Vascular Grafts ◽  
Uniaxial Tensile ◽  
Cauchy Stress ◽  
Mechanical Coupling ◽  
Biomechanical Behavior ◽  
Uniaxial Tensile Testing ◽  
Synthetic Grafts

Homografts and synthetic grafts are used in surgery for congenital heart disease (CHD). Determining these materials' mechanical properties will aid in understanding tissue behavior when subjected to abnormal CHD hemodynamics. Homograft tissue samples from anterior/posterior aspects, of ascending/descending aorta (AA, DA), innominate artery (IA), left subclavian artery (LScA), left common carotid artery (LCCA), main/left/right pulmonary artery (MPA, LPA, RPA), and synthetic vascular grafts, were obtained in three orientations: circumferential, diagonal (45 deg relative to circumferential direction), and longitudinal. Samples were subjected to uniaxial tensile testing (UTT). True strain-Cauchy stress curves were individually fitted for each orientation to calibrate Fung model. Then, they were used to calibrate anisotropic Holzapfel–Gasser model (R2 > 0.95). Most samples demonstrated a nonlinear hyperelastic strain–stress response to UTT. Stiffness (measured by tangent modulus at different strains) in all orientations were compared and shown as contour plots. For each vessel segment at all strain levels, stiffness was not significantly different among aspects and orientations. For synthetic grafts, stiffness was significantly different among orientations (p < 0.042). Aorta is significantly stiffer than pulmonary artery at 10% strain, comparing all orientations, aspects, and regions (p = 0.0001). Synthetic grafts are significantly stiffer than aortic and pulmonary homografts at all strain levels (p < 0.046). Aortic, pulmonary artery, and synthetic grafts exhibit hyperelastic biomechanical behavior with anisotropic effect. Differences in mechanical properties among vascular grafts may affect native tissue behavior and ventricular/arterial mechanical coupling, and increase the risk of deformation due to abnormal CHD hemodynamics.

scholarly journals The mechanical and morphological properties of systemic and pulmonary arteries differ in the earth boa, a snake without ventricular pressure separation

2021 ◽  
Author(s):  
Benjamin Jonathan van Soldt ◽  
Tobias Wang ◽  
Renato Filogonio ◽  
Carl Christian Danielsen
Keyword(s):  
Mechanical Properties ◽  
Pulmonary Artery ◽  
Mechanical Characteristics ◽  
Pulmonary Arteries ◽  
Uniaxial Tensile ◽  
Intraventricular Pressure ◽  
Python Regius ◽  
The Earth ◽  
Uniaxial Tensile Testing ◽  
Blood Pressures

The walls of the mammalian aorta and pulmonary artery are characterized by diverging morphologies and mechanical properties, which has been correlated with high systemic and low pulmonary blood pressures, as a result of intraventricular pressure separation in the mammalian ventricle. However, the relation between intraventricular pressure separation and diverging aortic and pulmonary artery wall morphologies and mechanical characteristics is not understood. The snake cardiovascular system poses a unique model for the study of this question, since representatives both with and without intraventricular pressure separation exist. In this study we perform uniaxial tensile testing on vessel samples taken from the aortas and pulmonary arteries of the earth boa, Acrantophis madagascariensis, a species without intraventricular pressure separation. We then compare these morphological and mechanical characteristics with samples from the ball python, Python regius, and the yellow anaconda, Eunectes notaeus, species with and without intraventricular pressure separation, respectively. Strikingly, we find that although the aortas and pulmonary arteries of A. madagascariensis respond similarly to the same intramural blood pressures, they diverge strongly in morphology, and that this is a common attribute among species without intraventricular pressure separation in this study. In contrast, P. regius aortas and pulmonary arteries diverge both morphologically and in terms of their mechanical properties. Altogether our data indicate that intraventricular pressure separation does not explain diverging aortic and pulmonary artery morphologies. Following the Law of Laplace, we propose that thin pulmonary arteries represent a mechanism to protect the fragile pulmonary vascular bed by reducing the blood volume that passes through, to which genetic factors may contribute more strongly than physiological parameters.

Effects of Freezing on the Mechanical Properties of Blood Vessels

2004 ◽  
Author(s):  
Erin D. Grassl ◽  
Victor H. Barocas ◽  
John C. Bischof
Keyword(s):  
Mechanical Properties ◽  
Blood Vessels ◽  
Mechanical Test ◽  
Vascular Grafts ◽  
Uniaxial Tensile ◽  
Ice Crystal ◽  
Cryoprotective Agents ◽  
Uniaxial Tensile Testing ◽  
Stress Region ◽  
Storage Methods

The mechanical properties of blood vessels are important to their ability to function properly. The effects of freezing/cooling on the mechanical properties are a concern for several reasons including preservation of vascular grafts, appropriate storage of samples prior to mechanical testing, and the effects and mechanisms of cryoplasty (cryotherapy for treatment of restenosis). Many have studied the effects of freezing vessels in the presence of cryoprotective agents (CPAs), and the results are mixed, depending on the type of artery and particular mechanical test. The few studies on freezing without CPAs have also given mixed results. To examine this issue further, we froze pig femoral arteries to −20 C in the absence of CPA, and then subjected them to uniaxial tensile testing. Our results suggest that freezing does have an effect on stress-strain properties, particularly in the low stress region corresponding to physiological conditions. The mechanisms of this change in mechanical properties may include the loss of smooth muscle viability, damage to extracellular matrix (ECM), or changes in alignment caused by ice crystal growth. Understanding these changes is important in understanding the mechanisms of cryoplasty, as well as choosing appropriate storage methods for tissues to be used in vascular grafts.

Bioengineering silk into blood vessels

2021 ◽  
Author(s):  
Yuen Ting Lam ◽  
Richard P. Tan ◽  
Praveesuda L. Michael ◽  
Kieran Lau ◽  
Nianji Yang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Inflammatory Responses ◽  
Vascular Grafts ◽  
Small Diameter ◽  
Biological Response ◽  
Endothelial Cell Layer ◽  
Significant Research ◽  
Rising Incidence ◽  
Highly Hydrophobic ◽  
Synthetic Grafts

The rising incidence of cardiovascular disease has increased the demand for small diameter (&lt;6 mm) synthetic vascular grafts for use in bypass surgery. Clinically available synthetic grafts (polyethylene terephthalate and expanded polytetrafluorethylene) are incredibly strong, but also highly hydrophobic and inelastic, leading to high rates of failure when used for small diameter bypass. The poor clinical outcomes of commercial synthetic grafts in this setting have driven significant research in search of new materials that retain favourable mechanical properties but offer improved biocompatibility. Over the last several decades, silk fibroin derived from Bombyx mori silkworms has emerged as a promising biomaterial for use in vascular applications. Progress has been driven by advances in silk manufacturing practices which have allowed unprecedented control over silk strength, architecture, and the ensuing biological response. Silk can now be manufactured to mimic the mechanical properties of native arteries, rapidly recover the native endothelial cell layer lining vessels, and direct positive vascular remodelling through the regulation of local inflammatory responses. This review summarises the advances in silk purification, processing and functionalisation which have allowed the production of robust vascular grafts with promise for future clinical application.

Structure Assessment Using Instrumented Indentation: Strength, Toughness and Residual Stress

2018 ◽  
Author(s):  
Dongil Kwon ◽  
Jong Hyoung Kim ◽  
Ohmin Kwon ◽  
Woojoo Kim ◽  
Sungki Choi ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Residual Stress ◽  
Tensile Properties ◽  
Hole Drilling ◽  
Uniaxial Tensile ◽  
Small Scale ◽  
Specimen Preparation ◽  
Instrumented Indentation ◽  
Uniaxial Tensile Testing

The instrumented indentation technique (IIT) is a novel method for evaluating mechanical properties such as tensile properties, toughness and residual stress by analyzing the indentation load-depth curve measured during indentation. It can be applied directly on small-scale and localized sections in industrial structures and structural components since specimen preparation is very easy and the experimental procedure is nondestructive. We introduce the principles for measuring mechanical properties with IIT: tensile properties by using a representative stress and strain approach, residual stress by analyzing the stress-free and stressed-state indentation curves, and fracture toughness of metals based on a ductile or brittle model according to the fracture behavior of the material. The experimental results from IIT were verified by comparing results from conventional methods such as uniaxial tensile testing for tensile properties, mechanical saw-cutting and hole-drilling methods for residual stress, and CTOD test for fracture toughness.

Mechanical Characterization of Polymer Nanowires Using MEMS

2006 ◽  
Author(s):  
B. A. Samuel ◽  
Bo Yi ◽  
R. Rajagopalan ◽  
H. C. Foley ◽  
M. A. Haque
Keyword(s):  
Mechanical Properties ◽  
Tensile Testing ◽  
Furfuryl Alcohol ◽  
Mechanical Characterization ◽  
Uniaxial Tensile ◽  
Testing Device ◽  
Uniaxial Tensile Testing ◽  
Polymer Nanowires

We present results on the mechanical properties of single freestanding poly-furfuryl alcohol (PFA) nanowires (aspect ratio &gt; 50, diameters 100–300 nm) from experiments conducted using a MEMS-based uniaxial tensile testing device in-situ inside the SEM. The specimens tested were pyrolyzed PFA nanowires (pyrolyzed at 800° C).

Microstructures and Mechanical Properties of Stainless Steel AISI 316L Processed by Selective Laser Melting

2014 ◽  
Vol 783-786 ◽  
pp. 898-903 ◽  
Author(s):  
Anne Mertens ◽  
Sylvie Reginster ◽  
Quentin Contrepois ◽  
Thierry Dormal ◽  
Olivier Lemaire ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Selective Laser Melting ◽  
Uniaxial Tensile ◽  
Layer By Layer ◽  
Aisi 316L ◽  
Laser Melting ◽  
Uniaxial Tensile Testing ◽  
Steel Aisi ◽  
Stainless Steel Aisi

In this study, samples of stainless steel AISI 316L have been processed by selective laser melting, a layer-by-layer near-net-shape process allowing for an economic production of complex parts. The resulting microstructures have been characterised in details in order to reach a better understanding of the solidification and consolidation processes. The influence of the processing parameters on the mechanical properties was investigated by means of uniaxial tensile testing performed on samples produced with different main orientations with respect to the building direction. A strong anisotropy of the mechanical behaviour was thus interpreted in relation with the microstructures and the processing conditions.

Effect of the Stretch Rate During Uniaxial Testing on the Mechanical Properties of Prolene®

2012 ◽  
Author(s):  
T. M. Bazi ◽  
A. H. Ammouri ◽  
R. F. Hamade
Keyword(s):  
Mechanical Properties ◽  
Tensile Testing ◽  
Relative Elongation ◽  
Testing Machine ◽  
Peak Load ◽  
Displacement Rate ◽  
Uniaxial Tensile ◽  
P Value ◽  
Stretch Rate ◽  
Uniaxial Tensile Testing

We assess the effects of stretch rate on the mechanical properties of Prolene® (Ethicon, Gynecare, Somerville, NJ, USA), a knitted polypropylene mesh. Prolene®, consisting of macroporous knitted polypropylene, is considered here as a suitable proxy to midurethral tape (MUT) as well as to many other prosthesis products used in surgery applications. Such products are utilized to treat urine incontinence, pelvic organ prolapse, as well as hernia in humans. Of the mechanical properties of special significance are the following three properties: peak load (N), extension (%) at peak load, and linear stiffness (N/mm). Uniaxial tensile testing was performed on mesh samples on a universal testing machine and involved loading different samples at 5 cross-head speeds of: 1, 10, 50, 100, and 500 mm/min. The corresponding properties were measured under these 5 conditions. In order to minimize damage to the specimens at the jaws, special dual action pneumatically operated grips with rubber faced jaws were used to hold the samples in place. The effectiveness of these grips was illustrated by the fact that none of the failed samples broke at grips. Statistically significant findings suggest an increasing trend for Prolene® stiffness vs. stretch rate (R2 = 0.9679; two-tailed p value = 0.0025) where the stiffness increases 26.2% when increasing the displacement rate from 1 to 500 mm/min. For extension (%) at peak load, a decreasing trend was found vs. stretch rate (R2 = 0.81; two-tailed p value = 0.037) where increasing the displacement rate from 1 mm/min to 500 mm/min corresponds to a 22% decrease in the relative elongation of the mesh. No statistically significant dependence of peak load on stretch rate was found. These findings may help workers in the biomedical field develop suitable uniaxial tensile testing protocols of such materials.

scholarly journals Incorporation of Fibrin Matrix into Electrospun Membranes for Periodontal Wound Healing

2019 ◽  
Vol 6 (3) ◽  
pp. 57 ◽  
Author(s):  
Choyi Wong ◽  
Suyog Yoganarasimha ◽  
Caroline Carrico ◽  
Parthasarathy Madurantakam
Keyword(s):  
Mechanical Properties ◽  
Three Dimensional ◽  
Fresh Frozen Plasma ◽  
Biologically Active ◽  
Uniaxial Tensile ◽  
Electrospun Membrane ◽  
Fibrin Matrix ◽  
Uniaxial Tensile Testing ◽  
Electrospun Membranes ◽  
Fresh Frozen

Guided tissue regeneration (GTR) aims to regenerate the lost attachment apparatus caused by periodontal disease through the use of a membrane. The goal of this study is to create and characterize a novel hybrid membrane that contains biologically active fibrin matrix within a synthetic polycaprolactone (PCL) electrospun membrane. Three-dimensional fibrin matrices and fibrin-incorporated electrospun membrane were created from fresh frozen plasma by centrifugation in glass vials under three different conditions: 400 g for 12 min, 1450 g for 15 min and 3000 g for 60 min. Half the membranes were crosslinked with 1% genipin. Degradation against trypsin indicated biologic stability while uniaxial tensile testing characterized mechanical properties. Continuous data was analyzed by ANOVA to detect differences between groups (p = 0.05). Fibrin-incorporated electrospun membranes showed statistically significant increase in mechanical properties (elastic modulus, strain at break and energy to break) compared to fibrin matrices. While crosslinking had marginal effects on mechanical properties, it did significantly increase biologic stability against trypsin (p < 0.0001). Lastly, membranes generated at 400 g and 1450 g were superior in mechanical properties and biologic stability compared to those generated at 3000 g. Fibrin-incorporated, crosslinked electrospun PCL membranes generated at lower centrifugation forces offers a novel strategy to generate a potentially superior membrane for GTR procedures.

scholarly journals Effect of Severe Plastic Deformation on Structure Refinement and Mechanical Properties of the Al-Zn-Mg-Fe-Ni Alloy

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 296
Author(s):  
Irina Brodova ◽  
Dmitriy Rasposienko ◽  
Irina Shirinkina ◽  
Anastasia Petrova ◽  
Torgom Akopyan ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
High Pressure ◽  
Severe Plastic Deformation ◽  
High Pressure Torsion ◽  
Structure Refinement ◽  
Tensile Yield Strength ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Testing ◽  
Radial Shear Rolling

This paper identifies the mechanisms of phase and structural transformations during severe plastic deformation by shearing under pressure (high-pressure torsion) of an Al-Zn-Mg-Fe-Ni-based aluminum alloy depending on different initial states of the material (an ingot after homogenizing annealing and a rod produced by radial-shear rolling). Scanning and transmission electron microscopy are used to determine the morphological and size characteristics of the structural constituents of the alloy after high-pressure torsion. It has been found that, irrespective of the history under high-pressure torsion, fragmentation and dynamic recrystallization results in a nanostructural alloy with a high microhardness of 2000 to 2600 MPa. Combined deformation processing (high-pressure torsion + radial-shear rolling) is shown to yield a nanocomposite reinforced with dispersed intermetallic phases of different origins, namely Al9FeNi eutectic aluminides and MgZn2, Al2Mg3Zn3, and Al3Zr secondary phases. The results of uniaxial tensile testing demonstrate good mechanical properties of the composite (ultimate tensile strength of 640 MPa, tensile yield strength of 628 MPa, and elongation of 5%).

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