scholarly journals BIOMECHANICAL REMODELING OF BIODEGRADABLE SMALL-DIAMETER VASCULAR GRAFTS IN SITU

2016 ◽  
Vol 18 (2) ◽  
pp. 99-109 ◽  
Author(s):  
T. V. Glushkova ◽  
V. V. Sevostyanova ◽  
L. V. Antonova ◽  
K. Yu. Klyshnikov ◽  
E. A. Ovcharenko ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Blood Vessels ◽  
Abdominal Aorta ◽  
Internal Mammary Artery ◽  
Vascular Grafts ◽  
Small Diameter ◽  
Uniaxial Tensile ◽  
Aortic Tissue ◽  
Uniaxial Tensile Test ◽  
Internal Mammary

Aim: to evaluate the biomechanical remodeling of polymer grafts modified with vascular endothelial growth factor (VEGF) after implantation into rat abdominal aorta.Materials and methods. Vascular grafts of2 mmdiameter were fabricated by electrospinning from polycaprolactone (PCL) and a mixture of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) and PCL. The grafts were modified with VEGF by biphasic electrospinning. Morphology of the grafts was assessed by scanning electron microscopy. Physico-mechanical properties of PCL and PHBV/PCL grafts were estimated using uniaxial tensile test and physiological circulating system equipped with state-of-theart ultrasound vascular wall tracking system. Physico-mechanical testing of PCL/VEGF and PHBV/PCL/VEGF was performed before and after implantation into rat abdominal aorta for 6 months. The modeling of coronary artery bypass grafting (CABG) was performed by finite element analysis for modified grafts.Results. Durability of PCL and PHBV/PCL grafts did not differ from that of human internal mammary artery; however, elasticity and stiffness of these grafts were higher compared to internal mammary artery. Viscoelastic properties of the grafts were comparable to those of native blood vessels. Modification of the grafts with VEGF reduced material stiffness. Six months postimplantation, PCL/VEGF and PHBV/PCL/VEGF were integrated with aortic tissue that induced changes in the physico-mechanical properties of the grafts similar to the native vessel. Biomechanical modeling confirmed the functioning of modified grafts in bypass position for CABG.Conclusion. PCL/VEGF and PHBV/PCL/VEGF grafts have satisfactory physico-mechanical properties and can be potentially used in the reconstruction of blood vessels. 

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.

scholarly journals Experimental and Numerical Evaluation of Mechanical Properties of 3D-Printed Stainless Steel 316L Lattice Structures

2021 ◽  
Author(s):  
M. Carraturo ◽  
G. Alaimo ◽  
S. Marconi ◽  
E. Negrello ◽  
E. Sgambitterra ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Mechanical Behavior ◽  
Numerical Simulations ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Lattice Structures ◽  
Stainless Steel 316L ◽  
Research Attention ◽  
Octet Truss

AbstractAdditive manufacturing (AM), and in particular selective laser melting (SLM) technology, allows to produce structural components made of lattice structures. These kinds of structures have received a lot of research attention over recent years due to their capacity to generate easy-to-manufacture and lightweight components with enhanced mechanical properties. Despite a large amount of work available in the literature, the prediction of the mechanical behavior of lattice structures is still an open issue for researchers. Numerical simulations can help to better understand the mechanical behavior of such a kind of structure without undergoing long and expensive experimental campaigns. In this work, we compare numerical and experimental results of a uniaxial tensile test for stainless steel 316L octet-truss lattice specimen. Numerical simulations are based on both the nominal as-designed geometry and the as-build geometry obtained through the analysis of µ-CT images. We find that the use of the as-build geometry is fundamental for an accurate prediction of the mechanical behavior of lattice structures.

scholarly journals Effect of PWHT on the Microstructure and Mechanical Properties of Friction Stir Welded DP780 Steel

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1097
Author(s):  
Umer Masood Chaudry ◽  
Seung-Chang Han ◽  
Fathia Alkelae ◽  
Tea-Sung Jun
Keyword(s):  
Mechanical Properties ◽  
Annealing Temperature ◽  
Tensile Elongation ◽  
Image Correlation ◽  
Frictional Heat ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Friction Stir ◽  
Microstructure And Mechanical Properties ◽  
Dp780 Steel

In the present study, the effect of post-weld heat treatment (PWHT) on the microstructure and mechanical properties of friction stir welded (FSW) DP780 steel sheets was investigated. FSW was carried out at a constant tool rotation speed of 400 rpm and different welding speeds (200 mm/min and 400 min/min). A defect free weld was witnessed for both of the welding conditions. The mutual effect of severe plastic deformation and frictional heat generation by pin rotation during the FSW process resulted in grain refinement due to dynamic recrystallization in the stir zone (SZ) and thermo-mechanically affected zone (TMAZ). Lower tensile elongation and higher yield and ultimate tensile strengths were recorded for welded-samples as compared to the base material (BM) DP780 steel. The joints were subsequently annealed at various temperatures at 450–650 °C for 1 h. At higher annealing temperature, the work hardening rate of joints gradually decreased and subsequently failed in the softened heat-affected zone (HAZ) during the uniaxial tensile test. Reduction in yield strength and tensile strength was found in all PWHT conditions, though improvement in elongation was achieved by annealing at 550 °C. The digital image correlation analysis showed that an inhomogeneous strain distribution occurred in the FSWed samples, and the strain was particularly highly localized in the advancing side of interface zone. The nanoindentation measurements covering the FSWed joint were consistent with an increase of the annealing temperature. The various grains size in the BM, TMAZ, and SZ is the main factor monitoring the hardness distribution in these zones and the observed discrepancies in mechanical properties.

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 (<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.

Viscoplastic Constitutive Model for High Strain Rate Mechanical Properties of SAC-Q Leadfree Solder After High-Temperature Prolonged Storage

2018 ◽  
Author(s):  
Pradeep Lall ◽  
Vikas Yadav ◽  
Jeff Suhling ◽  
David Locker
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
High Strain Rate ◽  
Strain Rate ◽  
Thermal Aging ◽  
High Strain ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Aging Effects ◽  
Model Predictions

Electronics in automotive underhood and downhole drilling applications may be subjected to sustained operation at high temperature in addition to high strain-rate loads. SAC solders used for second level interconnects have been shown to experience degradation in high strain-rate mechanical properties under sustained exposure to high temperatures. Industry search for solutions for resisting the high-temperature degradation of SAC solders has focused on the addition of dopants to the alloy. In this study, a doped SAC solder called SAC-Q solder have been studied. The high strain rate mechanical properties of SAC-Q solder have been studied under elevated temperatures up to 200°C. Samples with thermal aging at 50°C for up to 6-months have been used for measurements in uniaxial tensile tests. Measurements for SAC-Q have been compared to SAC105 and SAC305 for identical test conditions and sample geometry. Data from the SAC-Q measurements has been fit to the Anand Viscoplasticity model. In order to assess the predictive power of the model, the computed Anand parameters have been used to simulate the uniaxial tensile test and the model predictions compared with experimental data. Model predictions show good correlation with experimental measurements. The presented approach extends the Anand Model to include thermal aging effects.

scholarly journals The Influence of Sub-Zero Conditions on the Mechanical Properties of Polylactide-Based Composites

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5789
Author(s):  
Olga Mysiukiewicz ◽  
Mateusz Barczewski ◽  
Arkadiusz Kloziński
Keyword(s):  
Mechanical Properties ◽  
Room Temperature ◽  
Mechanical Performance ◽  
Mechanical Analysis ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Mechanical And Thermal Properties ◽  
Scanning Calorimetry ◽  
Linseed Cake ◽  
Static Mechanical

Polylactide-based composites filled with waste fillers due to their sustainability are a subject of many current papers, in which their structural, mechanical, and thermal properties are evaluated. However, few studies focus on their behavior in low temperatures. In this paper, dynamic and quasi-static mechanical properties of polylactide-based composites filled with 10 wt% of linseed cake (a by-product of mechanical oil extraction from linseed) were evaluated at room temperature and at −40 °C by means of dynamic mechanical analysis (DMA), Charpy’s impact strength test and uniaxial tensile test. It was found that the effect of plasticization provided by the oil contained in the filler at room temperature is significantly reduced in sub-zero conditions due to solidification of the oil around −18 °C, as it was shown by differential scanning calorimetry (DSC) and DMA, but the overall mechanical performance of the polylactide-based composites was sufficient to enable their use in low-temperature applications.

Characterization and Evaluation of Mechanical Properties and Residual Stress in Aluminum-Magnesium Alloys Welded by the FSW Process

2020 ◽  
Vol 1012 ◽  
pp. 349-353
Author(s):  
D.B. Colaço ◽  
M.A. Ribeiro ◽  
T.M. Maciel ◽  
R.H.F. de Melo
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Residual Stresses ◽  
Welding Process ◽  
Bending Test ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Friction Stir ◽  
Aluminum Magnesium Alloys

The demand for lighter materials with suitable mechanical properties and a high resistance to corrosion has been increasing in the industries. Therefore, aluminum appears as an alternative due to its set of properties. The aim of this work was to evaluate residual stress levels and mechanical properties of welded joints of Aluminum-Magnesium alloy AA 5083-O using the Friction Stir Welding process. For mechanical characterization were performed a uniaxial tensile test, Vickers hardness, bending test and, finally, the determination of residual stresses. It was concluded that welding by FSW process with an angle of inclination of the tool at 3o, established better results due to better mixing of materials. The best results of tensile strength and a lower level of residual stresses were obtained using a tool rotation speed of 340 RPM with welding advance speed of 180 mm/min and 70 mm/min.

Numerical Simulation Analysis of Aluminium Alloy Wheels Casting Defects and Casting Process Optimization

2013 ◽  
Vol 749 ◽  
pp. 125-132 ◽  
Author(s):  
Lv Ming Yang ◽  
Li Li Zhao ◽  
Qing Qing Zhang ◽  
Tie Tao Zhou
Keyword(s):  
Mechanical Properties ◽  
Numerical Simulation ◽  
Aluminum Alloy ◽  
Casting Process ◽  
Shrinkage Cavity ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Casting Defects ◽  
Pressure Casting ◽  
Aluminum Alloy Casting

In the low pressure casting process of A356 aluminum alloy wheel hub, casting defects including shrinkage cavity, shrinkage porosity, impurity and pore usually occur inside the casting. These defects affect the mechanical properties of the casting. To solve this problem, we conducted a study based on a cooperation project with a well-known domestic automobile wheel manufacturer. In the present study, uniaxial tensile test of aluminum alloy casting containing defects was simulated and analysed, and the effect of types and number of defects on mechanical properties was studied by finite element analysis software. Statistical analysis of the data was provided by the manufacturer. It has been found that the degassing technology is effective by the quantitative analysis method. Based on the analyses of experimental data and the numerical simulation it is deduced that the tensile strength of casting increases with the increase of the defects due to the presence of impurity. This was confirmed in this research project, it has been observed that the defect rate of the casting sample is reduced from 5%-6% to less than 1%.

Development of Small-Diameter Vascular Grafts Through Decellularization of Human Blood Vessels

2017 ◽  
Vol 7 (2) ◽  
pp. 101-110 ◽  
Author(s):  
Andrea Porzionato ◽  
Maria Martina Sfriso ◽  
Alex Pontini ◽  
Veronica Macchi ◽  
Maria Ida Buompensiere ◽  
...  
Keyword(s):  
Blood Vessels ◽  
Human Blood ◽  
Vascular Grafts ◽  
Small Diameter ◽  
Small Diameter Vascular Grafts

Fabrication and Preliminary Study of a Prototype Bi-Layered Small Diameter Vascular Prosthesis Composed of Nano-Fiber and Silk Fiber

2013 ◽  
Vol 843 ◽  
pp. 66-69 ◽  
Author(s):  
Hui Jing Zhao ◽  
Guo Li Zhou ◽  
Zhi Qing Yuan
Keyword(s):  
Mechanical Properties ◽  
Blood Vessels ◽  
Outer Layer ◽  
Small Diameter ◽  
Peak Stress ◽  
Silk Fiber ◽  
Content Increase ◽  
Peak Strain ◽  
Tissue Engineering Scaffolds ◽  
Vascular Prostheses

Biomaterials used for vascular prostheses should possess certain strength that can keep the normal blood fluidity, as well as certain flexibility and elasticity that can resist blood pulsation pressure. In order to fabricate small diameter vascular prostheses (SDVP) that possess matchable mechanical properties with natural blood vessels, a bi-layered tubular structure composed of electrospinning blended nanofiber and silk fiber was designed and prepared in this study. The inner layer of the structure, prepared through electrospinning, was composed of Poly (L-lactide-co-ε-caprolactone) (PLCL) and silk fibroin (SF) blended nanofibers. Braided silk tube was used as the outer layer of the structure. Morphological, structural and mechanical properties including peak stress, peak strain, and Youngs modulus of the prototype bi-layered SDVP were characterized initially. Results showed that the diameter range of the blended nanofiber was between 100 and 900 nm, and the fiber diameter increased with the content increase of PLCL. Through blending PLCL together with SF, peak stress and peak strain of the electrospun inner layer were improved, and that of the Youngs modulus decreased. Meanwhile, the outer layer of SDVP was stronger and had higher Youngs modulus. Those mechanical performances of the prototype bi-layered SDVP fabricated in this study are similar to natural blood vessels, which provide a promising biomaterial that could be applied on tubular tissue engineering scaffolds.

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