scholarly journals A realistic way to investigate the design, and mechanical properties of flow diverter stents

2021 ◽  
Author(s):  
Prasanth Velvaluri ◽  
Mariya S. Pravdivtseva ◽  
Johannes Hensler ◽  
Fritz Wodarg ◽  
Olav Jansen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Flow Diverter

scholarly journals Selection of helical braided flow diverter stents based on hemodynamic performance and mechanical properties

2016 ◽  
Vol 9 (10) ◽  
pp. 999-1005 ◽  
Author(s):  
Takashi Suzuki ◽  
Hiroyuki Takao ◽  
Soichiro Fujimura ◽  
Chihebeddine Dahmani ◽  
Toshihiro Ishibashi ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Reduction Rate ◽  
Flow Diverter ◽  
Outer Diameter ◽  
Cfd Simulations ◽  
Flow Reduction ◽  
Radial Stiffness ◽  
Flow Diverter Stent ◽  
Hemodynamic Performance ◽  
Longitudinal Flexibility

BackgroundAlthough flow diversion is a promising procedure for the treatment of aneurysms, complications have been reported and it remains poorly understood. The occurrence of adverse outcomes is known to depend on both the mechanical properties and flow reduction effects of the flow diverter stent.ObjectiveTo clarify the possibility of designing a flow diverter stent considering both hemodynamic performance and mechanical properties.Materials and methodsComputational fluid dynamics (CFD) simulations were conducted based on an ideal aneurysm model with flow diverters. Structural analyses of two flow diverter models exhibiting similar flow reduction effects were performed, and the radial stiffness and longitudinal flexibility were compared.ResultsIn CFD simulations, two stents–Pore2-d35 (26.77° weave angle when fully expanded, 35 μm wire thickness) and Pore3-d50 (36.65°, 50 μm respectively)–demonstrated similar flow reduction rates (68.5% spatial-averaged velocity reduction rate, 85.0% area-averaged wall shear stress reduction rate for Pore2-d35, and 68.6%, 85.4%, respectively, for Pore3-d50). However, Pore3-d50 exhibited greater radial stiffness than Pore2-d35 (40.0 vs 21.0 mN/m at a 3.5 mm outer diameter) and less longitudinal flexibility (0.903 vs 0.104 N·mm bending moments at 90°). These measurements indicate that changing the wire thickness and weave angle allows adjustment of the mechanical properties while maintaining the same degree of flow reduction effects.ConclusionsThe combination of CFD and structural analysis can provide promising solutions for an optimized stent. Stents exhibiting different mechanical properties but the same flow reduction effects could be designed by varying both the weave angle and wire thickness.

Relationships between geometrical parameters and mechanical properties for a helical braided flow diverter stent

2017 ◽  
Vol 25 (4) ◽  
pp. 611-623 ◽  
Author(s):  
Takashi Suzuki ◽  
Hiroyuki Takao ◽  
Soichiro Fujimura ◽  
Chihebeddine Dahmani ◽  
Toshihiro Ishibashi ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Flow Diverter ◽  
Geometrical Parameters ◽  
Flow Diverter Stent

Design and Mechanical Properties of a Novel Cerebral Flow Diverter Stent

2014 ◽  
Vol 42 (5) ◽  
pp. 960-970 ◽  
Author(s):  
Jiayao Ma ◽  
Zhong You ◽  
James Byrne ◽  
Rafik R. Rizkallah
Keyword(s):  
Mechanical Properties ◽  
Flow Diverter ◽  
Flow Diverter Stent

scholarly journals A realistic way to investigate the design, and mechanical properties of flow diverter stents

2021 ◽  
Author(s):  
Prasanth Velvaluri ◽  
Mariya Pravdivtseva ◽  
Johannes Hensler ◽  
Fritz Wodarg ◽  
Olav Jansen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Flow Diverter ◽  
Radial Force ◽  
Cell Area ◽  
Flow Properties ◽  
4D Flow ◽  
Flow Mri ◽  
Mechanical Devices ◽  
First Time

Purpose: Braided flow diverters (FD) are highly sophisticated, delicate, and intricate mechanical devices used to treat intracranial aneurysms and thus saving lives. Testing such devices in vitro, however, remains an unsolved challenge. Here, we evaluate methods that access flow, design, and mechanical properties in vitro. Methods: Flow properties, cell porosity, and cell area were evaluated by placing FDs in patient-derived, 3D printed models of human vasculature. 4D flow MRI was used to measure fluid dynamics. Laser microscopy was used to measure porosity and cell area with the top of aneurysm sac cut off for the model. New testing methods were developed to investigate the bending, circumferential, and longitudinal radial force continuously over varying diameters. Results: The placement and flow properties of the FD in the vasculature models were successfully measured by MRI, although artifacts occurred. The setup to measure porosity and cell area inside of the model proved successful. The newly discussed methods allowed us to measure the indicated forces, to our knowledge for the first time, continuously. Conclusion: Modern and specifically tailored techniques, some of which were presented here for the first time, allow detailed insights into the flow and mechanical properties of braided flow diverter stents.

Phase Transformations in Ti-7w/oMo-3w/oMe Alloy

1974 ◽  
Vol 32 ◽  
pp. 514-515
Author(s):  
S. Fujishiro
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Transmission Electron Microscopy ◽  
Tensile Strength ◽  
Mechanical Processing ◽  
Ray Method ◽  
X Ray ◽  
Transmission Electron ◽  
Water Quench ◽  
Alpha Beta

The mechanical properties of three titanium alloys (Ti-7Mo-3Al, Ti-7Mo- 3Cu and Ti-7Mo-3Ta) were evaluated as function of: 1) Solutionizing in the beta field and aging, 2) Thermal Mechanical Processing in the beta field and aging, 3) Solutionizing in the alpha + beta field and aging. The samples were isothermally aged in the temperature range 300° to 700*C for 4 to 24 hours, followed by a water quench. Transmission electron microscopy and X-ray method were used to identify the phase formed. All three alloys solutionized at 1050°C (beta field) transformed to martensitic alpha (alpha prime) upon being water quenched. Despite this heavily strained alpha prime, which is characterized by microtwins the tensile strength of the as-quenched alloys is relatively low and the elongation is as high as 30%.

Effects of cooling rate on the mechanical properties of dual phase treated vanadium steels

1983 ◽  
Vol 41 ◽  
pp. 220-221
Author(s):  
L.J. Chen ◽  
H.C. Cheng ◽  
J.R. Gong ◽  
J.G. Yang
Keyword(s):  
Mechanical Properties ◽  
Cooling Rate ◽  
Automobile Industry ◽  
High Strength ◽  
Weight Percent ◽  
Low Alloy Steels ◽  
Dual Phase ◽  
Resource Requirement ◽  
Alloy Steels ◽  
Potential Weight

For fuel savings as well as energy and resource requirement, high strength low alloy steels (HSLA) are of particular interest to automobile industry because of the potential weight reduction which can be achieved by using thinner section of these steels to carry the same load and thus to improve the fuel mileage. Dual phase treatment has been utilized to obtain superior strength and ductility combinations compared to the HSLA of identical composition. Recently, cooling rate following heat treatment was found to be important to the tensile properties of the dual phase steels. In this paper, we report the results of the investigation of cooling rate on the microstructures and mechanical properties of several vanadium HSLA steels.The steels with composition (in weight percent) listed below were supplied by China Steel Corporation: 1. low V steel (0.11C, 0.65Si, 1.63Mn, 0.015P, 0.008S, 0.084Aℓ, 0.004V), 2. 0.059V steel (0.13C, 0.62S1, 1.59Mn, 0.012P, 0.008S, 0.065Aℓ, 0.059V), 3. 0.10V steel (0.11C, 0.58Si, 1.58Mn, 0.017P, 0.008S, 0.068Aℓ, 0.10V).

Lattice Imaging of Grain Boundaries in Ceramics

1977 ◽  
Vol 35 ◽  
pp. 114-115
Author(s):  
D. R. Clarke ◽  
G. Thomas
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Silicon Nitride ◽  
Grain Boundaries ◽  
High Temperature Strength ◽  
Current Interest ◽  
Lattice Imaging ◽  
Special Significance ◽  
Structural Applications ◽  
Refractory Ceramics

Grain boundaries have long held a special significance to ceramicists. In part, this has been because it has been impossible until now to actually observe the boundaries themselves. Just as important, however, is the fact that the grain boundaries and their environs have a determing influence on both the mechanisms by which powder compaction occurs during fabrication, and on the overall mechanical properties of the material. One area where the grain boundary plays a particularly important role is in the high temperature strength of hot-pressed ceramics. This is a subject of current interest as extensive efforts are being made to develop ceramics, such as silicon nitride alloys, for high temperature structural applications. In this presentation we describe how the techniques of lattice fringe imaging have made it possible to study the grain boundaries in a number of refractory ceramics, and illustrate some of the findings.

Electron Microscopic Observation of the Longitudinal Organization of Poly (p-Phenylene Terephthalamide) Fibers

1982 ◽  
Vol 40 ◽  
pp. 680-681
Author(s):  
Li Li-Sheng ◽  
L.F. Allard ◽  
W.C. Bigelow
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Scanning Electron Microscopy ◽  
Microscopic Observation ◽  
Electron Microscopic Observation ◽  
Electron Microscopic ◽  
Aromatic Polyamides ◽  
Radial Arrangement ◽  
Scanning Electron ◽  
Better Than

The aromatic polyamides form a class of fibers having mechanical properties which are much better than those of aliphatic polyamides. Currently, the accepted morphology of these fibers as proposed by M.G. Dobb, et al. is a radial arrangement of pleated sheets, with the plane of the pleats parallel to the axis of the fiber. We have recently obtained evidence which supports a different morphology of this type of fiber, using ultramicrotomy and ion-thinning techniques to prepare specimens for transmission and scanning electron microscopy.

Mechanical Properties and Dislocation Structure of Single Crystal Cdte Deformed in Compression at 300°C

1976 ◽  
Vol 34 ◽  
pp. 592-593
Author(s):  
Ernest L. Hall ◽  
J. B. Vander Sande
Keyword(s):  
Mechanical Properties ◽  
Single Crystal ◽  
Dislocation Structure ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Optical Devices ◽  
Semiconductor Compound ◽  
Wide Range ◽  
Sample Orientation

The present paper describes research on the mechanical properties and related dislocation structure of CdTe, a II-VI semiconductor compound with a wide range of uses in electrical and optical devices. At room temperature CdTe exhibits little plasticity and at the same time relatively low strength and hardness. The mechanical behavior of CdTe was examined at elevated temperatures with the goal of understanding plastic flow in this material and eventually improving the room temperature properties. Several samples of single crystal CdTe of identical size and crystallographic orientation were deformed in compression at 300°C to various levels of total strain. A resolved shear stress vs. compressive glide strain curve (Figure la) was derived from the results of the tests and the knowledge of the sample orientation.

TEM Studies of Grain Boundary Films in Si3N4 Ceramics

1991 ◽  
Vol 49 ◽  
pp. 930-931
Author(s):  
H.-J. Kleebe ◽  
J.S. Vetrano ◽  
J. Bruley ◽  
M. Rühle
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Silicon Nitride ◽  
Hot Isostatic Pressing ◽  
Amorphous Film ◽  
Liquid Phase Sintering ◽  
Second Phase ◽  
High Temperature Mechanical Properties ◽  
Triple Points ◽  
Boundary Films

It is expected that silicon nitride based ceramics will be used as high-temperature structural components. Though much progress has been made in both processing techniques and microstructural control, the mechanical properties required have not yet been achieved. It is thought that the high-temperature mechanical properties of Si3N4 are limited largely by the secondary glassy phases present at triple points. These are due to various oxide additives used to promote liquid-phase sintering. Therefore, many attempts have been performed to crystallize these second phase glassy pockets in order to improve high temperature properties. In addition to the glassy or crystallized second phases at triple points a thin amorphous film exists at two-grain junctions. This thin film is found even in silicon nitride formed by hot isostatic pressing (HIPing) without additives. It has been proposed by Clarke that an amorphous film can exist at two-grain junctions with an equilibrium thickness.

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