scholarly journals Fluid Structural Analysis of Human Cerebral Aneurysm Using Their Own Wall Mechanical Properties

2013 ◽  
Vol 2013 ◽  
pp. 1-18 ◽  
Author(s):  
Alvaro Valencia ◽  
Patricio Burdiles ◽  
Miguel Ignat ◽  
Jorge Mura ◽  
Eduardo Bravo ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Internal Pressure ◽  
Cerebral Aneurysm ◽  
Variable Thickness ◽  
Solid Mechanics ◽  
Cfd Simulation ◽  
Realistic Model ◽  
Normal Variable ◽  
Computational Structural Dynamics ◽  
The One

Computational Structural Dynamics (CSD) simulations, Computational Fluid Dynamics (CFD) simulation, and Fluid Structure Interaction (FSI) simulations were carried out in an anatomically realistic model of a saccular cerebral aneurysm with the objective of quantifying the effects of type of simulation on principal fluid and solid mechanics results. Eight CSD simulations, one CFD simulation, and four FSI simulations were made. The results allowed the study of the influence of the type of material elements in the solid, the aneurism’s wall thickness, and the type of simulation on the modeling of a human cerebral aneurysm. The simulations use their own wall mechanical properties of the aneurysm. The more complex simulation was the FSI simulation completely coupled with hyperelastic Mooney-Rivlin material, normal internal pressure, and normal variable thickness. The FSI simulation coupled in one direction using hyperelastic Mooney-Rivlin material, normal internal pressure, and normal variable thickness is the one that presents the most similar results with respect to the more complex FSI simulation, requiring one-fourth of the calculation time.

SENSITIVITY ANALYSIS OF COMPUTATIONAL STRUCTURAL DYNAMICS IN A CEREBRAL ANEURYSM MODEL TO WALL THICKNESS AND MODEL

2012 ◽  
Vol 12 (03) ◽  
pp. 1250054 ◽  
Author(s):  
ALVARO VALENCIA ◽  
MAXIMILIANO ROJO ◽  
RODRIGO RIVERA ◽  
EDUARDO BRAVO
Keyword(s):  
Cerebral Aneurysm ◽  
Structural Dynamics ◽  
Wall Thickness ◽  
Three Dimensional ◽  
Image Data ◽  
Realistic Model ◽  
Aneurysm Wall ◽  
Computational Structural Dynamics ◽  
Different Thickness ◽  
Aneurysm Model

Intracranial saccular aneurysms tend to be thin walled and stiffer compared with a normal artery. The current work describes computational structural dynamics (CSD) in an anatomically realistic model of a cerebral aneurysm located in the ophthalmic region, using different wall thickness, model data for the artery and aneurysm, and geometry size. The model was obtained from three-dimensional rotational angiography image data. The wall was assumed three-dimensional hyperelastic solid with different thickness in the artery and in the aneurysm regions. The effects of carotid siphon length are reported. The CSD was solved with the finite elements package ADINA. The predictions of stress and strain on the aneurysm wall were compared.

scholarly journals Mechanical properties of a hybrid auxetic metamaterial and metastructure system

2021 ◽  
pp. 073168442110095
Author(s):  
Wenjiao Zhang ◽  
Shuyuan Zhao ◽  
Rujie Sun ◽  
Fabrizio Scarpa ◽  
Jinwu Wang
Keyword(s):  
Mechanical Properties ◽  
Finite Elements ◽  
Internal Pressure ◽  
Flexible Electronics ◽  
Mechanical Performance ◽  
Unit Cell ◽  
Geometric Parameters ◽  
Mechanical Behaviors ◽  
Unit Cells ◽  
The One

We propose in this work an innovative hybrid auxetic metamaterial with a centersymmetric unit cell and tessellation topology similar to the one provided by the missing rib configuration. The tessellation proposed is applied to different core unit cells (star shape, cross-chiral shape with same dimensions, and reentrant). The effects of the geometric parameters of the cells on the in-plane mechanical properties of this hybrid auxetic metamaterial system are investigated via finite elements (FEMs). Representative unit cells (RUCs) with optimal mechanical behaviors are identified; those configurations exhibit the larger negative Poisson’s ratios and enhanced specific moduli. Designs related to two groups of auxetic metastructures with cylindric and cubic shapes are then developed based on the optimized RUCs along x and y directions. The equivalent mechanical performance of these metastructures under internal pressure is evaluated from a numerical standpoint. Auxetic cylindrical metastructures can be tailored by adjusting the number of the optimized RUCs along the circumferential and longitudinal directions, together with the geometric parameters of the optimized RUC itself. These hybrid auxetic metamaterials and metastructures provide the potential for multifunctional applications in biomechanics, flexible electronics, and aerospace.

scholarly journals Two-phase CFD simulation of the monodyspersed suspension hydraulic behaviour in the tank apparatus from a circulatory pipe

2008 ◽  
Vol 10 (1) ◽  
pp. 22-27 ◽  
Author(s):  
Roch Plewik ◽  
Piotr Synowiec ◽  
Janusz Wójcik
Keyword(s):  
Cfd Simulation ◽  
Fluidised Bed ◽  
Cfd Simulations ◽  
Two Phase ◽  
Hydraulic Behaviour ◽  
Hydraulic Conditions ◽  
The One ◽  
Cfd Method ◽  
Multi Phase ◽  
The Ideal

Two-phase CFD simulation of the monodyspersed suspension hydraulic behaviour in the tank apparatus from a circulatory pipe The hydrodynamics in fluidized-bed crystallizers is studied by CFD method. The simulations were performed by a commercial packet of computational fluid dynamics Fluent 6.x. For the one-phase modelling (15), a standard k-ε model was applied. In the case of the two-phase flows the Eulerian multi-phase model with a standard k-ε method, aided by the k-ε dispersed model for viscosity, has been used respectively. The collected data put a new light on the suspension flow behaviour in the annular zone of the fluidised bed crystallizer. From the presented here CFD simulations, it clearly issues that the real hydraulic conditions in the fluidised bed crystallizers are far from the ideal ones.

scholarly journals The Influence of Different Plasma Cell Discharges on the Performance Quality of Surgical Gown Samples

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4329
Author(s):  
Atif H. Asghar ◽  
Ahmed Rida Galaly
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Exposure Time ◽  
Electrical Characteristics ◽  
Cathode Fall ◽  
Treatment Efficiency ◽  
Performance Quality ◽  
Surgical Gown ◽  
The One

An experimental study was performed on a low-density plasma discharge using two different configurations of the plasma cell cathode, namely, the one mesh system electrodes (OMSE) and the one mesh and three system electrodes (OMTSE), to determine the electrical characteristics of the plasma such as current–voltage characteristics, breakdown voltage (VB), Paschen curves, current density (J), cathode fall thickness (dc), and electron density of the treated sample. The influence of the electrical characteristics of the plasma fluid in the cathode fall region for different cathode configuration cells (OMSE and OMTSE) on the performance quality of a surgical gown was studied to determine surface modification, treatment efficiency, exposure time, wettability property, and mechanical properties. Over a very short exposure time, the treatment efficiency for the surgical gown surface of plasma over the mesh cathode at a distance equivalent to the cathode fall distance dc values of the OMTSE and for OMSE reached a maximum. The wettability property decreased from 90 to 40% for OMTSE over a 180 s exposure time and decreased from 90 to 10% for OMSE over a 160 s exposure time. The mechanisms of each stage of surgical gown treatment by plasma are described. In this study, the mechanical properties of the untreated and treated surgical gown samples such as the tensile strength and elongation percentage, ultimate tensile strength, yield strength, strain hardening, resilience, toughness, and fracture (breaking) point were studied. Plasma had a more positive effect on the mechanical properties of the OMSE reactor than those of the OMTSE reactor.

scholarly journals Insights into Mechanical Properties of the 1980 Irpinia Fault System from the Analysis of a Seismic Sequence

Geosciences ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 28
Author(s):  
Gaetano Festa ◽  
Guido Maria Adinolfi ◽  
Alessandro Caruso ◽  
Simona Colombelli ◽  
Grazia De Landro ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Early Warning Systems ◽  
Fault System ◽  
Minimum Size ◽  
Double Difference ◽  
Warning Systems ◽  
Initiation Mechanism ◽  
Earthquake Early Warning Systems ◽  
The One

Seismic sequences are a powerful tool to locally infer geometrical and mechanical properties of faults and fault systems. In this study, we provided detailed location and characterization of events of the 3–7 July 2020 Irpinia sequence (southern Italy) that occurred at the northern tip of the main segment that ruptured during the 1980 Irpinia earthquake. Using an autocorrelation technique, we detected more than 340 events within the sequence, with local magnitude ranging between −0.5 and 3.0. We thus provided double difference locations, source parameter estimation, and focal mechanisms determination for the largest quality events. We found that the sequence ruptured an asperity with a size of about 800 m, along a fault structure having a strike compatible with the one of the main segments of the 1980 Irpinia earthquake, and a dip of 50–55° at depth of 10.5–12 km and 60–65° at shallower depths (7.5–9 km). Low stress drop release (average of 0.64 MPa) indicates a fluid-driven initiation mechanism of the sequence. We also evaluated the performance of the earthquake early warning systems running in real-time during the sequence, retrieving a minimum size for the blind zone in the area of about 15 km.

scholarly journals The Rules for the Lattice Rotation Accompanying Slip as Derived From a Self-Consistent Model

1999 ◽  
Vol 31 (4) ◽  
pp. 217-230 ◽  
Author(s):  
R. A. Lebensohn ◽  
T. Leffers
Keyword(s):  
Solid Mechanics ◽  
Grain Shape ◽  
Rolling Plane ◽  
Lattice Rotation ◽  
Consistent Model ◽  
Plane Strain Deformation ◽  
Self Consistent ◽  
The One ◽  
Equiaxed Grains ◽  
Very High

The rules for the lattice rotation during rolling (plane strain) deformation of fcc polycrystals are studied with a viscoplastic self-consistent model. Very high values of the ratesensitivity exponent are used in order to establish Sachs-type conditions with large local deviations from the macroscopic strain. The lattice rotation depends on the grain shape. For equiaxed grains the lattice rotation follows the MA rule, which is the one normally used in solid mechanics. For elongated and flat grains the lattice rotation follows a different rule, the PSA rule. In the standard version the model performs a transition from MA to PSA with increasing strain. There is avery clear difference between the textures resulting from the two different rules. MA leads to a copper-type texture, and PSA leads to a brass-type texture.

Evaluation of changes in mechanical properties of O-ring in one-piece and two-piece ball retained implant-supported overdentures: A three-year retrospective study.

2021 ◽  
Author(s):  
Fathima Banu Raza ◽  
Anand Kumar
Keyword(s):  
Mechanical Properties ◽  
Wear Resistance ◽  
Retrospective Study ◽  
Statistical Analysis ◽  
Wear Rate ◽  
Digital Camera ◽  
Maximum Displacement ◽  
Pin On Disc ◽  
The One ◽  
Insight Into

The o-rings in ball retained overdentures deteriorate with time and need replacement to restore the retentive quality. We evaluated retrospectively the mechanical properties of o-rings after 3 years in function in one and two-piece implant-supported overdentures. The o-rings were retrieved from one-piece (Myriad snap, Equinox-Straumann, 3.3 x 13mm) and two-piece (Neo Biotech, 3.3 x 13mm) implant-supported overdenture patients. A total of 16 pairs of matrices were tested for wear, type of damage and elasticity using Pin on Disc method, USB Digital Camera in 30x zoom and Universal Tensile Machine respectively. The statistical analysis for independent groups were done with the Mann-Whitney U test. Assessment of used O-rings showed 84% more wear in the two-piece system with an abrasive type of damage while 46% wear in the one-piece system with a compressive type of damage. The o-rings in one-piece system showed increase in elongation and maximum displacement to 2% and 7% respectively, while two-piece system showed decrease in elongation and maximum displacement by 13% and 6% respectively. In one-piece system, the loss of retention was more with slow wear rate and in two-piece system, the wear resistance of O-rings decreased due to increased stiffness. Further studies to evaluate the changes in O-ring with increased sample size and at interval 1 year will pave way for insight into the progressive changes in the mechanical properties of an O-ring.

scholarly journals A filtered renewal process as a model for a river flow

2005 ◽  
Vol 2005 (1) ◽  
pp. 49-59 ◽  
Author(s):  
Mario Lefebvre
Keyword(s):  
Poisson Process ◽  
Exponential Distribution ◽  
Renewal Process ◽  
River Flow ◽  
Realistic Model ◽  
Delaware River ◽  
The Usa ◽  
The One ◽  
Peak Value

Various models, based on a filtered Poisson process, are used for the flow of a river. The aim is to forecast the next peak value of the flow, given that another peak was observed not too long ago. The most realistic model is the one when the time between the successive peaks doesnothave an exponential distribution, as is often assumed. An application to the Delaware River, in the USA, is presented.

EFFECT OF BORATES AND SILICATES ON WEARING PROPERTIES OF MAO COATINGS

2016 ◽  
Vol 24 (05) ◽  
pp. 1750061
Author(s):  
Yu ZHANG ◽  
YAN-WEI ZHAO ◽  
NAN XIANG ◽  
REN-GUO SONG
Keyword(s):  
Mechanical Properties ◽  
Aluminum Alloy ◽  
Treatment Time ◽  
Microarc Oxidation ◽  
Smooth Structure ◽  
Electrolytic Bath ◽  
Optimum Treatment ◽  
The One ◽  
Wear Tests

In the present study, microarc oxidation (MAO) coatings were formed on ZL101A aluminum alloy in an electrolytic bath containing 3[Formula: see text]g/L KOH [Formula: see text] 2[Formula: see text]g/L Na2WO[Formula: see text] 4[Formula: see text]g/L KF. The morphology and wearing behavior were investigated. In both electrolytes, the additives were borates (Na2B4O718[Formula: see text]g/L) and silicates (Na2SiO3 18[Formula: see text]g/L), respectively. It was found that the coating formed in borates-containing electrolyte was of compact and smooth structure than that of the one formed in silicates-containing electrolyte at the optimum treatment time. It was found that all the coatings were composed of á-Al2O3 and ã-Al2O3. The microhardness and wear tests proved that the coating formed in borates-containing electrolyte was having better mechanical properties than those of the coating formed in silicates-containing electrolyte.

Improving the Mechanical Properties of AZ31 Mg Alloy by High Ratio Extrusion

2006 ◽  
Vol 503-504 ◽  
pp. 865-870 ◽  
Author(s):  
Yongjun Chen ◽  
Qu Dong Wang ◽  
Jianguo Peng ◽  
Chun Quan Zhai
Keyword(s):  
Mechanical Properties ◽  
High Strength ◽  
High Ratio ◽  
Extrusion Ratio ◽  
Mg Alloy ◽  
Fine Grained ◽  
Az31 Mg Alloy ◽  
Industry Applications ◽  
One Step ◽  
The One

Experiments were conducted both to evaluate the potential for grain refinement, the subsequent mechanical properties at room temperature in samples of AZ31 Mg alloy and also to investigate the relationship between one-step and two-step high ratio extrusion (HRE). The one-step HRE was undertaken using a high extrusion ratio of 70:1 at 250, 300 and 350°C. And the two-step HRE was conducted with an extrusion ratio of 7 for the first step at 250, 300 and 350°C, followed by a second-step extrusion with an extrusion ratio of 10 at 250, 300 and 350°C. The initial grain size in the AZ31 ingot was 100μm and that after one-step HRE became similar to 5μm, after two-step HRE at 250, 300 and 350°C were 2, 4, 7μm, respectively, resulting in superior mechanical properties at ambient temperature. The microstructure of two-step HRE was finer and uniformer than that of one-step HRE and the strength of one-step and two-step HRE were similar, moreover, the elongation of one-step HRE was improved markedly than that of two-step HRE. Dynamic recrystallization and adjacent grain broking during HRE is introduced to explain the effects of one-step and two-step HRE on the microstructure and mechanical properties of AZ31 Mg alloy. The current results imply that the simple HRE method might be a feasible processing method for industry applications, and the multiply steps extrusion are effective to fabricate high strength of fine grained hcp metals.

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