scholarly journals Analysis of human emboli and thrombectomy forces in large-vessel occlusion stroke

2020 ◽  
pp. 1-9 ◽  
Author(s):  
Yang Liu ◽  
Yihao Zheng ◽  
Adithya S. Reddy ◽  
Daniel Gebrezgiabhier ◽  
Evan Davis ◽  
...  
Keyword(s):  
Glass Tube ◽  
Ultimate Tensile Stress ◽  
Material Behavior ◽  
Large Vessel ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Vessel Occlusion ◽  
Cell Percentage ◽  
Uniaxial Tensile Testing ◽  
Custom Made

OBJECTIVEThis study’s purpose was to improve understanding of the forces driving the complex mechanical interaction between embolic material and current stroke thrombectomy devices by analyzing the histological composition and strength of emboli retrieved from patients and by evaluating the mechanical forces necessary for retrieval of such emboli in a middle cerebral artery (MCA) bifurcation model.METHODSEmbolus analogs (EAs) were generated and embolized under physiological pressure and flow conditions in a glass tube model of the MCA. The forces involved in EA removal using conventional endovascular techniques were described, analyzed, and categorized. Then, 16 embolic specimens were retrieved from 11 stroke patients with large-vessel occlusions, and the tensile strength and response to stress were measured with a quasi-static uniaxial tensile test using a custom-made platform. Embolus compositions were analyzed and quantified by histology.RESULTSUniaxial tension on the EAs led to deformation, elongation, thinning, fracture, and embolization. Uniaxial tensile testing of patients’ emboli revealed similar soft-material behavior, including elongation under tension and differential fracture patterns. At the final fracture of the embolus (or dissociation), the amount of elongation, quantified as strain, ranged from 1.05 to 4.89 (2.41 ± 1.04 [mean ± SD]) and the embolus-generated force, quantified as stress, ranged from 63 to 2396 kPa (569 ± 695 kPa). The ultimate tensile strain of the emboli increased with a higher platelet percentage, and the ultimate tensile stress increased with a higher fibrin percentage and decreased with a higher red blood cell percentage.CONCLUSIONSCurrent thrombectomy devices remove emboli mostly by applying linear tensile forces, under which emboli elongate until dissociation. Embolus resistance to dissociation is determined by embolus strength, which significantly correlates with composition and varies within and among patients and within the same thrombus. The dynamic intravascular weakening of emboli during removal may lead to iatrogenic embolization.

Grain and Feature Size Effect on Material Behavior for Micro-Sheet-Forming

2014 ◽  
Vol 680 ◽  
pp. 77-80
Author(s):  
Mohd Azam Musa ◽  
Akhtar Razul Razali ◽  
Nazrul Idzham Kasim
Keyword(s):  
Sheet Forming ◽  
Material Behavior ◽  
Uniaxial Tensile ◽  
Surface Model ◽  
Uniaxial Tensile Test ◽  
Micro Forming ◽  
Feature Size ◽  
Uniaxial Tensile Testing ◽  
Feeding Process ◽  
Related Process

Negligible factors in bulk materials, such as grain-size effects, have proven inappropriate to be neglected for micro-forming processes. Studies had shown that material behavior varies greatly with the increasing of the scale in the micro-forming world. Therefore, in every micro-forming-related process, especially in micro-stamping, studies and analyses of each material used for the process have to be considered as indispensable in order to be able to understand their behavior and to be able to correlate their behavior with the process. Uniaxial tensile-testing experiments have been carried out to determine the strip’s properties, behavior and its correlation with the feeding process in micro-stamping/micro-sheet-forming application. Based on the results of the uniaxial tensile-test experiments conducted, the flow stress was found to decrease with the decrease of the strip thickness and vice versa, due to the size/scale effect. A surface model was used to explain the findings.

Design and development of aluminum alloy 6061-T6 pressure vessel liner for aerospace applications: A technical brief

2021 ◽  
pp. 146442072110651
Author(s):  
R Pramod ◽  
N Siva Shanmugam ◽  
C K Krishnadasan ◽  
G Radhakrishnan ◽  
Manu Thomas
Keyword(s):  
Tensile Strength ◽  
Aluminum Alloy ◽  
Weld Metal ◽  
Tensile Test ◽  
Pressure Vessel ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Aluminum Alloy 6061 ◽  
Custom Made ◽  
Alloy 6061

This work mainly focuses on designing a novel aluminum alloy 6061-T6 pressure vessel liner intended for use in launch vehicles. Fabrication of custom-made welding fixtures for the assembly of liner parts, namely two hemispherical domes and end boss, is illustrated. The parts of the liner are joined using the cold metal transfer welding process, and the welding trials are performed to arrive at an optimized parametric range. The metallurgical characterization of weld joint reveals the existence of dendritic structures (equiaxed and columnar). Microhardness of base and weld metal was 70 and 65 HV, respectively. The tensile strength of base and weld metal was 290 and 197 MPa, respectively, yielding a joint efficiency of 68%. Finite-element analysis of a uniaxial tensile test was performed to predict the tensile strength and location of the fracture in base and weld metal. The experimental and predicted tensile test results were found to be in good agreement.

Biomechanical and Elastographic Analysis of Mesenchymal Stromal Cell Treated Tissue Following Surgery

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
Hazel Marie ◽  
Yong Zhang ◽  
Jeremy Heffner ◽  
Heath A. Dorion ◽  
Diana L. Fagan
Keyword(s):  
Mechanical Property ◽  
Tensile Test ◽  
Tensile Testing ◽  
Recovery Period ◽  
Strain Analysis ◽  
Biomechanical Properties ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Ongoing Research ◽  
Uniaxial Tensile Testing

Hernia repair continues to be a problem facing surgeons today, particularly because of the high incidence of reoccurrence. This work presents preliminary data of a pioneering effort to investigate the effect of mesenchymal stromal cells (MSCs) on mechanical property enhancement in full thickness fascial defects. Heparinized MSCs harvested from a rabbit’s tibia/iliac crest were applied to two fascial defects on the rabbit’s abdominal wall, with two other defects acting as controls (no MSCs added). After an 8 week recovery period, the entire abdominal fascia was harvested for mechanical property testing and elastographic strain analysis. Preliminary results from uniaxial tensile testing indicate a significant increase in the modulus of toughness strain energy, with at least a 50% increase in the MSC treated defects as compared with the control defects. Results from the elastographic strain analysis show excellent correlation in the calibration of the elastography to the uniaxial tensile test, with nearly identical moduli of elasticity. In addition, the elastographs clearly show tissue property heterogeneity at all stages of tensile testing. The MSC treated tissue demonstrates promise of enhanced material properties over that of the nontreated tissue; testing and analysis is ongoing. The elastography provides pixel-level description of tissue property variations providing critical information on wound healing effectiveness that would be impossible with other methods. In the ongoing research, optical elastography, in combination with the traditional tensile test and tissue histology, will be used to characterize localized biomechanical properties directly within the defect area and to locate “crack” initiation and propagation sights as the material is strained to rupture.

Finite Element Analysis on Nitinol Medical Applications

2002 ◽  
Author(s):  
Xiao-Yan Gong ◽  
Alan R. Pelton
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Material Behavior ◽  
Nonlinear Material ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Element Analysis ◽  
Highly Nonlinear ◽  
Device Applications ◽  
Specific Material

Nitinol, an alloy of about 50% Ni and 50% Ti, is a very unique material. At constant temperature above its Austenite finish (Af) temperature, under uniaxial tensile test, the material is highly nonlinear and capable of large deformation to the ultimate strain on the order of 15%. This material behavior, known as superelasticity, along with its excellent biocompatibility and corrosion resistance, makes Nitinol a perfect material candidate for many medical device applications. However, the nonlinear material response also requires a specific material description to perform the stress analysis. The user developed material subroutine from HKS/West makes the simulation of the Nitinol devices possible. This article presents two case studies of the nonlinear finite element analysis using ABAQUS/Standard and the Nitinol UMAT.

SMALL PUNCH TESTING: AN ALTERNATIVE TESTING TECHNIQUE TO EVALUATE TENSILE BEHAVIOR OF CORTICAL BONE

2017 ◽  
Vol 17 (06) ◽  
pp. 1750102
Author(s):  
JAGJIT SINGH ◽  
N. K. SHARMA ◽  
SATBIR S. SEHGAL
Keyword(s):  
Elastic Modulus ◽  
Tensile Test ◽  
Cortical Bone ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Testing Technique ◽  
Bone Material ◽  
Small Punch ◽  
Uniaxial Tensile Testing ◽  
Deformational Behavior

The tensile properties of cortical bone are usually determined with the help of uniaxial tensile test which requires enough amount of bone material. Further, it is very complicated to examine the heterogeneity and anisotropy associated with the deformational properties of cortical bone with the help of uniaxial tensile test. Through this study, small punch testing has been proposed as an alternate technique to evaluate the deformational behavior of cortical bone utilizing optimum amount of bone material. The comparison between elastic modulus values obtained from tensile test and stiffness values obtained through small punch testing was done for validation. The values of these properties were found to be having a significant positive correlation with each other. The effects of bone density and compositional parameters on these properties were also found to be having a similar trend. It is observed through this study that stiffness values from small punch technique are having a similarity with elastic modulus values from uniaxial tensile testing. It is proposed that small punch testing technique can be used as an alternate to examine the deformational behavior of cortical bone.

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.

Mechanical Response of Ti-6Al-4V Alloy on Deformation at Moderate Temperatures

2013 ◽  
Vol 549 ◽  
pp. 311-316 ◽  
Author(s):  
Marion Merklein ◽  
Hinnerk Hagenah ◽  
Markus Kaupper ◽  
Adam Schaub
Keyword(s):  
Titanium Alloy ◽  
Elevated Temperatures ◽  
Mechanical Response ◽  
Material Behavior ◽  
High Yield ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Forming Process ◽  
Element Analysis ◽  
Specific Strength

Due to beneficial characteristics such as high specific strength, corrosion resistance and biocompatibility Ti-6Al-4V alloy has become the most important industrially produced titanium alloy during the last decades. Commonly used for aerospace technology and medical products, nowadays Ti-6Al-4V covers 50% of the worldwide produced titanium alloy parts. Different deformation operations as forging and casting as well as machining are used to shape titanium alloy components. For sheet metals, cost and time of fabrication can be reduced significantly via the near net shape technology sheet metal forming. Materials such as the α + β alloy Ti-6Al-4V with high yield stress and comparatively low elastic modules need to be formed at elevated temperatures to increase their formability. Numerical simulations are applied to calculate the forming behavior during the process and conclude the characteristics of the shaped part. Therefore in this paper the mechanical behavior of this titanium alloy is investigated by uniaxial tensile test within elevated temperatures ranging from 250 to 500 °C. Finally, the experimental results are adapted to models which predict the flow response in order to describe material behavior in finite element analysis of the forming process.

An innovation in finite element simulation via crystal plasticity assessment of grain morphology effect on sheet metal formability

2021 ◽  
pp. 146442072110246
Author(s):  
Mostafa Habibi ◽  
Roya Darabi ◽  
Jose C de Sa ◽  
Ana Reis
Keyword(s):  
Finite Element ◽  
Tensile Test ◽  
Crystal Plasticity ◽  
Forming Limit Diagram ◽  
Material Behavior ◽  
Forming Limit ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Polycrystal Plasticity ◽  
Grain Distribution

Experimental and numerical study regarding the uniaxial tensile test and the forming limit diagram are addressed in this paper for AL2024 with the face-centered cube structure. First, representation of a grain structure can be obtained directly by mapping metallographic observations via scanning electron microscopy approach. Artificial grain microstructures produced by Voronoi Tessellation method are employed in the model using VGRAIN software. By resorting to the finite element software (ABAQUS) capabilities, the constitutive equations of the crystal plasticity were utilized and implemented as a user subroutine material UMAT code. The hardening parameters were calibrated by a trial and error approach in order to fit experimental tensile results with the simulation. Then the effect of the changing grain size, the heterogeneity factor, and the grain aspect ratio were studied for a uniaxial tensile test to emphasize the importance of the microstudy behavior of grains in material behavior. Furthermore, the polycrystal plasticity grain distribution was employed in the Nakazima test in order to obtain the forming limit diagram. The crystal plasticity-driven forming limit diagram reveals more accurate strains, taking into account the involving the micromechanical features of the grains. An innovative approach is pursued in this study to discover the necking angle, both in tensile test or Nakazima samples, showing a good agreement with the experiment results.

scholarly journals In Situ Macroscopic Tensile Testing in SEM and Electron Channeling Contrast Imaging: Pencil Glide Evidenced in a Bulk β-Ti21S Polycrystal

Materials ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2479
Author(s):  
Meriem Ben Haj Slama ◽  
Nabila Maloufi ◽  
Julien Guyon ◽  
Slim Bahi ◽  
Laurent Weiss ◽  
...  
Keyword(s):  
Tensile Testing ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Contrast Imaging ◽  
Bulk Specimen ◽  
Electron Channeling ◽  
Uniaxial Tensile Testing ◽  
Stress States ◽  
Tangled Dislocation

In this paper, we report the successful combination of macroscopic uniaxial tensile testing of bulk specimen combined with In situ dislocation-scale observations of the evolution of deformation microstructures during loading at several stress states. The dislocation-scale observations were performed by Accurate Electron Channeling Contrast Imaging in order to follow the defects evolution and their interactions with grain boundaries for several regions of interest during macroscopic loading. With this novel in situ procedure, the slip systems governing the deformation in polycrystalline bulk β-Ti21S are tracked during the macroscopic uniaxial tensile test. For instance, curved slip lines that are associated with “pencil glide” phenomenon and tangled dislocation networks are evidenced.

scholarly journals Fibrin Prestress Due to Platelet Aggregation and Contraction Increases Clot Stiffness

2021 ◽  
Author(s):  
Suyog Jitendra Pathare ◽  
Wilson Eng ◽  
Sang-Joon J Lee ◽  
Anand Ramasubramanian
Keyword(s):  
Platelet Aggregation ◽  
Mechanical Response ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Fibrin Networks ◽  
Custom Made ◽  
Simulation Based ◽  
Blood Clots ◽  
Platelet Aggregates ◽  
Underlying Mechanisms

Efficient haemorrhagic control is attained through the formation of strong and stable blood clots at the site of injury. Although it is known that platelet-driven contraction can dramatically influence clot stiffness, the underlying mechanisms by which platelets assist fibrin networks in resisting external loads are not understood. In this study, we delineate the contribution of platelet-fibrin interactions to clot tensile mechanics using a combination of new mechanical measurements, image analysis, and structural mechanics simulation. Based on uniaxial tensile test data using custom-made microtensometer, and fluorescence microscopy of platelet aggregation and platelet-fibrin interactions, we show that integrin-mediated platelet aggregation and actomyosin-driven platelet contraction synergistically increase the elastic modulus of the clots. We demonstrate that the mechanical and geometric response of an active contraction model of platelet aggregates compacting vicinal fibrin is consistent with the experimental data. The model suggests that platelet contraction induces prestress in fibrin fibres, and increases the effective stiffness in both crosslinked and non-crosslinked clots. Our results provide evidence for fibrin compaction at discrete nodes as a major determinant of mechanical response to applied loads.

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