Highlighting the impact of shear strain on the SiO2 glass structure: From experiments to atomistic simulations

Abstract Ni-Ti is a key shape memory alloy (SMA) system for applications, being cheap and having good mechanical properties. Recently, atomistic simulations of Ni-Ti SMAs have been used with the purpose of revealing the nano-scale mechanisms that control superelasticity and the shape memory effect, which is crucial to guide alloying or processing strategies to improve materials performance. These atomistic simulations are based on molecular dynamics modelling that relies on (empirical) interatomic potentials. These simulations must reproduce accurately the mechanism of martensitic transformation and the microstructure that it originates, since this controls both superelasticity and the shape memory effect. As demonstrated by the energy minimization theory of martensitic transformations [Ball, James (1987) Archive for Rational Mechanics and Analysis, 100:13], the microstructure of martensite depends on the lattice parameters of the austenite and the martensite phases. Here, we compute the bounds of possible microstructural variations based on the experimental variations/uncertainties in the lattice parameter measurements. We show that both density functional theory and molecular dynamics lattice parameters are typically outside the experimental range, and that seemingly small deviations from this range induce large deviations from the experimental bounds of the microstructural predictions, with notable cases where unphysical microstructures are predicted to form. Therefore, our work points to a strategy for benchmarking and selecting interatomic potentials for atomistic modelling of shape memory alloys, which is crucial to modelling the development of martensitic microstructures and their impact on the shape memory effect.

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1178 High coronary wall shear strain developed more vulnerable plaque compared to low shear strain: a systematic review and meta-analysis

European Heart Journal - Cardiovascular Imaging ◽

10.1093/ehjci/jez319.677 ◽

2020 ◽

Vol 21 (Supplement_1) ◽

Author(s):

A B Bajraktari ◽

I B Bytyci ◽

S E Elezi ◽

M Y H Henein

Keyword(s):

Shear Strain ◽

Vulnerable Plaque ◽

Meta Analysis ◽

Necrotic Core ◽

Core Area ◽

Plaque Area ◽

Central Registry ◽

Wall Shear ◽

The Impact

Abstract Background and Aim Arterial wall strain has been proposed to impact the features of developed plaques. The aim of this meta-analysis is to assess the impact of different types of wall shear strain (WSS) on the changes of vulnerable plaque in coronary artery disease (CAD). Methods We systematically searched PubMed-Medline, EMBASE, Scopus, Google Scholar and the Cochrane Central Registry, from 1989 up to May 2019 in order to select clinical trials and observational studies, which assessed the relationship between WSS measured by intravascular ultrasound (IVUS) and morphology of plaque in CAD. Results In 7 studies, a total of 724 patients with 32,083 segments were recruited, with mean follow up 8.4 months. The pooled analysis showed that low WSS was associated with larger baseline lumen area WMD 2.55 [1.34 to 3.76, p < 0.001], smaller plaque area WMD -1.16 [-0.1.84 to -0.49, p = 0007] and necrotic core area WMD -0.45 [-0.78 to 0.14, p = 0.004], dense calcium score WMD -0.18 [-0.46 to 0.10, p = 0.01], and fibrous area WMD -0.79 [-1.84 to 0.30, p = 0.02] as well as smaller fibro-fatty area WMD -0.22 [-0.57 to 0.13, p = 0.02] compared to high WSS. At follow-up, the high WSS had regression of fibrous area, WMD -0.12 [-0.22 to -0.02, p = 0.02] and fibro-fatty area WMD -0.11 [-0.23 to -0.01, p = 0.04], reduction of plaque area WMD -0.09 [-0.17 to -0.02, p = 0.01] and increased dense calcium WMD 0.08 [0.02 to 0.14, p = 0.006] and necrotic core area WMD 0.07 [0.01 to 0.13, p = 0.03] compared to low WSS (Figure 1). The high WSS developed more profound remodeling compared to low WSS (40 vs. 18%, p < 0.05) with more constructive remodelling with low WSS (78%vs. 40 %, p < 0.01). Conclusions. Baseline high WSS is associated with higher necrotic core, calcium, fibrous and fibro-fatty area compared with low WSS, and during follow up the high WSS resulted in the development of more profound remodeling compared with low WSS. These findings highlighted the role of IVUS in detecting the vulnerable plaque in CAD. Abstract 1178 Figure 1. Mean change of plaque morpholo

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The Relationship between Coronary Artery Wall Shear Strain and Plaque Morphology: A Systematic Review and Meta-Analysis

Diagnostics ◽

10.3390/diagnostics10020091 ◽

2020 ◽

Vol 10 (2) ◽

pp. 91 ◽

Cited By ~ 2

Author(s):

Artan Bajraktari ◽

Ibadete Bytyçi ◽

Michael Y. Henein

Keyword(s):

Coronary Artery ◽

Shear Strain ◽

Meta Analysis ◽

Calcium Score ◽

Necrotic Core ◽

Plaque Burden ◽

Plaque Morphology ◽

Wall Shear ◽

The Impact ◽

The Relationship

Background and Aim: Arterial wall shear strain (WSS) has been proposed to impact the features of atherosclerotic plaques. The aim of this meta-analysis was to assess the impact of different types of WSS on plaque features in coronary artery disease (CAD). Methods: We systematically searched PubMed-Medline, EMBASE, Scopus, Google Scholar, and the Cochrane Central Registry, from 1989 up to January 2020 and selected clinical trials and observational studies which assessed the relationship between WSS, measured by intravascular ultrasound (IVUS), and plaque morphology in patients with CAD. Results: In four studies, a total of 72 patients with 13,098 coronary artery segments were recruited, with mean age 57.5 ± 9.5 years. The pooled analysis showed that low WSS was associated with larger baseline lumen area (WMD 2.55 [1.34 to 3.76, p < 0.001]), smaller plaque area (WMD −1.16 [−1.84 to −0.49, p = 0.0007]), lower plaque burden (WMD −12.7 [−21.4 to −4.01, p = 0.04]), and lower necrotic core area (WMD −0.32 [−0.78 to 0.14, p = 0.04]). Low WSS also had smaller fibrous area (WMD −0.79 [−1.88 to 0.30, p = 0.02]) and smaller fibro-fatty area (WMD −0.22 [−0.57 to 0.13, p = 0.02]), compared with high WSS, but the dense calcium score was similar between the two groups (WMD −0.17 [−0.47 to 0.13, p = 0.26]). No differences were found between intermediate and high WSS. Conclusions: High WSS is associated with signs of plaque instability such as higher necrotic core, higher calcium score, and higher plaque burden compared with low WSS. These findings highlight the role of IVUS in assessing plaque vulnerability.

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Twin boundary migration creating zero shear strain: In-situ TEM observations and atomistic simulations

Magnesium Technology 2013 ◽

10.1007/978-3-319-48150-0_18 ◽

2013 ◽

pp. 107-111 ◽

Cited By ~ 2

Author(s):

B. Y. Liu ◽

B. Li ◽

Z. W. Shan

Keyword(s):

Shear Strain ◽

Twin Boundary ◽

Boundary Migration ◽

Atomistic Simulations ◽

In Situ Tem

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The Wear Characteristics of Graphene as an Atomically-Thin Protective Coating

ASME/STLE 2012 International Joint Tribology Conference ◽

10.1115/ijtc2012-61135 ◽

2012 ◽

Author(s):

Emil Sandoz-Rosado ◽

Elon J. Terrell

Keyword(s):

Protective Coatings ◽

Solid Lubricants ◽

Atomistic Simulations ◽

Great Promise ◽

Load Carrying Capacity ◽

Sliding Velocity ◽

Substrate Rigidity ◽

Macro Scale ◽

Load Carrying ◽

The Impact

Lamellar atomically-thin sheets such as graphene (and its bulk equivalent graphite) and molybdenum disulfide have emerged as excellent solid lubricants at the macro scale and show great promise as protective coatings for nanoscopic applications. In this study, the failure mechanisms of graphene under sliding are examined using atomistic simulations. An atomic tip is slid over a graphene membrane that is adhered to a semi-infinite substrate. The impact of sliding velocity and substrate rigidity on the wear and frictional behavior of graphene is studied. In addition, the interplay of adhesive and abrasive wear on the graphene coating is also examined. The preliminary results indicate that graphene has excellent potential as a nanoscale due to its atomically-thin configuration and high load carrying capacity.

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Twist-driven separation of p-type and n-type dopants in single-crystalline nanowires

National Science Review ◽

10.1093/nsr/nwz014 ◽

2019 ◽

Vol 6 (3) ◽

pp. 532-539 ◽

Cited By ~ 3

Author(s):

Dong-Bo Zhang ◽

Xing-Ju Zhao ◽

Gotthard Seifert ◽

Kinfai Tse ◽

Junyi Zhu

Keyword(s):

Shear Strain ◽

Radial Distribution ◽

Atomistic Simulations ◽

Si Nanowires ◽

Modulation Doping ◽

Single Crystalline ◽

Host Atom ◽

Homogeneous Materials ◽

Radial Dimension ◽

P Type

The distribution of dopants significantly influences the properties of semiconductors, yet effective modulation and separation of p-type and n-type dopants in homogeneous materials remain challenging, especially for nanostructures. Employing a bond orbital model with supportive atomistic simulations, we show that axial twisting can substantially modulate the radial distribution of dopants in Si nanowires (NWs) such that dopants of smaller sizes than the host atom prefer atomic sites near the NW core, while dopants of larger sizes are prone to staying adjacent to the NW surface. We attribute such distinct behaviors to the twist-induced inhomogeneous shear strain in NW. With this, our investigation on codoping pairs further reveals that with proper choices of codoping pairs, e.g. B and Sb, n-type and p-type dopants can be well separated along the NW radial dimension. Our findings suggest that twisting may lead to realizations of p–n junction configuration and modulation doping in single-crystalline NWs.

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Numerical and Experimental Study on ECAP-Processing Parameters for Efficient Grain Refinement of AA5083 Sheet Metal

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.794.315 ◽

2019 ◽

Vol 794 ◽

pp. 315-323 ◽

Cited By ~ 1

Author(s):

Maximilian Gruber ◽

Christian Illgen ◽

Philipp Frint ◽

Martin F.X. Wagner ◽

Wolfram Volk

Keyword(s):

Shear Strain ◽

Grain Refinement ◽

Sheet Metal ◽

Electron Backscatter Diffraction ◽

Superplastic Forming ◽

Processing Parameters ◽

Geometrical Parameters ◽

Maximum Magnitude ◽

Applied Model ◽

The Impact

Equal-channel angular pressing (ECAP) is often used as effective tool for grain refinement for many different metallic materials. It is well known that grain size is an important microstructural feature influencing superplastic properties of fcc materials like aluminum alloys. The magnitude of introduced shear strain depends on geometrical parameters of the ECAP channel. In this contribution, the impact of different geometrical parameters of the ECAP channel on the resulting magnitude of introduced shear strain is analyzed. ECAP on AA5083 aluminum sheets with the dimensions of 200x200x1.8 mm3 is performed. Microhardness measurements reveal a considerable increase of hardness after ECAP and microstructural investigations by electron backscatter diffraction (EBSD) show the beginning formation of a deformation-induced substructure which is known to be a preliminary stage of the grain refinement process. It is assumed that this fine-grained microstructure results in an enhanced superplastic forming capability. Furthermore, a numerical model of the process based on the experimental results is established. The bending of the ECAP processed sheet metal as well as its microhardness are used for the validation of the model. The friction coefficient between the channel and the aluminum sheet significantly influences the results of the simulation. With the applied model different channel angles and inner corner radii are varied in order to determine a maximum magnitude of deformation resulting in sufficient grain refinement of the investigated material. With the help of the results gained in this study, suitable ECAP parameters for sheet metals can be derived that enable creating ultrafine-grained materials for superplastic forming operations.

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Atomistic Simulations on Metal Rod Penetrating Thin Target at Nanoscale Caused by High-Speed Collision

Nanomaterials ◽

10.3390/nano11113160 ◽

2021 ◽

Vol 11 (11) ◽

pp. 3160

Author(s):

Yong-Chao Wu ◽

Jin-Ming Liu ◽

Wei Xie ◽

Qing Yin ◽

Jian-Li Shao

Keyword(s):

High Speed ◽

Damage Mechanism ◽

Linear Increase ◽

Hypervelocity Impact ◽

Atomistic Simulations ◽

Micro Deformation ◽

Localized Plastic Deformation ◽

Scientific Value ◽

Solid Liquid ◽

The Impact

The penetration process has attracted increasing attention due to its engineering and scientific value. In this work, we investigate the deformation and damage mechanism about the nanoscale penetration of single-crystal aluminum nanorod with atomistic simulations, where distinct draw ratio (∅) and different incident velocities (up) are considered. The micro deformation processes of no penetration state (within 2 km/s) and complete penetration (above 3 km/s) are both revealed. The high-speed bullet can cause high pressure and temperature at the impacted region, promoting the localized plastic deformation and even solid-liquid phase transformation. It is found that the normalized velocity of nanorod reduces approximately exponentially during penetration (up < 3 km/s), but its residual velocity linearly increased with initial incident velocity. Moreover, the impact crater is also calculated and the corresponding radius is manifested in the linear increase trend with up while inversely proportional to the ∅. Interestingly, the uniform fragmentation is observed instead of the intact spallation, attributed to the relatively thin thickness of the target. It is additionally demonstrated that the number of fragments increases with increasing up and its size distribution shows power law damping nearly. Our findings are expected to provide the atomic insight into the micro penetration phenomena and be helpful to further understand hypervelocity impact related domains.

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Impact of Low Temperatures on Solder Joint Failures

Journal of Electronic Packaging ◽

10.1115/1.1465431 ◽

2002 ◽

Vol 124 (2) ◽

pp. 135-137 ◽

Cited By ~ 2

Author(s):

Boris Mirman

Keyword(s):

Solder Joint ◽

Shear Strain ◽

Low Temperatures ◽

Solder Joints ◽

Failure Criteria ◽

Plastic Shear ◽

Plastic Packages ◽

Plastic Shear Strain ◽

Thin Plastic ◽

The Impact

An experiment with solder joints of thin plastic packages, cycled between −10° and 110°C, has demonstrated that the majority of solder joint failures occurred at the low temperatures. In this experiment, the low temperatures caused high peeling stresses in the heel area of solder joints and, as usual, relatively low plastic shear strain (as compared with these strains at high temperatures). This fact suggests that the impact of solder peeling stresses on the solder failure is noticeably higher than is anticipated by applying the commonly used failure criteria.

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Study of Impact-Induced Mechanical Effects in Cell Direct Writing Using Smooth Particle Hydrodynamic Method

Journal of Manufacturing Science and Engineering ◽

10.1115/1.2896118 ◽

2008 ◽

Vol 130 (2) ◽

Cited By ~ 60

Author(s):

Wei Wang ◽

Yong Huang ◽

Mica Grujicic ◽

Douglas B. Chrisey

Keyword(s):

Shear Strain ◽

Mechanical Loading ◽

Cell Damage ◽

Smooth Particle Hydrodynamic ◽

Strain Component ◽

Direct Writing ◽

Maximum Shear Strain ◽

Smooth Particle Hydrodynamic Method ◽

Hydrodynamic Method ◽

The Impact

Biomaterial direct-write technologies have been receiving more and more attention as rapid prototyping innovations in the area of tissue engineering, regenerative medicine, and biosensor∕actuator fabrication based on computer-aided designs. However, cell damage due to the mechanical impact during cell direct writing has been observed and is a possible hurdle for broad applications of fragile cell direct writing. The objective of this study is to investigate the impact-induced cell mechanical loading profile in cell landing in terms of stress, acceleration, and maximum shear strain component during cell direct writing using a mesh-free smooth particle hydrodynamic method. Such cell mechanical loading profile information can be used to understand and predict possible impact-induced cell damage. It is found that the cell membrane usually undergoes a relatively severe deformation and the cell mechanical loading profile is dependent on the cell droplet initial velocity and the substrate coating thickness. Two important impact processes may occur during cell direct writing: the first impact between the cell droplet and the substrate coating and the second impact between the cell and the substrate. It is concluded that the impact-induced cell damage depends not only on the magnitudes of stress, acceleration, and∕or shear strain but also the loading history that a cell experiences.

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