Time dependent nonlinear shear stress effects in simple liquids: A molecular dynamics study

1980 ◽  
Vol 73 (8) ◽  
pp. 3987-3996 ◽  
Author(s):  
D. M. Heyes ◽  
J. J. Kim ◽  
C. J. Montrose ◽  
T. A. Litovitz
Keyword(s):  
Molecular Dynamics ◽  
Shear Stress ◽  
Time Dependent ◽  
Simple Liquids ◽  
Stress Effects ◽  
Nonlinear Shear

scholarly journals Studying dynamic stress effects on the behaviour of THP-1 cells by microfluidic channels

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Semra Zuhal Birol ◽  
Rana Fucucuoglu ◽  
Sertac Cadirci ◽  
Ayca Sayi-Yazgan ◽  
Levent Trabzon
Keyword(s):  
Endothelial Cells ◽  
Shear Stress ◽  
Vascular System ◽  
Circulatory System ◽  
Disease Process ◽  
Microfluidic Channels ◽  
Shear Stresses ◽  
Stress Effects ◽  
Adhesion Behavior ◽  
Cycling System

AbstractAtherosclerosis is a long-term disease process of the vascular system that is characterized by the formation of atherosclerotic plaques, which are inflammatory regions on medium and large-sized arteries. There are many factors contributing to plaque formation, such as changes in shear stress levels, rupture of endothelial cells, accumulation of lipids, and recruitment of leukocytes. Shear stress is one of the main factors that regulates the homeostasis of the circulatory system; therefore, sudden and chronic changes in shear stress may cause severe pathological conditions. In this study, microfluidic channels with cavitations were designed to mimic the shape of the atherosclerotic blood vessel, where the shear stress and pressure difference depend on design of the microchannels. Changes in the inflammatory-related molecules ICAM-1 and IL-8 were investigated in THP-1 cells in response to applied shear stresses in an continuous cycling system through microfluidic channels with periodic cavitations. ICAM-1 mRNA expression and IL-8 release were analyzed by qRT-PCR and ELISA, respectively. Additionally, the adhesion behavior of sheared THP-1 cells to endothelial cells was examined by fluorescence microscopy. The results showed that 15 Pa shear stress significantly increases expression of ICAM-1 gene and IL-8 release in THP-1 cells, whereas it decreases the adhesion between THP-1 cells and endothelial cells.

Impact of vibronic coupling effects on light-driven charge transfer in pyrene-functionalized middle and large-sized Metalloid Gold Nanoclusters from Ehrenfest dynamics.

2021 ◽  
Author(s):  
Adrian Dominguez-Castro ◽  
Thomas Frauenheim
Keyword(s):  
Molecular Dynamics ◽  
Charge Transfer ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Gold Nanoclusters ◽  
Tight Binding ◽  
Time Dependent ◽  
Effective Strategy ◽  
Dynamics Simulations ◽  
Dependent Density

Theoretical calculations are an effective strategy to comple- ment and understand experimental results in atomistic detail. Ehrenfest molecular dynamics simulations based on the real-time time-dependent density functional tight-binding (RT-TDDFTB) approach...

scholarly journals Time-Dependent Response of a Recycled C&D Material-Geotextile Interface under Direct Shear Mode

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3070
Author(s):  
Fernanda Bessa Ferreira ◽  
Paulo M. Pereira ◽  
Castorina Silva Vieira ◽  
Maria de Lurdes Lopes
Keyword(s):  
Shear Stress ◽  
Stress Relaxation ◽  
Shear Displacement ◽  
Time Dependent ◽  
Shear Behaviour ◽  
Displacement Rate ◽  
Shear Mode ◽  
Direct Shear ◽  
Constant Displacement ◽  
Shear Box

Geosynthetic-reinforced soil structures have been used extensively in recent decades due to their significant advantages over more conventional earth retaining structures, including the cost-effectiveness, reduced construction time, and possibility of using locally-available lower quality soils and/or waste materials, such as recycled construction and demolition (C&D) wastes. The time-dependent shear behaviour at the interfaces between the geosynthetic and the backfill is an important factor affecting the overall long-term performance of such structures, and thereby should be properly understood. In this study, an innovative multistage direct shear test procedure is introduced to characterise the time-dependent response of the interface between a high-strength geotextile and a recycled C&D material. After a prescribed shear displacement is reached, the shear box is kept stationary for a specific period of time, after which the test proceeds again, at a constant displacement rate, until the peak and large-displacement shear strengths are mobilised. The shear stress-shear displacement curves from the proposed multistage tests exhibited a progressive decrease in shear stress with time (stress relaxation) during the period in which the shear box was restrained from any movement, which was more pronounced under lower normal stress values. Regardless of the prior interface shear displacement and duration of the stress relaxation stage, the peak and residual shear strength parameters of the C&D material-geotextile interface remained similar to those obtained from the conventional (benchmark) tests carried out under constant displacement rate.

Analysis of tunnels in shaly rock considering three-dimensional stress effects on swelling

2005 ◽  
Vol 42 (1) ◽  
pp. 1-12 ◽  
Author(s):  
B C Hawlader ◽  
K Y Lo ◽  
I D Moore
Keyword(s):  
Finite Element ◽  
Closed Form ◽  
Cold Water ◽  
Principal Direction ◽  
Three Dimensional ◽  
Closed Form Solution ◽  
Time Dependent ◽  
Stress Effect ◽  
Stress Effects ◽  
Laboratory Test Results

Underground structures in shales or shaly rocks endure time-dependent swelling effects. Laboratory test results show that the swelling of these shales is dependent on three-dimensional stresses; an external stress on a specimen in one principal direction reduces the swelling not only in that direction but also perpendicularly. The effectiveness of a time-dependent swelling model that considers the three-dimensional stress effect is presented in this paper. A finite element algorithm incorporating the new constitutive model is used for a numerical analysis. The finite element program is used to analyze two tunnels in southern Ontario: the Heart Lake storm sewer tunnel, and the Darlington cold-water intake tunnel. The predicted results agree well with the records of field performance of these tunnels. The comparison between present analyses and the existing closed-form solution shows that the existing solution overestimates the time-dependent swelling effects. The three-dimensional stress effects on swelling are not considered in the closed-form solutions and are the cause of this discrepancy. The pseudo-Poisson's effect is a key parameter for modelling the observed time-dependent swelling. The use of these solutions in design is discussed.Key words: time-dependent swelling, shale, modelling, three-dimensional stress effect, finite element method, tunnel.

scholarly journals Soil irrigation frequencies, compaction, air porosity and shear stress effects on soybean root development

2015 ◽  
Vol 25 (1) ◽  
pp. 22-30 ◽  
Author(s):  
G. A. Hossne ◽  
J. Méndez ◽  
M. Trujillo ◽  
F. Parra
Keyword(s):  
Shear Stress ◽  
Root Development ◽  
Soybean Root ◽  
Stress Effects ◽  
Soil Irrigation

scholarly journals Shear-rate dependence of thermodynamic properties of the Lennard-Jones truncated and shifted fluid by molecular dynamics simulations

2021 ◽  
Author(s):  
Martin P. Lautenschlaeger ◽  
Hans Hasse
Keyword(s):  
Molecular Dynamics ◽  
Shear Stress ◽  
Shear Rate ◽  
Molecular Dynamics Simulations ◽  
Local Structure ◽  
Rate Dependence ◽  
Lennard Jones ◽  
Fluid Properties ◽  
Dynamics Simulations ◽  
Shear Rate Dependence

It was shown recently that using the two-gradient method, thermal, caloric, and transport properties of fluids under quasi-equilibrium conditions can be determined simultaneously from nonequilibrium molecular dynamics simulations. It is shown here that the influence of shear stresses on these properties can also be studied using the same method. The studied fluid is described by the Lennard-Jones truncated and shifted potential with the cut-off radius r*c = 2.5σ. For a given temperature T and density ρ, the influence of the shear rate on the following fluid properties is determined: pressure p, internal energy u, enthalpy h, isobaric heat capacity cp, thermal expansion coefficient αp, shear viscosity η, and self-diffusion coefficient D. Data for 27 state points in the range of T ∈ [0.7, 8.0] and ρ ∈ [0.3, 1.0] are reported for five different shear rates (γ ̇ ∈ [0.1,1.0]). Correlations for all properties are provided and compared with literature data. An influence of the shear stress on the fluid properties was found only for states with low temperature and high density. The shear-rate dependence is caused by changes in the local structure of the fluid which were also investigated in the present work. A criterion for identifying the regions in which a given shear stress has an influence on the fluid properties was developed. It is based on information on the local structure of the fluid. For the self-diffusivity, shear-induced anisotropic effects were observed and are discussed.

scholarly journals Research on the Mechanism of Surfactant Warm Mix Asphalt Additive-Based on Molecular Dynamics Simulation

Coatings ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1303
Author(s):  
Pinhui Zhao ◽  
Mingliang Dong ◽  
Yansheng Yang ◽  
Jingtao Shi ◽  
Junjie Wang ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Shear Stress ◽  
Shear Rate ◽  
Asphalt Binder ◽  
Warm Mix Asphalt ◽  
Dynamics Simulation ◽  
Stone Surface ◽  
Lubricating Film ◽  
Lubrication Performance ◽  
Shear Friction

Warm mix asphalt (WMA) technology can bring certain environmental and technical benefits through reducing the temperature of production, paving, and compaction of mixture asphalt. Recent studies have shown that some WMA additives are able to reduce the temperature by increasing the lubricating properties of asphalt binder.-based on the tribological theory, this paper studied the mechanism of adsorbing and lubricating film of base asphalt and WMA on the surface of stone by molecular dynamics (MD) simulation method, and the effect of surfactant WMA additive on the lubrication performance of the shear friction system of “stone–asphalt–stone”. The model of base asphalt lubricating film, including saturates, aromatics, resin and asphaltene, as well as the model of warm mix asphalt lubricating film containing imidazoline-type surfactant WMA (IMDL WMA) additive molecule, were established. The shear friction system of “stone–asphalt–stone” of base asphalt and warm mix asphalt was built on the basis of an asphalt lubrication film model and representative calcite model. The results show that the addition of IMDL WMA additive can effectively improve the lubricity of asphalt, reduce the shear stress of asphalt lubricating film, and increase the stability of asphalt film. The temperature in the WMA lubricating film rises, while the adsorption energy on the stone surface decreases with the increase of shear rate, indicating that the higher the shear rate is, the more unfavorable it is for the WMA lubricating film to wrap on the stone surface. In addition, the shear stress of the WMA lubricating film decreased with increasing temperature, while the shear stress of the base asphalt lubricating film increased first and then decreased, demonstrating that the compactability of the asphalt mixture did not improve linearly with the increase of temperature.

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