A Shear Stress Component to the Modulation of Capillary Hydraulic Conductivity (Lp)

1996 ◽  
Vol 3 (2) ◽  
pp. 229-232 ◽  
Author(s):  
Donna A. Williams
Keyword(s):  
Shear Stress ◽  
Hydraulic Conductivity ◽  
Stress Component ◽  
Shear Stress Component

Characterization of Thermally Induced Stress in IC Packages Using PiFETs Over a Temperature Range of −180°C to 80°C

2014 ◽  
Vol 2014 (1) ◽  
pp. 000500-000504 ◽  
Author(s):  
Francy J. Akkara ◽  
Uday S. Goteti ◽  
Richard C. Jaeger ◽  
Michael C. Hamilton ◽  
Michael J. Palmer ◽  
...  
Keyword(s):  
Shear Stress ◽  
Stress Component ◽  
Shear Stress Component ◽  
Thermally Induced ◽  
Temperature Changes ◽  
Temperature Range ◽  
Induced Stress ◽  
Highly Sensitive ◽  
Stress Components

In certain applications, IC packages may be exposed to extreme temperatures and knowledge of thermally induced stress aids the prediction of performance degradation or failure of the IC. In the devices that are used in extreme conditions, the stress is caused mainly by the mismatch in expansion of various materials triggered by the different coefficients of thermal expansion. This work performed in this study is conducted using NMOS current mirror circuits that are cycled through a wide temperature range of −180°C to 80°C. These circuits are highly sensitive to stress and provide well-localized measurements of shear stress. The sensors are fabricated in such a way that the effects of certain stress components are isolated. These sensors are also temperature compensated so that only the effect of mechanical stress components is observed and changes in device performance due to temperature changes are minimal. Current readings obtained from the sensors are used to extract the shear stress component. Finite element simulations, using expected materials performance parameter information were also performed for similar packages and these results are compared to the measured results.

The Influence of Turbulence Memory on Idealized Tornado Simulations

2020 ◽  
Vol 148 (12) ◽  
pp. 4875-4892
Author(s):  
Aaron Wang ◽  
Ying Pan ◽  
Paul M. Markowski
Keyword(s):  
Boundary Condition ◽  
Shear Stress ◽  
Stress Component ◽  
Lower Boundary ◽  
Surface Friction ◽  
Surface Shear Stress ◽  
Normal Surface ◽  
Shear Stress Component ◽  
Surface Shear ◽  
Lower Boundary Condition

AbstractSurface friction contributes to tornado formation and maintenance by enhancing the convergence of angular momentum. The traditional lower boundary condition in atmospheric models typically assumes an instant equilibrium between the unresolved stress and the resolved shear. This assumption ignores the physics that turbulent motions are generated and dissipated at finite rates—in effect, turbulence has a memory through its lifetime. In this work, a modified lower boundary condition is proposed to account for the effect of turbulence memory. Specifically, when an air parcel moves along a curved trajectory, a normal surface-shear-stress component arises owing to turbulence memory. In the accompanying large-eddy simulation (LES) of idealized tornadoes, the normal surface-shear-stress component is a source of additional dynamic instability, which provides an extra pathway for the development of turbulent motions. The influence of turbulence memory on the intensity of quasi-steady-state tornadoes remains negligible as long as assumptions employed by the modified lower boundary condition hold over a relatively large fraction of the flow region of interest. However, tornadoes in a transient state may be especially sensitive to turbulence memory.Significance StatementFriction between the wind and the ground can influence atmospheric phenomena in important ways. For example, surface friction can be a significant source of rotation in some thunderstorms, and it can also help to intensify rotation when rotation is already present. Unfortunately, the representation of friction’s effects in atmospheric simulations is especially error-prone in phenomena characterized by rapid temporal evolution or strong spatial variations. Our work explores a new framework for representing friction to include the effect of the so-called turbulence memory. The approach is tested in idealized tornado simulations, but it may be applied to a wide range of atmospheric vortices.

scholarly journals Experimental study on granite acoustic emission and micro-fracture behavior with combined compression and shear loading: phenomenon and mechanism

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Yue Cao ◽  
Jinhai Xu ◽  
Liang Chen ◽  
Peng Wu ◽  
Faiz Shaikh
Keyword(s):  
Shear Stress ◽  
Acoustic Emission ◽  
Fracture Mode ◽  
Inclination Angle ◽  
Fracture Behavior ◽  
Shear Failure ◽  
Stress Component ◽  
Shear Loading ◽  
Shear Stress Component ◽  
Microcrack Initiation

AbstractOne element that is essential to consider in underground mining engineering applications is the possibility of pillar failure, which can result in deadly geological disasters, including earthquakes and surface subsidence. Pillars are commonly present under an inclined state and are significantly dependent upon combined compression and shear loading. However, many scholars regard the pure uniaxial compression strength (UCS) of rock as the main evaluation index of pillar strength, which is inconsistent with the field practice. Hence, the present study developed a novel combined compression and shear test (C-CAST) system, which was applied in the investigative acoustic emission (AE) experiments to characterize the failure mechanism and micro-fracture behavior of granite specimens at different inclination angles. The experimental results presented the exponential decrease of UCS of inclined specimens with increase in the shear stress component. Changes in the inclination angle with a range of 0°–10° produced a splitting-shear failure fracture mode from the initial splitting failure. In comparison, an increase in the inclination angle from 10° to 20° produced a single shear failure fracture mode from the initial combined splitting-shear failure. The specimens exhibited nonlinearly reduced microcrack initiation (CI) and damage (CD) thresholds following an increase in the inclination angle, suggesting the dependence of the microcrack initiation and propagation on the shear stress component. The ratio of CI and CD thresholds to inclined UCS varies within a certain range, indicating that the ratio may be an inherent property of granite specimens and is not affected by external load conditions. Additionally, the rock fracture behavior was largely dependent upon the mechanism of shear stress component, as validated by the microcrack initiation and growth. Finally, a modified empirical formula for pillar strength is proposed to investigate the actual strength of inclined pillar. Results of a case study show that the modified formula can be better used to evaluate the stability of inclined pillars.

Off-axis tensile strength and evaluation of the in-plane shear strength of paper

Holzforschung ◽  
2014 ◽  
Vol 68 (5) ◽  
pp. 583-590 ◽  
Author(s):  
Hiroshi Yoshihara ◽  
Masahiro Yoshinobu
Keyword(s):  
Tensile Strength ◽  
Shear Stress ◽  
Shear Strength ◽  
Stress Component ◽  
Shear Stress Component ◽  
Plane Shear ◽  
Dog Bone ◽  
Paper Filter ◽  
Failure Conditions ◽  
The Relationship

Abstract The off-axis tensile strength (OATS) of copy paper, filter paper, and sack paper was obtained from dog-bone specimens. The relationship between OATS and the off-axis angle (OAA) was predicted under several failure conditions. Additionally, the shear strengths (SS) of these papers were evaluated based on the results of OAT tests. The OATS could be accurately predicted under several Hill-type failure conditions. An equation for deriving the in-plane SS of these papers was proposed based on the tensile strength of the specimen with a 35° OAA, in which the contribution of the shear stress component was maximum.

Fiber Breakage in Plain Woven Glass Fabric Composites Under Tension/Shear Biaxial Cyclic Stress

2001 ◽  
Author(s):  
Hiroyuki Maeyama ◽  
Kazuya Okubo ◽  
Toru Fujii
Keyword(s):  
Shear Stress ◽  
Fiber Bundle ◽  
Stress Component ◽  
Cyclic Stress ◽  
Biaxial Stress ◽  
Fiber Bundles ◽  
Fiber Breakage ◽  
Shear Stress Component ◽  
Fabric Composites ◽  
Longitudinal Fiber

Abstract Fiber breakage occurring in fiber bundles of plain-woven glass fabric composites is investigated under tension/shear biaxial cyclic stress. The experimental results show an existence of the strong effect of biaxial stress ratio on fiber breakage and its accumulation. Under pure tension (uniaxial) loading, the variation of fiber breakage ratio with respect to loading cycles is divided into two stages in the longitudinal fiber bundles. In the first stage, the fiber breakage scarcely occurs. In the final stage, fibers in a fiber bundle are broken remarkably. Under the biaxial cyclic stress, the fiber breakage in the longitudinal fiber bundle is observed in initial fatigue stage. In the case of the biaxial stress with large shear stress component, the fiber breakage is also observed in the transverse fiber bundle. The fiber breakage is accelerated by the combined stress with large shear stress component, which is called the shear constraint effect.

Fluctuations in wall-shear stress and pressure at low streamwise wavenumbers in turbulent boundary-layer flow

1991 ◽  
Vol 225 ◽  
pp. 545-555 ◽  
Author(s):  
D. M. Chase
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Turbulent Boundary Layer ◽  
Stress Component ◽  
Wall Pressure ◽  
Inviscid Limit ◽  
Pressure Amplitude ◽  
Shear Stress Component ◽  
Wall Shear

Turbulent boundary-layer fluctuations in the incompressive domain are expressed in terms of fluctuating velocity-product 'sources’ in order to elucidate relative characteristics of fluctuating wall-shear stress and pressure in the subconvective range of streamwise wavenumbers. Appropriate viscous wall conditions are applied, and results are obtained to lowest order in this Strouhal-scaled wavenumber which serves as the expansion parameter. The spectral amplitudes of pressure and of the shear stress component directed along the wavevector both contain additive terms proportional to source integrals with exponential wall-distance weighting characteristic respectively of the irrotational and the rotational fields. At low wavenumbers, barring unexpected relative smallness of the pertinent boundary-layer source term, the rotational terms become dominant. There the wall pressure and shear-stress component have spectra that approach the same non-vanishing, wavevector-white but generally viscous-scale-dependent level and are totally coherent with phase difference ½π. The other, irrotational contributions to the shear-stress and pressure amplitudes likewise bear a simple and previously known, generally wavevector– and frequency-dependent, ratio to one another. In an inviscid limit this contribution to the pressure amplitude reduces to the one obtained previously from inviscid treatments. A representative class of models is introduced for the source spectrum, and the resulting rotational contribution to the spectral density of wall pressure and K-aligned shear stress at low (but incompressive) wavenumbers is estimated. It is suggested that this contribution may predominate and account for measured low-wavenumber levels of wall pressure.

Effect of pressure on hydraulic conductivity of endothelial monolayers: role of endothelial cleft shear stress

1999 ◽  
Vol 87 (1) ◽  
pp. 261-268 ◽  
Author(s):  
John M. Tarbell ◽  
Lucas Demaio ◽  
Mark M. Zaw
Keyword(s):  
Nitric Oxide ◽  
Shear Stress ◽  
Hydraulic Conductivity ◽  
Elevated Pressure ◽  
Transmural Pressure ◽  
Luminal Surface ◽  
Aortic Endothelial Cells ◽  
Effect Of Pressure ◽  
Steady State Levels ◽  
Transmural Flow

Significant changes in transvascular pressure occur in pulmonary hypertension, microgravity, and many other physiological and pathophysiological circumstances. Using bovine aortic endothelial cells grown on porous, rigid supports, we demonstrate that step changes in transmural pressure of 10, 20, and 30 cmH2O induce significant elevations in endothelial hydraulic conductivity ( L p) that require 5 h to reach new steady-state levels. The increases in L p can be reversed by addition of a stable cAMP analog (dibutyryl cAMP), and the increases in L pin response to pressure can be inhibited significantly with nitric oxide synthase inhibitors ( N G-monomethyl-l-arginine and nitro-l-arginine methyl ester). The increase in L p was not due to pressure-induced stretch because the endothelial cell (EC) support was rigid. It is unlikely that the increase in L p was due to a direct effect of pressure because exposure of the cells to elevated pressure (25 cmH2O) for 4 h had no effect on the volume flux driven by a transmural pressure of 10 cmH2O. We hypothesize that elevated endothelial cleft shear stress induced by elevated transmural flow in response to elevated pressure stimulates the increase in L p through a nitric oxide-cAMP-dependent mechanism. This is consistent with recent studies of the effects of shear stress on the luminal surface of ECs. We provide simple estimates of endothelial cleft shear stress, which suggest magnitudes comparable to those imposed by blood flow on the luminal surface of ECs.

scholarly journals Quantification of Preferential Contribution of Reynolds Shear Stresses and Flux of Mean Kinetic Energy Via Conditional Sampling in a Wind Turbine Array

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Hawwa Falih Kadum ◽  
Devin Knowles ◽  
Raúl Bayoán Cal
Keyword(s):  
Shear Stress ◽  
Kinetic Energy ◽  
Wind Turbine ◽  
Momentum Flux ◽  
Wind Farm ◽  
Reynolds Shear Stress ◽  
Stress Component ◽  
Wake Flow ◽  
Shear Stresses ◽  
Balanced Distribution

Conditional statistics are employed in analyzing wake recovery and Reynolds shear stress (RSS) and flux directional out of plane component preference. Examination of vertical kinetic energy entrainment through describing and quantifying the aforementioned quantities has implications on wind farm spacing, design, and power production, and also on detecting loading variation due to turbulence. Stereographic particle image velocimetry measurements of incoming and wake flow fields are taken for a 3 × 4 model wind turbine array in a scaled wind tunnel experiment. Reynolds shear stress component is influenced by ⟨uv⟩ component, whereas ⟨vw⟩ is more influenced by streamwise advection of the flow; u, v, and w being streamwise, vertical, and spanwise velocity fluctuations, respectively. Relative comparison between sweep and ejection events, ΔS⟨uiuj⟩, shows the role of streamwise advection of momentum on RSS values and direction. It also shows their tendency to an overall balanced distribution. ⟨uw⟩ intensities are associated with ejection elevated regions in the inflow, yet in the wake, ⟨uw⟩ is linked with sweep dominance regions. Downward momentum flux occupies the region between hub height and top tip. Sweep events contribution to downward momentum flux is marginally greater than ejection events'. When integrated over the swept area, sweeps contribute 55% of the net downward kinetic energy flux and 45% is the ejection events contribution. Sweep dominance is related to momentum deficit as its value in near wake elevates 30% compared to inflow. Understanding these quantities can lead to improved closure models.

The mechanosorptive effect in Pinus radiata D. Don.

Holzforschung ◽  
2005 ◽  
Vol 59 (5) ◽  
pp. 552-558 ◽  
Author(s):  
Kenneth M. Entwistle
Keyword(s):  
Applied Stress ◽  
Pinus Radiata ◽  
Cell Walls ◽  
Cellulose Microfibril ◽  
Stress Component ◽  
Single Specimen ◽  
Shear Stress Component ◽  
Effect Analysis ◽  
Detailed Model ◽  
Valid Data

Abstract Measurements are reported of the mechanosorptive strain in Pinus radiata specimens stressed either in torsion or in bending. It is demonstrated that, to secure valid data, correction must be made for the moisture-induced distortion at zero load. A series of measurements can be made on a single specimen if two successive mechano-sorptive loading cycles are used and the sense of the stress is reversed for the second cycle. At the end of this procedure the specimen has reverted to its original dimensions. The mechanosorptive strain is shown to vary linearly with the applied stress; the ratio of the mechanosorptive strain to the initial elastic strain is therefore an appropriate way of quantifying the mechanosorptive effect. Analysis of torsion and bending data reveals that there is a strong correlation between the magnitude of the mechanosorptive strain and the shear stress component of the applied stress along the cellulose microfibril direction. It is suggested that the mechanosorptive effect arises from the effect of stress on the distribution of hydrogen bonds in hemicelluloses. A detailed model must await more information about the molecular structure of hemicelluloses in the cell walls.

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