scholarly journals Sliding-friction-dependent stress at the graphene/LiNbO3 interface around the critical temperature of the stress-free state

AIP Advances ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 025316
Author(s):  
Yong Sun ◽  
Kenta Kirimoto ◽  
Hiroyuki Kamada ◽  
Koichi Onishi ◽  
Daichi Etoh ◽  
...  
Keyword(s):  
Critical Temperature ◽  
Sliding Friction ◽  
Free State ◽  
Stress Free State

scholarly journals Stress-free state of the red blood cell membrane and the deformation of its skeleton

2012 ◽  
Vol 17 (2) ◽  
Author(s):  
Tjaša Švelc ◽  
Saša Svetina
Keyword(s):  
Blood Cell ◽  
Red Blood Cell ◽  
Variational Calculation ◽  
Lateral Distribution ◽  
Free State ◽  
Initial State ◽  
Proposed Model ◽  
Deformed State ◽  
Concentric Circles ◽  
Stress Free State

AbstractThe response of a red blood cell (RBC) to deformation depends on its membrane, a composite of a lipid bilayer and a skeleton, which is a closed, twodimensional network of spectrin tetramers as its bonds. The deformation of the skeleton and its lateral redistribution are studied in terms of the RBC resting state for a fixed geometry of the RBC, partially aspirated into a micropipette. The geometry of the RBC skeleton in its initial state is taken to be either two concentric circles, a references biconcave shape or a sphere. It is assumed that in its initial state the skeleton is distributed laterally in a homogeneous manner with its bonds either unstressed, presenting its stress-free state, or prestressed. The lateral distribution was calculated using a variational calculation. It was assumed that the spectrin tetramer bonds exhibit a linear elasticity. The results showed a significant effect of the initial skeleton geometry on its lateral distribution in the deformed state. The proposed model is used to analyze the measurements of skeleton extension ratios by the method of applying two modes of RBC micropipette aspiration.

STUDY OF THE SHELF LIFE OF SEALANTS BASED ON LIQUID THIOKOL IN A STRESS-FREE STATE

2021 ◽  
pp. 85-94
Author(s):  
Ja.A. Vakhrusheva ◽  
◽  
D.N. Smirnov ◽  
I.S. Makushchenko ◽  
◽  
...  
Keyword(s):  
Shelf Life ◽  
Physicomechanical Properties ◽  
Free State ◽  
Optimal Time ◽  
Thermal Light ◽  
Stress Free State ◽  
The Impact

The work carried out studies of the physicomechanical properties of polysulfide sealants of brands of U-30M and UT-31 after thermal, light aging, and the assessment of mushrooms. The data on the resistance of sealants of brands U-30M and UT-31 are investigated and summarized after the impact of accelerated climatic tests and aggressive environments. The optimal time and conditions for the storage of vulcanized sealants in the unattended state and components of sealants in warehouse conditions are determined, as well as the causes of different storage of sealing pastes based on liquid thiocola.

scholarly journals On the recovery of the stress-free configuration of the human cornea

2020 ◽  
Vol 2 (4) ◽  
pp. 11-33
Author(s):  
Anna Pandolfi ◽  
Andrea Montanino
Keyword(s):  
Numerical Simulations ◽  
Inverse Analysis ◽  
Material Model ◽  
Free State ◽  
Human Cornea ◽  
Material Models ◽  
Material Parameters ◽  
Optimal Values ◽  
Stress Free State ◽  
Actual Stress

Purpose: The geometries used to conduct numerical simulations of the biomechanics of the human cornea are reconstructed from images of the physiological configuration of the system, which is not in a stress-free state because of the interaction with the surrounding tissues. If the goal of the simulation is a realistic estimation of the mechanical engagement of the system, it is mandatory to obtain a stress-free configuration to which the external actions can be applied. Methods: Starting from a unique physiological image, the search of the stress-free configuration must be based on methods of inverse analysis. Inverse analysis assumes the knowledge of one or more geometrical configurations and, chosen a material model, obtains the optimal values of the material parameters that provide the numerical configurations closest to the physiological images. Given the multiplicity of available material models, the solution is not unique. Results: Three exemplary material models are used in this study to demonstrate that the obtained, non-unique, stress-free configuration is indeed strongly dependent on both material model and on material parameters. Conclusion: The likeliness of recovering the actual stress-free configuration of the human cornea can be improved by using and comparing two or more imaged configurations of the same cornea.

Modeling of subsurface ceramic inclusions in metallic matrices

2020 ◽  
Vol 55 (5-6) ◽  
pp. 134-144
Author(s):  
Andrew C Pickard ◽  
David E Mills
Keyword(s):  
Stress Field ◽  
Fatigue Cracks ◽  
Matrix Material ◽  
Metallic Matrix ◽  
Uniaxial Stress ◽  
Free State ◽  
Nickel Base Superalloy ◽  
Stress Free State ◽  
Nickel Base ◽  
The Impact

All engineering materials have the potential to contain inhomogeneities that can act as initiators for fatigue cracks during cyclic loading. One class of inhomogeneity that can occur as a result of the processes used to create metallic materials is a ceramic inclusion, typically resulting from the raw material contamination during the melting process. This article examines the predicted behavior of hard ceramic inclusions in a nickel-base superalloy metallic matrix. Compressive residual stresses are created in the inclusion during cool down from a stress-free state at high temperature. The influence of the proximity of the inclusion to the surface of the matrix material is examined, together with the impact of subsequent uniaxial loading on the stress field in the inclusion and in the surrounding material. The stress field in the ceramic inclusion is observed to transition from compressive to tensile as a function of the proximity of the inclusion to the surface of the material and the applied uniaxial stress field. For deep subsurface inclusions, the uniaxial stress field required to achieve a tensile stress in the inclusion is close to the yield stress of the material. The sensitivity of this critical stress to material cyclic hardening behavior and to the temperature difference between the stress-free state and the operating state is also explored. The significance of these modeling results is discussed in terms of the sensitivity of nickel-base superalloys to crack formation and growth from ceramic inclusions and hence the impact on probabilistic fatigue life assessments of the presence, location and size of the ceramic inclusions.

Passive ventricular mechanics in tight-skin mice

1994 ◽  
Vol 266 (3) ◽  
pp. H1169-H1176 ◽  
Author(s):  
J. H. Omens ◽  
H. A. Rockman ◽  
J. W. Covell
Keyword(s):  
Left Ventricle ◽  
Free State ◽  
Opening Angle ◽  
Ventricular Mechanics ◽  
Tight Skin ◽  
Ventricular Compliance ◽  
Volume Relationship ◽  
Pressure Volume Relationship ◽  
Stress Free State ◽  
Collagen Layer

Although changes in the extracellular matrix have been associated with changes in ventricular compliance in certain diseased states, this relationship has not been entirely established. Accordingly, we studied passive ventricular mechanics in the tight-skin (TSk) mouse, a mutant strain known to have increased cardiac collagen. In the arrested left ventricle, we determined the pressure-volume relationship and the stress-free state, as defined by the "opening angle" of an equatorial ring with a radial cut. The results showed the mean opening angle in the TSk mouse to be smaller than that in phenotypic negative controls (7 +/- 6 vs. 21 +/- 9 degrees), and there was no statistical difference in the pressure-volume curves. Histological quantification of the transmural collagen showed a uniform increase of collagen area fraction across the wall in TSk mouse, and a significantly thicker superficial epicardial collagen layer (4.68 +/- 0.87 vs. 3.34 +/- 0.76 micron). Thus, although there appears to be a decrease of residual stress in the TSk mouse heart, which may be related to the thicker epicardial collagen layer, the combination of increased myocardial collagen and the change in stress-free state did not seem to affect the passive pressure-volume relationship of the left ventricle.

Determination of Residual-Stress-Free State and Mapping of Residual Stress Fields Using Speckle Interferometry and Thermal Relaxation

2003 ◽  
Vol 795 ◽  
Author(s):  
Dong-Won Kim ◽  
Jong-jin Kim ◽  
Dongil Son ◽  
Nak-Kyu Lee ◽  
Kyung-Hoan Na ◽  
...  
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Speckle Pattern ◽  
Thermal Relaxation ◽  
Free State ◽  
Stress Fields ◽  
Lead Frame ◽  
Surface Residual Stress ◽  
Au Film ◽  
Stress Free State

ABSTRACTWe used an electronic speckle pattern interferometer (ESPI) for nondestructive measurement in-situ displacement fields in microsystems. A four-step phase-shift technique and magnifier with long working distance were adopted to increase displacement resolution to ∼10−2 μm and spatial resolution to ∼2 μm. A thermal vacuum chamber was designed to induce thermal treatments, including annealing. From the identification of the residual-stress-free state, we quantitatively modeled thermal strains/stress fields, relaxation stresses during annealing, and residual stress fields. Thermoelasticity theory was applied to model the relationship between the relaxation stresses and the displacements measured by ESPI during the evolution of the residual-stress-free state. We assessed the surface residual stress fields of indented bulk Cu; a Fe-Ni lead frame of 100 μm width; and 0.5 μm Au film. In the indented Cu, the normal and shear residual stresses around the indented point range from –1.7 GPa to 700 MPa and –800 MPa to 600 MPa, respectively, and the residual stress in the bending area of the Fe-Ni lead frame was estimated at 148 MPa and verified using beam-bending theory. In the Au film, tensile residual stresses are uniformly distributed from 500 MPa to 800 MPa as verified by X-ray diffraction.

Sign in / Sign up

Export Citation Format

Share Document