scholarly journals Blood Clot Phenotyping by Rheometry: Platelets and Fibrinogen Chemistry Affect Stress-Softening and -Stiffening at Large Oscillation Amplitude

Molecules ◽  
2020 ◽  
Vol 25 (17) ◽  
pp. 3890
Author(s):  
Ursula Windberger ◽  
Jörg Läuger
Keyword(s):  
Shear Stress ◽  
Stress Amplitude ◽  
Blood Clot ◽  
Oscillation Amplitude ◽  
High Stress ◽  
Cyclic Stress ◽  
Treatment Protocols ◽  
Fibrin Networks ◽  
Applied Shear Stress ◽  
Native Plasma

(1) Background: Together with treatment protocols, viscoelastic tests are widely used for patient care. Measuring at broader ranges of deformation than currently done will add information on a clot’s mechanical phenotype because fibrin networks follow different stretching regimes, and blood flow compels clots into a dynamic non-linear response. (2) Methods: To characterize the influence of platelets on the network level, a stress amplitude sweep test (LAOStress) was applied to clots from native plasma with five platelet concentrations. Five species were used to validate the protocol (human, cow, pig, rat, horse). By Lissajous plots the oscillation cycle for each stress level was analyzed. (3) Results: Cyclic stress loading generates a characteristic strain response that scales with the platelet quantity at low stress, and that is independent from the platelet count at high shear stress. This general behavior is valid in the animal models except cow. Here, the specific fibrinogen chemistry induces a stiffer network and a variant high stress response. (4) Conclusions: The protocol provides several thresholds to connect the softening and stiffening behavior of clots with the applied shear stress. This points to the reversible part of deformation, and thus opens a new route to describe a blood clot’s phenotype.

Rate Dependent Constitutive Equations of Cyclic Softening

1985 ◽  
Vol 40 (7) ◽  
pp. 653-665
Author(s):  
J. S. Mshana ◽  
A. S. Krausz
Keyword(s):  
Stress Relaxation ◽  
Low Temperature ◽  
Constitutive Equations ◽  
Strain Softening ◽  
Structural Characteristics ◽  
High Stress ◽  
Cyclic Strain ◽  
Cyclic Stress ◽  
Cyclic Softening ◽  
Stress Softening

Constitutive equations of cyclic strain and stress softening for materials with low internal stress levels are derived from the rate theory. The study shows that over the high stress and low temperature range where the description of plastic flow in cyclic softening can be approximated with activation over a single energy barrier, cyclic strain softening is well related to stress relaxation process while cyclic stress softening is related to creep process. The material structural characteristics for cyclic strain softening, cyclic stress softening and stress relaxation are identical. Subsequently, it is shown that cyclic stress and strain softening within the high stress and low temperature range can be evaluated from the constitutive equations using the material structural characteristics measured from a simple stress relaxation test.

scholarly journals Simulation of the Load Evolution of an Anchoring System under a Blasting Impulse Load Using FLAC3D

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Xigui Zheng ◽  
Jinbo Hua ◽  
Nong Zhang ◽  
Xiaowei Feng ◽  
Lei Zhang
Keyword(s):  
Shear Stress ◽  
Dynamic Response ◽  
Axial Force ◽  
Mechanical Characteristics ◽  
Oscillation Amplitude ◽  
Anchoring System ◽  
Impulse Load ◽  
The Stability ◽  
Calculation Software ◽  
Dynamic Perturbation

A limitation in research on bolt anchoring is the unknown relationship between dynamic perturbation and mechanical characteristics. This paper divides dynamic impulse loads into engineering loads and blasting loads and then employs numerical calculation software FLAC3Dto analyze the stability of an anchoring system perturbed by an impulse load. The evolution of the dynamic response of the axial force/shear stress in the anchoring system is thus obtained. It is revealed that the corners and middle of the anchoring system are strongly affected by the dynamic load, and the dynamic response of shear stress is distinctly stronger than that of the axial force in the anchoring system. Additionally, the perturbation of the impulse load reduces stress in the anchored rock mass and induces repeated tension and loosening of the rods in the anchoring system, thus reducing the stability of the anchoring system. The oscillation amplitude of the axial force in the anchored segment is mitigated far more than that in the free segment, demonstrating that extended/full-length anchoring is extremely stable and surpasses simple anchors with free ends.

scholarly journals Exaggerated cation leak from oxygenated sickle red blood cells during deformation: evidence for a unique leak pathway

Blood ◽  
1992 ◽  
Vol 80 (9) ◽  
pp. 2374-2378
Author(s):  
T Sugihara ◽  
RP Hebbel
Keyword(s):  
Shear Stress ◽  
Lipid Hydroperoxide ◽  
Viscous Medium ◽  
Permeability Barrier ◽  
Biochemical Basis ◽  
Rbc Membrane ◽  
Gardos Channel ◽  
Ambient Oxygen ◽  
Applied Shear Stress ◽  
Leak Pathway

An abnormal susceptibility of the sickle red blood cell (RBC) membrane to deformation could compromise its permeability barrier function and contribute to the exuberant cation leakiness occurring during the sickling phenomenon. We examined this hypothesis by subjecting RBCs at ambient oxygen tension to elliptical deformation, applying shear stress in a viscous medium under physiologic conditions. Compared with normal and high-reticulocyte control RBCs, sickle RBCs manifest an exaggerated K leak response to deformation. This leak is fully reversible, is both Cl and Ca independent, and at pHe 7.4 is fully balanced so that Kefflux equals Nainflux. This abnormal susceptibility is also evident in that the K leak in response to deformation occurs at an applied shear stress of only 141 dyne/cm2 for sickle RBCs, as compared to 204 dyne/cm2 for normal RBCs. Fresh sickle RBC membranes contain elevated amounts of lipid hydroperoxide, the presence of which is believed to provide the biochemical basis for enhanced deformation susceptibility. When examined at pHe 6.8, oxygenated sickle RBCs acquire an additional, unbalanced (Kefflux > Nainflux) component to the K leak increment specifically ascribable to deformation. Studies with inhibitors suggest that this additional component is not caused by a known leak pathway (eg, either K:Cl cotransport or the Gardos channel). This abnormal susceptibility of the sickle membrane to development of cation leakiness during deformation probably contributes to the exuberant cation leak taking place during RBC sickling.

Cyclic Softening and Over-Softening of a 1 Percent Cr-Mo-V Steel at Elevated Temperature

1981 ◽  
Vol 23 (6) ◽  
pp. 305-308
Author(s):  
T. Gardiner
Keyword(s):  
Shear Stress ◽  
High Strain ◽  
Cyclic Stress ◽  
Cyclic Softening ◽  
Stress Range ◽  
Continuous Cycling ◽  
History Effect ◽  
Initial Cycle ◽  
Range Variation ◽  
Total Shear

Detailed results are presented of shear stress range variation during cycling of 1 per cent Cr-Mo-V test specimens within controlled total shear strain limits at 565°C. The cyclic softening induced during continuous and two-step cycling are compared. A saw-toothed pattern for the strain was maintained for each cycle giving a constant straining rate. Normal cyclic softening was found throughout the tests but another phenomenon of over-softening occurred during the two-step tests when high strain cycles took place first. A permanent history effect had been produced within the steel. This over-softening did not depend on the straining rate of the cycling or the magnitude of the initial cycle ratio. The generally accepted method of determining cyclic stress-strain curves using continuous cycling is shown to be invalid when over-softening is present.

Interaction Between Lattice Dislocations and Grain Boundaries In Ordered Compounds

1990 ◽  
Vol 213 ◽  
Author(s):  
B.J. Pestman ◽  
J. Th. M. De Hosson ◽  
V. Vitek ◽  
F.W. Schapink
Keyword(s):  
Shear Stress ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Partial Dislocation ◽  
Atomistic Simulations ◽  
Many Body ◽  
Shockley Partial Dislocation ◽  
Screw Dislocations ◽  
Applied Shear Stress ◽  
Tilt Boundaries

ABSTRACTThe interaction of 1/2<1 1 0> screw dislocations with symmetric [1 1 0] tilt boundaries was investigated by atomistic simulations using many-body potentials representing ordered compounds. The calculations were performed with and without an applied shear stress. The observations were: absorption into the grain boundary, attraction of a lattice Shockley partial dislocation towards the grain boundary and transmission through the grain boundary under the influence of a shear stress. It was found that the interaction in ordered compounds shows similarities to the interaction in fcc.

Fretting Induced Fatigue Failure in Steam Turbine Blades

2019 ◽  
Author(s):  
Vamadevan Gowreesan ◽  
Kyrylo Grebinnyk
Keyword(s):  
Crack Initiation ◽  
Fatigue Failure ◽  
Relative Motion ◽  
Turbine Blades ◽  
High Stress ◽  
Cyclic Stress ◽  
Element Analysis ◽  
Surface Cracking ◽  
Blade Failure ◽  
Fretting Damage

Abstract Fretting occurs when there is cyclic relative motion of extremely small amplitude between two tightly fit mating surfaces. In this process, the tight fitting load may lead to adhesion of mating surface. The subsequent relative movement breaks the adhesion and lead to local grooves and pits. The localized damage in conjunction with the stresses associated with the cyclic relative motion may lead to surface cracking. This crack subsequently may propagate by fatigue provided there is high enough cyclic stress at that location. The paper discusses a blade failure induced by such fretting related fatigue. The metallurgical evaluation of the fracture surfaces of the blades showed evidence of classical fatigue failure. However, the crack initiation location did not coincide with high stress location identified by the finite element analysis. This discrepancy along with the evidence of fretting at the crack initiation sites confirms that failures were induced by fretting. Finally, some methods to eliminate or minimize fretting damage are discussed.

MAGNETOPHORETIC CIRCUIT BIOCOMPATIBILITY

2020 ◽  
Vol 20 (07) ◽  
pp. 2050050
Author(s):  
ROOZBEH ABEDINI-NASSAB
Keyword(s):  
Shear Stress ◽  
Single Cell ◽  
Single Cell Analysis ◽  
Cell Behavior ◽  
Cell Analysis ◽  
Applied Shear Stress ◽  
Cell Handling ◽  
Magnetic Labeling ◽  
Long Term Studies

Recently, we introduced magnetophoretic circuits, composed of overlaid magnetic and metallic layers, as a novel single-cell analysis (SCA) tool. We showed the ability of these circuits in organizing large single-particle and particle-pair arrays. Assembling the cells in microarrays is performed with the ultimate goal of running temporal phenotypic analyses. However, for long-term studies, a suitable microenvironment for the cells to normally grow and differentiate is needed. Towards this goal, in this study, we run required biocompatibility tests, based on which we make the magnetophoretic-based microchip a suitable home for the cells to grow. The results confirm the ability of these chips in cell handling and show no unwanted cell behavior alteration due to the applied shear stress on them, the magnetic labeling, or the microenvironment. After this achievement, this tool would be ready for running important single-cell studies in oncology, virology, and medicine.

scholarly journals A Fatigue Life Prediction Model Based on Modified Resolved Shear Stress for Nickel-Based Single Crystal Superalloys

Metals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 180 ◽  
Author(s):  
Jialiang Wang ◽  
Dasheng Wei ◽  
Yanrong Wang ◽  
Xianghua Jiang
Keyword(s):  
Shear Stress ◽  
Fatigue Life ◽  
Prediction Model ◽  
Single Crystal ◽  
Life Prediction ◽  
Stress Amplitude ◽  
Damage Parameter ◽  
Fatigue Life Prediction ◽  
Model Based ◽  
Life Prediction Model

In this paper, the viewpoint that maximum resolved shear stress corresponding to the two slip systems in a nickel-based single crystal high-temperature fatigue experiment works together was put forward. A nickel-based single crystal fatigue life prediction model based on modified resolved shear stress amplitude was proposed. For the four groups of fatigue data, eight classical fatigue life prediction models were compared with the model proposed in this paper. Strain parameter is poor in fatigue life prediction as a damage parameter. The life prediction results of the fatigue life prediction model with stress amplitude as the damage parameter, the fatigue life prediction model with maximum resolved shear stress in 30 slip directions as the damage parameter, and the McDiarmid (McD) model, are better. The model proposed in this paper has higher life prediction accuracy.

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