scholarly journals Smart sealing for magnetorheological fluid actuators

2018 ◽  
Vol 30 (5) ◽  
pp. 689-700 ◽  
Author(s):  
Christian Hegger ◽  
Jürgen Maas
Keyword(s):  
Movement Control ◽  
Magnetorheological Fluid ◽  
Experimental Investigations ◽  
Stray Field ◽  
Fluid Movement ◽  
Shear Rates ◽  
High Shear Rates ◽  
Viscous Losses ◽  
Simulation Based ◽  
Novel Design

In automotive and industrial environments, magnetorheological fluid–based applications such as clutches and brakes are gaining continuously more attention. However, one of the serious challenges for their application are drag losses at high shear rates. While viscous losses of the magnetorheological fluid can be eliminated by a magnetorheological fluid movement control based on partially filled shear gaps, commonly utilized sealings also cause drag losses based on dry friction. To overcome these challenges, in this contribution, a novel design of sealings for magnetorheological fluid–based actuators is introduced eliminating the adverse drag losses. The intended sealing is based on the magnetorheological fluid itself, positioned in a sealing gap and exposed to a well-defined magnetic stray field of a permanent magnet to prevent any leakage. To eliminate drag torques, a superimposed functional principle with the magnetorheological fluid movement control is utilized. An analytical and a simulation-based modeling approach is proposed describing the torque behavior of the magnetorheological fluid sealing. In experimental investigations, the drag torque-free operation is proven by showing a lossless operation above a defined rotational speed.

Two-Speed Transmission Based on MRF Coupling Elements

2017 ◽  
Author(s):  
Christian Hegger ◽  
Jürgen Maas
Keyword(s):  
Energy Efficient ◽  
Conceptual Development ◽  
Movement Control ◽  
Coupling Element ◽  
Efficient Operation ◽  
Torque Transmission ◽  
Viscous Losses ◽  
Power Split ◽  
Industrial Use ◽  
Novel Design

In this contribution the conceptual development of a two-speed transmission utilizing coupling elements based on magnetorheological fluids (MRF) will be presented. The transmission concept is based on a mechanical power split. The transmission ratios are optimized for an appropriate utilization of MRF coupling elements. This transmission concept can be applied in several applications, like vehicles or industrial use. Besides, the electrical feeding power of the coupling elements will be investigated for certain scenarios considering the proposed transmission concept. MRF coupling elements provide a highly dynamical and continuously adjustable torque transmission. In combination with the MR fluid movement control to avoid viscous losses, a very energy efficient operation in contrast to conventional coupling elements can be achieved. For a reduction of the weight, space and feeding energy also a novel design with serpentine flux guidance will be introduced. Due to this design, combined arrangements of MRF coupling elements can be achieved, to create a very compact dual coupling element for the proposed transmission concept.

Asialo von Willebrand Factor Enhances Platelet Adhesion to Vessel Subendothelium

1988 ◽  
Vol 60 (01) ◽  
pp. 030-034 ◽  
Author(s):  
Eva Bastida ◽  
Juan Monteagudo ◽  
Antonio Ordinas ◽  
Luigi De Marco ◽  
Ricardo Castillo
Keyword(s):  
Von Willebrand Factor ◽  
Platelet Adhesion ◽  
Human Albumin ◽  
Membrane Receptors ◽  
Shear Rates ◽  
High Shear Rates ◽  
Platelet Deposition ◽  
Platelet Spreading ◽  
Von Willebrand ◽  
Willebrand Factor

SummaryNative von Willebrand factor (N-vWF) binds to platelets activated by thrombin, ADP or ristocetin. Asialo vWF (As-vWF) induces platelet aggregation in absence of platelet activators. N-vWF mediates platelet adhesion to vessel subendothelium at high shear rates. We have investigated the role of As-vWF in supporting platelet deposition to rabbit vessel subendothelium at a shear rate of 2,000 sec-1, using the Baumgartner perfusion system. We have studied the effects of the addition of As-vWF (from 2 to 12 μg/ml) to perfusates consisting of washed red blood cells, 4% human albumin and washed platelets. Our results show a significant increase in platelet deposition on subendothelium (p <0.01) in perfusions to which As-vWF had been added. Blockage of the platelet glycoproteins Ib and IIb/IIIa (GPIb and GPIIb/IIIa) by specific monoclonal antibodies (LJIb1 and LJCP8, respectively) resulted in a decrease of platelet deposition in both types of perfusates prepared with N-vWF and As-vWF. Our results indicate that As-vWF enhances platelet deposition to vessel subendothelium under flow conditions. Furthermore, they suggest that this effect is mediated by the binding of As-vWF to platelet membrane receptors, which in turn, promote platelet spreading and adhesion to the subendothelium.

Relative Involvement of GPIb/IX-vWF Axis and GPIIb/IIIa in Thrombus Growth at High Shear Rates in the Guinea Pig

1997 ◽  
Vol 17 (5) ◽  
pp. 919-924 ◽  
Author(s):  
Patrick André ◽  
Patricia Hainaud ◽  
Claire Bal dit Sollier ◽  
Leonard I. Garfinkel ◽  
Jacques P. Caen ◽  
...  
Keyword(s):  
Guinea Pig ◽  
High Shear ◽  
Shear Rates ◽  
High Shear Rates

scholarly journals Microfluidic rheology: A new approach to measure viscosity of ceramic suspensions at extremely high shear rates

Open Ceramics ◽  
2021 ◽  
Vol 5 ◽  
pp. 100052
Author(s):  
V. Carnicer ◽  
C. Alcázar ◽  
M.J. Orts ◽  
E. Sánchez ◽  
R. Moreno
Keyword(s):  
High Shear ◽  
New Approach ◽  
Shear Rates ◽  
High Shear Rates ◽  
Ceramic Suspensions

Flow curves of mixtures of acrylonitrile–styrene copolymers with different molecular weights at extremely high shear rates (abstract)

1991 ◽  
Vol 35 (4) ◽  
pp. 706-706
Author(s):  
Hideroh Takahashi ◽  
Yoshinori Inoue ◽  
Satoru Yamamoto ◽  
Osami Kamigaito
Keyword(s):  
High Shear ◽  
Flow Curves ◽  
Shear Rates ◽  
Molecular Weights ◽  
Styrene Copolymers ◽  
High Shear Rates

Comparison of antithrombotic efficacy between edoxaban, a direct factor Xa inhibitor, and fondaparinux, an indirect factor Xa inhibitor under low and high shear rates

2011 ◽  
Vol 106 (12) ◽  
pp. 1062-1068 ◽  
Author(s):  
Naoki Tsuji ◽  
Yuko Honda ◽  
Chikako Kamisato ◽  
Yoshiyuki Morishima ◽  
Toshiro Shibano ◽  
...  
Keyword(s):  
Shear Rate ◽  
Arterial Thrombosis ◽  
Factor Xa ◽  
High Shear ◽  
Shear Rates ◽  
Thrombosis Model ◽  
Perfusion Chamber ◽  
High Shear Rates ◽  
Antithrombotic Effects ◽  
Antithrombotic Efficacy

SummaryEdoxaban is an oral, direct factor Xa (FXa) inhibitor under late-phase clinical development. This study compared the antithrombotic efficacy of edoxaban with that of an indirect FXa inhibitor, fondaparinux, in in vivo venous and arterial thrombosis models and in ex vivo perfusion chamber thrombosis model under low and high shear rates in rats. Venous and arterial thrombi were induced by platinum wire insertion into the inferior vena cava and by application of FeCl3 to the carotid artery, respectively. The perfusion chamber thrombus was formed by blood perfusion into a collagen-coated capillary at 150 s-1 (low shear rate) and 1,600 s-1 (high shear rate). Effective doses of edoxaban that reduced thrombus formation by 50% (ED50) in venous and arterial thrombosis models were 0.076 and 0.093 mg/kg/h, respectively. In contrast, ED50 of fondaparinux in the arterial thrombosis model (>10 mg/kg/h) was markedly higher compared to ED50 in the venous thrombosis model (0.021 mg/kg/h). In the perfusion chamber thrombosis model, the ratio of ED50 under high shear rate (1.13 mg/kg/h) to that under low shear rate (0.63 mg/kg/h) for edoxaban was 1.9, whereas that for fondaparinux was more than 66. While the efficacy of fondaparinux markedly decreased in arterial thrombosis and in a high-shear state, edoxaban exerted consistent antithrombotic effects regardless of flow conditions. These results suggest that shear rate is a key factor in different antithrombotic effects between edoxaban and fondaparinux.

“Viscosity-plus” Effect in Whole Blood at High Shear Rates

Nature ◽  
1969 ◽  
Vol 221 (5178) ◽  
pp. 365-366 ◽  
Author(s):  
WILLIAM I. ROSENBLUM
Keyword(s):  
Whole Blood ◽  
High Shear ◽  
Shear Rates ◽  
High Shear Rates

The Place of Dielectric Spectroscopy in Probing Electrorheology

1999 ◽  
Vol 13 (14n16) ◽  
pp. 1829-1836 ◽  
Author(s):  
S. Kyvelidis ◽  
G. M. Maistros ◽  
P. Rattray ◽  
H. Block ◽  
J. Akhavan ◽  
...  
Keyword(s):  
Electric Fields ◽  
Working Conditions ◽  
High Shear ◽  
Empirical Correlations ◽  
Electrical Parameters ◽  
Shear Rates ◽  
Uniform Shear ◽  
High Shear Rates ◽  
Er Fluids ◽  
Er Fluid

The measurement of the dielectric spectra of PAnQR based ER fluids under shear and electric fields is discussed and results presented. Data in which either but not both shear or electric fields are present are submitted to analysis in terms of known theories. For flow alone, that analysis provides information on the attenuation of polarization by the uniform shear fields whilst the polarization of quiescent fluids by electric fields may lead to estimates of particles packing within the columns. Permittivity data when both fields are acting is presented, but in the absence of suitable theory, not modelled quantitatively. Empirical correlations are discussed and the conclusion drawn that fibrillation is readily suppressed by even moderate shear rates, although long range dipolar forces still persist to high shear rates. The dc conductance of these fluids have also been measured. This together with permittivity data under ER fluid working conditions has importance in establishing the electrical parameters for any ER fluid.

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