A New Type of Hydraulic Actuator Using Electrorheological Fluids

1999 ◽  
Vol 13 (14n16) ◽  
pp. 2176-2182 ◽  
Author(s):  
Eckhard Wendt ◽  
Klaus W. Büsing
Keyword(s):  
Silicone Oil ◽  
Response Times ◽  
Electrical Signal ◽  
Electrorheological Fluids ◽  
Shear Stresses ◽  
Hydraulic Fluid ◽  
High Shear ◽  
Hydraulic Systems ◽  
Hydraulic Actuator ◽  
Inorganic Particles

Electrorheological Fluids (ERF) are usually used in semi active damping elements, e.g. shock absorbers or engine mounts because of their continuously controllable shear stress. A totally new field of application may be achieved, if an ERF is used as a hydraulic fluid and not only as a control medium. In this case a fundamental need is the capability to produce a volume flow by using normal hydraulic pumps, e.g. gear pumps. The ERF and the hydraulic components both must have a long lifetime without unusual wear. Bayer AG has developed an ERF based on soft crosslinked PU-particles dispersed in silicone oil. These ERF are characterised by a low basic viscosity, a high ER-effect and a moderate conductivity. Compared with previous ERF where hard inorganic particles were used, the new fluid is not abrasive. It is foremostly this characteristic which gives the possibility of using the ERF in hydraulic systems with high shear rates and high shear stresses. The usage of ERF as hydraulic fluid allows the construction of proportional valves without mechanically driven parts. The control of the pressure drop over the valves is realised directly by an electrical signal. It is possible to realise actuators with very fast response times since the reaction time of ERF is within milliseconds. For demonstration purpose Bayer AG has built an actuator which is controlled by an electrorheological valve-block. The calculation of the dimension of this actuator and the valves will be shown and the realised response time will be demonstrated.

On/Off Valves Synchronization and Reliability Evaluation of a Digital Hydraulic Actuator

2020 ◽  
Author(s):  
Ivan J. Mantovani ◽  
Heitor A. Kagueiama ◽  
Artur T. de C. Gama ◽  
Alessandro Dell' Amico ◽  
Petter Krus ◽  
...  
Keyword(s):  
Energy Efficiency ◽  
Flight Control ◽  
Response Times ◽  
Reliability Evaluation ◽  
Similar Response ◽  
Efficiency Gain ◽  
Hydraulic Systems ◽  
Hydraulic Actuator ◽  
Opening And Closing ◽  
Control Surfaces

Abstract The development of actuators for flight control surfaces based on electrical technologies had a breakthrough in the last decade. Nevertheless, servo-hydraulic systems are still widely used. Servo Hydraulic Actuators (SHA) have the advantages of precise positioning, high dynamic response and being a jam-free solution in case of failures, but they present low energy efficiency. Digital hydraulics has become a topic of interest in improving energy efficiency in the fluid power community. A Digital Hydraulic Actuator (DHA) for aircraft is being developed to be used in primary flight control surfaces. The DHA concept is based on secondary control with multi-chamber cylinders and shows an energy efficiency gain with a similar response when compared to SHA. However, the opening and closing times of on/off valves are different and uncertain. These aspects may result in short circuits, bringing energy losses, or in blocked chambers, which may cause pressure peaks or cavitation. Consequently, the DHA system may have a lower energy efficiency or presents vibration due to fluid blocking. The present paper presents a solution for these issues and the reliability evaluation of the DHA. The opening and closing times issues are addressed using the synchronization between on/off valves through a method to find the correct time for valve opening control. As a result, the synchronization of pressure shifting without knowledge of the response times of on/off valves was accomplished. Moreover, when used periodically, this method can estimate future failures in valves due to a change of the required time delay. In order to evaluate the system reliability, FTA models were developed considering valve and pressure line failures, modelling how the failures affect force availability to move the control surfaces. The resulting FTAs were reduced to the minimum cut-sets that lead to force profiles that are insufficient for a safe flight and also may lead to an aircraft crash. Considering that the on/off valves have similar failure rates to those of servo valves, the results show that DHA and SHA have comparable reliability levels.

Simulacija i odstranjivanje stick-slip efekta servosistema sprovodnog aparata hidraulične turbine

2021 ◽  
Vol 23 (1) ◽  
pp. 37-41
Author(s):  
Darko Babunski ◽  
◽  
Emil Zaev ◽  
Atanasko Tuneski ◽  
Laze Trajkovski ◽  
...  
Keyword(s):  
Hydraulic Cylinder ◽  
Friction Model ◽  
Slip Effect ◽  
Hydraulic Systems ◽  
Hydraulic Actuator ◽  
Stick Slip ◽  
Hydro Turbine ◽  
Servo Mechanism ◽  
The Mathematical Model ◽  
Slip Phenomenon

Friction is a repeatable and undesirable problem in hydraulic systems where always has to be a tendency for its removal. In this paper, the friction model is presented through which the most accurate results are achieved and the way of friction compensation, approached trough technique presented with the mathematical model of a hydraulic cylinder of a hydro turbine wicket gate controlled by a servomechanism. Mathematical modelling of a servo mechanism and hydraulic actuator, and also the simulation of hydraulic cylinder as a part of a hydro turbine wicket gate hydraulic system where the stick-slip phenomenon is present between the system components that are in contact is presented. Applied results in this paper and the theory behind them precisely demonstrate under what circumstances the stick-slip phenomenon appears in such a system. The stick-slip effect is simulated using Simulink and Hopsan software and the analysis of the results are given in this paper. Removal of the stick-slip effect is presented with the design of a cascade control implemented to control the behaviour of the system and remove the appearance of a jerking motion.

Release of ADP from Erythrocytes Under High Shear Stresses in Tube Flow

1979 ◽  
Author(s):  
H. Schmid-Schönbein ◽  
I. Rohling-Winkel ◽  
P. Blasberg ◽  
E. Jüngling ◽  
A. Wehmeyer ◽  
...  
Keyword(s):  
Fluid Layer ◽  
Shape Change ◽  
Total Concentration ◽  
Shear Stresses ◽  
Tube Flow ◽  
High Shear ◽  
Hemoglobin Content ◽  
Before And After ◽  
Adp Release ◽  
Adenosine Nucleotides

ADP stemning from red blood has been shown to “activate platelets” producing shape change, as well as aggregation and release. However, the mode of release of ADP from intact RBC has never been established. Contrary to popular misconceptions, high shear stresses (τ) prevail during natural hemostatic plug formationin arteries and arterioles. Therefore, we tested ADP-release from RBC subjected for 5-100 msec in tube flow (τ-0-200N/m2) during passage through a hollow fiber (0 400 μm, L = 20 cm) with semipermeable walls (AMICON R). Samples from the fluid layer near the wall were ultrafiltered through it and became accessible for chemical analysis. Concentrations of K+, adenosine nucleotides (HPLC), and Hb (In the supernatant) before and after shear exposure were measured. At T > 50 N/m2T K+, adenosine nue Ieotides, and hemoglobin concentrations rose in the supernatant. Only K+ was higher in the u1 trafiltrate than in the latter, whereas total concentration of adenosine nucleotides were not different and hemoglobin did not permeate. There was no difference between the relative molar concentration of total adenosine nucleotides of hemoglobin, i.e. the nucleotides and hemoglobin content of 10-4 and 10-3 of all RBC were liberated. In the ultrafiltrate (ADP) > 2 χ 10-7 M/L, sufficient to activate platelets in the presence of Ca++.

Effects Of Short Time High Shear Exposure Upon Platelet Function And The Coagulation System Under Heparin Anticoagulation

1981 ◽  
Author(s):  
L J Wurzinger ◽  
R Opitz ◽  
P Blasberg ◽  
K Bialonski ◽  
H Schmid-Schönbein
Keyword(s):  
Platelet Function ◽  
Lactic Dehydrogenase ◽  
Arterial Stenosis ◽  
Coagulation System ◽  
Shear Stresses ◽  
High Shear ◽  
Platelet Factor ◽  
Shear Rates ◽  
Heparin Anticoagulation ◽  
Short Time

The fact that high shear activates and damages platelets has been suspected to be a major cause of thromboembolism in artificial internal organs (AIO) or in arterial stenosis. In AIO wall shear stresses well above 50 Nm-2 have been computed to which blood cells are exposed for times in the order of milliseconds (ms). Unfortunately, the studies on this subject employing defined flow conditions operate with exposure times higher than 10 seconds. The pupose of the present study was to elucidate the effects of high shear exposure for ms upon platelet function (ADP induced platelet aggregation (PA), platelet procoagulant activity {PF- 3)) under heparin anticoagulation, which is also used in AIO.To apply shear rates ranging from 50 - 220 Nm-2 to heparinized PRP for defined exposure times between 7 - 700 ms a flow through Couette-viscometer was employed. Platelet factor 3 (PF-3) availability was estimated by using a modified Stypven time technique. Lactic dehydrogenase (LDH) liberation was taken as a measure for platelet destruction. All steps of the experimental procedure were carried out at 37°C.From our data we conclude that, in the presence of physiological calcium levels (heparin anticoagulation) shear stresses and exposure times that certainly occur in AIO are able to activate platelets and procoagulant potential of blood.

Rheology of Fluoride Gels

1976 ◽  
Vol 55 (3) ◽  
pp. 353-356 ◽  
Author(s):  
M. Braden ◽  
Ratna Perera
Keyword(s):  
Infrared Spectroscopy ◽  
Shear Rate ◽  
Elastic Behavior ◽  
Shear Stresses ◽  
High Shear ◽  
Shear Rates ◽  
Extreme Stress ◽  
Thickening Agents ◽  
Shear Rate Dependence ◽  
Low Shear

Six commercial fluoride gels have been studied, using a cone and plate viscometer. Also, the thickening agents have been analyzed using infrared spectroscopy. All gels showed stress thinning, which is the decrease of viscosity with shear rate. Such shear rate dependence is clinically convenient in that the gel will flow readily at the high shear stresses present when the gel is applied but will not flow readily under its own weight when on the tooth. Five materials containing hydroxyalkyl celluloses showed similar degrees of shear thinning. One material with a non-cellulosic thickener showed much more extreme stress thinning together with elastic behavior at low shear rates; such behavior may be clinically advantageous. All of the gels showed only slight temperature dependence of rheological properties.

Response times of electrorheological fluids

1991 ◽  
Vol 70 (3) ◽  
pp. 1207-1211 ◽  
Author(s):  
John C. Hill ◽  
Thomas H. Van Steenkiste
Keyword(s):  
Response Times ◽  
Electrorheological Fluids

Eulerian-Eulerian Multiphase Modeling of Blood Cells Segregation in Flow Through Microtubes

2017 ◽  
Author(s):  
Yertay Mendygarin ◽  
Luis R. Rojas-Solórzano ◽  
Nurassyl Kussaiyn ◽  
Rakhim Supiyev ◽  
Mansur Zhussupbekov
Keyword(s):  
Shear Stress ◽  
Red Blood Cells ◽  
Blood Cells ◽  
Heart Diseases ◽  
Accurate Determination ◽  
Shear Stresses ◽  
High Shear ◽  
Blood Damage ◽  
Solid Phases

Cardiovascular Diseases, the common name for various Heart Diseases, are responsible for nearly 17.3 million deaths annually and remain the leading global cause of death in the world. It is estimated that this number will grow to more than 23.6 million by 2030, with almost 80% of all cases taking place in low and middle income countries. Surgical treatment of these diseases involves the use of blood-wetted devices, whose relatively recent development has given rise to numerous possibilities for design improvements. However, blood can be damaged when flowing through these devices due to the lack of biocompatibility of surrounding walls, thermal and osmotic effects and most prominently, due to the excessive exposure of blood cells to shear stress for prolonged periods of time. This extended exposure may lead to a rupture of membrane of red blood cells, resulting in a release of hemoglobin into the blood plasma, in a process called hemolysis. Moreover, exposure of platelets to high shear stresses can increase the likelihood of thrombosis. Therefore, regions of high shear stress and residence time of blood cells must be considered thoroughly during the design of blood-contacting devices. Though laboratory tests are vital for design improvements, in-vitro experiments have proven to be costly, time-intensive and ethically controversial. On the other hand, simulating blood behavior using Computational Fluid Dynamics (CFD) is considered to be an inexpensive and promising tool to help predicting blood damage in complex flows. Nevertheless, current state-of-the-art CFD models of blood flow to predict hemolysis are still far from being fully reliable and accurate for design purposes. Previous work have demonstrated that prediction of hemolysis can be dramatically improved when using a multiphase (i.e., phases are plasma, red blood cells and platelets) model of the blood instead of assuming the blood as a homogeneous mixture. Nonetheless, the accurate determination of how the cells segregate becomes the critical issue in reaching a truthful prediction of blood damage. Therefore, the attempt of this study is to develop and validate a numerical model based on Granular Kinetic Theory (GKT) for solid phases (i.e., cells treated as particles) that provides an improved prediction of blood cells segregation within the flow in a microtube. Simulations were based on finite volume method using Eulerian-Eulerian modeling for treatment of three-phase (liquid-red blood cells and platelets) flow including the GKT to deal with viscous properties of the solid phases. GKT proved to be a good model to predict particle concentration and pressure drop by taking into account the contribution of collisional, kinetic and frictional effects in the stress tensor of the segregated solid phases. Preliminary results show that the improved segregated model leads to a better prediction of spatial distribution of blood cells. Simulations were performed using ANSYS FLUENT platform.

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