Приборы и методы измерений № 2 (3), 2011  71 
МЕТОДЫ ИЗМЕРЕНИЙ, 
КОНТРОЛЯ, ДИАГНОСТИКИ 
 
УДК 681.2.08: 537.622  
 
RESEARCH OF ULTRASONIC SENSING AND MIXING ELEMENTS FOR CONTROL 
OF MAGNETORHEOLOGICAL FLUIDS STABILITY 
 
Dragašius E., Jūrėnas V., Mačiukienė V., Mažeika D. 
 
Kaunas University of Technology, Kaunas, Lithuania 
 
Using of magnetorheological fluids (MRF) can reduce energy costs and weight and increase the 
devices speed and lifetime. In order to fully use all the qualities of MRF properties one must 
from time to time mix them and measure their properties. These systems are still being designed 
and tested in the laboratories. There are many structures with rheological fluid, but in many de-
vices fluids are sealed and mechanical mixing and direct measurement of fluid properties are 
not possible. Effective stability control system for the rheological fluids, which supports homo-
geneity of the fluid, is described. (Е-mail: edraga@ktu.lt) 
 
Key Words: magnetorheological fluid, ultrasound, control system, oscillation frequency. 
 
Introduction 
 
This article describes several ways of using 
ultrasonic mixing and sensing elements for control 
of magnetorheological fluids (MRF) stability. De-
scribed devices have been developed and tested in 
the laboratory. At the beginning mixers have been 
designed similar to an ultrasound bath design, but 
when they were tested in the laboratory they 
showed that using of these mixers with large vo-
lumes of MRF will result in insufficiently good 
mixing. Therefore using piezoceramic elements 
has been developed ultrasonic cavitations, which 
have mixed small and large quantities of the rheo-
logical fluid. 
 
MRF mixing using the ultrasound 
 
Using piezoceramic elements some mixers were 
developed and tested in two ways: 
1
st
 – piezoceramic element was attached to the 
bottom of vessel and immersed into MRF or pie-
zoceramic element was attached to the bottom of ves-
sel outside (figures 1); 
2
nd
 – piezoceramic element was used for excita-
tion of the ultrasonic horn, which was immersed into 
the MRF. 
First construction was designed with two func-
tions, because you can mix MRF and find fluid viscos-
ity and volume from measured resonant characteristics 
of the device. 
In the experiment resonant frequency of the ves-
sel was measured by the KD91 accelerometer as a 
function of MRF level in the vessel. The results are 
presented in the figure 2. 
In this experiment it was shown that the mixing 
quality is good only in particular cases. For the small 
MRF volumes mixer has good performance, but with 
increase in MRF volume or viscosity element which 
generates ultrasound is damped very hard. So we can 
say that this mixer is more suitable for lower viscosity 
materials or very small volumes of MRF.  
In another mixing method ultrasonic horn was 
immersed in vessel with the MRF, which was affected 
by the sedimentation. Oscillation frequency was 
20 kHz, ultrasonic horn end diameter – 4 mm, excita-
tion power – 100 W, vessel volume – 50 cm3. MRF 
mixing quality will depend on excitation power, pro-
cessing time and volume of fluid. In the considered 
case MRF was efficiently mixed only in volume of 
small radius (about 12 mm) around the immersed ul-
trasonic horn. For mixing of MRF in all volume it is 
necessary to provide additional rotational movement 
of the ultrasonic horn. 
 Методы измерений, контроля, диагностики 
 
72  Приборы и методы измерений № 2 (3), 2011 
 
                       
a b 
 
Figure 1 – MRF mixer with piezoelectric element: a – piezoelectric element is attached to the bottom of the 
vessel inside and immersed into the MRF; b – piezoelectric element is attached to the bottom of the vessel 
outside; 1 – metal vessel, 2 – MRF, 3 – piezoelectric element 
 
 
 
 
Figure 2 – Dependence of resonant frequency on the volume of MRF 
 
 
In the second case ultrasonic horn was im-
mersed into the vessel with volume 2 cm
3
 filled 
with the MRF affected by the sedimentation. Os-
cillation frequency was 20 kHz, ultrasonic horn 
end diameter – 4 mm, excitation power – 20 W. 
In this case processing time was 15 seconds and 
the fluid temperature variation amounted about 
20 degree of Celsius. 
Concentration of particles in the mixed fluid 
was determined by measuring inductance of coil 
with short circuit connection of one ring. The 
measurement results are presented in figure 3. 
 
Conclusion 
 
During experiments it was found that mixers 
which have piezoelectric elements on the bottom 
of vessel inside or outside it are not suitable for 
mixing of larger volumes of MRF or fluids with 
high viscosity. Therefore, the system is ideal for 
 Методы измерений, контроля, диагностики 
 
Приборы и методы измерений № 2 (3), 2011  73 
mixing of small volumes of low-viscous MRF. 
Resonant frequencies of the vessel can be used 
as indicator of fluid volume and viscosity. 
Mixing of MRF using high-frequency ultra-
sonic horn resulted in formation of vortices in 
the fluid. The fluid was mixed in the radius 
about 20 mm around the ultrasonic horn end. In 
the mixing zone the fluid was strongly heated, 
but below the critical temperature. If you want 
to completely mix the MRF in a small volume, 
there is no need to dip the ultrasonic horn to the 
bottom of the vessel, but if you want to mix the 
MRF in a large volume, then ultrasonic horn 
needs to be provided with additional move-
ments or it is necessary to use several ultrasonic 
horns. 
 
 
 
Figure 3 – Measurement results of particle concentration in MRF on different levels of fluid 
Numbers indicate values of ultrasonic horn immersion depth 
 
 
 
Acknowledgments  
 
This research was funded by grants from the 
Agency for Science, Innovation and Technology 
and the Research Council of Lithuania. 
 
References 
 
1. Jolly, M.R. Properties and Applications of 
MR Fluids / M.R. Jolly, J.W. Bender, J.D. 
Carlson // SPIE 5-th Annual Int. 
Symposium on Smart Structures and 
Materials, San Diego, CA, 15 March, 1994. 
2. Carlson, J.D. Controllable Fluids / J.D. 
Car-lson, J.L. Spronston // Status of ER 
and MR Fluid Technology, «Actuator 
2000». – 7-th International Conference on 
New Actuators, 19–21 June, 2000. 
3. Bydoń, S. Construction and Operation of 
Magnetorheological Rotary Brake / S. By-
doń // Proceedings of STOC'2002, Ostrava, 
April 26–27, 2001. 
 
 Методы измерений, контроля, диагностики 
 
74  Приборы и методы измерений, № 2 (3), 2011 
 
 
 
 
Драгашиус Е., Юренас В., Мачюкене В., Мажейка Д. 
 
Исследование ультразвуковых чувствительных и перемешивающих элементов для 
управления стабильностью магнитореологических жидкостей 
 
Использование магнитореологических жидкостей позволяет снизить энергетические затраты, вес 
и увеличить быстродействие и срок службы устройств. Для полного качественного использования 
свойств магнитореологических жидкостей их необходимо периодически перемешивать и измерять их 
свойства. Такие системы в настоящее время разрабатываются и тестируются в лабораториях. 
Существует множество структур с реологической жидкостью, однако во многих устройствах 
жидкости герметизированы и механическое перемешивание и прямое измерение свойств жидкости 
невозможны. Описана эффективная система управления стабильностью для реологических 
жидкостей, поддерживающая их однородность. (Е-mail: edraga@ktu.lt) 
 
Ключевые слова: магнитореологическая жидкость, ультразвук, системы управления, частота ко-
лебания. 
 
Поступила в редакцию 23.08.2011.