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Magnetic Fluids and Porous Media for Active Dampers.


Foreseen Results

The direct output of this project is the final product: active dampers for a wide range of utilization. These active dampers could be used on aircrafts (landing dampers) on trains, buses, underground carriages (damping of lateral vibration and improvement during acceleration and decceleration periods) on cars (improvement of comfort and security). Other applications are expected in isolation of vibrations transmitted by engines or machines with moving parts. Bumpers could be built as special dampers whose function is to dissipate the energy of a shock with an optimal law of decceleration for a given impact force and stroke of the piston. Small size active dampers could also serve on deformable structures submitted to random forces (for instance cables or any suspended structure acted on by the wind).
On the other hand this study should bring a significant contribution to other fields of research:
The understanding of flow magnetic fluids in channels is important for other applications of these magnetic fluids (pressure distribution in actuators, heat exchanger, even flow of magnetic particles in blood vessels for medical diagnostic or curing).
The understanding of invasion of porous media by a non wetting fluid and especially of the microscopic mechanisms responsible for the hysteresis and the dissipation during a series of cycles is a very promising domain both for theoretical and applied research.
In Western Europe no company sells magnetic fluids. These companies are either in USA (Ferrofluidics, Lord Corporation) or in Japan. A few laboratories or recently created firms are proposing ferrofluids in Eastern countries (among them the laboratory of Pr. Bashtovoi). Our study should contribute both to the improvement of these fluids (stability, higher change of viscosity in a magnetic field) and to the development of the potential market for applications.
The purpose of this project is to manufacture adaptative dampers whose mechanical response from soft to firm can be controlled by electronics.
The proposed technological solution is a synthesis of two technologies: the first one on magnetic fluids which begin to be widely used in industry ( magnetic seals of hard disks, loudspeakers etc...) and the second one on porous materials which are for instance commonly used in chromatography.
A non wetting fluid for a given porous material only invades the pores if the pressure is larger than a critical one proportional to the surface tension and inversely proportional to the radius of the pores. This effect can be used to store or to dissipate the energy due to a shock and patents have been taken by one of the proposers for damping applications. The drawback is that the liquid used with the porous material is water which is not suitable for mechanical applications, furthermore the damping characteristics are definitively fixed by the choice of the porous material.
On the other hand the volume flow rate of magnetic fluids in channels, and so the dissipation rate of energy, can be controlled by the application of a magnetic field. This technology is still not completely applicable principally because efficient magnetic fluids are made of large magnetic grains (larger than one micron) which are abrasive and quickly sediment. Other possibilities of damping with stable ferrofluid (a magnetic fluid made of very small grains: 100 Angstrom of ferrous oxide) also exist and are patented by the laboratory of Pr. Bashtovoi but they would not be able to damp the large loads required in automotive industry and furthermore they use permanent magnet with no possibility of controlling the damping rate.
By combining the two technologies: the porous material to absorb large shocks and the application of a variable magnetic field to control the dissipation rate of a magnetic fluid, we can obtain adaptative and efficient dampers in a very wide range of loads. The two technologies will be juxtaposed in a first time and then merged by putting the magnetic fluid directly in contact with a porous material specially processed to be non wettable by the magnetic fluid.
This new technology for adaptative dampers should initiate a qualitative jump for the comfort and the security in the field of transportation (automotive, buses, railway, aircraft) and of environment ( damping of vibrations produced in the low frequency acoustic range ).

Funding Scheme

CSC - Cost-sharing contracts


Parc Valrose, Université De Nice - Sophia Antipoli
06108 Nice

Participants (5)

Belarussian State Polytechnical Academy
65,F. Scoryna Avenue
220027 Minsk
Centre National de la Recherche Scientifique
Avenue Des Etats Unis
78000 Versailles
Centre for Thermomolecular Energetic and Thermonic
1,Laboratorny Pereulok
252133 Kiev
Moscow State University 'Lomonosov'
234 B,vorobievy Gory
119899 Moskva
647,Avenida Diagonal 647
08028 Barcelona