Tham khảo tài liệu 'new tribological ways part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 5 Ferrofluid Seals V. Lemarquand1 and G. Lemarquand2 1 LAPLACE UMR CNRS 5213 IUT Figeac Universite de Toulouse Avenue de Nayrac 46100 Figeac 2Laboratoire d Acoustique de l Universite du Maine UMR CNRS 6613 Avenue Olivier Messiaen 72085 Le Mans Cedex 9 France 1. Introduction Ferrofluids are very peculiar materials. Indeed a stable colloidal suspension of magnetic particles in a liquid carrier is something special. These magnetic particles of about 10 nanometers in diameter are coated with a stabilizing dispersing agent that prevents their agglomeration. The liquid can be either water or synthetic hydrocarbon or mineral oil. But this material class discovered in the 1960s proves specific various chemical and physical properties whose increasing knowledge leads to ever more numerous technological applications. Indeed they are efficiently used in various engineering areas such as heat transfers motion control systems damping systems 1 sensors 2 3 . Their use to design fluid linear pumps for medical applications seems also very promising 4 5 . However they are more commonly used as squeeze films in seals and bearings for rotating devices. Tarapov carried out some pioneering work regarding the ferrofluid lubrication in the case of a plain journal submitted to a non-uniform magnetic field 6 but more recent works show and discuss the recent trends in such a use 7 - 13 . Moreover ferrofluid dynamic bearings have been regularly studied and their static and dynamic characteristics have been described theoretically 14 - 21 . The various properties of ferrofluids enable them to fulfill such functions as heat transfer ensuring airtightness working as a radial bearing. Therefore they are used in electrodynamic loudspeakers. Moreover a ferrofluid seal can replace the loudspeaker suspension and leads to a better linearity of the emissive face movement 22 - 26 . This chapter intends to explain how ferrofluid seals are formed in magnetic structures by presenting a simple analytical .
