Structured magnetic circuit for magnetorheological damper made by selective laser melting technology

Abstract

Eddy currents are the main reason causing for the long response time of a magnetorheological (MR) damper. Eddy currents are often unwanted parasitic phenomenon for many electromagnetic machines working with an alternating magnetic field. Their reduction can be secured by the use of material with high electrical resistivity such as ferrites or soft magnetic composites. These materials, however, exhibit bad mechanical properties and cannot be used in mechanically loaded parts. Eddy currents can also be reduced by the appropriate structure which must secure high conductivity for the magnetic flux but low electrical conductivity for the electric current flowing perpendicularly to the magnetic flux. This leads to complex structures which, in most cases, cannot be manufactured by conventional methods. This paper describes the design, manufacturing and verification of simulations of the magnetic circuit for a MR damper. Structured magnetic cores printed by selective laser melting technology connects the benefits of low-carbon steel (good mechanical properties, high magnetic saturation and high relative permeability) with benefits of sintered materials (high electric resistivity). The results proved that using the potential of additive manufacturing can not only reduce the eddy currents (and thus shorten the response time and reduce losses), but significantly reduce the weight as well. This technology enables the combination of performance parameters of electromagnetic machines, which cannot be reached by any other existing method.

Multiphysics Model of an MR Damper including Magnetic Hysteresis

“…However, the primary response time for control current drop is independent of piston velocity. It is noteworthy that similar trends were experimentally determined in other research studies [42,43].…”

Stribeck Curve of Magnetorheological Fluid within Pin-on-Disc Configuration: An Experimental Investigation

“…The cohesion of chain formations causes an increase in the apparent viscosity of MR fluid [ 2 ]. This property is most often exploited by MR dampers [ 3 , 4 , 5 ], brakes/clutches [ 6 , 7 , 8 ], seals [ 9 , 10 ], or flexible structures [ 11 , 12 ]. The applicability of these MR devices in smart mechanical systems has several limitations.…”

The magnetic circuit dynamics of a magnetorheological valve with a permanent magnet

“…The change of apparent viscosity is caused by particles aligning in the direction of the magnetic field. Several designs of the MR damper can be found that differ in the number of coils [2,3,4] , the arrangement of the magnetic circuit [3,4,5] and the number of gaps [6,7] etc. If the power supply of the electromagnetic coil is interrupted during damper operation, the damper will remain at the minimum damping level.…”

“…Strecker et al [17] and Kubík et al [4] published the design of the MR damper with a short response time in which the ferrite material of the magnetic circuit was used. Strecker et al [5] published an MR damper with a magnetic circuit manufactured by 3D metal printing. This design method provides a MR damper with a short response time of 1.68 ms and a high dynamic force range.…”