Soft magnetorheological elastomers as new actuators for valves

Abstract

The actuation behavior of soft silicone-based magnetorheological elastomers in magnetic fields of variable strength was investigated. An inhomogeneous magnetic field gives rise to a reversible actuation effect, which is the result of the competition between magnetic and elastic forces in the material. Magnetorheological elastomers are capable of performing more pronounced deformations than known rigid actuator materials. In this article, the actuation behavior of magnetorheological elastomer ring-shaped bodies in a valve-type device for the control of an air flow is demonstrated. For this purpose, magnetorheological elastomer rings with different Shore hardness were prepared and used in the valve. In addition to the common isotropic magnetorheological elastomer samples, rings with an anisotropic arrangement of the magnetic particles were also prepared. The actuation of these anisotropic magnetorheological elastomers was compared with that of the isotropic samples. Based on simulations, the inhomogeneity of the magnetic field at the magnetorheological elastomer material which is required for the actuation could be strongly affected by the shape in the design of the magnetic yoke. In this study, the closing characteristics of the valve with different yoke shapes and magnetorheological elastomer materials were evaluated by measuring the dependence of the air flow rate on the magnetic field strength. It is demonstrated that the air flow through the valve can be controlled by the current in the field-generating coil, which yields the base for a new type of magnetic valve.

Nonlinear magneto-viscoelasticity of transversally isotropic magneto-active polymers

“…Equation (3. 4 is the statement of impossibility of the existence of magnetic monopoles. It is important to note that in the case of problems studied here through magneto-mechanics, the speed of motions is much smaller than the speed of light c; and the frequency of oscillations of all physical quantities is much smaller than the frequency of oscillation of electromagnetic fields involved in the propagation of a light wave.…”

Limit points in the free inflation of a magnetoelastic toroidal membrane

“…In the presence of an external magnetic field, individual magnetization vectors of the ferromagnetic particles align with the applied field and the resulting interaction leads to a change in the observed macroscopic stiffness and dimensions of the polymer (Böse and Röder, 2009;Ginder et al, 2002). This possibility to alter mechanical properties has found applications in sensors and actuators, active vibration control and waveguides (for example, see the works of, Ginder et al (1999Ginder et al ( , 2001, Holmes et al (2012), Li and Zhang (2008), Böse et al (2012), Keh et al (2013), and Saxena (2017)). …”

Tailoring superelasticity of soft magnetic materials

“…Similarly to magnetic fluids [11][12][13][14][15][16][17][18] , magnetic gels allow to reversibly adjust their material properties by external magnetic fields. In this way, switching the elastic properties 19-23 offers a route to construct readily tunable dampers 24 or vibration absorbers 25 , while the possibility to switch the shape 19,[26][27][28] allows application as soft actuators [29][30][31] . Here, we show that magnetic gels due to the interplay between magnetic and elastic interactions likewise feature superelastic behavior: it is enabled by a detachment mechanism of embedded magnetic particle aggregates and by a reorientation mechanism of magnetic moments.…”