Two-particle element of a magnetorheological elastomer under oscillating magnetic field and cyclic mechanical load

Abstract

This paper presents the results of modeling the behavior of a pair of magnetizable particles embedded in a viscoelastic elastomer subjected to two different types of external loading. The dynamics of a cylindrical sample loaded with a constant force at its ends in an ac magnetic field and a sample in a constant field under mechanical load of varying magnitude are investigated. The described system can serve as a mesoscopic structural element of magnetorheological elastomer. This element exhibits hysteretic behavior in the quasistatic regime. The particles initially positioned well apart fall, at some finite field strength, onto one another (cluster) and dwell in this state until the field decreases well below the value at which the cluster has been formed. Under cyclic stretching or compression, the sample exhibits similar behavior in the field with a fixed intensity. Because of dynamic changes in external loads, viscous friction reduces the strength of particle motion, thus impeding the occurrence of a magnetodeformational hysteresis of the element. The hysteresis is suppressed by high frequency oscillations and tensile forces applied to the sample. With a decrease in the frequency of forced oscillations or an increase of the external field intensity, the response of the system becomes nonharmonic, which is caused by the nonlinearity of the increasing interaction of magnetizable particles. Thus, the examined element approaches qualitatively different oscillation modes, which involve the collapse of particles. Clustering of particles inside the magnetorheological elastomer in dynamic processes is important from the viewpoint of improving the mechanical properties of the composite.