Effects of loading rate, applied shear strain, and magnetic field on stress relaxation behavior of anisotropic magnetorheological elastomer

Abstract

Experimental research and numerical computation of stress relaxation behavior of an anisotropic magnetorheological elastomer (MRE) have been conducted in this paper. The anisotropic MRE has been formed from silicone matrix and micro-sized carbonyl iron particles under a magnetic field. Stress relaxation response of the anisotropic MRE was examined by single- and multi-step relaxation tests in shear mode using double-lap shear specimens. The effects of loading rate, applied constant strain, and external magnetic field on the stress relaxation behavior of the anisotropic MRE were studied. Experimental results showed that the stress relaxation of the anisotropic MRE was slightly dependent on the loading rate, but strongly depended on the constant strain level and the magnitude of external magnetic field. When increasing the constant strain level the shear stress of the anisotropic MRE in the single-step relaxation enhanced, while the relaxation modulus declined. The shear stress and modulus of the anisotropic MRE in the relaxation periods increased with increasing the magnetic field intensity. The four-parameter fractional derivative Zener model was used to describe the stress relaxation behavior of the anisotropic MRE. The presented model was fitted well to experimental data of the anisotropic MRE in both single- and multi-step relaxation tests. The fittings of relaxation modulus and shear stress with long-term predictions for the anisotropic MRE are in a very good agreement with the experimental ones. The maximal relative error of the fitted curves compared with measured data for both relaxation modulus and shear stress is less than 5.0%. As a result, the presented model is applicable to predict the long-term stress relaxation behavior of the anisotropic MRE.