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Fatigue life prediction is of great significance in ensuring magnetorheological elastomer (MRE) based rubber components exhibit reliability and do not compromise safety under complex loading, and this necessitates the development of plausible fatigue life predictors for MREs. In this research, silicone rubber based MREs were fabricated by incorporating soft carbonyl iron magnetic particles. Equi-biaxial fatigue behaviour of the fabricated MREs was investigated by using the bubble inflation method. The relationship between fatigue life and maximum engineering stress, maximum strain and strain energy density were studied. The results showed that maximum engineering stress and stored energy density can be used as reliable fatigue life predictors for SR based MREs when they are subjected to dynamic equi-biaxial loading. General equations based on maximum engineering stress and strain energy density were developed for fatigue life prediction of MREs. [ABSTRACT FROM AUTHOR]

The equi-biaxial fatigue behaviour of silicone based magnetorheological elastomers (MREs) with various volume fractions of carbonyl iron particles ranging between 15% and 35% was studied. Wöhler curves for each material were derived by cycling test samples to failure over a range of stress amplitudes. Changes in complex modulus ( E ∗ ) and dynamic stored energy during the fatigue process were observed. As for other elastic solids, fatigue resistance of MREs with different particle contents was shown to be dependent on the stress amplitudes applied. MREs with low particle content showed the highest fatigue life at high stress amplitudes while MREs with high particle content exhibited the highest fatigue resistance at low stress amplitudes. E ∗ fell with the accumulation of cycles for each material, but the change was dependent on the particle content and stress amplitude applied. However, each material failed in a range suggesting a limiting value of E ∗ for the material between 1.22 MPa and 1.38 MPa regardless of the particle content and the magnitude of the stress amplitude. In keeping with results from previous testing, it was shown that dynamic stored energy can be used to predict the fatigue life of MREs having a wide variation in particle content. [ABSTRACT FROM AUTHOR]

Prediction of fatigue life is of great significance in ensuring that dynamically loaded rubber components exhibit safety and reliability in service. In this text, the dynamic equi-biaxial fatigue behaviour of magnetorheological elastomer (MREs) using a bubble inflation method is described. Wöhler (S–N) curves for both isotropic and anisotropic MREs were produced by subjecting the compounds to cycling over a range of stress amplitudes (σ a) between 0.75 MPa and 1.4 MPa. Changes in physical properties, including variation in stress–strain relations and complex modulus (E*) during the fatigue process were analysed. It was found that the complex modulus of MRE samples decreased throughout the entire fatigue test and failure took place at a limiting value of approximately 1.228MPa ± 4.38% for isotropic MREs and 1.295 ± 10.33% for anisotropic MREs. It was also determined that a dynamic stored energy criterion can be used as a plausible predictor in determining the fatigue life of MREs. [ABSTRACT FROM AUTHOR]

Abstract: For materials in modern machines, fatigue strength is probably the most critical physical property that needs to be understood. In particular, the high dynamic loading experienced by machine parts necessitates understanding fatigue properties in life limiting components. However, rubber fatigue is imperfectly understood and even less is known about fatigue resistance in adaptive or smart elastomers. Preliminary research into the equi-biaxial fatigue behaviour of magnetorheological elastomers (MREs) is described here. Test samples were fabricated by incorporating carbonyl iron particles, typically of 6–7μm in diameter, in room temperature vulcanised (RTV) silicone rubber. Physical testing was conducted using a bubble inflation testing system and test samples were fatigued at stress amplitudes between 0.75MPa and 1.4MPa under engineering stress control. S–N (Wöhler) curves of stress amplitude (σ a = S) versus cycles to failure (N) are presented. Stress–strain behaviour throughout the fatigue process is also described. For a stress amplitude of 0.75MPa and zero minimum stress, stress softening was observed for the entire test, though it was particularly pronounced in the first 100 cycles of testing. A limiting value of complex modulus (E* ), observed previously in dynamic testing of conventional elastomers, was determined in these tests. [Copyright &y& Elsevier]

Magnetorheological elastomers (MREs) are smart materials whose mechanical properties can quickly respond to changes in the external magnetic field. This phenomenon is known as the magnetorheological (MR) effect and is the key to the application of magnetorheological elastomers. Previous studies have found that the interface between magnetic particles and elastomers is a critical factor that influencing the MR effect of MREs. To improve the interfacial interaction between silicone rubber (SR) and carbonyl iron (CI) particles, in the MREs considered in this work, CI particles were subjected to surface modification through polydopamine (PDA) deposition and n-dodecyltrimethoxysilane (DTMS) grafting. X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirmed the successful deposition of PDA@DTMS coating layer with a thickness of about 30.6 nm. The tensile strength of anisotropic MREs increased by 31.5% after surface modification of CI particles. The study of magnetic field induced changes in viscoelastic properties showed that CI-PDA@DTMS based MREs exhibited a superior MR effect to the CI-based MREs. • Carbonyl iron (CI) particles were modified by polydopamine and n-dodecyltrimethoxysilane. • Surface modification improved the dispersibility of CI in silicone rubber. • The mechanical properties of the MREs were enhanced through CI modification. • MREs with surface modified CI exhibited a superior magnetorheological effect. [ABSTRACT FROM AUTHOR]