The Effect of Microstructure on the Dynamic Equi-Biaxial Fatigue Behaviour of Magnetorheological Elastomers

摘要: Dynamic equi-biaxial fatigue behaviour of isotropic and anisotropic magnetorheological elastomers (MREs) based on a silicone rubber matrix was investigated using the bubble inflation method. Constant engineering stress amplitude used as control mode samples were fatigued over different ranges between 0.75MPa 1.4MPa. S-N (Wohler) curves showing plots (σa) versus cycles to failure (N) are presented. Stress-strain throughout process is described. Elastic modulus (E*) studied for specific measured. It found that MREs exhibited greater resistance than given magnetic particle content. Stress softening hysteresis continued tests though they most pronounced in first dozen at lower amplitudes. A limiting value E*, below which likely take place observed both MREs, although initial higher MREs. Figure 1. The equal-biaxial test system (a), graph depicting tracking displacement dots pole bubble; (b) an inflated MRE sample 2.2 Fabrication Both with carbonyl iron content 20vol% produced. Firstly, mixed catalyst 10:1 ratio. Then particles incorporated into mixture mechanically stirred distribute evenly elastomer matrix. whole degassed vacuum remove entrapped air bubbles then poured mould. After further degassing mould, compound kept room temperature 48h allow solidification. For cured presence field Halbach Array after degassing. can provide mean flux 400mT ± 5% 50mm nominal diameters samples. thickness fabricated 1mm. 2.3 Microscopy observation microstructures Scanning Electron Microscope (SEM, Zeiss Supra). Samples coated fine layer gold make them conductive SEM images taken accelerating voltage 5KV. 2.4 Bubble testing retained hydraulic system’s orifice cycling. Initially, quasi-static carried out determine stress-strain relationship loading. This allowed equibiaxial dynamic parameters be set. Thereafter, conducted range amplitudes minimum zero. Typically, pressure applied causing inflate. vision system, utilizing two charge coupled device (CCD) cameras, recorded movement points surface during deflation. values simultaneously calculated from geometry, while strain change distance surface, three dimensional position coordinates obtained output. Throughout these tests, facility continually changes corrected limits maintain constant (σEng). integrated programme count accumulated cycles. theory obtaining relations described elsewhere (Jerrams et al. 2012).Test not cycled here. 2. image 3. arrow shows direction 3 RESULTS AND DISCUSSION 3.1 Microstructure shown 2 respectively. As seen figures, distributed randomly but formed chain-like structures 3.2 Quasi-static average strength 3.5MPa 4.1MPa These set subsequent tests. 4 observed, curve results similar ‘S’ shaped configuration typical uniaxial tensile compounds. Unsurprisingly, stiffer extensibility.