Magnetorheological elastomer-based variable stiffness flexible coupling for vibration isolation

Rotating mechanical equipment such as pumps and motors can suffer from unattenuated torsional vibration. The causes of such vibration range from imbalance within the rotating system to misalignment, or even operating at frequencies close to the system's natural frequency. Smart composite materials are materials for which exposure to external stimuli changes their properties. Magnetorheological elastomers (MRE) are smart composite materials whose mechanical properties, such as stiffness, are changed when exposed to a magnetic field. In this article, we report on the fitting of a variable stiffness coupling (VSC) within a shaft to isolate torsional vibration, which can adapt and change its attenuation frequency range. We experimentally tested the VSC concept for isolating torsional vibration. MRE samples with 40% volume fraction were fabricated and manufactured using a 3D mold design and fixed within a coupling in a shaft to investigate the effects of magnetic fields on the torsional rigidity. Impact hammer tests were conducted in combination with an accelerometer to analyze the transmissibility factor. Our results show that the level of vibration decreased when the magnetic field increased. The first natural frequency of the system happened at 26 Hz and moved to 28 Hz when the applied magnetic field increased from 0 to 12.38 mT. The torsional stiffness of the MRE samples increased from from 37.4 to 61.6 N.m/rad when the magnetic field increased from 0 to 12.38 mT. Variation in the torsional damping coefficient fluctuated as the damping effect of MRE was ignored.