Analytical and experimental free vibration analysis of multi-layer MR-fluid circular plates under varying magnetic flux

Free vibration characteristics of sandwich annular circular plates comprising magneto-rheological (MR) fluid as the core layer are evaluated analytically and experimentally. An analytical model of the sandwich annular plate was formulated using Ritz method based on the classical plate theory. The numerical analyses were performed to study the free vibration responses of the sandwich plate in terms of resonant frequencies and loss factors considering variations in the magnetic flux and boundary conditions. The experiments were conducted on a free-free sandwich circular plate comprising two PETG (Polyethylene Terephthalate Glycol) face layers constraining the MR fluid core layer. A hollow-core electromagnet was developed for inducing variable magnetic flux over the structure. The free vibration properties of the sandwich plate were measured using MEscop VES modal analyzer. The measured data were analyzed to determine natural frequencies of the MR sandwich plate under different levels of the magnetic flux, which were subsequently used to examine validity of the analytical model. Furthermore, the effects of plate parameters on the natural frequencies and damping of the structure were investigated. The results suggested that increasing the flexibility of the face layers yields more pronounced effect of magnetic flux on the structure stiffness properties.