| The combination of electrorheological (ER) fluids and piezoelectric actuators into one actively controlled intelligent sandwich plate structure for either noise or vibration control is investigated in this study. The simply supported sandwich plate consists of a core of four cavities filled with ER fluid, two elastic outer face plates, bottom plate cross stiffeners and symmetrically bonded surface piezoceramic (PZT) actuator patches. Analytical and computational simulations are performed to obtain the resultant structural response to random inputs, noise transmission into a rectangular enclosure, and sound radiation into a semi-infinite acoustic half space.; An equivalent, homogeneous plate model is used in the modal decomposition of the derived governing equations of motion. This equivalency is obtained by taking the modal frequencies and mode shapes, calculated by the finite element method, to be that of the sandwich plate. The effect of actively controlling the ER fluid's stiffness material properties is incorporated into the modal frequencies and mode shapes by altering the sandwich plate's core shear and elastic moduli whereas ER fluid controllable damping is directly incorporated into the governing equations of motion as equivalent modal damping. The effect of the PZT actuators is incorporated into the governing equations of motion through direct velocity feedback utilizing collocated control. A two part control strategy is developed. First, the appropriate ER fluid voltage potential and then the PZT actuator gains are selected.; Numerical results obtained in this study indicate that using ER and PZT active control up to 50 dB of noise reduction is possible at certain frequency ranges. In addition, about 15 dB reduction of the overall radiated sound pressure level can be obtained. However, for the available ER and PZT materials, the reduction of overall sound pressure to random input is shown to be on the order of 5 to 8 decibels. To improve on noise transmission and noise radiation attenuation, advances of the ER fluids and PZT devices along with more refined control theories are necessary. |
