ABSTRACT

This paper demonstrates the possibility of the shock wave reduction of ER/MR smart structures. ER (electrorheological) and MR (magnetorheological) fluids are smart materials of which stiffness and damping properties can be controlled by applying electric or magnetic fields, respectively. Thus, when ER or MR fluid is inserted into a structure and an appropriate magnitude of electric or magnetic field is applied, propagating waves can be selectively isolated. To experimentally verify the shock wave reduction, a wave transmission test set is made by using piezoceramic transmitter and receiver on a large aluminum plate. The wave transmission characteristics of ER/MR inserts are investigated in terms of field strength and the wave frequency as well. Since the use of ER/MR smart structures has merits in terms of lightweight and controllability, this technology can be used for many applications--impact resistance system for civil and warship structures.

INTRODUCTION

The problem of isolating shocks and waves in structures is getting important. The intensity of the vibrations generated by oscillating machine foundations or massive impact produced by earthquake and underwater explosion is increasing, at the same time the use of vibrationsensitive equipment is also increasing for example, computers and highly accurate instrumentation for mechanical or optical measurement. Shock waves result in fatal structural damage or functional disorder of important equipment (Chung 1998). In the mean time, people no longer deserve to tolerate the inconvenience caused by these vibrations. Currently, heavy and over-designed mounting structures are adopted to protect sophisticated equipments from shock waves. Smart structure is a structural system that can sense changes in its environment and produces a useful or optimal response by changing its material properties, geometry and mechanical or electrical response. In such structures, both sensor and actuator functions, with an appropriate control, must be integrated.

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