Controlling Tube Vibration Using an Electro-Rheological Fluid

The vibration transmissibility characteristics of a cantilevered brass tube are controlled by means of an electro-rheological (ER) fluid which is employed as a constrained layer damping medium. The ER fluid, which is a 50 wt.% mixture of silicone oil and starch, was contained in the annular space formed between the outer surface of the tube and the inner surface of a bigger brass tube. It is shown that the modal characteristics of the tube depend on the electric field strength and on the height of the ER fluid. The modal frequencies of the tube increase as the electric field strength is increased and as the height of the ER fluid is increased. Also, the loss factors generally increase as the electric field is increased, but decrease as the height of ER fluid in the annular space is increased. When the annular space is 100% filled with ER fluid, the fluid effectively couples the inner and outer tubes into one vibrating system. Overall, the modal transmissibility of the tube is least when the annular space is filled with the ER fluid to a level of 12.5% of the maximum and an electric field strength of 1 k V/mm is applied.