2020 年 5 巻 p. 169-177
In this study, a broad band frequency tunable dynamic absorber was designed and fabricated based on the primary design principle of a mass damper. A magneto-rheological elastomer (MRE) that can change the relative stiffness when an external magnetic field is applied was used to control the natural frequency of the movable mass of the absorber. A coil to generate the magnetic field was also used as a movable mass to decrease the total weight and to create a constant closed loop of the magnetic force. The hammer impact test results showed that the present absorber could change its natural frequency and had an almost constant damping ratio. In addition, the natural frequency and damping ratio of the absorber could be changed by adjusting the mixing ratio of materials to prepare MRE. Further, experimental results of vibration absorbing of a flat plate and a vibrating part of the commercial vehicle showed that the vibrational acceleration could be reduced automatically in the frequency range from 50 to 150 Hz with simple techniques to determine the strength of the magnetic field to be applied to the MRE by controlling the electric current applied to the coil.
