Design of Vibration Absorbers for Structures Subject to Multiple-Tonal Excitations

The purpose of this paper is to introduce a systematic method of designing a vibration absorber that affects vibration attenuation at multiple frequencies. This vibration absorber is a nonprismatic beam with natural frequencies intentionally designed to coincide with the frequencies of excitation, e.g., the rotating speed of a rotary machine and its harmonic orders. Therefore, it can reduce the vibration response due to rotor eccentric, rotor shaft bending, mechanical looseness, etc. The thickness profile of the nonprismatic beam can be approximated discretely by a large amount of block masses. Each block mass behaves as an elastic structure member, and its thickness can be determined systematically using the impedance technique proposed in this paper. A design is given to demonstrate the methodology, and the result is experimentally validated.