구조물 동특성 변경에 의한 효과적인 전달 진동파워 저감

Abstract

When a mechanical system is engaged to a vibratory source, force is transmitted and generates structure borne noise and vibration. Vibrational power transmission is an important concept to examine structure borne noise and vibration problem. The concept of vibrational power transmission is related with the force and the velocity of both exciter and receiver. That means transmitting energy through the coupling points depends on the properties of exciter. receiver and isolator. To reduce structure borne noise and vibration, its vibrational power inflow from exciter to receiver should be reduced. In this paper, using the concept of structural dynamic modification, vibrational power transmitting through connecting points is attempted to reduce. Two kinds of index are introduced to find an optimal modification point. Those are Power Reduction Index which is the ratio of vibrational input power between pre- and post-modified receiver and Band Power Reduction Index which is the ratio of average of vibratonal input power along the interesting frequency band between pre- and post-modification. The former is used to find the frequency band in which vibrational input power is reduced and the later is applied to find an optimal structural dynamic modification point where the average vibrational input power becomes a minimum value. Using an experimental setup composed of a d.c. motor and plate, vibrational power variations are calculated using the structural dynamic modification technique at the receiving structure. Finally in order to verify the modification in the receiving structure, its vibration level was measured and compared.