力学共振吸收谱探测耦合振动模式

Detection of a coupled vibration by mechanical resonant absorption spectra

提出探测复杂力学振动系统耦合振动模式的方法:通过测量力学振动系统中某一易于探测的振动模式对外力的响应行为,在该振动模式应变落后于应力的相位差-频率谱(表观机械能耗散-频率谱)中,除了能观察到与被测量振动模式本征频率所对应的相位变化外,与被测量振动模式耦合的其他振动模式也表现为共振吸收峰;从共振吸收峰的性质,如峰位、峰宽、峰高等可以得到相应耦合振动模式的本征频率、损耗以及耦合强度等信息.以倒扭摆力学系统为例,通过测量扭摆的扭转振动模式应变落后于应力的相位差-频率谱研究了扭摆系统中摆杆的进动振动模式.

In this paper, we propose a novel scheme of measuring a coupled but uneasy detected vibration mode through surveying another much easier detected vibration mode in a complex mechanical system. Through measuring the frequency dependence of phase lag of strain behind stress, i.e., the apparent mechanical dissipation-frequency spectrum, for the easy detected vibration mode, we are able to obtain the corresponding resonant absorption peak for the coupled vibration mode in addition to the expected main system resonance. By studying the observed resonant absorption peak： peak position, peak width and peak height, we can obtain the detailed information about the coupled vibration mode： the intrinsic resonant frequency, dissipation and coupling coefficient. Through measuring the apparent mechanical dissipation frequency spectrum of torsion vibration, the detection of the progression vibration about the pendulum axis is presented as a representative example of our scheme.