Experimental study on an impact vibration absorber
Desen, Ihsan Cem
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An Impact Vibration Absorber (IVA), which is also referred to as an impact damper, consists of a free mass moving between the motion limiting stops of a primary system. When the amplitude of vibration of the primary system exceeds the gap between the stops, the absorber mass collides with the stop. Under sufficient excitation, the IVA undergoes cyclic motion, colliding intermittently with the stops. By this mechanism, the IVA reduces the vibration of the primary system through momentum transfer by collision and dissipation of kinetic energy as acoustic and heat energy. The aim of the current study is to investigate the effects of mass ratio, clearance between stops, and excitation amplitude on IVA effectiveness and system dynamics. Vibration absorption is studied for both free and forced vibrations. Constant frequency and frequency sweep experiments are conducted to study between stops, and excitation amplitude on IVA effectiveness and system dynamics. Vibration absorption is studied for both free and forced vibrations. Constant frequency and frequency sweep experiments are conducted to study system dynamics. Coherence between the forcing function and primary mass response is studied, as a first step in proposing a new method for determining the efficiency of vibration absorbers. Extensive parametric studies were performed on the IVA. Free vibration studies revealed the effect of system parameters on rate of decay of vibrations. For forced vibrations, it was shown that an optimum clearance exists for which the energy absorption is greatest. The efficiency of the absorber is highest around the natural frequency of the primary structure, and diminishes as excitation frequency moves away from the natural frequency. The characteristic jump phenomenon was observed for the case without the IVA, at different locations for upsweep and downs weep. In the absence of the IVA, the high response amplitude at resonance caused the coherence to drop. The introduction of the IVA was shown to attenuate the vibrations in such a maimer that the response amplitude of the primary mass is consistently low for the whole range of theswept frequency. This results in a coherence function that is close to unity for the range of the swept frequency. Therefore, coherence between the forcing function and response of a system may be used as a measure the absorber effectiveness.