Acceleration Signal Characteristics for Loose Part Impact

Abstract

Characteristics of acceleration frequency spectra for an impact signal were studied and loose part mass was estimated, using variation in the frequency spectral patterns. The frequency spectral pattern for the acceleration induced by impact depends on the loose part mass and not on the impact energy and the loose part shape. It was found that the frequency spectral pattern for an impact which occurred at the lower plenum vessel wall is not influenced by the impact point. On the other hand, the maximum acceleration am-plitude depends not only on the loose part mass but also on the impact energy, the loose part shape and the distance from the impact point. It was also found that the foremost portion of the accelerometer output signal is influenced by the impact force between a loose part and the vessel. However, a second portion is influeuced by the sensor resonance and structural resonances. Loose part mass estimation, using "FR" values (ratio between low frequency component and high frequency component), is useful. The uncertainty range for the estimated loose part mass is about 0.7 decade.