Summary
For nondestructive internal quality measurement, the shock, sweep and random vibration methods are in general use. In this paper, the effects which the differences in fundamental terms such as vibrating and detecting point had on the transfer characteristics, and points of the differences and the sameness in the transfer characteristics obtained by the each method were investigated by the power spectrum density function and frequency response function.HomePage
1. The power spectrum density function for a melon by shock vibration had one sharp peak and its variation was +- 1.1 Hz, so the reappearance of spectra was very high. We need to find a suitable angle of the pendulum which had little effect on the power spectrum density function. A level or opposite side for the hitting point proved to be suitable for the detecting point.
2. There were differences in the frequency response function between equator and stem-calyx side exciting by random vibration, because each melon has a different structure, weight, size and so on. Averaging the spectrum made the uneven spectra smooth at only 32times/15seconds. The spectra had 3 to 5 peaks and the first one was the biggest and the variation of the first and second peak frequency was within an observational error, +- 2.2 Hz. As above, the reappearance was very high and the random vibration method proved to be more useful than the sweep vibration method.