The shadow moiré deflection-measuring method has been used successfully in the past to determine deflections in flat plates under static loading and to visualize nodal lines of vibrating plates. To demonstrate how this method may also be used to visualize the lateral displacements of vibrating plates, a circular plate with a free boundary was resonated and the resulting moiré patterns were recorded photographically. The lateral deflections represented by the moiré patterns were plotted and analysed. As long as the motion was periodic it was found that peak amplitudes of approximately 0·001 in or more could be measured.
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