<title>Three-dimensional velocity measurement of a periodically ribbed aircraft panel surface by optical vibrometry</title>

Abstract

Experimental data were collected in this study and used to identify structural characteristics and features that ultimately effect sound radiation on an aircraft fuselage panel.A periodically reinforced flat plate was excited by an electromagnetic shaker and the 3D velocity vector response was measured at an array of points on the surface using a 3D laser vibrometer mounted on a scanning robot. These velocity measurements, along with force cell data, were used to produce force normalized modal mosaics and dispersion curves of both the out-of-plane and in-plane data. Results show low frequency global deformation of the structure occurs when the structural wavelengths are longer than the spacing between the reinforcing members. Local modes become evident when wavelengths are comparable to the spacing of the reinforces. We also observe evidence of in-plane resonances and Bloch wave effects.