Measurement of flexural and longitudinal vibration intensity by a two-channel laser vibrometer

Abstract

In the flexural farfield, vibrational intensity can be measured by using the cross spectrum of two accelerometer signals. However, accelerometers can mass load a structure and they can impede the process of mapping intensity over the surface. Consequently, the use of a scanning two-channel laser Doppler vibrometer was investigated for flexural intensity measurements. Results from vibrometer cross-spectral intensity measurements on a small aluminum beam are given and compared with results obtained by other (one-dimensional) approaches. An investigation was also conducted into measuring longitudinal intensity using the vibrometer in the differential Doppler mode. Results are given and comparisons made with one-dimensional longitudinal methods.