Measurement of the elastic modulus of homogeneous materials by a bending wave speed method
Résumé
Elastic modulus is one of the most important mechanical properties of homogeneous materials. It describes the dynamic behavior of elastic and viscoelastic materials strongly affecting both panel modes and coincidence frequencies, so is an important quantity to consider in noise and vibration control. In this paper a method to obtain the elastic modulus of materials is reported, based on the measurement of the surface velocity field occurring due to the propagation of bending waves through the panel. A 2D spatial Fourier transform applied to the measured velocity field allowed to evaluate the wavevectors of the free bending waves propagating in the panel. By averaging over wave direction, the overall amplitude distribution versus wavenumber can be found and from this the dominant wavenumber obtained. From the latter it is straightforward to calculate the flexural wave speed, which can, via classical plate theory, be related to the static elastic modulus value of the material. A preliminary experimental test-rig was based on laser Doppler vibrometer measurements in order to assess the surface velocity of a freely suspended sample, acoustically excited by means of a broadband signal. The experimental results show a reasonable agreement to the technical data provided by the manufacturer although some issues require further research.
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