Comparison of Laser Doppler Vibrometry and Digital Image Correlation measurement techniques for applications vibroacoustics

Kurzfassung

Laser-Doppler Vibrometry (LDV) is a state-of-the-art contactless measurement technique able of capturing the velocity response at a single measurement point, up into the high-frequency range with high accuracy. With scanning LDV, even the velocity field of the surface of a test object can be observed from a sequence of repeated measurements. A 3D LDV system is able to measure all 3 spatial components of velocity, in-plane as well as out-of-plane. However, the most common 1D LDV systems are only able to measure the velocity component in the direction of the laser beam. With proper setup of the system, this corresponds to the out-of-plane component. An alternative contactless measurement technique that had arisen in the last decade is the Digital Image Correlation (DIC). This technique allows to measure the displacement fields of structures based on a full-field method using a series of images taken over time at discrete time intervals. While the measurement time of both methods highly depend on the set parameters, the DIC has the advantage that in-plane velocities are measured without additional effort. In this paper a comparison between measured data acquired using both techniques will be performed. The targeted application is conducting measurements on lightweight structures in the vibroacoustic frequency range. To this end, the upper frequency limit shall be determined, at which the DIC data quality is comparable to the LDV data, regarding out-of-plane components. Additionally, both data sets will be used to estimate structural intensity vector fields for quality and performance estimation.