Using Scanning Laser Doppler Vibrometry for Experimental Frequency-based Substructuring

Frequency-based substructuring is a practical technique to predict the response of larger dynamic systems. Experimental substructuring is carried out today by measuring the response after a hammer impact with accelerometers on selected positions on the structures. The impacts are repeated in several positions on the structure (the rowing hammer principle). This work investigates the potential of using a scanning laser Doppler vibrometer (SLDV) instead. The classical accelerometer technique has proven to be efficient in many cases. It is, however, cumbersome to attach the many accelerometers. The virtual point (VP) transformation is often used when coupling complex structures, requiring a minimum of three three-directional sensors close to the interface (where the two substructures are to be connected). If the structure is small, it may not be possible. An SLDV is contactless, and the laser pointer is very small, which is why it is possible to have a fine grid of measurement points near the interface. However, to take advantage of the”scanning” feature, attaching a shaker or piezoelectric-electric actuator is necessary. In this work, we design a novel numerical framework for SLDV/shaker testing, make the first preliminary SLDV tests, and discuss the benefits and limitations of this new approach.