Vibration analysis of a metal plate by using laser vibrometry and fringe projection

Mechanical devices are normally used under conditions of dynamic motion. Due to resonance effects, this condition produces undesired modes of vibration, which are necessary to be measured for satisfactory design. This work describes the use of laser vibrometry in conjunction with fringe projection and the proper orthogonal decomposition method to analyze the dynamical behaviour of a metal plate when subjected to external vibration. In the proposed method, point velocity measurements of the metal plate obtained by a laser vibrometer are put in phase by the use of an instantaneous out-of-plane displacement image obtained by the fringe projection technique. In this case, the plate was driven by an electromagnetic shaker which in turn was fed with a range of frequencies that covered the first 4 resonant modes.