Quantitative dynamical measurements for model updating using electronic speckle interferometry

Electronic Speckle Pattern Interferometry (ESPI) is a recent optical way to measure a vibrating structure under sine excitation. The spatial density of the obtained information is about 10000 times larger than with the classical accelerometric technique, leading to the possibility of knowing the displacement at each node of the Finite Element Model (FEM). We present here some of the techniques we developed to solve the following questions: how can we know where the nodes of the FEM are located in the picture ? What is the sensitivity direction and how to take it into account ? How can we obtain a reliable measurement of the amplitude and phase of the displacement with respect to the driving force ? Each of these points needs to be treated before using the optical data in a FEM updating procedure.