VIBRATION ANALYSIS AND NONDESTRUCTIVE TESTING WITH REAL-TIME SHEAROGRAPHY

Real-time laser speckle shearography coupled with vibration stressing is shown to be an effective means of vibration analysis and non-destru ctive testing. The shearograms are modulated by a system of live fring es. These fringes are shown to be described by the zeroth-order Bessel function of the first kind and their visibility decreases with increa sing fringe order. In vibration analysis, the instantaneous fringe pat tern depicts the out-of-plane surface displacement gradient of the obj ect surface at various resonance modes. In non-destructive testing, th e flaw depth in a component can be determined without having to determ ine fringe orders. There is good agreement between the results obtaine d using the method and those from theory and time-average holography. A major advantage of real-time shearography is its facility for contin uous assessment of a vibrating object without the need for secondary s hearogram reconstruction.