Simple model of compound waveguide structures used as fiber-optic sensors

Transient out-of-plane displacements generated in a steel cantilever beam by an impact load are measured using a double-pulsed electronic speckle pattern interferometry system. The state of deformation of the object is freezed using a ruby laser and the pulse emission is synchronised with the impact load. Correlation fringes for different times after the start of the impact are obtained using a digital image system. For each time. transient displacements are evaluated by digital analysis of the fringes. In order to test the experimental results, the time response of the beam subjected to the impact load is evaluated using a 3-D finite element analysis. A close agreement is found between the experimental and numerical results, which prove the reliability of the optical technique to measure high-speed transient deformations.