Study On Optical Fiber Sensor For Ultrasonic Testing Of Metal Surfaces

The application of ultrasonic techniques to the determination of metal-related physical parameters has an important place. With increasingly demanding requirements, it is urgent to develop more sensitive and reliable methods in non-destructive testing. Using optical fiber sensor technology together with surface wave detection and analyses is promising in this area.In this paper, Sagnac fiber optic interferometer technology is used to detect the velocity of sound transmission in solids. A cast iron triangular object is used in the experiment with two Sagnac loops attached to the ends of the object (for longitudinal wave) or on same side of the iron (for SAW). Data acquisition card and PC are used for data processing. When the ultrasonic signal propagates in solids and the role of aura in the sensitive optical fiber sensor, the output side of the data acquisition card will show two spectra. And the object's Young's modulus and Poisson's ratio can be obtained from experimental data and the theoretical formulas.The working principle of fiber optic sensor is presented in detail with a review of brief history of nondestructive testing of surface acoustic wave technology, detailed description of the type of surface acoustic wave analysis in the absence of the boundary of SAW propagation properties of isotropic solids, in a detailed analysis of surface acoustic wave propagation in bounded solids characteristics and conditions for the boundary changes, restrictions on the Rayleigh wave, Electric sound wave, Love wave, the generalized Rayleigh wave, Lamb wave, etc. in detail the nature of analysis and part of the derivation of their properties are given a more comprehensive overview. And it is described the SAW reflection and mode conversion, diffraction effects and beam deviation and surface acoustic wave attenuation. For the isotropic surface acoustic wave propagation medium, it is given the theoretical model, anisotropic media because of the relatively more complicated, it is given some explanations in this paper, then derived in the acoustic wave equation in the solid. The acoustic effect of fiber in fiber length due to changes in refractive index caused is shown by the re-distribution of the phase change of the phase analysis of the contribution of each variable.