Study On Strain Related Dynamic Parameter-based Damage Identification By Fiber Bragg Grating Sensing

Damages affect the safety and performance of structures.particularly, micro size local damage in continual operating device can cause irreversible structural fracture. Local damage is often hard to be identified by displacement related parameters, but strain related parameters are quite sensitive to it, which is optimal choice for local damage identification. Currently, damage detection based on dynamic parameters is a hotspot of structural health monitoring, and strain dynamic parameter related damage identification indicators is receiving more and more attention. The accuracy of strain related damage identification indicators depends on the accurate measurement of strain field in damaged structure by strain tranducers, which would be trivial and inefficient by traditional electric strain transducers.With the advantages of micro size, light weight, anti-electromagnetism interference and wavelength division multiplexing, fiber bragg grating sensor is a exceptional choice for strain field measurement of mechanical structures.In this work, a damage identification method combined Fiber Bragg Grating sensing with strain dynamic index was proposed, the main content of the work is as follow.The derivation of strain mode was achieved by different methods. The test methods and characteristics of strain mode and strain frequency response function were summarized. Four damage identification indicators respectively based on strain mode, strain frequency response function, curvature mode and strain energy were analysed comparatively. Strain mode variation rate and strain frequency response function index were chosen for verification study.For finite element analysis of corners fixed supported plate structure, parameters such as displacement model, element stiffness matrix, element mass matrix and Strain transition matrix were calculated. Strain modal variation rate-based identification of thickness-reduced damage was simulated by finite element method using MATLAB, the relationship curves between damage severity and damage index were obtained. Hole damage and multi-damage identification by strain frequency response damage indicator was simulated by ANSYS.To local hole damage in a corners fixed supported plate, the high-sensitivity of strain frequency response function index was verificated by experimental test using Fiber Bragg Grating sensing.