Research On Crack Damage Identification Method In Mechanical Structure Based On FBG Distribution Sensing

The high efficient development of modern production makes machinery equipment face increasingly complex working conditions and longer working time, so mechanical equipment structures are injured inevitably, and serious fatal accidents caused by all sorts of small damages is common. For the tiny damage identification of structure, the strain related index which is more sensitive to injury should be applied. Currently, the damage identification based on vibration is most widely used at practical engineering, and strain kind of frequency response function parameters related to damage identification indicators has been 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 an exceptional choice for strain field measurement of mechanical structures.In the work, the four points fixed supported45#steel thin plate which is common in Engineering application is used as the research object. As a vibration damage identification index foundation, the strain kind of frequency response function related parameters are used to identify the crack damage of the thin plate.In this paper, the transverse vibration characteristics of the plate structure were analysed detailedly, the numerical analysis and a large number of experimental research were conducted, and the measured signals were processed and analysed. Based on the sensitivity parameter βsfrf of strain frequency function and the sensitivity parameter βpsd of strain power spectral density, the finite element analysis software ANSYS was used to realize simulation analysis about the different position crack damage identification of the plate structure; and on this basis, the test system of FBG distribution sensing was built. Through analysing the strain matrix of structure from experiments, the strain kind of frequency response functions were extracted successfully. The damage identification effect based on the sensitivity parameter βsfrf of strain frequency response function and the sensitivity parameter βpsd of strain power spectral density frequency response function were showed respectively, that parameter βpsd can better identify crack damage in practical application.