Bolt loosening positioning detection method based on working mode strain fiber bragg grating sensing

Abstract

The invention discloses a bolt loosening positioning detection method based on working mode strain fiber grating sensing. The wavelength time history before bolt loosening is collected through a fiberbragg grating demodulator, then part of bolts on the structure are loosened through a tightening torque wrench, meanwhile, all orders of modalities after bolt loosening are excited through knocking of a forcible hammer, and the wavelength time history after bolt loosening is collected. A positive strain power spectrum of a single measuring point is fit through fast Fourier transform, a Forsythe orthogonal polynomial and a least square method, a steady-state diagram is constructed to obtain an inherent frequency and a damping ratio of the structure, and a strain modal shape of the structure iscalculated by adopting a strain transmissibility method on the basis of the inherent frequency and the damping ratio; and after the inherent frequency and modal strain before and after the structureis loosened are obtained, the bolt loosening damage identification quantity and threshold value of inherent frequency and strain vibration mode hybridization are obtained to identify the bolt loosening position. According to the method, whether bolt loosening occurs in a bolt set in the structure or not can be efficiently detected, and the positions of the loosened bolts in the bolt set can be accurately positioned.

Description

technical field [0001] The invention belongs to the technical field of bolt loosening detection, and in particular relates to a bolt loosening positioning detection method based on working mode strain fiber grating sensing. Background technique [0002] Bolts are commonly used fasteners widely used in railways, vehicles, bridges, engineering equipment and other fields. Due to the influence of vibration, corrosion and impact during use, it is easy to cause threaded fasteners to loosen, Deformation, breakage or fall off, resulting in equipment failure, or even major accidents. Therefore, the loose inspection of bolts has always been an important item in the inspection and maintenance of engineering equipment. [0003] Among the detection technologies that have been disclosed at home and abroad, the relatively prominent methods are: vibration signal analysis method and image recognition method. In the vibration signal analysis method, the bolt looseness is usually identified ...

AI Technical Summary

Problems solved by technology

In the vibration signal analysis method, the bolt looseness is usually identified according to the displacement mode of the structure, but for the local structural damage of the bolt looseness, the strain is more sensitive than the displacement; It is easy to reduce the recognition accuracy due to electromagnetic interference

The image recognition method needs to mark symbols on the rotating and non-rotating parts of the bolt connection, but after the equipment has been in service for a long time, the marking symbols will fall off or be covered by dirt, making image judgment impossible, so the existing image recognition methods are difficult to meet Actual demand

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