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

A fiber grating and working modal technology, which is applied in the field of bolt loosening positioning detection based on working modal strain fiber grating sensing, can solve the problems of decreased recognition accuracy, difficulty in image recognition methods to meet actual needs, covered by dirt, etc.

CN111854828AInactive Publication Date: 2020-10-30WUHAN UNIV OF TECH
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Publication Date
2020-10-30
Estimated Expiration
Not applicable · inactive patent

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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.
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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 ...

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Embodiment Construction

[0015] In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

[0016] In an embodiment of the present invention, a method for detecting bolt looseness based on working mode strain-fiber grating sensing is provided, such as figure 1 , figure 2 , image 3 shown. The specific operation process is as follows:

[0017] (1) in figure 2 A fiber grating sensor 7 is attached to the middle bolts 1-6;

[0018] (2) Connect the fiber grating sensor, demodulator and computer;

[0019] (3) Tighten six M8 bolts to 9N m with a tightening torque wrench;

[0020] (4) Run the software system of the demodulator, knock the thin plate 8 with a force hammer, simulate the imp...