CN-122017139-A - Method for positioning embedded defects of curved fiber variable-angle wire laying member under different working conditions

CN122017139ACN 122017139 ACN122017139 ACN 122017139ACN-122017139-A

Abstract

The invention discloses a method for positioning embedded defects of a curved fiber variable-angle wire laying member under different working conditions, which belongs to the technical field of nondestructive testing of materials, and comprises the steps of arranging a distributed fiber bragg grating sensing array and a mechanical sensor on the surface or inside of the member, and synchronously acquiring an input load and a dynamic strain response signal; the method comprises the steps of establishing a reference transfer function of each sensing point in a healthy state, calculating a real-time transfer function of each point and distortion quantity of each point relative to the reference during online service, generating a continuous distortion quantity field and calculating a spatial gradient field of each sensing point through spatial interpolation based on spatial coordinates and distortion quantity of all sensing points, finally dividing the gradient field through a self-adaptive threshold value to extract a defect contour, converting a changed service load into effective excitation, and realizing defect positioning through analyzing a transfer function distortion gradient, wherein the method is particularly suitable for curve fiber layering components with complex anisotropic characteristics, and realizes online, real-time and accurate defect positioning under real working conditions.

Inventors

CUI FUJIANG
LIU PENG
WANG HAN
LI ZHIQIANG

Assignees

太原理工大学

Dates

Publication Date: 20260512
Application Date: 20260210

Claims (9)

1. The method for positioning the embedded defects of the curved fiber variable-angle wire laying member under different working conditions is characterized by comprising the following steps: S1, integrally arranging distributed fiber bragg grating sensing arrays on the surface or inside of a curve fiber variable angle wire laying member in a grid shape or along a critical path, and synchronously measuring dynamic strain response signals of all sensing points of the curve fiber variable angle wire laying member in space distribution; s2, when the curve fiber angle-changing wire laying component is confirmed to be in a healthy and defect-free state, enabling the curve fiber angle-changing wire laying component to operate in an expected typical working condition range or applying dynamic load covering future service spectrum through a test bed, acquiring the dynamic strain response signals and input load signals of all sensing points in real time based on S1, selecting the dynamic strain response signals and the input load signals of each sensing point, calculating a reference transfer function of each sensing point in the healthy and defect-free state through signal processing, and obtaining a health reference value of each sensing point; S3, calculating to obtain a real-time frequency response value of each sensing point based on a reference transfer function of each sensing point in a real-time sequence, comparing the real-time frequency response value of each sensing point with a health reference value, and calculating to obtain an abnormal quantity; s4, taking the distortion quantity as a scalar field value of the position of each sensing point, combining the space coordinates of all the sensing points, generating a continuous distortion quantity field covering the whole curve fiber variable angle wire laying component through a space difference algorithm, carrying out space gradient operation on the continuous distortion quantity field, and calculating a gradient module value of each sensing point; S5, presetting a gradient threshold value, and carrying out binarization or contour tracking treatment on the gradient modulus value to obtain a high gradient region corresponding to the position, the size and the contour of the embedded defect.
2. The method for positioning the embedded defect of the curved fiber variable angle wire laying member under different working conditions according to claim 1, wherein the signal processing is used for calculating a reference transfer function between a dynamic strain response signal and an input load signal in a frequency domain based on the dynamic strain response signal and the input load signal, wherein the reference transfer function is a ratio of a frequency spectrum of the dynamic strain response signal to a frequency spectrum of the input load signal, the reference transfer function is expressed in a complex form and comprises amplitude-frequency characteristics and phase-frequency characteristics, and the calculated reference transfer function is stored as a health reference value of each sensing point in a healthy and non-defective state.
3. The method for positioning the embedded defect of the curved fiber variable-angle wire laying member under different working conditions according to claim 2 is characterized in that for each sensing point, the difference between the real-time frequency response value and the health reference value on a preset key frequency band is calculated in a frequency domain, and the distortion is obtained by calculating the norm of the difference.
4. The method for positioning the embedded defect of the curved fiber variable-angle wire laying member under different working conditions according to claim 3, wherein the calculating process of the deformation is as follows: And taking the modulus of the complex difference between the real-time frequency response value and the health reference value at each frequency point in the preset key frequency band, and then carrying out integral or square sum operation to obtain a non-negative scalar value representing the overall deviation, namely the abnormal quantity.
5. The method for positioning the embedded defect of the curved fiber variable angle wire laying member under different working conditions according to claim 4, wherein the generating process of the continuous distortion variable field comprises the following steps: S401, taking the space coordinates of each sensing point and the corresponding distortion amount as input data; s402, processing the input data by adopting a spatial interpolation algorithm, and estimating a distortion value in a region of the surface of the curve fiber variable-angle wire laying member, wherein sensing points are not directly arranged; S403, constructing a variation function model based on the spatial autocorrelation of the input data, and carrying out optimal unbiased estimation on the area estimation distortion value by taking the variation function model as a basis to generate the continuous distortion field which is continuously distributed in space.
6. The method for positioning the embedded defect of the curved fiber variable angle wire laying member under different working conditions according to claim 5, wherein the calculation process of the gradient modulus value of each sensing point comprises the following steps: s411, performing two-dimensional space discrete derivative operation on the continuous distortion variable field; s412, respectively calculating first partial derivatives of the continuous distortion variable field along two orthogonal coordinate directions at the position of each sensing point; S413, forming a two-dimensional gradient vector by the two partial derivative components obtained through calculation; S414, calculating the modular length of the two-dimensional gradient vector, wherein the modular length is the gradient modular value of each sensing point and is used for quantifying the spatial change rate of the distortion quantity at each sensing point.
7. The method for positioning the embedded defect of the curved fiber variable angle wire laying member under different working conditions according to claim 1, wherein the presetting of the gradient threshold value comprises the following steps: s501, calculating a statistical characteristic value of the gradient module value based on the gradient module values of all the sensing points obtained by calculation in the S4, wherein the statistical characteristic value is a linear combination of the mean value and the standard deviation of all the gradient module values; s502, taking the result of the linear combination as the gradient threshold value.
8. The method for positioning the embedded defect of the curved fiber variable-angle wire laying member under different working conditions according to claim 1 is characterized in that the distribution principle of the distributed fiber bragg grating sensing array is as follows: S101, determining a structural stress concentration area or a defect easily-occurring area as the key path according to the geometric shape and the fiber laying path of the curved fiber variable-angle fiber laying member; S102, distributing sensing points in the distributed fiber grating sensing array at preset intervals along the critical path, and distributing other sensing points in a regular grid form in a main body area of the curve fiber variable-angle wire laying member, so that the spatial distribution density of the sensing points is matched with the structural risk level.
9. The method for positioning the embedded defect of the curved fiber variable angle wire laying member under different working conditions according to claim 2, wherein the process for obtaining the health reference value comprises the following steps: S201, repeatedly collecting the dynamic strain response signal and the input load signal for a plurality of times in the process that the curve fiber variable-angle wire laying member operates under different typical working conditions, and calculating to obtain a plurality of reference transfer function samples; S202, carrying out statistical analysis on a plurality of reference transfer function samples under the same working condition aiming at each sensing point, and calculating a mean value or a median value; S203, taking the calculated mean value or median value as a health reference value of each sensing point corresponding to the working condition in the health defect-free state.

Description

Method for positioning embedded defects of curved fiber variable-angle wire laying member under different working conditions Technical Field The invention relates to the technical field of nondestructive testing and testing of materials, in particular to a positioning method for embedded defects of a curved fiber variable-angle wire laying member under different working conditions. Background Fiber reinforced composite materials, particularly curved fiber variable angle wire laying members manufactured by an automatic wire laying technology, have become key material systems of aerospace main load-carrying structures due to their excellent designability and lightweight potential. However, such components are prone to embedded defects such as delamination and voids during manufacturing and service, which seriously threatens structural safety. Therefore, it is important to develop reliable embedded defect detection and localization techniques. In the prior art, the defect detection of the components mainly depends on offline nondestructive detection methods such as ultrasonic C scanning and X-ray. The methods need to detach the components from the assembly body and are carried out under specific equipment, so that real-time health monitoring and early warning of the structure in a real service state cannot be realized. In order to realize on-line monitoring, the existing scheme mostly adopts the steps of pasting a piezoelectric sensor array on the surface of a structure and actively exciting ultrasonic guided waves, and realizing damage diagnosis by analyzing scattered and reflected signals of the guided waves. However, the method is applied to curve fiber variable angle wire laying components, and is faced with inherent bottlenecks that firstly, the continuous change of the fiber direction in the components causes strong spatial anisotropy of materials, so that the propagation path of guided waves is complex, the wave speed direction is dependent, defect scattering signals are seriously distorted and covered, and are difficult to accurately interpret and position, and secondly, the actual engineering structure is always under dynamic working conditions such as variable load, temperature and the like, and the working condition changes can cause remarkable change of structural vibration response, generate strong background noise, seriously submerge and interfere weak signal changes caused by tiny defects, and cause the reliability of the traditional method based on fixed excitation or static reference comparison to be suddenly reduced in a variable working condition environment. Disclosure of Invention The invention overcomes the defects of the prior art and provides a positioning method for the embedded defects of the curved fiber variable-angle wire laying member under different working conditions. In order to achieve the aim, the technical scheme adopted by the invention is that the method for positioning the embedded defect of the curved fiber variable-angle wire laying member under different working conditions comprises the following steps: S1, integrally arranging distributed fiber bragg grating sensing arrays on the surface or inside of a curve fiber variable angle wire laying member in a grid shape or along a critical path, and synchronously measuring dynamic strain response signals of all sensing points of the curve fiber variable angle wire laying member in space distribution; s2, when the curve fiber angle-changing wire laying component is confirmed to be in a healthy and defect-free state, enabling the curve fiber angle-changing wire laying component to operate in an expected typical working condition range or applying dynamic load covering future service spectrum through a test bed, acquiring the dynamic strain response signals and input load signals of all sensing points in real time based on S1, selecting the dynamic strain response signals and the input load signals of each sensing point, calculating a reference transfer function of each sensing point in the healthy and defect-free state through signal processing, and obtaining a health reference value of each sensing point; S3, calculating to obtain a real-time frequency response value of each sensing point based on a reference transfer function of each sensing point in a real-time sequence, comparing the real-time frequency response value of each sensing point with a health reference value, and calculating to obtain an abnormal quantity; s4, taking the distortion quantity as a scalar field value of the position of each sensing point, combining the space coordinates of all the sensing points, generating a continuous distortion quantity field covering the whole curve fiber variable angle wire laying component through a space difference algorithm, carrying out space gradient operation on the continuous distortion quantity field, and calculating a gradient module value of each sensing point; S5, presetting a gradient threshold value, and carrying