CN-122017031-A - Flange bolt loosening positioning monitoring method based on ultrasonic guided wave probability imaging

CN122017031ACN 122017031 ACN122017031 ACN 122017031ACN-122017031-A

Abstract

The application provides a flange bolt loosening positioning monitoring method based on ultrasonic guided wave probability imaging, belongs to the technical field of structural health monitoring and nondestructive testing, and can fully utilize the advantages of ultrasonic guided wave large-scale detection to perform loosening positioning and monitoring on a flange bolt. The damage index is calculated by utilizing different ultrasonic guided wave signals of the bolts in a healthy state and a damaged state, the guided wave signal change is converted into an intuitive damage probability cloud chart through a probability imaging technology, the loosening index of each bolt is obtained, and the visual accurate positioning of the loosening bolts is realized, so that the loosening indexes of all bolts in a monitoring range are judged and compared. The application utilizes the space coverage capability of guided wave 'one-point excitation, multi-point receiving' and probability imaging, and can realize synchronous monitoring of all bolt states of the whole flange ring only by a small number of sensors.

Inventors

DU FEI
ZHANG KEYUAN
WANG PENGHUI
CHEN ZIHAO
WANG YUNHAO
XU CHAO

Assignees

西北工业大学

Dates

Publication Date: 20260512
Application Date: 20260130

Claims (10)

1. A flange bolt loosening positioning monitoring method based on ultrasonic guided wave probability imaging is characterized by comprising the following steps: Step 1, measuring structural parameters, namely acquiring key geometric parameters and material acoustic properties of a flange, calculating the guided wave speed of an S0 mode in a thin-wall cylinder of the flange, and primarily selecting an excitation frequency band in a frequency band range with the S0 mode as a dominant mode; step 2, sensor optimization arrangement, namely arranging a plurality of sensor pairs on the surfaces of the thin-wall cylinders on two sides of a flange connection interface, wherein the sensor pairs are composed of an excitation sensor on one side of the connection interface and a receiving sensor on the other side, and guided waves received by excitation of the sensor pairs cover monitoring areas where all bolts are positioned; Step 3, exciting signals preferably, exciting the exciting sensor by adopting different exciting signals and collecting ultrasonic guided wave signals in an exciting frequency band, selecting an optimal exciting signal from different exciting signals based on a preset criterion, wherein if the ultrasonic guided wave signals of the bolt in a healthy state and a damaged state can be obtained, the first criterion of maximizing the difference of the ultrasonic guided wave signals is followed; Step 4, screening spiral guided wave paths, namely calculating the lengths of each order of spiral guided wave paths from each excitation sensor to all receiving sensors based on key geometric parameters of a flange and arrangement positions of the sensors, and calculating theoretical arrival time of signals propagating along each spiral guided wave path from the excitation sensor to the receiving sensors based on the guided wave speed of S0 mode and the lengths of each order of spiral guided wave paths; Step 5, acquiring a reference signal and a damage signal, namely exciting each excitation sensor in sequence by utilizing an optimal excitation signal under a healthy state and a damage state, and collecting ultrasonic guided wave signals received by all receiving sensors; taking theoretical arrival time as a starting point, and intercepting ultrasonic guided wave signals in a healthy state and a damaged state respectively by taking a section of a subsequent complete direct wave packet in the healthy state to obtain a reference signal and a damaged signal of each sensor pair; Step 6, calculating and correcting damage indexes, namely eliminating abnormal data by utilizing a characteristic function if the amplitude of a damage signal of a certain interception section exceeds a reference signal, introducing an interception length balance function to perform unified standardization processing on all signals, and calculating the damage indexes based on the reference signal and the damage signal of each pair of processed sensors; step 7, probability imaging based on the RAPID algorithm, namely dividing a monitoring area into pixel grids, and calculating the total damage probability of each pixel point based on the corrected damage index to obtain a damage probability cloud image of the whole monitoring area; and 8, calculating a loosening index and loosening positioning of each bolt, namely defining a circular region of interest by taking the theoretical center position of each bolt as a circle, calculating the loosening index of each bolt based on the total damage probability of all pixel points in the circular region of interest of each bolt, and comparing the loosening indexes of all bolts, wherein bolts higher than other positions are loosening bolts.
2. The flange bolt looseness positioning and monitoring method of claim 1, wherein in step 2, the arrangement position of the sensors follows the principle of maximally locating a plurality of bolts on the shortest propagation path of different sensor pairs.
3. The method for monitoring the loosening and positioning of flange bolts according to claim 1, wherein in step 3, The state of health refers to the state after the flange is installed or the bolt pretightening force is recalibrated, the damage state refers to the unknown state to be detected, and the data detected each time can be used as the data in the state of health in the next positioning monitoring.
4. The method for positioning and monitoring loosening of flange bolts according to claim 1, wherein in the step 3, the first criterion is that an excitation signal which makes the difference between the ultrasonic guided wave signals in the healthy state and the damaged state the largest is selected as an optimal excitation signal; The second criterion is to select the signal that maximizes the signal-to-noise ratio of the ultrasound guided wave signal in the healthy state as the optimal excitation signal.
5. The flange bolt looseness positioning and monitoring method is characterized in that in the step 5, each excitation sensor is excited in sequence in a health state, ultrasonic guided wave signals received by all receiving sensors are collected for multiple times, and an average value is taken as reference health state data; And based on the damage state data, intercepting a direct wave packet by utilizing theoretical arrival time to serve as a damage signal.
6. The method for positioning and monitoring loosening of flange bolts according to claim 5, wherein in step 6, defining The method is characterized by comprising the following steps: Then the truncated length balance function represents: the damage index is expressed as: Wherein the method comprises the steps of The index of the damage is indicated and the index of the damage is indicated, 、 Indicating the start time and the end time of the intercepted direct wave packet, A signal indicative of the impairment is indicated, The reference signal is represented by a reference signal, Indicating the number of the excitation sensor, Indicating that the number of the sensor is received, Representing the order of the helical guided wave path, Representing the intercept length balance function.
7. The flange bolt looseness positioning and monitoring method of claim 6, wherein the modified damage index is represented by the formula: Wherein the method comprises the steps of The damage index after the correction is indicated, The weight factor is represented by a weight factor, Representing the helical guided wave path length of each order.
8. The flange bolt looseness positioning and monitoring method of claim 7, wherein in step 7, the total damage probability of each pixel point is as follows: Wherein the method comprises the steps of Representing pixel points Is used for the total probability of damage of the patient, Indicating the number of sensors to be used, Representing linear probability distribution weights.
9. The flange bolt looseness positioning and monitoring method of claim 8, wherein the linear probability distribution weights The following formula is shown: Wherein the method comprises the steps of Indicating the preset proportion distribution parameter, Representing the path length of the helical guided wave of each order, Representing pixel points The sum of the distances to the excitation sensor i and the receiving sensor j.
10. The flange bolt looseness positioning and monitoring method of claim 9, wherein in step 8, the looseness index is represented by the following formula: Wherein the method comprises the steps of Indicating the loosening index, the loosening index is displayed, Representing a circular region of interest in terms of the theoretical center position of the bolt Is the center of a circle.

Description

Flange bolt loosening positioning monitoring method based on ultrasonic guided wave probability imaging Technical Field The invention belongs to the technical field of structural health monitoring and nondestructive testing, and particularly relates to a flange bolt loosening positioning monitoring method based on ultrasonic guided wave probability imaging, which is particularly suitable for on-line monitoring and damage visual positioning of multiple bolt connection states of flanges in key structures such as an aerospace engine, a pressure pipeline and the like. Background The flange multi-bolt connection structure is one of the most critical connection modes in industrial equipment, and is widely applied to important equipment such as aerospace engine shell connection, chemical pipeline systems, wind generating sets and the like. These structures often work under strong vibration, alternating load and extreme temperature environments, and bolts are prone to loosening due to stress relaxation, fatigue and other factors, leading to failure of the sealing of the connecting interface, reduced structural rigidity, and even catastrophic accidents. Therefore, the real-time and accurate monitoring of the connection state of the flange bolts has extremely important engineering significance. The existing bolt looseness detection technology mainly comprises a physical quantity direct measurement method, a vibration-based analysis method, a piezoresistance method and an ultrasonic guided wave method. The physical quantity direct measurement method has higher precision, such as torque wrench tightening, ultrasonic bolt axial force instrument measurement and the like, but belongs to an off-line detection method, cannot realize real-time on-line monitoring, and has low efficiency when bolts are more. According to the vibration-based analysis method, the state of the bolt is indirectly judged by analyzing the vibration response (such as natural frequency and modal shape) change of the whole or partial structure, and the method has insufficient sensitivity to partial looseness and is easy to be interfered by environmental noise. The piezoelectric impedance method utilizes the coupling relation between the impedance of a piezoelectric ceramic plate (Lead Zirconate Titanate, PZT) stuck on the surface of a bolt or a structure and the mechanical impedance of the structure to monitor. The method is sensitive to near field damage, but has a smaller monitoring range, and a single PZT can only effectively monitor 1-2 bolts of an accessory. The ultrasonic guided wave method monitors the change of energy, amplitude or phase of ultrasonic guided waves when the ultrasonic guided waves propagate in a structure by using the change of energy, amplitude or phase of the ultrasonic guided waves when the ultrasonic guided waves pass through a bolt connection interface as a damage index, and has a wide ultrasonic guided wave monitoring range, but the current bolt positioning method based on the guided waves can only position a single bolt or a few bolts and relies on a machine learning technology for loosening multiple bolts. However, the machine learning model is usually a black box, and has the problems of poor interpretability, poor generalization capability and the like. At present, various damage imaging positioning methods such as an ellipse positioning method, a phased array guided wave damage imaging method and a probability imaging method exist for damage such as cracks, corrosion, impact and the like of structures such as flat plates and the like by an ultrasonic guided wave technology. Its application in flange bolt construction still presents significant challenges. The method is mainly characterized in that the structure of the bolt connection part is complex, complex scattering and modal conversion of guided waves are easy to cause, and meanwhile, multipath effects such as spiral guided waves in a thin-wall cylinder structure also increase the difficulty of signal analysis, so that an effective bolt loosening imaging positioning method is not available at present. The probability imaging method (Reconstruction Algorithm for Probabilistic Inspection of Damage, RAPID algorithm) is an ultrasonic guided wave damage positioning imaging technology, and reconstructs probability distribution of damage to each point on a structure through signal change acquired by a sensor array, so that damage positions are visually presented in an image form. The technology is suitable for complex guided wave signals and is expected to be used for imaging positioning of bolt looseness. Literature (Lv Bawang. Research on key flange bolt looseness monitoring technology of reactor based on guided wave [ D ] Harbin university of industry, 2024.DOI:10.27061/d.cnki.ghgdu.2024.001866.) adopts ultrasonic guided wave technology, and the loose flange bolts are positioned by combining probability imaging, so that the detection method is closer to that of a flat