CN-121705690-B - Self-adaptive configuration method for optimal working point of concrete hidden crack ultrasonic thermal excitation system

CN121705690BCN 121705690 BCN121705690 BCN 121705690BCN-121705690-B

Abstract

The invention discloses a self-adaptive configuration method of an optimal working point of a concrete hidden crack ultrasonic thermal excitation system, which comprises the steps of collecting multi-physical field response data of the system under different parameter combinations by constructing a parameter space containing initial coupling pressure and working frequency, constructing an excitation efficiency evaluation index based on transducer active power response or thermal image temperature difference, locking the initial optimal working point by identifying extremum characteristics of an index response function, carrying out second-order sensitivity analysis on an optimal point neighborhood by utilizing a Hessian matrix, constructing a tolerance elliptic model to quantify parameter control boundaries, and simultaneously monitoring frequency and pressure drift in real time based on a power-phase decoupling mechanism of voltage and current. According to the invention, the optimal working parameters can be adaptively matched aiming at loading devices with different rigidities, engineering tolerance is scientifically set, and the energy conversion efficiency and detection robustness of the ultrasonic thermal excitation system are improved.

Inventors

JIA YU
LI SHIXIN
CHENG XIAOFEI
CAO XIANGYU
PENG ZIJIAN
LIU ZHIHAO
Wang Enzhun

Assignees

水利部交通运输部国家能源局南京水利科学研究院

Dates

Publication Date: 20260508
Application Date: 20260211

Claims (8)

1. The self-adaptive configuration method for the optimal working point of the concrete hidden crack ultrasonic thermal excitation system is characterized by comprising the following steps of: Acquiring an excitation control parameter space to be searched of an ultrasonic thermal excitation system, wherein the excitation control parameter space at least comprises an initial coupling pressure dimension and a working frequency dimension; driving an ultrasonic thermal excitation system to operate in a to-be-searched excitation control parameter space, and collecting multi-physical-field response data of the system under different parameter combinations, wherein the multi-physical-field response data are electric power data or infrared thermal image temperature data; constructing an excitation efficiency evaluation index based on the multi-physical field response data, searching parameter points enabling the excitation efficiency evaluation index to meet extreme value conditions, and determining the parameter points as initial optimal working points; Calculating sensitivity characteristics of the excitation efficiency evaluation index relative to excitation control parameters in the vicinity of the initial optimal working point, and determining a parameter tolerance boundary based on the sensitivity characteristics to obtain optimal working point configuration comprising a parameter central value and a parameter tolerance range; The method comprises the steps of taking an initial optimal working point as a center, establishing a second-order performance curved surface model of the excitation efficiency evaluation index with respect to the initial coupling pressure dimension and the working frequency dimension, calculating a Hessian matrix of the second-order performance curved surface model at the initial optimal working point, carrying out characteristic decomposition on the Hessian matrix, and extracting a normalized curvature coefficient as a sensitivity characteristic for representing the control sensitivity of the parameter; The parameter tolerance boundary is determined based on sensitivity characteristics, and comprises the steps of constructing a tolerance ellipse model taking an initial optimal working point as a center according to characteristic values and characteristic vectors of a Hessian matrix, calculating projection intercept of the tolerance ellipse model on an initial coupling pressure dimension axis and a working frequency dimension axis, and determining the projection intercept as an allowable tolerance range of the initial coupling pressure parameter and an allowable tolerance range of the working frequency parameter respectively, wherein the dimension axis corresponding to the larger characteristic value has a smaller allowable tolerance range.
2. The method of claim 1, wherein the multi-physical field response data is electrical power data, the electrical power data comprising voltage data, current data, and active power data at different excitation control parameters; The method comprises the steps of calculating active power data corresponding to different frequencies based on voltage data and current data obtained by frequency sweeping under a fixed initial coupling pressure parameter, constructing a response function of active power along with frequency change to obtain an active power response, and extracting a peak value or a statistical characteristic quantity of the active power response to be used as an excitation efficiency evaluation index for representing the effective conversion capability of system electric energy.
3. The method of claim 2, wherein searching for parameter points that satisfy the excitation performance evaluation index as extreme conditions comprises: Calling an active power response function which changes along with the initial coupling pressure parameter; Identifying a standing point of the active power response function on initial coupling pressure, which is a standing point of positive rotation and negative rotation, and determining the pressure corresponding to the standing point as the optimal initial coupling pressure; Under the optimal initial coupling pressure, analyzing an active power response function changing along with the working frequency, and determining the frequency reaching the maximum value as the optimal working frequency; the optimal initial coupling pressure is combined with the optimal operating frequency to an initial optimal operating point.
4. The method of claim 1, further comprising monitoring an operating state characteristic of the system in real time during the probing based on the optimal operating point configuration, identifying a parameter drift type based on the operating state characteristic, Wherein, the operation state characteristic of real-time supervision system in the detection process includes: Collecting current voltage and current data of a system in real time, calculating corresponding active power and voltage and current phase difference, and comparing the corresponding active power and the corresponding voltage and current phase difference with the active power and the corresponding phase difference at the initial optimal working point to obtain an active power variation and a phase variation; when the active power variation exceeds a preset power threshold and the phase variation does not exceed the preset phase threshold, judging that the system generates coupling pressure drift; When the phase change amount exceeds a preset phase threshold value, whether the active power change amount exceeds the preset power threshold value or not is judged, and the system is subjected to working frequency drift.
5. The method of claim 1, wherein the multi-physical field response data is infrared thermographic temperature data comprising a sequence of thermographs obtained by infrared imaging of the surface of the object under different excitation control parameters; constructing an excitation efficacy evaluation index based on the multi-physical field response data, comprising: identifying heat generating areas before and after hidden crack excitation in a thermal image sequence; And calculating the average temperature difference of the heat generating area after the hidden crack is excited relative to the background heat generating area before the hidden crack is excited, and taking the average temperature difference as an excitation efficiency evaluation index for representing the heat excitation conversion efficiency of the system.
6. The method of claim 5, wherein searching for parameter points that satisfy the excitation performance evaluation index as extreme conditions comprises: Respectively carrying out sweep frequency excitation in a preset frequency range under a discrete initial coupling pressure level; Comparing the average temperature differences at different pressure levels with the frequency combinations; the pressure level and frequency combination that produces the maximum average temperature difference is determined as the initial optimal operating point.
7. The method of claim 1, wherein the ultrasonic thermal excitation system comprises a separate excitation topology ultrasonic generator supporting a broadband modulation of 17kHz to 135kHz and a PZT-4 sandwich piezoelectric transducer with a nominal frequency of 40kHz and a power rating of 50W, the loading device being selected from an aluminum alloy loading device or a fiberglass nylon loading device.
8. The method of claim 7, wherein when the aluminum alloy loading device is selected, the initial optimal operating point determined by the method is an initial coupling pressure of 2900N and an operating frequency in the range of 38.1kHz to 38.2kHz; When the glass fiber reinforced nylon loading device is selected, the initial optimal working point determined by the method is that the initial coupling pressure is 3100N and the working frequency range is 38.3kHz to 38.4kHz.

Description

Self-adaptive configuration method for optimal working point of concrete hidden crack ultrasonic thermal excitation system Technical Field The invention relates to the technical field of ultrasonic nondestructive testing, in particular to a self-adaptive configuration method for an optimal working point of a concrete hidden crack ultrasonic thermal excitation system. Background Under the action of long-term service load, the concrete structure inevitably generates cracks, wherein hidden cracks are early key characterization of macroscopic crack formation and structural performance degradation. Hidden cracks developed in the dark often cause interlocking effects such as reinforcement corrosion, bearing capacity attenuation and the like, and burst danger of the structure is easily caused. Because the hidden cracks are small in scale, the width is generally 0.01 mm level, the distribution is hidden, and the initial form and the evolution process of the hidden cracks are difficult to be reliably captured by the conventional nondestructive detection technology. The ultrasonic infrared thermal imaging technology combines the ultrasonic excitation and the infrared thermal imaging with a novel nondestructive detection means, and utilizes high-energy ultrasonic to excite defects (such as cracks and layering) of materials to generate energy dissipation, local heat is generated at the defects and is continuously accumulated, and visual temperature difference distribution is formed on the surfaces of the materials. The technology has important application value in concrete structure health monitoring and early damage identification due to the characteristics of non-contact, rapid response, high sensitivity to concrete hidden cracks and the like. The existing ultrasonic infrared thermal image detection system is generally composed of an ultrasonic generator, a piezoelectric transducer and a pressurizing device. In practical operation, the working parameters are mostly set by relying on manual experience or simple sweep frequency test, namely, the initial coupling pressure of the pressurizing device and the working frequency of the ultrasonic generator-transducer system are manually adjusted before detection, and the signal intensity is observed to estimate and determine the working point. For example, operators tend to fix the frequency near the nominal resonant frequency of the transducer, with the estimated preload applied by a manual knob. However, the above empirical settings have difficulty ensuring that the system is at the optimal operating point. Under ideal conditions, the separate excitation topology ultrasonic generator and the sandwich piezoelectric transducer can realize impedance conjugate matching, so that the reactance of the ultrasonic system is close to zero when the ultrasonic system works at the nominal frequency of the transducer, and the maximum electric-acoustic power transmission is realized. However, in an actual ultrasonic system, due to the fact that the structural shapes of transducers with different frequencies are different, and the equivalent impedance of a sandwich transducer changes along with mechanical load under the action of coupling pressure, a certain reactance is inevitably present in an ultrasonic circuit when the transducer is designed to work at a frequency, the internal resistance of a generator and the equivalent resistance of the transducer are difficult to realize matching, so that a power peak point correspondingly shifts, the electrical state of the system deviates from an optimal working point, and the ultrasonic thermal excitation effect of a concrete hidden crack is poor. Thus, the sandwich piezoelectric transducer nominal frequency does not necessarily correspond to the maximum electric power output state of the ultrasound system. When the three are matched in a cooperative optimization mode, the ultrasonic thermal excitation system is at an optimal working point, so that the transducer outputs higher acoustic energy and the detectability of hidden cracks is improved. Disclosure of Invention The invention aims to provide a self-adaptive configuration method for an optimal working point of a concrete hidden crack ultrasonic thermal excitation system, so as to solve the problems in the prior art. According to one aspect of the application, the self-adaptive configuration method for the optimal working point of the concrete hidden crack ultrasonic thermal excitation system comprises the following steps: Acquiring an excitation control parameter space to be searched of an ultrasonic thermal excitation system, wherein the excitation control parameter space at least comprises an initial coupling pressure dimension and a working frequency dimension; driving an ultrasonic thermal excitation system to operate in an excitation control parameter space to be searched, and collecting multi-physical field response data of the system under different parameter combinations; Construct