CN-121994344-A - Laser tester for nondestructive testing of concrete cavity

CN121994344ACN 121994344 ACN121994344 ACN 121994344ACN-121994344-A

Abstract

The invention relates to the technical field of nondestructive testing of constructional engineering, and discloses a laser tester for nondestructive testing of concrete cavities, which comprises a laser interferometry assembly, a paraxial acoustic wave excitation assembly, coaxially arranged anti-interference equipment and a cooperative control processing system. The acoustic wave excitation assembly carries out wide-area excitation on the concrete surface, and the laser interferometry assembly receives return light through a clean light path constructed by the anti-interference equipment. The cooperative control processing system establishes acousto-optic time-frequency association by utilizing the self-adaptive control module, generates a phase compensation angle according to the ranging data so as to eliminate phase lock loss caused by acoustic wave propagation delay, and monitors the spectral gradient to automatically trigger fixed frequency locking so as to capture resonance response. The signal analysis module utilizes the phase compensation correction signal to analyze and output cavity characteristics through double data cleaning and thermodynamic diagram. The invention effectively solves the problems of time-space synchronization and weak signal extraction of long-distance non-contact detection in a complex environment.

Inventors

LI ZHUOMIN
WU JIANQIU
LI XING
YANG CHANGQING
SUN MIN
WU YUANHAO
DOU JINZHONG
WANG WEI
LV XINGXING

Assignees

中国建筑第八工程局有限公司

Dates

Publication Date: 20260508
Application Date: 20251217

Claims (10)

1. A laser tester for nondestructive testing of concrete voids, comprising: A laser interferometry assembly for emitting a coherent light beam and performing a gridding scan, receiving a diffusely reflected return light, generating an original interference electrical signal based on interference of a reference beam (11) with the diffusely reflected return light; The side shaft of the acoustic wave excitation assembly is arranged at one side of the laser interferometry assembly and is used for responding to a control instruction and converting the control instruction into an acoustic wave beam so as to carry out wide-area excitation on the surface of the concrete (8) and induce forced vibration, and a vibration measurement object is provided for the laser interferometry assembly; the anti-interference device (9) is coaxially arranged on the optical path of the laser interferometry assembly and is used for constructing an optical transmission path and filtering ambient light entering the optical path so as to output incident light rays of a linear working area to the laser interferometry assembly; The cooperative control processing system is in communication connection with the laser interferometry component and the acoustic wave excitation component and comprises an adaptive control module and a signal analysis module; the self-adaptive control module is used for establishing the association of the acoustic wave beam and the coherent light beam in time and frequency dimensions, generating a phase compensation angle, transmitting the phase compensation angle to the signal analysis module, and generating the control instruction to feed back the control instruction to the acoustic wave excitation assembly; The signal analysis module is used for receiving the original interference electric signal, correcting and analyzing the original interference electric signal by utilizing the phase compensation angle and finally outputting cavity characteristic information.
2. A laser gauge for the non-destructive inspection of concrete cavities according to claim 1, characterized in that said anti-interference device (9) comprises: An air curtain generator for continuously spraying rectified laminar compressed air in front of a beam receiving and transmitting port of the laser interferometry assembly to form an air barrier, and constructing the optical transmission path by blocking suspended particulate matter in a building environment from adhering; and the optical filtering unit is used for monitoring external environment light by using the light intensity sensor as the environment light entering the light path, adjusting the transmissivity of the liquid crystal filter through closed loop feedback so as to execute filtering operation, and outputting the incident light of the linear working area to the laser interferometry assembly.
3. A laser meter for the nondestructive testing of concrete voids according to claim 1, wherein said acoustic excitation assembly comprises: The signal generation driver is used for receiving the control instruction and generating an electric excitation signal according to the control instruction; -a directional acoustic wave emitter (7) for receiving said electrical excitation signal and converting it into said acoustic wave beam, covering said acoustic wave beam over said vibration measurement object, inducing said forced vibration of said concrete (8) surface; the control instruction comprises a frequency locking instruction and a default frequency sweeping instruction.
4. A laser gauge for non-destructive inspection of concrete voids according to claim 3, wherein said laser interferometry assembly comprises: -a laser (1) for emitting the coherent light beam; a beam splitting prism (4) for splitting the coherent light beam into the reference beam (11) and a measuring beam (10); -a reference total reflection mirror (3) for reflecting the reference beam (11) back to the splitting prism (4); a scanning galvanometer (2) for directing the measuring beam (10) to the concrete (8) surface and performing the gridding scan while receiving the diffusely reflected return light from the concrete (8) surface and returning its return light path to the beam splitting prism (4); A photodetector (5) for receiving an interference light field (12) formed by the reference beam (11) combined at the beam splitting prism (4) and the diffusely reflected return light, and converting a light intensity variation into the original interference electrical signal; and the electric sliding table (6) is used for bearing the scanning galvanometer (2) and the laser (1) and is used for receiving a focusing driving instruction sent by the self-adaptive control module and moving along the optical axis direction so as to adjust the focusing point position of the measuring beam (10).
5. The laser gauge for non-destructive testing of concrete voids according to claim 4, wherein said adaptive control module comprises: The distance phase synchronization unit is used for controlling the laser interferometry assembly to execute the gridding scanning, resolving the linear distance of the current scanning point relative to the detection system based on the original interference electric signal, generating the focusing driving instruction and sending the focusing driving instruction to the laser interferometry assembly, and executing a phase compensation calculation formula according to the linear distance to calculate the phase compensation angle so as to eliminate phase unlocking caused by acoustic wave propagation delay.
6. The laser gauge for non-destructive testing of a concrete void according to claim 5, wherein said adaptive control module further comprises: The resonance locking unit is used for monitoring the change trend of the vibration amplitude of the surface of the concrete (8) in real time in the process that the sound wave excitation assembly responds to the default frequency sweep instruction to emit a broadband frequency sweep signal, and executing resonance trend judgment type to calculate the change rate of the vibration amplitude relative to the instantaneous emission frequency of the sound wave excitation assembly, namely, the spectrum gradient; When the spectral gradient does not exceed a preset gradient threshold value, the resonance locking unit generates the default frequency sweep instruction and sends the default frequency sweep instruction to the acoustic wave excitation assembly to maintain broadband frequency sweep; when the spectral gradient exceeds the preset gradient threshold value, the resonance locking unit generates the frequency locking instruction and sends the frequency locking instruction to the acoustic wave excitation assembly to trigger fixed frequency locking; The preset gradient threshold is preset according to the statistical distribution of the historical resonance response data.
7. The laser gauge for nondestructive testing of concrete voids of claim 6, wherein said signal analysis module comprises: The interference demodulation unit is used for receiving the original interference electric signal, extracting instantaneous phase change information by utilizing a phase demodulation algorithm, calling the phase compensation angle output by the self-adaptive control module to correct the instantaneous phase change information, and outputting surface vibration speed data after differential processing.
8. The laser gauge for nondestructive testing of concrete voids according to claim 7, wherein said interferometric demodulation unit performs a dual data cleaning logic before outputting said surface vibration velocity data, said dual data cleaning logic specifically being: monitoring the return light intensity of the original interference electric signal, if the return light intensity is lower than a preset optical detection threshold value, marking the return light intensity as an invalid point, and performing interpolation replacement by using data of a neighborhood valid point in a pixel matrix with a preset size taking the invalid point as a center; if the return light intensity is not lower than the preset optical detection threshold value, but the amplitude of the demodulated surface vibration speed data exceeds the preset multiple of the average amplitude value of the neighborhood effective points, judging that the surface vibration speed data is an effective physical signal and retaining an original numerical value; the preset optical detection threshold is preset according to the signal-to-noise ratio characteristic of the photoelectric detector (5), the preset size pixel matrix is preset according to the scanning resolution and interpolation precision requirements, and the preset multiple is preset according to the statistical distribution of background noise.
9. The laser gauge for non-destructive testing of a concrete void according to claim 7, wherein said signal analysis module further comprises: the defect identification unit is used for receiving the surface vibration speed data and mapping the surface vibration speed data to a space coordinate system to construct a vibration thermodynamic diagram, identifying a region which has a vibration amplitude exceeding a preset amplitude threshold and corresponds to the frequency locking instruction and has a resonance frequency response in the vibration thermodynamic diagram, calculating the space coordinates, the estimated area and the corresponding resonance frequency of the region, and finally generating the cavity characteristic information; the preset amplitude threshold value is calculated based on a reference plane determined by vibration amplitudes of all scanning points in the vibration thermodynamic diagram.
10. The laser detector for nondestructive testing of concrete voids according to claim 6, wherein said distance phase synchronization unit, when executing said phase compensation calculation formula, specifically comprises: Calculating the phase lag amount caused by the time delay of sound wave propagation by utilizing the instantaneous emission frequency of the sound wave excitation assembly, the linear distance and the air sound velocity at the current environment temperature to obtain the phase compensation angle; the resonance lock unit specifically includes, when executing the resonance tendency determination formula: And calculating the absolute value of the difference between the vibration amplitude values of the concrete (8) surface at the current time and the last sampling time, calculating the difference between the sound wave emission frequency of the sound wave excitation assembly at the current time and the last sampling time, and dividing the absolute value of the difference between the vibration amplitude values by the difference between the sound wave emission frequency to obtain the spectrum gradient.

Description

Laser tester for nondestructive testing of concrete cavity Technical Field The invention relates to the technical field of nondestructive testing of constructional engineering, in particular to a laser tester for nondestructive testing of concrete cavities. Background The laser vibration measurement technology is used as a high-precision optical measurement means, and is mainly based on the laser Doppler effect and the interference principle, and vibration parameters of the target surface are obtained by demodulating frequency movement or interference fringe variation of reflected light. At present, the technology is widely applied to the fields of engine performance analysis, aerospace component detection, vibration monitoring of precision industrial equipment and the like. However, the existing commercial laser vibrometer is generally designed for high reflectivity targets such as metal surfaces, and is not mature in application to internal defect detection for rough and low reflectivity media such as concrete. At present, the detection of concrete cavities in the construction engineering mainly depends on a knocking method or an ultrasonic method. The traditional methods belong to contact detection, often require detection personnel to approach to detected parts such as high altitude or tunnel top and the like by building a scaffold and the like, and part of the methods require the use of coupling agents, so that detection operation is time-consuming and labor-consuming, and the requirements of remote and large-area rapid screening of large-scale infrastructures are difficult to meet. Although the infrared thermal imaging and other non-contact methods avoid direct contact, the detection depth is generally limited by the heat conduction characteristics, and the deep hidden holes inside the concrete are difficult to effectively find. In addition, the construction site is usually filled with dust pollution, mechanical vibration and complex background light environment, and the existing precise detection equipment lacks a targeted physical protection and signal anti-interference mechanism, so that the signal-to-noise ratio of a measurement signal is easily reduced due to light path pollution or environmental noise interference, and further the detection result is distorted. Meanwhile, under the condition of lacking of acousto-optic cooperative self-adaptive control, the problem of phase asynchronism caused by long-distance transmission is difficult to solve in the prior art, weak defect resonance signals cannot be effectively locked in the rapid scanning process, and detection omission or misjudgment are easy to cause. Disclosure of Invention Aiming at the defects of the prior art, the invention provides a laser detector for nondestructive detection of concrete cavities, which solves the problems that the prior art depends on close-range contact operation, has insufficient environment interference resistance and is difficult to consider the detection efficiency and the detection precision under long-range complex working conditions. The invention provides a laser tester for nondestructive testing of concrete cavities, which mainly comprises a laser interferometry component, an acoustic wave excitation component, anti-interference equipment and a cooperative control processing system. The laser interferometry assembly is used for emitting a coherent light beam, performing gridding scanning on the concrete surface, receiving return light formed by diffuse reflection of the concrete surface, and generating an original interference electric signal based on interference action of the reference light beam and the diffuse reflection return light. The paraxial of the acoustic wave excitation assembly is arranged on one side of the laser interferometry assembly and used for responding to the control instruction and converting the electric signal into an acoustic wave beam, carrying out wide-area excitation on the concrete surface and inducing forced vibration, so as to provide a vibration measurement object for the laser interferometry assembly. The anti-interference device is coaxially arranged on the optical path of the laser interferometry assembly and is used for constructing an optical transmission path and filtering ambient light entering the optical path, and outputting incident light of the linear working area to the laser interferometry assembly. The cooperative control processing system is in communication connection with the laser interferometry component and the acoustic wave excitation component and is responsible for space-time cooperative control and data processing of the system, and the inside of the cooperative control processing system comprises an adaptive control module and a signal analysis module. In the specific implementation of the anti-interference device, the air curtain generator continuously sprays rectified laminar compressed air in front of the light beam receiving and transmitting por