Calibration method and system for realizing photoacoustic signal time axis synchronization based on arc triggering

Abstract

The application relates to a calibration method and system for realizing photoacoustic signal time axis synchronization based on arc triggering, and relates to the field of material dynamic testing. The existing synchronization scheme only solves the starting point synchronization, cannot eliminate the transmission path difference and processing algorithm time difference, and cannot solve the problems of time domain misalignment of the time-frequency analysis result of the acoustic emission signal and the fracture failure image of the high-speed camera, etc. The method comprises the following steps: an arc generator is arranged at a drop hammer impact position; a trigger end of the arc generator is connected with a synchronous trigger, which is used for controlling the arc generator to generate a transient arc light signal; a high-speed camera is used for collecting an image sequence of the arc light signal; an air-coupled acoustic emission sensor is used for collecting a time-frequency graph of the arc response; based on the frame number in the image sequence of the arc light signal and the arrival time of the arc response in the collected time-frequency graph of the arc response, a time deviation amount is calculated; the acoustic emission signal time domain data is shifted by the time deviation amount, and the calibration of the photoacoustic signal in the time axis synchronization is completed.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of material dynamic testing, in particular to a calibration method and system for realizing photoacoustic signal time axis synchronization based on arc triggering. BACKGROUND

[0002] In the field of material dynamic testing, photoacoustic signal synchronization technology is the key to analyzing the failure mechanism of the main component materials of the photoelectric load pod in drop hammer impact test. In the traditional technology, the time alignment of the optical signal (such as high-speed camera) and the acoustic emission signal is mainly realized through the following two ways: 1. Physical path compensation: by measuring the spatial position difference of the photoacoustic sensor, calculating the signal propagation time difference and compensating. However, due to the complex crack propagation path in the material, it is difficult to accurately model the physical distance, resulting in large compensation error. 2. Software delay correction: by adjusting the buffer length or trigger threshold in the signal processing flow, the output time sequence of the photoacoustic signal is aligned. However, the nonlinear delay introduced by software processing (such as filtering algorithm, data transmission delay) is difficult to quantify, and the compatibility difference between different devices further aggravates the time domain misalignment.

[0003] The above methods have the following fundamental defects: 1. Accumulative error: the superimposed effect of physical path and software delay leads to the increase of time domain alignment deviation with the increase of test time, the time lag caused by the difference in physical distance is difficult to accurately model, and the propagation speed of optical signal is , while the propagation speed of acoustic signal in the material is only order of magnitude, resulting in physical lag (such as 1ms delay of 1m distance acoustic signal) of sensor received signal, nonlinear delay introduced by software processing flow, which cannot be quantitatively compensated, high-speed camera image processing needs interframe calculation (about 0.1ms), acoustic emission signal needs filtering, time-frequency transformation algorithm (about 0.5ms), the delay magnitude of the two is different and unpredictable; 2. Result distortion: the time-frequency characteristics (such as crack propagation stage) of acoustic emission signal and the fracture failure image of high-speed camera exist second-level misalignment, which cannot be directly correlated and analyzed; 3. Verification difficulty: the process alignment method cannot guarantee the time domain consistency of the final result (such as material fracture moment), resulting in reduced credibility of test data.

[0004] The existing synchronization scheme (such as hardware trigger alignment) only solves the synchronization of the starting point of acquisition, and cannot eliminate the difference in propagation path and the time difference of processing algorithm, resulting in time domain misalignment between the time-frequency analysis result of acoustic emission signal and the fracture failure image of high-speed camera, which limits the accuracy of material dynamic testing. Therefore, a method for directly aligning photo-acoustic signals on the time axis of the final result is needed, rather than relying on process synchronization. SUMMARY

[0005] The application is a calibration method and system for realizing time axis synchronization of photoacoustic signals based on arc triggering, which overcomes the problems in the prior art that the synchronization scheme (such as hardware trigger alignment) only solves the synchronization of the starting point of acquisition, cannot eliminate the difference in propagation paths and the time difference in processing algorithms, causes the time domain misalignment between the time-frequency analysis results of acoustic emission signals and the fracture failure images of high-speed cameras, and limits the accuracy of material dynamic testing.

[0006] To solve the above technical problems, the application is implemented by the following technical scheme:

[0007] Scheme one, the application provides a calibration method for realizing time axis synchronization of photoacoustic signals based on arc triggering, which is realized by a calibration device for realizing time axis synchronization of photoacoustic signals based on arc triggering, the device comprises a measured material, a high-speed camera, an arc generator, and an air-coupled acoustic emission sensor.

[0008] The measured material is a rectangular aluminum plate structure with a circular through hole in the center position, the discharge electrode tip of the arc generator is coaxially arranged with the axis of the circular through hole of the measured material, the air-coupled acoustic emission sensor is fixed on the surface of the measured material through a vacuum grease coupling agent, the installation position of the air-coupled acoustic emission sensor is parallel to the center of the circular through hole, the high-speed camera is provided with a fixed-focus lens and is arranged 1.5 m in front of the measured material to form a 15° angle with the normal direction of the surface of the measured material, and the high-speed camera trigger signal and the air-coupled acoustic emission sensor realize nanosecond-level synchronization through a BNC coaxial cable.

[0009] The method comprises the following steps:

[0010] Step 1, an arc generator is arranged at the position of the falling hammer impact, the trigger end of the arc generator is connected with a synchronous trigger, which is used for controlling the arc generator and generating a transient arc light signal at a preset frequency;

[0011] Step 2, a high-speed camera is used to collect an image sequence containing the arc light signal in step 1, and an air-coupled acoustic emission sensor is used to collect a time-frequency graph containing an arc response;

[0012] Step 3, based on the frame number in the image sequence of the arc light signal and the arrival time of the arc response in the time-frequency graph of the arc response collected in step 2, a time deviation Δt is calculated.

[0013] Step 4, the time domain data of the acoustic emission signal is shifted by the time deviation Δt in step 3, and the calibration of the time axis synchronization of the photoacoustic signal is completed.

[0014] Further, a preferred embodiment is provided, in which the air-coupled acoustic emission sensor is realized by a piezoelectric sensor with a resonant frequency of 200 kHz.

[0015] Further, a preferred embodiment is provided, the image sequence of the arc light signal collected by the high-speed camera in step 2 includes an arc flash mark, and the acoustic emission time-frequency diagram has an arc response peak per second.

[0016] Further, a preferred embodiment is provided, the trigger period of the arc generator is greater than or equal to 0.1 seconds and less than or equal to 2 seconds.

[0017] Further, a preferred embodiment is provided, the high-speed camera and the air-coupled acoustic emission sensor are controlled to start simultaneously by a hardware synchronization mode through a synchronous trigger.

[0018] Scheme II, a calibration system for realizing time axis synchronization of photoacoustic signals based on arc triggering, the system comprising:

[0019] An arc mark module is configured to set an arc generator at a drop hammer impact position, a trigger end of the arc generator is connected to a synchronous trigger, and the synchronous trigger is configured to control the arc generator and generate a transient arc light signal at a preset frequency.

[0020] A multi-source data acquisition module is configured to collect an image sequence of the arc light signal by using a high-speed camera, and collect a time-frequency diagram containing an arc response by using an air-coupled acoustic emission sensor.

[0021] A timestamp extraction module is configured to calculate a time offset Δt based on a frame number in the image sequence of the arc light signal and a time of arrival of the arc response in the time-frequency diagram of the arc response collected by the multi-source data acquisition module.

[0022] A data correction module is configured to shift the acoustic emission signal time domain data by the time offset Δt calculated by the timestamp extraction module, and complete calibration of the photoacoustic signals in time axis synchronization.

[0023] Scheme III, a computer readable storage medium, the computer readable storage medium stores a computer program, and the computer program is executed by a processor to realize the steps of the method in scheme I.

[0024] Scheme IV, a computer device, comprising a memory and a processor, the memory stores a computer program, and when the processor runs the computer program stored in the memory, the processor executes the method in scheme I.

[0025] The present application has the following advantages:

[0026] The calibration method and system for synchronizing photoacoustic signals based on arc triggering described in this invention eliminates accumulated errors by directly introducing a marker at the final result time point, thus avoiding the accumulated delay introduced by the physical path and software processing. It improves synchronization accuracy by achieving nanosecond-level timing control through hardware synchronization triggering, and the calculation error of the time offset Δt is lower than that of a single frame time, such as ≤1ms at 1000fps.

[0027] The calibration method and system for synchronizing photoacoustic signals based on arc triggering described in this invention simplifies the verification process, eliminating the need for complex modeling or parameter adjustments, and directly verifying the photoacoustic alignment effect through the temporal correspondence of arc markers.

[0028] The calibration method and system for synchronizing photoacoustic signals based on arc triggering described in this invention enhances data correlation, and the crack propagation stage of the acoustic emission signal and the fracture failure stage of the high-speed camera are precisely correlated on the time axis, thereby improving the reliability of time-frequency analysis. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the calibration device in the calibration method for synchronizing the time axis of photoacoustic signals based on arc triggering, as described in Embodiment 1.

[0030] Figure 2 This is a flowchart illustrating a calibration method for synchronizing the time axis of photoacoustic signals based on arc triggering, as described in Embodiment 2.

[0031] Among them, the material under test is 1, the high-speed camera is 2, the arc generator is 3, and the air-coupled acoustic emission sensor is 4. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them.

[0033] Implementation Method 1, see [link] Figure 1 This embodiment describes a calibration device for synchronizing the time axis of photoacoustic signals based on arc triggering, specifically including:

[0034] The measured material 1 adopts a rectangular aluminum plate structure, a circular through hole (diameter 15 mm, depth 10 mm) is arranged at the center position, and the hole wall is precisely milled to form a smooth surface with a perpendicularity error of ≤0.02 mm. The coincidence error of the through hole axis and the normal direction of the surface of the measured material 1 is controlled within ±0.5°; the arc generator 3 adopts a pulsed plasma arc device, the tip of the discharge electrode is coaxially arranged with the axis of the through hole of the measured material 1, and the electrode spacing is calibrated to 5 mm ± 0.1 mm in real time by a laser range finder. The arc triggering frequency is set to 1 Hz ± 0.02 Hz, the single discharge energy is controlled within 50 J ± 2 J, and the discharge duration is accurately controlled to 20 ms ± 1 ms by an IGBT module; the air-coupled acoustic emission sensor 4 adopts a piezoelectric sensor with a resonance frequency of 200 kHz, which is fixed to the surface of the measured material 1 through a vacuum grease coupling agent. The thickness of the coupling layer is controlled to 0.1 mm ± 0.02 mm by a micrometer, the installation position of the air-coupled acoustic emission sensor 4 is parallel to the center of the through hole, and the distance from the through hole edge is 20 mm ± 1 mm. The signal of the air-coupled acoustic emission sensor 4 is processed by a preamplifier (gain 40 dB) and then connected to the data acquisition system; the high-speed camera 2 is configured with a fixed-focus lens (focal length 50 mm, aperture f / 2.8), arranged 1.5 m in front of the measured material 1, forming a 15° angle with the normal direction of the surface of the measured material 1, and the shooting parameters are set as: resolution 1920×1080, frame rate 1000 fps, shutter speed 1 / 2000 s, and the trigger signal of the high-speed camera 2 is synchronized with the air-coupled acoustic emission sensor 4 through a BNC coaxial cable to achieve nanosecond-level synchronization.

[0035] Embodiment two, see Figure 2 In order to illustrate the embodiment, the embodiment proposes a calibration method for realizing time axis synchronization of photoacoustic signals based on arc triggering, which specifically includes the following steps:

[0036] The present application introduces an arc generator 3 as a synchronization marker source to generate a detectable photoacoustic double signal at the final result time point of the drop hammer impact test, realizing the time alignment of photoacoustic signals at the result level. The specific technical scheme is as follows:

[0037] 1. Arc marking method: an arc generator 3 is arranged near the drop hammer impact position, and a synchronous trigger is used to control it to generate a transient arc at a preset frequency (such as 1 Hz);

[0038] 2. Multi-source data acquisition: the high-speed camera 2 captures an image sequence containing arc light signals, and the air-coupled acoustic emission sensor 4 collects a time-frequency graph containing arc responses;

[0039] 3. Time stamp extraction: based on the frame number (t_camera) of the arc light signal in the image sequence and the arrival time (t_AE) of the arc response in the time-frequency graph, the time offset Δt is calculated;

[0040] 4. Data correction: shift the acoustic emission signal time domain data by At, complete the alignment of photoacoustic signal at the final result level.

[0041] Step 1: install an arc generator 3 (voltage 2kV, frequency 1Hz) at 5cm above the drop hammer impact position, the trigger end is connected to the synchronous trigger;

[0042] Step 2: set the synchronous trigger output TTL level pulse, synchronously control the arc generator 3, high-speed camera 2 (frame rate 1000fps) and air-coupled acoustic emission sensor 4 (sampling rate 2MHz);

[0043] Step 3: carry out drop hammer impact test, the high-speed camera 2 contains arc flash mark in each frame image, and the acoustic emission time-frequency diagram has arc response peak per second;

[0044] Step 4: extract the frame number of the arc occurrence (t_camera=0.001s) by image processing algorithm, and extract the arrival time (t_AE=0.003s) of the arc response in the acoustic emission time-frequency diagram by wavelet transform;

[0045] Step 5: calculate the time offset At=0.002s, shift the acoustic emission signal time domain data by 2ms in whole, complete the photoacoustic alignment.

[0046] Embodiment three, the embodiment proposes a calibration system for realizing photoacoustic signal time axis synchronization based on arc triggering, the system comprises:

[0047] An arc mark module is arranged for setting an arc generator 3 at the drop hammer impact position, the trigger end of the arc generator 3 is connected to a synchronous trigger, which is used for controlling the arc generator 3 and generating a transient arc light signal at a preset frequency;

[0048] A multi-source data acquisition module is arranged for collecting an image sequence containing the arc light signal of the arc mark module by using a high-speed camera 2, and collecting a time-frequency diagram containing the arc response by using an air-coupled acoustic emission sensor 4;

[0049] A timestamp extraction module is arranged for calculating a time offset At based on the frame number in the arc light signal image sequence and the arrival time of the arc response in the time-frequency diagram of the arc response collected by the multi-source data acquisition module;

[0050] A data correction module is arranged for shifting the acoustic emission signal time domain data by the time offset At calculated by the timestamp extraction module in whole, and completing the calibration of the photoacoustic signal in the time axis synchronization.

[0051] Further, a preferred embodiment is provided, which establishes the time alignment relationship of the photoacoustic signal based on the timestamp of the arc light signal in the image sequence and the timestamp of the arc response in the acoustic emission time-frequency map.

[0052] Further, a preferred embodiment is provided, in which the trigger period of the arc generator 3 is greater than or equal to 0.1 seconds and less than or equal to 2 seconds.

[0053] Further, a preferred embodiment is provided, in which the synchronous trigger controls the simultaneous start of the air-coupled acoustic emission sensor 4 and the high-speed camera 2 through hardware synchronization.

[0054] In summary, the present embodiment eliminates cumulative errors by directly introducing a marker at the final result time point, avoiding cumulative delays introduced by physical paths and software processing; improves synchronization accuracy by achieving nanosecond-level timing control through hardware synchronization triggering, with a calculation error of the time offset Δt being less than a single frame time (e.g. error ≤1 ms at 1000 fps); simplifies the verification process without complex modeling or parameter adjustment, directly verifying the photoacoustic alignment effect through the time-domain correspondence of the arc marker; enhances data correlation, with the crack propagation stage of the acoustic emission signal accurately corresponding to the fracture failure stage of the high-speed camera 2 on the time axis, improving the reliability of time-frequency analysis.

[0055] Those skilled in the art can understand that the above description is only a preferred embodiment of the present application, and the features described in each embodiment and / or technical solution of the present disclosure can be combined or combined, even if such combination or combination is not explicitly described in the present disclosure. The present application is not intended to limit the present application, although the present application has been described in detail with reference to the foregoing embodiments, and those skilled in the art can modify the technical solutions described in the foregoing embodiments or make equivalent replacements of part of the technical features, and any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

[0056] Although the preferred embodiments of the present application have been described, those skilled in the art can make further changes and modifications to these embodiments once they understand the basic creative concept. Therefore, the appended technical solutions are intended to include the preferred embodiments and all modifications and modifications falling within the scope of the present application. Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the technical solutions of the present application and their equivalents, the present application also intends to include these modifications and variations.

Claims

1. A calibration method for achieving photoacoustic signal time axis synchronization based on arc triggering, characterized in that, The calibration method is based on arc triggering to realize the calibration of photoacoustic signal time axis synchronization, and a calibration device is used to realize the calibration, the device comprises a measured material (1), a high-speed camera (2), an arc generator (3), and an air-coupled acoustic emission sensor (4); The measured material (1) is a rectangular aluminum plate structure, a circular through hole is arranged at the center position, the discharge electrode tip of the arc generator (3) is coaxially arranged with the axis of the circular through hole of the measured material (1), the air-coupled acoustic emission sensor (4) is fixed on the surface of the measured material (1) through a vacuum grease coupling agent, the installation position of the air-coupled acoustic emission sensor (4) is parallel to the center of the circular through hole, the high-speed camera (2) is provided with a fixed-focus lens and is arranged 1.5 m in front of the measured material (1) to form an angle of 15° with the normal direction of the surface of the measured material (1), the trigger signal of the high-speed camera (2) is realized nanosecond-level synchronization with the air-coupled acoustic emission sensor (4) through a BNC coaxial cable; The method comprises the following steps: Step 1, an arc generator (3) is arranged at the position of the falling hammer impact, the trigger end of the arc generator (3) is connected with a synchronous trigger, which is used to control the arc generator (3) and generate a transient arc light signal at a preset frequency; Step 2, an image sequence containing the arc light signal in step 1 is collected by using a high-speed camera (2), and a time-frequency graph containing an arc response is collected by using an air-coupled acoustic emission sensor (4); Step 3, based on the frame number in the arc light signal image sequence and the arrival time of the arc response in the time-frequency graph of the arc response collected in step 2, the time offset Δt is calculated; Step 4, the acoustic emission signal time domain data is shifted by the time offset Δt in step 3, and the calibration of photoacoustic signal time axis synchronization is completed.

2. The calibration method for achieving photoacoustic signal time axis synchronization based on arc triggering according to claim 1, characterized in that, The air-coupled acoustic emission sensor (4) is realized by using a piezoelectric sensor with a resonance frequency of 200 kHz.

3. The calibration method for achieving photoacoustic signal time axis synchronization based on arc triggering according to claim 1, characterized in that, The image sequence of the arc light signal collected by the high-speed camera (2) in step 2 includes an arc flash mark, and the acoustic emission time-frequency graph appears an arc response peak per second.

4. The calibration method for realizing photoacoustic signal time axis synchronization based on arc triggering according to claim 1, characterized in that, The trigger period of the arc generator (3) is greater than or equal to 0.1 seconds and less than or equal to 2 seconds.

5. The calibration method for achieving photoacoustic signal time axis synchronization based on arc triggering according to claim 1, characterized in that, The high-speed camera (2) and the air-coupled acoustic emission sensor (4) are controlled to start at the same time by using a synchronous trigger through a hardware synchronization mode.

6. A calibration system for achieving photoacoustic signal time axis synchronization based on arc triggering, characterized in that, The system is realized based on the method in claim 1, and the system comprises: An arc marking module is arranged at the position of the falling hammer impact, the trigger end of the arc generator (3) is connected with a synchronous trigger, which is used to control the arc generator (3) and generate a transient arc light signal at a preset frequency; A multi-source data collection module is used to collect an image sequence containing the arc light signal of the arc marking module by using a high-speed camera (2), and a time-frequency graph containing an arc response is collected by using an air-coupled acoustic emission sensor (4); A timestamp extraction module is used to calculate the time offset Δt based on the frame number in the arc light signal image sequence and the arrival time of the arc response in the time-frequency graph of the arc response collected by the multi-source data collection module; The air-coupled acoustic emission sensor (4) is realized by using a piezoelectric sensor with a resonance frequency of 200 kHz. A data correction module is configured to shift the time domain data of the acoustic emission signal by the time offset Δt extracted by the time stamp extraction module, so as to calibrate the photoacoustic signal in the time axis.

7. A computer storage medium having stored thereon a computer program, characterized in that The computer program is executed by a processor to implement the method of claim 1.

8. A computer device, comprising: Comprising: A memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the method of claim 1.

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