Fracture test acoustic emission and high-speed imaging synchronous monitoring system and monitoring method

Abstract

The invention provides a fracture test acoustic emission and high-speed imaging synchronous monitoring system and monitoring method, and belongs to the technical field of material fracture test monitoring. The monitoring system comprises a loading test device, an acoustic emission monitoring device, a high-speed imaging device and a synchronous control system, the synchronous control system collects a load signal output by the loading sensor and generates a synchronous pulse through a peak detection algorithm when the load reaches a peak value, and the synchronous pulse is recorded by the acoustic emission system and triggers the high-speed camera at the same time, so that a unified time reference is established, and accurate alignment of acoustic emission data and high-speed image data is realized. The system is simple in structure, high in synchronization precision and capable of stably capturing the rapid crack initiation and expansion process near the fracture peak value.

Description

Technical Field

[0001] This invention relates to the field of high-precision measurement technology, specifically to a simultaneous monitoring system and method for acoustic emission and high-speed imaging in fracture tests. Background Technology

[0002] During tensile or splitting failure of materials and brittle media such as rocks, crack initiation and rapid propagation events often occur on the order of microseconds. Acoustic emission (AE) monitoring can record elastic wave information generated by crack evolution with high temporal resolution, but it is difficult to directly present crack morphology and propagation path. High-speed imaging can visualize and record crack propagation morphology, but without a unified time reference with acoustic emission data, it is difficult to achieve a precise correspondence between "acoustic emission event and image frame".

[0003] In existing fracture tests, high-speed cameras and image acquisition (AE) systems are often used for collaborative data acquisition through methods such as independent triggering, manual triggering, or synchronous startup at the process level. However, in situations where fractures typically occur near peak loads and crack propagation is extremely transient, these methods may encounter issues such as fluctuating trigger times, insufficient coverage of critical transients, or large alignment errors between multi-source data in certain scenarios. This can affect the detailed analysis of fracture initiation and propagation mechanisms.

[0004] For example, Chinese patent document CN110186957B discloses a synchronous information acquisition and processing system and method for fatigue testing scenarios. It utilizes a lower-level computer to collaboratively control the acquisition of data from detection devices such as high-speed cameras, thermal imagers, and industrial cameras. Based on the output voltage data of the fatigue testing machine, it generates corresponding control commands for the detection devices, achieving collaborative acquisition and data management across multiple devices. While this document provides an approach to the collaborative control of multiple detection devices, its triggering criteria and control logic primarily revolve around the signals and threshold settings of the fatigue testing machine. Regarding the specific implementation method in fracture testing, which uses "load peak value" as the triggering basis and establishes a unified hardware time reference between the acoustic emission system and the high-speed camera, based on its disclosed content, further design and integration may still be required depending on the specific test object.

[0005] For example, Chinese patent document CN113466044A discloses a method for testing the generation of explosive defects during a Brazilian test. This method involves arranging a light source, a high-speed camera, and an acoustic emission instrument during the loading process of the Brazilian test, and synchronizing three actions: internal defect detection, end-face defect characterization, and mechanical loading, to obtain multiple types of data at the same starting time and identify parameters. This document emphasizes the synergistic characterization of multiple methods and the synchronization of the test process. Based on its disclosure, its synchronization method is mainly at the process level. For the establishment and recording of a unified synchronization pulse or hardware-level time reference used for "frame-by-frame alignment," further configuration and calibration may be needed in specific applications to meet the analytical requirements of higher time alignment accuracy.

[0006] For example, Chinese patent document CN110501218A discloses a Hopkinson pressure bar system for measuring the strain rate constitutive relationship in ultrasoft materials. The system includes a high-speed camera and a camera triggering device. The triggering device can use a laser velocimeter, strain gauge, etc., to provide a trigger signal at a specific moment, which is then processed by a waveform amplifier and oscilloscope to trigger the camera shutter. A delay time can be set to meet shooting requirements. This document primarily focuses on dynamic testing and imaging triggering control under medium strain rate conditions. Its disclosure does not emphasize the implementation path of incorporating acoustic emission monitoring into the same time reference and simultaneously recording synchronous pulses in the AE system for triggering the high-speed camera; related details are relatively limited.

[0007] For example, Chinese patent document CN114581284A discloses a multi-camera high-speed synchronous shooting system and method. It outputs hardware control trigger signals to multiple cameras via a hardware synchronizer motherboard / slave board, achieving synchronous shooting under multi-camera, multi-viewpoint, and high-speed conditions to reduce post-processing correction work. This document focuses on synchronous shooting between cameras; sharing a unified synchronization pulse with non-destructive testing systems such as acoustic emission, and triggering strategies targeting the peak load of fracture tests, are not its primary concerns based on the disclosed content. Therefore, further adaptation may be needed for multi-source data fusion in fracture tests.

[0008] Furthermore, Chinese patent document CN112261283B discloses a synchronous acquisition method, device, and system for a high-speed camera. It utilizes satellite timing signals to decode and generate a synchronization signal, and then combines the rising edge of the synchronization signal with the occurrence of a target event to generate a camera acquisition signal, achieving time synchronization and error reduction in high-speed camera acquisition. This document focuses on synchronous camera acquisition assisted by timing signals; however, in fracture test scenarios, if it is necessary to integrate load peak determination and acoustic emission data alignment into a unified scheme, further targeted integration and implementation using the test load signal and the AE system interface may still be required.

[0009] In summary, existing patents have proposed different implementation schemes from the perspectives of multi-device collaborative control, test process synchronization, camera trigger control, multi-camera synchronization, and time synchronization. For the typical condition in fracture tests where "fracture usually occurs near the load peak," how to use the load peak as the trigger and output a synchronization pulse that can be simultaneously recorded by the acoustic emission system and used to trigger the high-speed camera, without significantly increasing system complexity, thus facilitating accurate correspondence between acoustic emission events and image frames, still requires further development of more suitable technical solutions. Summary of the Invention

[0010] The technical problem to be solved by the present invention is that the existing technology has the shortcomings of making it difficult to achieve high-precision time synchronization of acoustic emission monitoring and high-speed imaging, and difficult to stably capture key transient processes near the fracture peak. The purpose is to provide a synchronous monitoring system and method for acoustic emission and high-speed imaging based on load peak triggering.

[0011] To achieve the above objectives, the present invention provides a synchronous monitoring system for acoustic emission and high-speed imaging in fracture tests, used to monitor the fracture state of rock samples, including a loading test device, an acoustic emission monitoring device, a high-speed imaging device, a synchronous control system, and a computer; the rock sample is loaded in the loading test device, and at least one loading sensor is mounted on the rock sample; the acoustic emission monitoring device includes an acoustic emission sensor and an acoustic emission acquisition instrument; The synchronization control system includes a signal conditioning module, an analog-to-digital converter, a control module, and a digital-to-analog converter, which are sequentially and unidirectionally electrically connected. The signal conditioning module is electrically connected to the load sensor and is used to receive and condition the load signal from the load sensor. The analog-to-digital converter is used to acquire the conditioned load signal and transmit it to the controller. The control module has a built-in peak detection algorithm for continuous monitoring of the load signal and outputs a trigger command when the load signal reaches its peak value. The digital-to-analog converter is used to generate a synchronization pulse after receiving the trigger command and simultaneously send the synchronization pulse to the acoustic emission acquisition instrument and the high-speed imaging device via electrical connection. The acoustic emission sensor is used to collect the sound generated by the rock sample during the loading test. The acoustic emission acquisition instrument is used to receive and record the synchronization pulse, establish a time reference, and realize the time alignment between the acoustic emission data and the high-speed image data. The high-speed imaging device uses the synchronization pulse as a trigger signal to collect the image data of the rock sample during the loading test.

[0012] Preferably, the high-speed imaging device includes a high-speed camera and a supplementary lighting device. The high-speed camera has a frame rate of not less than 50,000 frames per second and a preferred resolution of 256×232 pixels. The supplementary lighting device includes at least two high-brightness LED supplementary lights for forming uniform illumination on the surface of the rock sample.

[0013] Preferably, the analog-to-digital conversion module acquires data at a preset acquisition frequency, and is preferably implemented using a National Instruments data acquisition system; the signal conditioning module is preferably implemented using a hardware module for loading sensor signal conditioning.

[0014] Preferably, the peak detection algorithm is used to detect the maximum value point in the real-time sequence of the load signal, and outputs the trigger command when the load changes from increasing to decreasing.

[0015] The present invention also provides a method for simultaneous monitoring of acoustic emission and high-speed imaging in fracture tests, comprising the following steps: S1. Build a fracture test monitoring system, assemble the loading sensor between the loading test device and the specimen, arrange the acoustic emission sensor in contact with the surface of the specimen, align the high-speed imaging device with the monitoring area of ​​the specimen, and establish signal transmission links with the loading sensor, acoustic emission acquisition instrument and high-speed imaging device through electrical connection. S2, start the loading test device to apply load to the sample, and the analog-to-digital conversion module in the synchronous control system continuously collects the load signal output by the loading sensor at a preset time interval Δt to form a continuous real-time load signal sequence. S3, the control module of the synchronous control system has a built-in peak detection algorithm. Based on the real-time load signal sequence, it determines the load change trend between the current sampling point and the previous sampling point in real time and identifies the critical state where the load changes from increasing to decreasing. S4. Determine whether the load change trend meets the preset peak value determination condition. If not, return to step S2 to continue load signal acquisition and trend determination. If it meets the condition, determine it as the critical fracture trigger moment and execute step S5. S5, the synchronous control system generates a synchronization pulse (7) through a digital-to-analog conversion module, and the synchronization pulse is simultaneously transmitted to the acoustic emission acquisition instrument and the high-speed imaging device through an electrical connection; S6, the acoustic emission acquisition instrument records the synchronization pulse to establish a time reference, synchronously acquires and stores the acoustic emission data generated during the sample fracture process, and transmits the acoustic emission data to the computer; the high-speed imaging device uses the synchronization pulse as a trigger command to start image acquisition according to the preset frame rate, records the visual data of crack initiation and propagation in the sample, and transmits the visual data to the computer. S7. Based on a unified time reference corresponding to the synchronization pulse, the computer performs time alignment processing on the received acoustic emission data and high-speed image data. Through precise matching of acoustic emission data and image frames, it provides synchronized data support for fracture mechanism analysis. Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention uses the load peak as the trigger criterion, which can stably cover the critical period of fracture occurrence and improve the success rate of high-speed imaging capture.

[0016] (2) The present invention establishes a unified time reference by simultaneously entering the acoustic emission acquisition instrument and the trigger port of the high-speed camera with a synchronous pulse, thereby improving the time alignment accuracy of "acoustic emission event - image frame".

[0017] (3) The synchronous control system of the present invention has a simple structure, can be implemented based on general data acquisition hardware and algorithms, is easy to be ported to different fracture test platforms, and is low in cost and reusable. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the synchronous monitoring system for acoustic emission and high-speed imaging in fracture tests according to the present invention.

[0019] Figure 2 This is a flowchart of the method for simultaneous monitoring of acoustic emission and high-speed imaging in fracture tests according to the present invention.

[0020] Figure 3 This is a schematic diagram of the synchronization timing in an embodiment of the present invention.

[0021] Reference numerals: 1. Loading test apparatus; 2. Loading sensor; 3. Acoustic emission monitoring device; 31. Acoustic emission sensor; 32. Acoustic emission acquisition instrument; 4. High-speed imaging device; 5. Sample; 6. Synchronous control system; 61. Signal conditioning module; 62. Analog-to-digital conversion module; 63. Control module; 64. Digital-to-analog conversion module; 7. Synchronization pulse; 8. Computer. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0023] Figure 1 This is a schematic diagram of the overall structure of the synchronous monitoring system for acoustic emission and high-speed imaging in fracture tests according to the present invention. As shown in the diagram, the present invention provides a synchronous monitoring system for acoustic emission and high-speed imaging in fracture tests for monitoring the fracture state of a rock sample 5. The system is characterized by comprising a loading test device 1, an acoustic emission monitoring device 3, a high-speed imaging device 4, a synchronous control system 6, and a computer 8. The rock sample 5 is mounted in the loading test device 1, and at least one loading sensor 2 is mounted on the rock sample. The acoustic emission monitoring device 3 includes an acoustic emission sensor 31 and an acoustic emission acquisition instrument 32.

[0024] The synchronous control system 6 includes a signal conditioning module 61, an analog-to-digital converter 62, a control module 63, and a digital-to-analog converter 64 connected in sequence by unidirectional electrical connection. The signal conditioning module 61 is electrically connected to the load sensor 2 and is used to receive and condition the load signal from the load sensor 2. The analog-to-digital converter 62 is used to acquire the conditioned load signal and transmit it to the controller 63. The control module 63 has a built-in peak detection algorithm for continuous monitoring of the load signal and outputs a trigger command when the load signal reaches its peak value. The digital-to-analog converter 64 is used to generate a synchronization pulse 7 after receiving the trigger command and simultaneously send the synchronization pulse 7 to the acoustic emission acquisition instrument 32 and the high-speed imaging device 4 via electrical connection.

[0025] The acoustic emission sensor 31 is used to collect the sound generated by the rock sample 5 during the loading test. The acoustic emission acquisition instrument 32 is used to receive and record the synchronization pulse 7, establish a time reference, and realize the time alignment of acoustic emission data and high-speed image data. The high-speed imaging device 4 uses the synchronization pulse 7 as a trigger signal to collect image data of the rock sample 5 during the loading test.

[0026] In this embodiment, the high-speed imaging device 4 includes a high-speed camera and a supplementary lighting device. The high-speed camera has a frame rate of not less than 50,000 frames / second and a preferred resolution of 256×232 pixels. The supplementary lighting device includes at least two high-brightness LED supplementary lights for forming uniform illumination on the surface of the rock sample 5.

[0027] In this embodiment, the analog-to-digital conversion module 62 acquires data at a preset acquisition frequency, preferably using a National Instruments data acquisition system; the signal conditioning module 61 is preferably implemented using a hardware module for loading sensor signal conditioning.

[0028] In this embodiment, the peak detection algorithm is used to detect the maximum value point in the real-time sequence of the load signal, and outputs the trigger command when the load changes from increasing to decreasing.

[0029] Specifically, in implementation, the high-speed camera 4 can be a FASTCAM SA-Z 200K-C-16GB-FD model. The high-speed camera 4 acquires images of the fracture process at a frame rate of 200,000 frames per second and a resolution of 256×232 pixels to achieve a balance between high temporal resolution and image information content. The supplementary lighting module 5 is equipped with two high-brightness LED supplementary lights 51 to provide uniform illumination to the surface of the sample 7.

[0030] Analog-to-digital converter module 62 and digital-to-analog converter module 64 can be integrated into a National Instruments data acquisition system; signal conditioning of the load sensor 2 can be implemented using a hardware module for load signal conditioning. The load signal sampling frequency is 1 kHz. The peak detection algorithm uses a sliding window maximum value judgment, derivative sign change judgment, or a combination of both to adapt to the peak determination requirements under different loading rates.

[0031] Figure 2 This is a flowchart of the synchronous monitoring method for acoustic emission and high-speed imaging in fracture tests according to the present invention. Figure 2 Therefore, the present invention also provides a method for simultaneous monitoring of acoustic emission and high-speed imaging in fracture tests, comprising the following steps: S1, build a fracture test monitoring system, assemble the loading sensor 2 between the loading test device 1 and the sample 5, arrange the acoustic emission sensor 31 against the surface of the sample 5, align the high-speed imaging device 4 with the monitoring area of ​​the sample 5, and establish a signal transmission link with the loading sensor 2, the acoustic emission acquisition instrument 32 and the high-speed imaging device 4 respectively through electrical connection. S2, the loading test device 1 is started to apply a load to the specimen 5. The analog-to-digital conversion module 62 in the synchronous control system 6 continuously collects the load signal output by the loading sensor 2 at a preset time interval Δt, forming a continuous real-time load signal sequence. S3, the control module 63 of the synchronous control system 6 has a built-in peak detection algorithm, which, based on the real-time load signal sequence, determines the load change trend between the current sampling point and the previous sampling point in real time, and identifies the critical state where the load changes from increasing to decreasing. S4. Determine whether the load change trend meets the preset peak value determination condition. If not, return to step S2 to continue load signal acquisition and trend determination. If it meets the condition, determine it as the critical fracture trigger moment and execute step S5. S5, the synchronous control system 6 generates a synchronous pulse 7 through the digital-to-analog conversion module 64, and the synchronous pulse 7 is simultaneously transmitted to the acoustic emission acquisition instrument 32 and the high-speed imaging device 4 through an electrical connection; S6, the acoustic emission acquisition instrument 32 records the synchronization pulse 7 to establish a time reference, synchronously acquires and stores the acoustic emission data generated during the fracture process of the sample 5, and transmits the acoustic emission data to the computer 8; the high-speed imaging device 4 uses the synchronization pulse 7 as a trigger command to start image acquisition according to the preset frame rate, records the visual data of crack initiation and propagation of the sample 5, and transmits the visual data to the computer 8. Based on the unified time reference corresponding to the synchronization pulse 7, S7 and computer 8 perform time alignment processing on the received acoustic emission data and high-speed image data, and provide synchronized data support for fracture mechanism analysis through precise matching of acoustic emission data and image frames.

[0032] Figure 3 This is a schematic diagram of the synchronization timing in an embodiment of the present invention. Figure 3 As shown, the synchronization pulse 7 is simultaneously recorded by the acoustic emission acquisition instrument 32 and used as the trigger signal for the high-speed camera 4. The trigger delay of the high-speed camera is on the order of nanoseconds, and the synchronous recording delay of the acoustic emission system can be as low as hundreds of nanoseconds, both far less than the duration of the fracture event on the microsecond scale. Therefore, it can meet the synchronization alignment requirements of acoustic emission data and high-speed image data. Acoustic emission signals are used to acquire the fracture process.

Claims

1. A simultaneous monitoring system for acoustic emission and high-speed imaging in fracture tests, used to monitor the fracture state of rock samples (5), characterized in that, It includes a loading test device (1), an acoustic emission monitoring device (3), a high-speed imaging device (4), a synchronous control system (6), and a computer (8); the rock sample (5) is installed in the loading test device (1), and at least one loading sensor (2) is installed on the rock sample; the acoustic emission monitoring device (3) includes an acoustic emission sensor (31) and an acoustic emission acquisition instrument (32). The synchronous control system (6) includes a signal conditioning module (61), an analog-to-digital converter (62), a control module (63), and a digital-to-analog converter (64) connected in sequence by unidirectional electrical connection. The signal conditioning module (61) is electrically connected to the load sensor (2) and is used to receive and condition the load signal from the load sensor (2). The analog-to-digital converter (62) is used to collect the conditioned load signal and transmit it to the controller (63). The control module (63) has a built-in peak detection algorithm for continuous monitoring of the load signal and outputs a trigger command when the load signal reaches its peak value. The digital-to-analog converter (64) is used to generate a synchronization pulse (7) after receiving the trigger command and simultaneously send the synchronization pulse (7) to the acoustic emission acquisition instrument (32) and the high-speed imaging device (4) through electrical connection. The acoustic emission sensor (31) is used to collect the acoustic emission signal generated by the rock sample (5) during the loading test. The acoustic emission acquisition instrument (32) is used to receive and record the synchronization pulse (7), establish a time reference and realize the time alignment of acoustic emission data and high-speed image data. The high-speed imaging device (4) uses the synchronization pulse (7) as a trigger signal to collect the image data of the rock sample (5) during the loading test.

2. The simultaneous monitoring system for acoustic emission and high-speed imaging in fracture tests according to claim 1, characterized in that, The high-speed imaging device (4) includes a high-speed camera and a supplementary lighting device. The high-speed camera has a frame rate of not less than 50,000 frames / second and a preferred resolution of 256×232 pixels. The supplementary lighting device includes at least two high-brightness LED supplementary lights for forming uniform illumination on the surface of the rock sample (5).

3. The simultaneous monitoring system for acoustic emission and high-speed imaging in fracture tests according to claim 1, characterized in that, The analog-to-digital conversion module (62) acquires data at a preset acquisition frequency, preferably using a National Instruments data acquisition system; the signal conditioning module (61) is preferably implemented using a hardware module for loading sensor signal conditioning.

4. The simultaneous monitoring system for acoustic emission and high-speed imaging in fracture tests according to claim 1, characterized in that, The peak detection algorithm is used to detect the maximum value point in the real-time sequence of the load signal, and outputs the trigger command when the load changes from increasing to decreasing.

5. A method for simultaneous monitoring of acoustic emission and high-speed imaging in fracture tests, characterized in that, Includes the following steps: S1, build a fracture test monitoring system, assemble the loading sensor (2) between the loading test device (1) and the sample (5), arrange the acoustic emission sensor (31) against the surface of the sample (5), align the high-speed imaging device (4) with the monitoring area of ​​the sample (5), and establish a signal transmission link with the loading sensor (2), the acoustic emission acquisition instrument (32) and the high-speed imaging device (4) respectively through electrical connection; S2, start the loading test device (1) to apply load to the specimen (5), and the analog-to-digital conversion module (62) in the synchronous control system (6) continuously collects the load signal output by the loading sensor (2) at a preset time interval Δt to form a continuous real-time load signal sequence; S3, the control module (63) of the synchronous control system (6) has a built-in peak detection algorithm. Based on the real-time load signal sequence, it determines the load change trend between the current sampling point and the previous sampling point in real time and identifies the critical state where the load changes from increasing to decreasing. S4. Determine whether the load change trend meets the preset peak value determination condition. If not, return to step S2 to continue load signal acquisition and trend determination. If it meets the condition, determine it as the critical fracture trigger moment and execute step S5. S5, the synchronization control system (6) generates a synchronization pulse (7) through the digital-to-analog conversion module (64), which is transmitted simultaneously to the acoustic emission acquisition instrument (32) and the high-speed imaging device (4) via electrical connection. S6, the acoustic emission acquisition instrument (32) records the synchronization pulse (7) to establish a time reference, synchronously acquires and stores the acoustic emission data generated during the fracture process of the sample (5), and transmits the acoustic emission data to the computer (8); the high-speed imaging device (4) uses the synchronization pulse (7) as a trigger command to start image acquisition according to the preset frame rate, records the visual data of crack initiation and propagation of the sample (5), and transmits the visual data to the computer (8). S7, the computer (8) performs time alignment processing on the received acoustic emission data and high-speed image data based on the unified time reference corresponding to the synchronization pulse (7), and provides synchronized data support for fracture mechanism analysis through precise matching of acoustic emission data and image frames.

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