Bolt crack detection method and device, electronic equipment and storage medium

Abstract

This application relates to the field of crack detection technology, and particularly to a method, apparatus, electronic device, and storage medium for detecting bolt cracks. The bolt head end face is equipped with an array of piezoelectric thin-film sensors. The method includes: acquiring array ultrasonic signals and converting them into full-matrix ultrasonic data; performing full-focus imaging processing on the area to be imaged, combining the bolt's geometric dimensions, the spatial coordinates of the array elements, and the equivalent wave velocity, to obtain a crack image; determining the region of interest based on the image and the bolt's geometry, and extracting crack characterization regions within the region of interest that meet preset threshold conditions; determining the crack location based on the geometric center or local peak value of the crack characterization region, calculating the axial propagation length, transverse characterization width, and / or characterization area at the crack location, and thus determining the crack length and depth. This solves the problems of poor accuracy and stability of detection results in related technologies using ultrasonic detection.

Description

Technical Field

[0001] This application relates to the field of crack detection technology, and in particular to a method, apparatus, electronic device and storage medium for detecting bolt cracks. Background Technology

[0002] Bolted connections are widely used in wind turbines, bridges, rail transportation, aerospace, mining machinery, pressure vessels, and large electromechanical equipment. As a crucial basic component for connection, pre-tightening, and load-bearing, bolts often endure complex alternating stresses, impact loads, and environmental effects during long-term service. Cracks are particularly prone to initiation and propagation in the head-shank transition zone, stress concentration zones, and fatigue-sensitive areas. Once cracks form and continue to propagate, they lead to a decrease in connection stiffness and a reduction in residual load-bearing capacity, and in severe cases, may cause connection failure or even structural accidents.

[0003] The bolt crack detection methods in related technologies mainly use ultrasonic testing. Although it can obtain internal reflection information, in practical applications, the accuracy and stability of the detection results are poor because it is difficult to keep the coupling state between the probe and the bolt surface consistent, and the incident angle and position of the probe are different. Summary of the Invention

[0004] This application provides a method, apparatus, electronic device, and storage medium for detecting bolt cracks, in order to solve the problems of poor accuracy and stability of detection results in the ultrasonic testing method used in related technologies.

[0005] The first aspect of this application provides a method for detecting bolt cracks. An array piezoelectric thin-film sensor is disposed on the head end face of the bolt. The method includes the following steps: acquiring array ultrasonic signals using the array piezoelectric thin-film sensor, and converting the array ultrasonic signals into full-matrix ultrasonic data; determining the imaging area based on the bolt's geometric dimensions; performing full-focus imaging processing on the imaging area based on the array unit spatial coordinates, equivalent wave velocity, and full-matrix ultrasonic data of the array piezoelectric thin-film sensor to obtain a crack image of the bolt; determining the region of interest to be analyzed based on the crack image and the bolt's geometry, and extracting crack characterization regions that meet preset threshold conditions within the region of interest; determining the crack location based on the geometric center or local peak value of the crack characterization region, calculating the axial propagation length, transverse characterization width, and / or characterization area at the crack location, and determining the crack length and crack depth of the bolt based on the axial propagation length, transverse characterization width, and / or characterization area.

[0006] Optionally, the imaging area is determined based on the geometric parameters of the bolt, including: determining the axial measurement range of the bolt shank based on the bolt geometric parameters; determining the imaging area based on the axial measurement range of the shank; and discretizing the imaging area into multiple candidate pixels.

[0007] Optionally, based on the spatial coordinates of the array units of the piezoelectric thin film sensor, the equivalent wave velocity, and the full-matrix ultrasonic data, a full-focus imaging process is performed on the area to be imaged to obtain a crack imaging map. This includes: constructing an imaging model of the bolt based on the bolt's geometric dimensions and the spatial coordinates of the array units; calculating the propagation path length between the corresponding pixel and each pair of transmitting and receiving array units using the imaging model for any candidate pixel coordinates within the area to be imaged; converting the propagation path length into a propagation delay by combining the equivalent wave velocity, and performing time-delay superposition on the full-matrix ultrasonic data based on the propagation delay to obtain the focusing response value of the corresponding pixel; and traversing all candidate pixels within the imaging area to generate a crack imaging map.

[0008] Optionally, array ultrasonic signals are acquired using an array piezoelectric thin film sensor, and the array ultrasonic signals are converted into full-matrix ultrasonic data, including: controlling each array unit in the array piezoelectric thin film sensor to transmit ultrasonic signals in sequence as a transmitting unit, and controlling the remaining array units to receive echo signals as receiving units, thereby obtaining multiple sets of time-domain response signals; and combining the multiple sets of time-domain response signals to construct full-matrix ultrasonic data.

[0009] Optionally, the region of interest to be analyzed is determined based on the crack imaging image and the bolt geometry, including: cropping the crack imaging image based on the bolt geometry and the effective propagation window to remove the external region of the bolt and the invalid signal region to obtain the region of interest.

[0010] Optionally, calculating the axial spread length, lateral characterization width, and / or characterization area at the crack location includes: calculating the axial projection length of the crack characterization region and using the projection length as the axial spread length; calculating the lateral projection width of the crack characterization region and using the projection width as the lateral characterization width; and calculating the sum of the areas of all pixels within the crack characterization region as the characterization area.

[0011] Optionally, determining the crack length and crack depth of the bolt based on the axial propagation length, transverse characterization width, and / or characterization area includes: obtaining a pre-calibrated first calibration relationship table of axial propagation length, characterization area, and crack length; obtaining a pre-calibrated second calibration relationship table of transverse characterization width, characterization area, and crack depth; determining the crack length of the bolt based on the axial propagation length, characterization area, and first calibration relationship table at the crack location within the crack characterization area; and determining the crack depth of the bolt based on the transverse characterization width, characterization area, and second calibration relationship table at the crack location within the crack characterization area.

[0012] A second aspect of this application provides a bolt crack detection device, wherein an array piezoelectric thin film sensor is disposed on the head end face of the bolt. The device includes: an acquisition module for acquiring array ultrasonic signals using the array piezoelectric thin film sensor and converting the array ultrasonic signals into full-matrix ultrasonic data; a processing module for determining the imaging area based on the geometric dimensions of the bolt, and performing full-focus imaging processing on the imaging area based on the array unit spatial coordinates, equivalent wave velocity, and full-matrix ultrasonic data of the array piezoelectric thin film sensor to obtain a crack image of the bolt; an extraction module for determining the region of interest to be analyzed based on the crack image and the bolt geometry, and extracting crack characterization regions that meet preset threshold conditions within the region of interest; and a determination module for determining the crack location based on the geometric center or local peak of the crack characterization region, calculating the axial propagation length, transverse characterization width, and / or characterization area at the crack location, and determining the crack length and crack depth of the bolt based on the axial propagation length, transverse characterization width, and / or characterization area.

[0013] Optionally, the processing module is further configured to: determine the axial measurement range of the bolt shank based on the bolt's geometric dimensions; determine the imaging area based on the axial measurement range of the shank; and discretize the imaging area into multiple candidate pixels.

[0014] Optionally, the processing module is further used to construct an imaging model of the bolt based on the bolt's geometric dimensions and the spatial coordinates of the array units; for any candidate pixel coordinates in the imaging area, the imaging model is used to calculate the propagation path length between the corresponding pixel and each pair of transmitting and receiving array units; combined with the equivalent wave velocity, the propagation path length is converted into propagation delay, and the full matrix ultrasonic data is time-delayed and superimposed according to the propagation delay to obtain the focusing response value of the corresponding pixel; and all candidate pixels in the imaging area are traversed to generate a crack imaging map.

[0015] Optionally, the acquisition module is further configured to: control each array unit in the array piezoelectric thin film sensor to transmit ultrasonic signals in sequence as a transmitting unit, and control the remaining array units to receive echo signals as receiving units, thereby obtaining multiple sets of time-domain response signals; and combine the multiple sets of time-domain response signals to construct full-matrix ultrasonic data.

[0016] Optionally, the extraction module is further configured to: crop the crack imaging image based on the bolt geometry and effective propagation time window, removing the external region of the bolt and the invalid signal region; and select the region with a signal amplitude exceeding a preset threshold as the region of interest in the cropped imaging image.

[0017] Optionally, the determining module is further configured to: calculate the projected length of the crack characterization region in the axial direction, and use the projected length as the axial spreading length; calculate the projected width of the crack characterization region in the transverse direction, and use the projected width as the transverse characterization width; and calculate the sum of the areas of all pixels in the crack characterization region as the characterization area.

[0018] Optionally, the determining module is further configured to: obtain a first calibration relationship table of pre-calibrated axial spread length, characterization area, and crack length; obtain a second calibration relationship table of pre-calibrated transverse characterization width, characterization area, and crack depth; determine the crack length of the bolt based on the axial spread length, characterization area, and first calibration relationship table at the crack location within the crack characterization area; and determine the crack depth of the bolt based on the transverse characterization width, characterization area, and second calibration relationship table at the crack location within the crack characterization area.

[0019] A third aspect of this application provides an electronic device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor. The processor executes the program to implement the bolt crack detection method as described in the above embodiments.

[0020] A fourth aspect of this application provides a computer-readable storage medium having a computer program or instructions stored thereon, which, when executed, are used to implement the bolt crack detection method as described in the above embodiments.

[0021] Therefore, this application has at least the following beneficial effects: This application embodiment utilizes an array of piezoelectric thin-film sensors disposed on the end face of the bolt head to acquire array ultrasonic signals and construct full-matrix ultrasonic data. The imaging area is determined based on the bolt's geometric dimensions. Using the array unit spatial coordinates, equivalent wave velocity, and full-matrix ultrasonic data of the piezoelectric thin-film sensor array, the imaging area is subjected to full-focus imaging processing to obtain a crack image of the bolt. A region of interest is defined and analyzed within the generated crack image, extracting the crack characterization region within that region. This avoids misjudging bottom echoes or strong boundary echoes caused by directly referencing the maximum response value of the entire image. Based on the axial length, transverse width, and area of ​​the crack characterization region, and combined with pre-established calibration relationships, the actual length and depth of the crack are accurately calculated. This solves the problems of poor accuracy and stability of detection results in related technologies using ultrasonic testing.

[0022] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0023] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a flowchart of a bolt crack detection method provided according to an embodiment of this application; Figure 2 This is a schematic diagram illustrating the construction of a full-matrix ultrasound data according to an embodiment of this application; Figure 3 This is a schematic diagram of region-of-interest constrained total focusing imaging according to an embodiment of this application; Figure 4 This is a schematic diagram illustrating the comprehensive calculation of crack location and quantity according to an embodiment of this application; Figure 5 A flowchart for detecting bolt cracks is provided according to one embodiment of this application; Figure 6 This is a block diagram of a bolt crack detection device provided according to an embodiment of this application; Figure 7 This is a schematic diagram of the structure of an electronic device according to an embodiment of this application. Detailed Implementation

[0024] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0025] The following description, with reference to the accompanying drawings, describes a bolt crack detection method, apparatus, electronic device, and storage medium according to embodiments of this application. Addressing the problems mentioned in the background art, this application provides a bolt crack detection method. In this method, an array piezoelectric thin-film sensor disposed on the end face of the bolt head acquires array ultrasonic signals and constructs full-matrix ultrasonic data. The imaging area is determined based on the bolt's geometric dimensions. Based on the spatial coordinates of the array elements of the piezoelectric thin-film sensor, the equivalent wave velocity, and the full-matrix ultrasonic data, the imaging area is subjected to full-focus imaging processing to obtain a crack image of the bolt. A region of interest is defined and analyzed within the generated crack image. The crack characterization region within this region is extracted, avoiding misjudgments of bottom echoes or strong boundary echoes caused by directly referencing the maximum response value of the entire image. Based on the axial length, transverse width, and area of ​​the crack characterization region, and combined with pre-established calibration relationships, the actual length and depth of the crack are accurately calculated. This solves the problems of poor accuracy and stability of detection results in related technologies using ultrasonic detection.

[0026] Specifically, Figure 1 This is a schematic flowchart illustrating a bolt crack detection method provided in an embodiment of this application. In this embodiment, an array of piezoelectric thin-film sensors is disposed on the head end face of the bolt.

[0027] like Figure 1 As shown, the method for detecting bolt cracks includes the following steps: In step S101, array ultrasonic signals are acquired using an array piezoelectric thin film sensor and converted into full-matrix ultrasonic data.

[0028] It is understandable that the array piezoelectric thin film sensor for acquiring array ultrasonic signals is fabricated on the end face of the bolt head. Preferably, the end face of the bolt head is first mechanically polished, degreased, and surface cleaned to improve the adhesion stability of the subsequent thin film layer; then an insulating layer is formed on the end face of the head to achieve electrical isolation between the bolt metal substrate and the electrode layer.

[0029] A lower electrode layer is formed on top of an insulating layer; then, a ZnO piezoelectric thin film layer is deposited on the lower electrode layer using a magnetron sputtering process; an upper electrode layer is formed on top of the ZnO piezoelectric thin film layer. To obtain an array of ultrasonic units, a hard mask process is preferably used to partition and pattern the upper and / or lower electrodes, thereby forming multiple independently ultrasonic array units on the bolt head end face; if necessary, a protective layer can be formed on the outermost side to improve the stability of the thin film array in long-term service environments.

[0030] In one embodiment of this application, array ultrasonic signals are acquired using an array piezoelectric thin film sensor, including: controlling each of the multiple array units in the array piezoelectric thin film sensor to sequentially transmit ultrasonic signals as a transmitting unit, and controlling the remaining array units to receive echo signals as receiving units, thereby obtaining multiple sets of time-domain response signals; and combining the multiple sets of time-domain response signals to construct full-matrix ultrasonic data.

[0031] like Figure 2 As shown, this embodiment of the application can acquire array ultrasonic signals based on an array piezoelectric thin-film sensor. Assuming there are N array ultrasonic units, the i-th unit transmits and the j-th unit receives the signal in a preset order, resulting in a time-domain response signal s. ij (t), which consists of the complete matrix ultrasound data S(t) composed of all transmit-receive combinations. ij (t)}. In a preferred embodiment, the array piezoelectric film is a ZnO thin film array directly deposited on the end face of the bolt head, and its electrode partitions are formed by a hard mask process.

[0032] In step S102, the imaging area is determined according to the geometric dimensions of the bolt. Based on the spatial coordinates of the array unit of the piezoelectric thin film sensor, the equivalent wave velocity, and the full matrix ultrasonic data, the imaging area is subjected to full-focus imaging processing to obtain the crack imaging image of the bolt under test.

[0033] It is understood that the embodiments of this application precisely define the imaging area based on the bolt's geometric dimensions, effectively eliminating interference signals from non-target paths such as bolt boundaries and bottom waves, significantly improving the imaging signal-to-noise ratio. Simultaneously, based on precise array coordinates and wave velocity parameters, full-focusing processing is performed, achieving high-resolution imaging of minute cracks inside the bolt. This provides a high-quality data foundation for subsequent precise crack localization and quantitative calculation, overcoming the shortcomings of traditional general algorithms in detecting rod-shaped structures, such as blurred imaging and severe interference. In one embodiment of this application, determining the imaging area based on the geometric dimensions of the bolt includes: determining the axial measurement range of the bolt shank based on the bolt geometric dimensions; determining the imaging area based on the axial measurement range of the shank; and discretizing the imaging area into multiple candidate pixels.

[0034] Understandably, in order to accurately pinpoint the defect location of the bolt, this embodiment can precisely calculate the axial measurement range of the bolt shank based on the bolt's geometric parameters (such as shank diameter, total length, and the boundary between the threaded and unthreaded sections), thereby focusing the imaging target on the core stress area prone to fatigue fracture. The imaging area is located within the axial range of the bolt shank. This embodiment performs discrete meshing on this area to obtain multiple candidate pixel points P(x, z). Here, z represents the position coordinate along the bolt axis, and x represents the equivalent lateral coordinate perpendicular to the axis.

[0035] In one embodiment of this application, a crack imaging map is obtained by performing full-focus imaging processing on the region to be imaged based on the spatial coordinates of the array units of the piezoelectric thin film sensor, the equivalent wave velocity, and the full-matrix ultrasonic data. This includes: constructing an imaging model of the bolt based on the bolt's geometric dimensions and the spatial coordinates of the array units; calculating the propagation path length between the corresponding pixel and each pair of transmitting and receiving array units using the imaging model for any candidate pixel coordinates within the region to be imaged; converting the propagation path length into a theoretical propagation delay by combining the equivalent wave velocity, and performing time-delay superposition on the full-matrix ultrasonic data based on the propagation delay to obtain the focusing response value of the corresponding pixel; and traversing all candidate pixels within the imaging region to generate a crack imaging map.

[0036] This application embodiment constructs an acoustic imaging model that conforms to the actual physical structure of the bolt based on the bolt's geometric dimensions and the spatial coordinates of each element of the piezoelectric thin-film sensor array. During the calculation process, for any candidate pixel within the imaging area, the imaging model accurately calculates the complete propagation path length of the ultrasonic wave from each transmitting element to that pixel, and then reflects it to each receiving element. Subsequently, combined with a pre-calibrated equivalent wave velocity, the propagation path length is converted into a theoretical propagation delay, and the corresponding moment's signal is extracted from the full matrix ultrasonic data and time-delayed superimposed to obtain the focused response value of the corresponding pixel. By traversing all candidate pixels within the imaging area, a high-resolution crack image is finally generated. Therefore, this application embodiment, by constructing a dedicated imaging model and calculating the precise propagation path, achieves full-matrix data focusing delay superposition, effectively overcoming beam distortion and artifact interference caused by the complex boundaries of the bolt, greatly improving the signal-to-noise ratio and spatial resolution of the ultrasonic signal, and clearly and intuitively presenting the true morphology and location of the micro-cracks inside the bolt, providing reliable data support for subsequent quantitative crack assessment.

[0037] Specifically, for any pixel P, the propagation path length from the i-th emission array element to pixel P is denoted as L. i Let Lj(P) be the propagation path length from pixel P to the j-th receiving element. Assume the equivalent wave velocity is c, then the theoretical propagation delay of the corresponding transmit-receive combination at pixel P is τij(P) = [Li(P) + Lj(P)] / c, and the pixel focusing value is expressed as I(P) = Σs ij (τ ij (P)).

[0038] In step S103, the region of interest to be analyzed is determined based on the crack imaging image and the bolt geometry, and crack characterization regions that meet the preset threshold conditions are extracted within the region of interest.

[0039] In this embodiment, after obtaining the crack imaging image, the maximum response value of the entire image is not directly used as the crack reference value. Instead, the region of interest (ROI) to be analyzed is determined first based on the bolt geometry, propagation time window, and / or initial imaging results. In actual implementation, this embodiment can crop the crack imaging image according to the bolt geometry and effective propagation time window, removing the external region of the bolt and invalid signal regions to obtain the ROI.

[0040] like Figure 4 As shown, the local peak response within the region of interest is... For reference, the crack characterization region Ωc corresponding to the preset dB threshold is extracted, satisfying: Where ΔdB is the preset dB threshold. The preset dB threshold is... 3dB threshold 6dB threshold or at 3dB to The threshold between 6dB can also be set according to the actual situation, without specific limitation.

[0041] like Figure 4 As shown in the embodiments of this application, the crack location is represented by the crack characterization region Ω. c The local peak location or geometric center is determined; when using the geometric center, for Ω c The axial coordinates of all pixels within the crack are averaged to obtain the axial position of the crack relative to the bolt head end face. Wherein, if Ω c The number of pixels is n, and the axial coordinate of the m-th pixel is z. m The crack location is z c satisfy: Horizontal position x c satisfy When using a local peak location, the crack location zc can be determined by Ω. c The axial coordinates corresponding to the local peak values ​​are given.

[0042] In a preferred embodiment, such as Figure 3 As shown, for pixel P in the region of interest m Calculate the transmission array element from the i-th element to P. m propagation path length L i (P m ) and P m The propagation path length L to the j-th receiving element j (P m And combining the equivalent wave velocity c, we obtain the theoretical propagation delay satisfying: Only when pixel P is located within the region of interest and the corresponding propagation path satisfies the geometric boundary and propagation window constraints, are all transmit-receive channels subjected to the corresponding propagation delay τ. ij (P m The time-domain response signal at point () is directly delayed and superimposed to obtain the focused response value. After traversing all pixels that satisfy the constraints, a crack image is formed within the region of interest. These constraints may include: the imaging area is limited by the region of interest; candidate pixels are limited by bolt geometric boundaries; the propagation path is limited by an effective propagation window; and only signals participating in the superposition retain the effective propagation path corresponding to the candidate crack response.

[0043] In step S104, the crack location is determined based on the geometric center or local peak of the crack characterization region, the axial propagation length, transverse characterization width and / or characterization area at the crack location are calculated, and the crack length and crack depth of the bolt are determined based on the axial propagation length, transverse characterization width and / or characterization area.

[0044] It is understood that in this embodiment, the geometric center of the crack characterization region is located and used as the precise spatial coordinate position of the crack inside the bolt. Using this geometric center as a reference, and combining the spatial distribution characteristics of high-response pixels in the crack imaging image, the axial propagation length and transverse characterization width of the crack are calculated, and the characterization area of ​​the crack is calculated by counting the number of effective pixels. Finally, based on a preset physical mapping relationship or calibration model, the extracted axial propagation length, transverse characterization width, and / or characterization area are converted to accurately determine the physical length and crack depth of the actual crack in the bolt.

[0045] In one embodiment of this application, calculating the axial spread length, lateral characterization width, and / or characterization area at the crack location includes: calculating the axial projection length of the crack characterization region and using the projection length as the axial spread length; calculating the lateral projection width of the crack characterization region and using the projection width as the lateral characterization width; and calculating the sum of the areas of all pixels within the crack characterization region as the characterization area.

[0046] To accurately extract the physical morphology of the crack from the crack imaging image of the region of interest, this application first performs spatial projection analysis on the crack characterization region. Specifically, the system calculates the projected length of the crack characterization region along the bolt axis and uses this projected length directly as the axial propagation length of the crack; simultaneously, it calculates the projected width of the crack characterization region in the transverse direction and uses it as the transverse characterization width. Furthermore, by traversing and counting the number of all high-response pixels within the crack characterization region, and combining this with the physical area of ​​each individual pixel, the areas of all pixels are summed to obtain the characterization area of ​​the crack.

[0047] Specifically, the crack size calculation is based on the crack characterization region Ω. c Based on the geometric parameters. For example... Figure 4 As shown, specifically, from Ω c At least one geometrical characterization quantity is extracted, including the axial propagation length Lc, the transverse characterization width Wc, and the region area Ac. These geometrical quantities characterize the propagation range of the high-response crack region in the axial, transverse, and area directions, respectively. Wherein, Lc can be represented as Ω. c The projected length along the axial direction, i.e., L c =z max z min Wc can be represented as Ω c The width of the projection in the horizontal direction, i.e., W c =x max x min Ac can be represented as Ω cThe sum of the areas of all pixels within the crack. It should be noted that the above geometric quantities are not directly equivalent to the actual crack boundary dimensions, but are used as crack imaging characterization parameters in subsequent quantitative conversions.

[0048] In one embodiment of this application, determining the crack length and crack depth of a bolt based on the axial spread length, transverse characterization width, and / or characterization area includes: obtaining a pre-calibrated first calibration relationship table of axial spread length, characterization area, and crack length; obtaining a pre-calibrated second calibration relationship table of transverse characterization width, characterization area, and crack depth; determining the crack length of the bolt based on the axial spread length, characterization area, and first calibration relationship table at the crack location within the crack characterization area; and determining the crack depth of the bolt based on the transverse characterization width, characterization area, and second calibration relationship table at the crack location within the crack characterization area.

[0049] To convert image-level characterization parameters into actual physical damage dimensions, this application introduces pre-calibrated mapping relationships. First, a first calibration relationship table for "axial spread length, characterization area, and crack length" and a second calibration relationship table for "transverse characterization width, characterization area, and crack depth" are obtained. To establish crack size calibration relationships, multiple sets of pre-cracked specimens with different crack lengths and / or different crack depths can be prepared. Preferably, the pre-cracked specimens are consistent with the actual bolt under test in terms of material, shank diameter, head size, and end-face array ultrasonic layout. The pre-cracks can be formed by wire cutting, narrow-slit machining, or fatigue pre-cracking. For each set of pre-cracked specimens, imaging processing is performed using the same excitation parameters, ultrasonic parameters, imaging grid, and dB threshold settings as the actual test, and the corresponding Lc, Wc, and Ac are extracted. Subsequently, the Lc and / or Ac of the length calibration specimen are correlated with the known true crack length to establish a crack length calibration relationship; the Wc and / or Ac of the depth calibration specimen are correlated with the known true crack depth to establish a crack depth calibration relationship.

[0050] When determining the crack size, the extracted axial spread length and characterization area are substituted into the first calibration relationship table to accurately match and determine the actual crack length of the bolt; similarly, the transverse characterization width and characterization area are substituted into the second calibration relationship table to determine the actual crack depth of the bolt.

[0051] In practical implementation, this embodiment of the application can image a set of pre-fabricated cracked specimens with known crack lengths and / or known crack depths using the same detection parameters, imaging grid, and dB threshold settings as the bolt to be tested, and extract the corresponding Lc, Wc, and / or Ac. Then, the Lc and / or Ac of the length-calibrated specimens are correlated with the actual crack length to establish a crack length calibration relationship; the Wc and / or Ac of the depth-calibrated specimens are correlated with the actual crack depth to establish a crack depth calibration relationship. After repeating the same process to obtain the Lc, Wc, and / or Ac of the bolt to be tested, the corresponding calibration relationships can be used to calculate the crack length and / or crack depth.

[0052] In addition, when using one-dimensional axial imaging, the crack length can be obtained by using Lc and its corresponding length calibration relationship first; when using two-dimensional imaging, the crack depth can be obtained by combining Wc and / or Ac.

[0053] The following is combined Figure 5 The bolt crack detection method according to the embodiments of this application is described in detail below: S1 signal acquisition and data construction: By collecting ultrasonic signals generated by an array of piezoelectric films arranged on the end face of the bolt, a full-matrix ultrasonic dataset containing rich spatial information is constructed. In the S2 full-focus imaging stage, the algorithm is optimized for bolt rod structures by combining the geometric dimensions of the bolt, the spatial coordinates of the array unit, the effective propagation path and the equivalent wave velocity, so as to achieve high-precision full-focus imaging and obtain a clear crack image. S3 crack characterization region extraction: The region of interest is determined by bolt geometry, propagation time window and initial imaging results, and high-response crack characterization regions are selected by preset dB threshold. S4 crack location: Based on the local peak position or geometric center of the characterization area, the spatial coordinates of the crack inside the bolt are precisely locked; S5 crack quantitative analysis extracts geometric features such as axial propagation length, transverse width, and surface area of ​​the crack characterization region, and preliminarily calculates the crack length and depth based on these features. S6 calibration relationship establishment and unknown crack quantification: By imaging samples with known crack lengths and locations under the same detection conditions, characteristic parameters (L) are extracted. c W c and A c The calibration relationship between crack length, depth and these parameters is established respectively. For unknown bolts to be tested, the above process is repeated and the extracted parameters are substituted into the established calibration relationship, so as to achieve accurate and automated inversion evaluation of crack location and size.

[0054] The bolt crack detection method proposed in this application utilizes an array piezoelectric thin film sensor disposed on the end face of the bolt head to acquire array ultrasonic signals and construct full-matrix ultrasonic data. The imaging area is determined based on the bolt's geometric dimensions. Full-focus imaging processing is performed on the imaging area based on the array unit spatial coordinates, equivalent wave velocity, and full-matrix ultrasonic data of the array piezoelectric thin film sensor to obtain a crack image of the bolt. A region of interest is defined and analyzed within the generated crack image, and the crack characterization region within this region is extracted. This avoids misjudging bottom echoes or strong boundary echoes caused by directly referencing the maximum response value of the entire image. Based on the axial length, transverse width, and area of ​​the crack characterization region, and combined with pre-established calibration relationships, the actual length and depth of the crack are accurately calculated. This solves the problems of poor accuracy and stability of detection results in related technologies using ultrasonic detection.

[0055] Next, referring to the accompanying drawings, a bolt crack detection device according to an embodiment of this application is described, wherein an array of piezoelectric thin film sensors is provided on the head end face of the bolt.

[0056] Figure 6 This is a block diagram of a bolt crack detection device according to an embodiment of this application.

[0057] like Figure 6 As shown, the bolt crack detection device 10 includes: an acquisition module 100, a processing module 200, an extraction module 300, and a processing module 400.

[0058] The acquisition module 100 is used to acquire array ultrasonic signals using an array piezoelectric thin film sensor and convert the array ultrasonic signals into full-matrix ultrasonic data. The processing module 200 is used to determine the imaging area based on the geometric dimensions of the bolt, and to perform full-focus imaging processing on the imaging area based on the array unit spatial coordinates, equivalent wave velocity, and full-matrix ultrasonic data of the array piezoelectric thin film sensor to obtain a crack image of the bolt. The extraction module 300 is used to determine the region of interest to be analyzed based on the crack image and the bolt geometry, and to extract the crack characterization region that meets the preset threshold conditions within the region of interest. The determination module 400 is used to determine the crack location based on the geometric center or local peak of the crack characterization region, calculate the axial propagation length, transverse characterization width, and / or characterization area at the crack location, and determine the crack length and crack depth of the bolt based on the axial propagation length, transverse characterization width, and / or characterization area.

[0059] In one embodiment of this application, the processing module 200 is further configured to: determine the axial measurement range of the bolt shank based on the bolt's geometric dimensions; determine the imaging area based on the axial measurement range of the shank; and discretize the imaging area into multiple candidate pixels.

[0060] In one embodiment of this application, the processing module 200 is further configured to construct an imaging model of the bolt based on the bolt's geometric dimensions and the spatial coordinates of the array units; for any candidate pixel coordinates in the imaging area, calculate the propagation path length between the corresponding pixel and each pair of transmitting and receiving array units using the imaging model; combine the equivalent wave velocity to convert the propagation path length into a theoretical propagation delay, and perform time-delay superposition on the full matrix ultrasonic data according to the propagation delay to obtain the focusing response value of the corresponding pixel; traverse all candidate pixels in the imaging area to generate a crack imaging map.

[0061] In one embodiment of this application, the acquisition module 100 is further configured to: control each of the multiple array units in the array piezoelectric thin film sensor to transmit ultrasonic signals in sequence as a transmitting unit, and control the remaining array units to receive echo signals as receiving units, thereby obtaining multiple sets of time-domain response signals; and combine the multiple sets of time-domain response signals to construct full-matrix ultrasonic data.

[0062] In one embodiment of this application, the extraction module 300 is further configured to: crop the crack imaging image according to the bolt geometry and the effective propagation time window, removing the external region of the bolt and the invalid signal region; and select the region with a signal amplitude exceeding a preset threshold as the region of interest in the cropped imaging image.

[0063] In one embodiment of this application, the determining module 400 is further configured to: calculate the projected length of the crack characterization region in the axial direction, and use the projected length as the axial spreading length; calculate the projected width of the crack characterization region in the transverse direction, and use the projected width as the transverse characterization width; and calculate the sum of the areas of all pixels in the crack characterization region as the characterization area.

[0064] In one embodiment of this application, the determining module 400 is further configured to: obtain a first calibration relationship table of pre-calibrated axial spread length, characterization area, and crack length; obtain a second calibration relationship table of pre-calibrated transverse characterization width, characterization area, and crack depth; determine the crack length of the bolt based on the axial spread length, characterization area, and the first calibration relationship table at the crack location within the crack characterization area; and determine the crack depth of the bolt based on the transverse characterization width, characterization area, and the second calibration relationship table at the crack location within the crack characterization area.

[0065] It should be noted that the explanation of the above-mentioned bolt crack detection method embodiment also applies to the bolt crack detection device of this embodiment, and will not be repeated here.

[0066] The bolt crack detection device proposed in this application utilizes an array of piezoelectric thin film sensors disposed on the end face of the bolt head to acquire array ultrasonic signals and construct full-matrix ultrasonic data. The imaging area is determined based on the bolt's geometric dimensions. Based on the spatial coordinates of the array units of the piezoelectric thin film sensors, the equivalent wave velocity, and the full-matrix ultrasonic data, the imaging area is subjected to full-focus imaging processing to obtain a crack image of the bolt. A region of interest is defined and analyzed within the generated crack image, and the crack characterization region within this region is extracted. This avoids misjudging bottom echoes or strong boundary echoes caused by directly referencing the maximum response value of the entire image. Furthermore, based on the axial length, transverse width, and area of ​​the crack characterization region, and combined with pre-established calibration relationships, the actual length and depth of the crack are accurately calculated. This solves the problems of poor accuracy and stability of detection results in related technologies using ultrasonic detection.

[0067] Figure 7 A schematic diagram of the structure of an electronic device provided in an embodiment of this application. The electronic device may include: The memory 701, the processor 702, and the computer program stored on the memory 701 and capable of running on the processor 702.

[0068] When the processor 702 executes the program, it implements the bolt crack detection method provided in the above embodiments.

[0069] Furthermore, electronic devices also include: Communication interface 703 is used for communication between memory 701 and processor 702.

[0070] The memory 701 is used to store computer programs that can run on the processor 702.

[0071] The memory 701 may include high-speed RAM (Random Access Memory) memory, and may also include non-volatile memory, such as at least one disk storage.

[0072] If the memory 701, processor 702, and communication interface 703 are implemented independently, then the communication interface 703, memory 701, and processor 702 can be interconnected via a bus to complete communication between them. The bus can be an ISA (Industry Standard Architecture) bus, a PCI (Peripheral Component Interconnect) bus, or an EISA (Extended Industry Standard Architecture) bus, etc. The bus can be divided into address bus, data bus, control bus, etc. For ease of representation, Figure 7 The bus is represented by a single thick line, but this does not mean that there is only one bus or one type of bus.

[0073] Optionally, in a specific implementation, if the memory 701, processor 702, and communication interface 703 are integrated on a single chip, then the memory 701, processor 702, and communication interface 703 can communicate with each other through an internal interface.

[0074] The processor 702 may be a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), or one or more integrated circuits configured to implement the embodiments of this application.

[0075] This application also provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the bolt crack detection method described above.

[0076] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0077] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "N" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0078] Any process or method described in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more N executable instructions for implementing custom logic functions or processes, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of this application pertain.

[0079] It should be understood that the various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, the N steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (FPGAs), field-programmable gate arrays (FPGAs), etc.

[0080] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0081] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method of detecting a bolt crack, characterized by, The head end face of the bolt is provided with an array of piezoelectric thin film sensors, wherein the method includes the following steps: The arrayed piezoelectric thin film sensor is used to acquire arrayed ultrasonic signals, which are then converted into full-matrix ultrasonic data. The imaging area is determined based on the geometric dimensions of the bolt. Based on the spatial coordinates of the array unit of the piezoelectric thin film sensor, the equivalent wave velocity, and the full matrix ultrasonic data, the imaging area is subjected to full-focus imaging to obtain the crack image of the bolt under test. Based on the crack imaging image and bolt geometry, the region of interest to be analyzed is determined, and crack characterization regions that meet preset threshold conditions are extracted within the region of interest. The crack location is determined based on the geometric center or local peak value of the crack characterization region. The axial propagation length, transverse characterization width, and / or characterization area at the crack location are calculated. The crack length and crack depth of the bolt are determined based on the axial propagation length, transverse characterization width, and / or characterization area.

2. The method of claim 1, wherein The step of determining the imaging area based on the geometric dimensions of the bolt includes: The axial measurement range of the bolt shank is determined based on the bolt's geometric dimensions. The imaging region is determined based on the axial measurement range of the rod, and the imaging region is discretized into multiple candidate pixels.

3. The method of claim 2, wherein The step of performing full-focus imaging processing on the area to be imaged based on the spatial coordinates of the array units of the piezoelectric thin film sensor, the equivalent wave velocity, and the full-matrix ultrasonic data to obtain a crack image of the bolt under test includes: Based on the geometric dimensions and the spatial coordinates of the array elements, an imaging model of the bolt is constructed; For the coordinates of candidate pixels within the imaging area, the propagation path length between the corresponding pixel and each pair of transmitting and receiving array units is calculated using the imaging model. Combining the equivalent wave velocity, the propagation path length is converted into propagation delay, and the full matrix ultrasound data is time-stacked according to the propagation delay to obtain the focusing response value of the corresponding pixel. The crack imaging map is generated by traversing all candidate pixels in the imaging area.

4. The method of claim 1, wherein The array of piezoelectric thin-film sensors is used to acquire array ultrasonic signals, and the array ultrasonic signals are converted into full-matrix ultrasonic data, including: Each array unit in the array piezoelectric thin film sensor is controlled to transmit ultrasonic signals in sequence as a transmitting unit, and the remaining array units are controlled to receive echo signals as receiving units, thereby obtaining multiple sets of time-domain response signals; The multiple sets of time-domain response signals are combined to obtain the full matrix ultrasound data.

5. The method of claim 1, wherein Based on the crack imaging and bolt geometry, the region of interest to be analyzed is determined, including: Based on the bolt geometry and effective propagation window, the crack imaging image is cropped to remove the external region of the bolt and the invalid signal region to obtain the region of interest.

6. The method of claim 1, wherein Calculating the axial propagation length, transverse characterization width, and / or characterization area of ​​the crack location includes: Calculate the axial projection length of the crack characterization region and use the projection length as the axial spread length. Calculate the projected width of the crack characterization region in the transverse direction, and use the projected width as the transverse characterization width; The sum of the areas of all pixels within the crack characterization region is calculated as the characterization area.

7. The method for detecting bolt cracks according to claim 1 or 6, characterized in that, Determining the crack length and crack depth of the bolt based on the axial spread length, transverse characterization width, and / or characterization area includes: Obtain a pre-calibrated first calibration relationship table of axial spread length, characterization area, and crack length; Obtain a second calibration relationship table that pre-calibrates the transverse characterization width, characterization area, and crack depth; The crack length of the bolt is determined based on the axial propagation length at the crack location within the crack characterization area, the characterization area, and the first calibration relationship table. The crack depth of the bolt is determined based on the transverse width of the crack location within the crack characterization area, the characterization area, and the second calibration relationship table.

8. A bolt crack detection device, characterized in that, The head end face of the bolt is provided with an array of piezoelectric thin film sensors, wherein the device includes: The acquisition module is used to acquire array ultrasonic signals using the array piezoelectric thin film sensor and convert the array ultrasonic signals into full-matrix ultrasonic data. The processing module is used to determine the imaging area based on the geometric dimensions of the bolt, and to perform full-focus imaging processing on the imaging area based on the spatial coordinates of the array unit of the array piezoelectric thin film sensor, the equivalent wave velocity, and the full matrix ultrasonic data to obtain a crack imaging image of the bolt under test. The extraction module is used to determine the region of interest to be analyzed based on the crack imaging image and the bolt geometry, and to extract the crack characterization region that meets the preset threshold condition within the region of interest; The determination module is used to determine the crack location based on the geometric center or local peak value of the crack characterization region, calculate the axial propagation length, transverse characterization width and / or characterization area at the crack location, and determine the crack length and crack depth of the bolt based on the axial propagation length, transverse characterization width and / or characterization area.

9. An electronic device, characterized in that, include: A memory, a processor, and a computer program stored in the memory and executable on the processor, the processor executing the program to implement the bolt crack detection method as described in any one of claims 1-7.

10. A computer-readable storage medium having a computer program or instructions stored thereon, characterized in that, When the computer program or instructions are executed, they implement the bolt crack detection method according to any one of claims 1-7.

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