An automatic calibration method and a flat-bottom hole test block placement device

Abstract

The application provides an automatic calibration method and a flat-bottom hole test block placing device. The method comprises the following steps: moving a water-immersed ultrasonic probe above a first flat-bottom hole test block; adjusting the posture of the probe so that the sound beam axis of the probe is perpendicular to the upper surface of the current flat-bottom hole test block; in the state that the sound beam axis is perpendicular to the upper surface, controlling the probe to move in a plane parallel to the upper surface to find the position with the maximum flat-bottom hole reflection echo amplitude; recording the embedding depth value of the current flat-bottom hole test block and the gain value required for the flat-bottom hole reflection echo to reach a predetermined reference amplitude; repeating steps 1-4 for the remaining flat-bottom hole test blocks in the calibration sequence; and generating a distance-amplitude correction curve based on the recorded embedding depth values and gain values of the multiple flat-bottom hole test blocks. The method does not require manual intervention, shortens the calibration time from dozens of minutes in the traditional manual mode to several minutes, ensures the complete consistency of each calibration process, and improves the calibration efficiency and repeatability.

Description

Technical Field

[0001] This application belongs to the field of ultrasonic testing technology, and specifically relates to an automatic calibration method and a flat-bottomed hole test block placement device. Background Technology

[0002] Ultrasonic testing is a key technology widely used in industrial non-destructive testing. Its basic principle is to use an ultrasonic probe to emit ultrasonic waves into the workpiece being inspected. When the sound waves encounter defects within the material (such as cracks or pores) or at the workpiece interface, they generate reflected echoes. By analyzing information such as the time and amplitude of the received echo signals, the location and size of defects can be assessed, or thickness can be measured.

[0003] However, ultrasonic waves attenuate as they propagate through materials, resulting in significant differences in echo amplitude for defects of the same size due to variations in their burial depth. To eliminate the influence of propagation distance on echo amplitude and achieve quantitative evaluation of defects at different depths, sensitivity calibration must be performed before testing. Currently, relevant domestic and international standards (such as GB / T 6402-2018 and GB / T 18851.2-2012) generally stipulate the use of a set of comparative test blocks containing artificial regular reflectors (usually flat-bottomed holes) at different depths to create distance-amplitude correction (DAC) curves.

[0004] To improve testing efficiency and consistency, automated immersion ultrasonic testing equipment has emerged. This type of equipment, through precise mechanical motion modules and automatic control systems, can automatically position and scan the probe in three-dimensional space, as well as automatically acquire and record echo signals, thus enabling rapid and accurate testing of complex workpieces and representing a highly automated and advanced testing method. However, although the core value of immersion ultrasonic equipment lies in "automated" testing, its automation advantages are not fully realized in the crucial preliminary step of DAC calibration. During calibration, operators typically need to manually control the immersion probe, moving it one by one to a roughly preset position above each flat-bottomed hole test block, and then manually and repeatedly fine-tuning the probe's position and angle. By observing the instrument screen, they rely on experience to find and locate the optimal detection point where the reflected echo from the flat-bottomed hole reaches its maximum amplitude. The entire process is not only cumbersome and time-consuming, but more importantly, the accuracy and consistency of the calibration results highly depend on the operator's personal experience, judgment, and patience, introducing significant subjective human factors. This leads to discrepancies in calibration results performed by different personnel, or even by the same personnel at different times, directly affecting the reliability of quantitative defect evaluation in subsequent automated inspections and preventing the full realization of the detection potential of high-precision automated equipment.

[0005] Therefore, existing technologies in water immersion ultrasonic automatic testing systems suffer from problems such as lack of automation in key calibration steps, reliance on manual labor, low efficiency, and unreliable results. Summary of the Invention

[0006] To address the aforementioned problems, this application provides an automatic calibration method applied to a water immersion ultrasonic testing system comprising a multi-axis motion mechanism and a water immersion ultrasonic probe. The method includes: Control the multi-axis motion mechanism to move the water immersion ultrasonic probe above the first flat-bottomed hole test block; Adjust the probe's orientation so that the probe's acoustic beam axis is perpendicular to the upper surface of the current flat-bottomed hole test block; With the sound beam axis perpendicular to the upper surface, control the probe to move in a plane parallel to the upper surface to find the position with the largest amplitude of the reflected echo from the flat-bottomed hole. Record the current burial depth of the flat-bottomed hole test block, as well as the gain value required to make the reflected echo from the flat-bottomed hole reach a predetermined reference amplitude; For the remaining flat-bottomed well test blocks in the calibration sequence, repeat steps one through four; Based on the recorded burial depth and gain values ​​of multiple flat-bottomed hole test blocks, a distance-amplitude correction curve is generated. In particular, the processes of adjusting the probe posture and finding the maximum echo position in steps two and three are based on closed-loop control through the analysis of ultrasonic echo signals.

[0007] Furthermore, adjusting the probe's orientation includes: The probe is controlled to reciprocate around at least one rotation axis within an angular range including a preset zero position. During the deflection process, the interface echo signal emitted by the probe and reflected by the upper surface of the flat-bottomed hole test block is acquired; Based on the amplitude change of the interface echo signal within the preset gate, the perpendicularity of the current sound beam axis to the upper surface is determined, and the angle of the rotation axis is iteratively adjusted until the amplitude of the interface echo signal meets the preset conditions.

[0008] Furthermore, based on the amplitude change of the interface echo signal within the preset gate, the perpendicularity of the current sound beam axis to the upper surface is determined, and the angle of the rotation axis is iteratively adjusted until the amplitude of the interface echo signal meets the preset conditions, including: During the reciprocating deflection process, the amplitude of the interface echo signal at multiple locations is collected at equal intervals to form a set of amplitude-position sequences, and the maximum amplitude value is determined. The maximum value is compared with a first threshold and a second threshold, where the first threshold is less than the second threshold; If the maximum value is greater than or equal to the second threshold, the current amplitude is determined to be saturated. The probe is then moved to the position where the maximum value is obtained, and the gain of the ultrasonic testing equipment is reduced. The reciprocating deflection and judgment process is then repeated. If the maximum value is less than or equal to the first threshold, it is determined that the current amplitude is too low. The probe is then moved to the position where the maximum value is obtained, and the gain of the ultrasonic testing equipment is increased. Then the reciprocating deflection and judgment process is repeated. If the maximum value is greater than the first threshold and less than the second threshold, the current amplitude is determined to be appropriate. The probe is then moved to the position where the maximum value is obtained. The above process is repeated until the deviation between the positions of the maximum value determined in two consecutive steps is less than the first preset value. This position is then set as the zero position of the rotating axis, and the adjustment of the rotating axis is ended. If the number of times the above process is repeated reaches the first preset upper limit, the adjustment of the rotating axis will end and a prompt message will be issued.

[0009] Furthermore, the equidistant step size is 0.1°.

[0010] Furthermore, the first threshold is 40% of the full screen height, and the second threshold is 100% of the full screen height.

[0011] Furthermore, the step size for decreasing or increasing the gain is 6dB.

[0012] Furthermore, the reciprocating deflection specifically involves controlling the probe to first deflect from a preset position to a first direction by a fixed angle, and then deflect in the opposite direction by an angle twice the fixed angle.

[0013] Furthermore, the fixed angle is 5°.

[0014] Furthermore, based on the rate of change of the amplitude-angle sequence, the probe is adjusted to deflect a predetermined angle in the first direction next, and then deflected in the opposite direction by an angle twice the predetermined angle.

[0015] Furthermore, the predetermined deflection angle is controlled between 5° and 10°, and the greater the rate of change of the amplitude-angle sequence, the smaller the deflection angle.

[0016] Furthermore, the first preset value is 0.2°.

[0017] Furthermore, the first preset upper limit for the number of repetitions is 5 times.

[0018] Furthermore, with the sound beam axis perpendicular to the upper surface, the probe is moved in a plane parallel to the upper surface to locate the position with the largest amplitude of the reflected echo from the flat-bottomed aperture, including: The probe is controlled to reciprocate along at least one translation axis within a distance range including a preset center position; During the movement, the echo signal reflected by the flat-bottomed hole is collected; Based on the amplitude change of the reflected echo from the flat-bottomed hole within the preset gate, it is determined whether the probe is aligned with the center of the flat-bottomed hole, and the position of the translation axis is iteratively adjusted until the amplitude of the reflected echo from the flat-bottomed hole meets the preset conditions.

[0019] Furthermore, based on the amplitude change of the reflected echo from the flat-bottomed hole within the preset gate, it is determined whether the probe is aligned with the center of the flat-bottomed hole, and the position of the translation axis is iteratively adjusted until the amplitude of the reflected echo from the flat-bottomed hole meets the preset conditions, including: During the reciprocating movement, the amplitude of the reflected echo signal from the flat-bottomed hole at multiple locations is collected at equal intervals, and the maximum value is determined. The maximum value is compared with the third and fourth thresholds, where the third threshold is less than the fourth threshold. If the maximum value is greater than or equal to the fourth threshold, it is determined that the current amplitude is saturated. The probe is then moved to the position where the maximum value is obtained, and the gain of the ultrasonic testing equipment is reduced. The process of moving and judging is then repeated. If the maximum value is less than or equal to the third threshold, it is determined that the current amplitude is too low. The probe is then moved to the position where the maximum value is obtained, and the gain of the ultrasonic testing equipment is increased. The process of moving and judging is then repeated. If the maximum value is greater than the third threshold and less than the fourth threshold, the current amplitude is determined to be appropriate. The probe is then moved to the position where the maximum value is obtained. The above process is repeated until the deviation between the two consecutive determined maximum value positions is less than the second preset value, at which point the adjustment of the translation axis ends. If the number of times the above process is repeated reaches the second preset upper limit, the adjustment of the translation axis will end and a prompt message will be issued.

[0020] Furthermore, the equal interval step size is 0.1 mm.

[0021] Furthermore, the third threshold is 40% full screen height, and the fourth threshold is 100% full screen height.

[0022] Furthermore, the step size for decreasing or increasing the gain is 6dB.

[0023] Furthermore, the reciprocating movement specifically involves controlling the probe to first move a fixed distance from a preset position in a third direction, and then moving in the opposite direction twice the fixed distance.

[0024] Furthermore, the fixed distance is 3mm.

[0025] Furthermore, the second preset value is 0.2mm.

[0026] Furthermore, the second preset upper limit for the number of repetitions is 5 times. Furthermore, in recording the current burial depth of the flat-bottomed hole test block and the gain value required for the flat-bottomed hole reflected echo to reach a predetermined reference amplitude, after finding the position of the maximum echo, the process further includes: adjusting the gain of the ultrasonic testing equipment so that the amplitude of the flat-bottomed hole reflected echo reaches the predetermined reference amplitude, and recording the gain value at this time as the required gain value.

[0027] Furthermore, based on the recorded burial depth and gain values ​​of multiple flat-bottomed hole test blocks, a distance-amplitude correction curve is generated, including: fitting multiple data points with the burial depth value on the horizontal axis and the desired gain value on the vertical axis to generate the distance-amplitude correction curve.

[0028] Furthermore, the generated distance-amplitude correction curve is compared with the historically stored correction curves using residuals, and outliers exceeding the preset residual range are marked.

[0029] Furthermore, the preset residual range for the burial depth value is ±2mm, and the preset residual range for the gain value is ±2dB.

[0030] This application also provides a flat-bottomed hole test block placement device for implementing an automatic calibration method, comprising: Matrix; Multiple accommodating holes formed on the substrate are used to accommodate multiple flat-bottomed test blocks of different heights; The depth of each receiving hole is configured such that when it accommodates a flat-bottomed hole test block with a corresponding height, the upper surface of the flat-bottomed hole test block is flush with the upper surface of the flat-bottomed hole test block placed in other receiving holes.

[0031] Furthermore, the receiving hole is a cylindrical hole; for any flat-bottomed hole test block, the diameter of the cylindrical hole that receives it is larger than the outer diameter of the flat-bottomed hole test block, and there is a reserved thickness between the bottom of the cylindrical hole and the bottom of the substrate, and the depth of the cylindrical hole is equal to the height of the flat-bottomed hole test block minus a preset protrusion.

[0032] Furthermore, the substrate is made of plexiglass; multiple accommodating holes are arranged in an array on the substrate.

[0033] Compared with the prior art, this application has the following advantages: By automatically executing all steps—probe attitude adjustment, finding the maximum echo location, data recording, and curve generation—using the multi-axis motion mechanism and signal processing module of the immersion ultrasonic testing system according to a preset method, this method completely eliminates the cumbersome and time-consuming drawbacks of existing technologies that require manual positioning and finding of the maximum echo. The system can automatically and continuously process all flat-bottomed hole test blocks in the calibration sequence without manual intervention, thereby reducing calibration time from tens of minutes in traditional manual methods to several minutes, while ensuring complete consistency in each calibration process, greatly improving calibration efficiency and repeatability.

[0034] Other features and advantages of this application will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 A schematic flowchart of an automatic calibration method according to an embodiment of this application is shown; Figure 2 This diagram illustrates the process of adjusting the probe orientation and finding the maximum echo position in the automatic calibration method according to an embodiment of this application. Figure 3 A schematic diagram of a flat-bottomed hole test block placement device according to an embodiment of this application is shown; Figure 4 A schematic diagram illustrating the definition of an axis in an automatic calibration method flow according to an embodiment of this application is shown. Detailed Implementation

[0037] 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 some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0038] The automatic calibration method of this invention is applied to a multi-axis motion mechanism comprising at least three linear axes (X, Y, Z) and two angular rotation axes (A, B), as well as a water immersion ultrasonic testing system with a water immersion ultrasonic probe. This method aims to achieve fully automated generation of the distance-amplitude correction curve for flat-bottomed hole test blocks. Figure 4 As shown, the directions of each motion axis are defined. A zeroing operation is performed on all mechanical motion axes.

[0039] like Figure 1 As shown, in step S1, the probe is moved to the starting position. This involves controlling the multi-axis motion mechanism to move the immersion ultrasonic probe above the first flat-bottomed hole test block. First, all mechanical motion axes of the immersion ultrasonic testing equipment are zeroed to establish a coordinate system reference. The controller in this scheme pre-stores the absolute coordinates of the first flat-bottomed hole test block (e.g., the shallowest burial block) on the flat-bottomed hole test block placement device. The controller drives the multi-axis motion mechanism to control the immersion ultrasonic probe to move along the X and Y axes, bringing it directly above the first flat-bottomed hole test block. Simultaneously, the probe is controlled to move along the Z axis, adjusting the distance between the probe and the upper surface of the test block to a preset initial water distance, for example, 1.5 times the focal length P of the currently used probe.

[0040] Step S2: Automatically adjust the probe's acoustic beam to be perpendicular to the upper surface of the test block. This involves adjusting the probe's orientation so that the probe's acoustic beam axis is perpendicular to the upper surface of the current flat-bottomed hole test block. The purpose of this step is to adjust the A-axis and B-axis of the probe clamping module to ensure that the axis of the acoustic beam emitted by the probe is precisely perpendicular to the upper surface of the current flat-bottomed hole test block. This is a prerequisite for obtaining stable, repeatable interface waves and flat-bottomed hole reflected waves.

[0041] Based on the currently set initial water distance, a gate, called the interface wave gate, is set on the time axis of the ultrasonic echo signal. The initial value and width of this gate should ensure that the interface echo signal generated by reflection from the upper surface of the test block is completely included. For example, if the water distance is 230 mm, the initial value of the gate can be set to 200 mm and the width to 60 mm. Based on the currently set water distance of 1.5P, the initial value and width of the gate IF are set so that the gate IF spans the interface wave in the ultrasonic echo signal. If the probe focal length P is 152.4 mm, then the distance is 230 mm. Based on the currently set water distance of 230 mm, the initial value and width of the gate IF are set, for example, the initial value of the gate IF can be set to 200 mm and the width to 60 mm, so that the gate IF spans the interface wave in the ultrasonic echo signal.

[0042] A-axis closed-loop adjustment, such as Figure 2 The process shown executes the following closed-loop operation: Control the probe to rotate around the A-axis. Starting from the current position (which can be regarded as a temporary zero position), first deflect negatively by a fixed angle θ. θ is 5°, and then deflect in the reverse (positive) direction by an angle of 2θ. 2θ is 10°. In the next adjustment of the probe, according to the change rate of the amplitude-angle sequence, adjust the negative deflection around the A-axis to be between 5° and 10°, and then deflect in the reverse (positive) direction by an angle of 2θ (θ ranges from 5° to 10°). During this positive deflection process, the system will collect ultrasonic echo signals at multiple position points at an equal angular interval of 0.1°, and extract the maximum echo amplitude within the interface wave gate at each position point, so as to obtain a set of amplitude-position data. Extract the maximum value from this set of data and denote it as max.

[0043] Compare max with a preset first threshold (such as 40% of the full screen height) and a second threshold (such as 100% of the full screen height), and make a decision based on the comparison result: If max ≥ 100%, it means the current signal is saturated and the peak value cannot be accurately judged. The system controls the A-axis to move to the position where this max value is generated, and reduces the gain of the ultrasonic detection device by a fixed step, such as 6dB, and then repeats the above deflection and acquisition process.

[0044] If max ≤ 40%, it means the signal is too weak. Control the A-axis to move to the position where this max value is generated, increase the gain by 6dB, and then repeat the above process.

[0045] If 40% < max < 100%, it means the signal amplitude is moderate and in the linear region, and the peak position is distinguishable. Control the A-axis to move to the position where this max value is generated, and continue to repeat the above process until the deviation between the positions of the max values determined continuously twice is less than the first preset value of 0.2°, then end the adjustment of the A-axis and set the current position as the zero position of the A-axis.

[0046] If the number of times of repeating the above process reaches the first preset upper limit value of 5 times, end the adjustment of the A-axis and send a prompt message.

[0047] Closed-loop adjustment of the B-axis. After completing the adjustment of the A-axis, use exactly the same steps, thresholds, and decision logic as the above A-axis adjustment to perform an independent closed-loop adjustment on the B-axis. That is, control the probe to perform a deflection scan of "negative θ, positive 2θ" around the B-axis, collect the interface wave amplitude, find max, and perform gain adjustment or zero position setting according to the max value until the B-axis is also adjusted in place.

[0048] Adjust the water distance. After both the A-axis and the B-axis are adjusted to the zero position, that is, when the sound beam is perpendicular to the upper surface of the test block, the system automatically controls the Z-axis to move according to the standard water distance required for finally drawing the distance-amplitude curve, and accurately adjusts the distance between the probe and the upper surface of the test block to this standard water distance.

[0049] Step S3: Automatically find the position of the maximum echo amplitude of the flat-bottomed hole. That is, with the sound beam axis perpendicular to the upper surface, control the probe to move in a plane parallel to the upper surface to find the position of the maximum reflected echo amplitude of the flat-bottomed hole.

[0050] The purpose of this step is to find the point with the largest amplitude of the reflected echo from the flat-bottomed hole by finely adjusting the position of the probe in the XY plane, under the condition that the sound beam is already vertical, that is, the position where the probe's sound beam axis is aligned with the center of the flat-bottomed hole.

[0051] During the setup of the flat-bottomed hole reflection wave gate, another gate, called the measurement gate, needs to be set first. Its initial value should follow the position of the interface wave. Based on the nominal burial depth D of the current flat-bottomed hole test block, the initial position of this gate is set to D-Δd (Δd is a small value, generally 2mm for test blocks with a burial depth greater than 2.5mm; the width is a fixed value W=6mm, or 1mm for shallow holes less than 2.5mm). The gate width W is a fixed value, for example, 6mm to 8mm, ensuring that the reflected echo from the flat-bottomed hole is completely contained within it.

[0052] X-axis closed-loop scan, please refer to Figure 2 Perform the following operations according to the process shown: The probe is controlled to move along the X-axis, first moving a fixed distance L in the negative direction from its current position, and then moving in the opposite direction (positive direction) by a distance of 2L (L can be 3mm). During this positive movement, ultrasonic echo signals are acquired at equal intervals of 0.1mm, and the maximum echo amplitude inside the gate at each location point is extracted to obtain a set of data.

[0053] Extract the maximum value (max) from this set of data.

[0054] The same threshold and decision logic as in step S2 (i.e., comparison with 40% and 100%) are used to determine the max value. Based on the determination result, it is decided whether to move the probe to the max position and adjust the gain (±6dB) and repeat the scan, or to move it to the max position and end the X-axis scan.

[0055] After the X-axis scan is completed, the Y-axis is scanned independently using the same method, distance L (which can be 3mm), threshold, and logic as the X-axis scan, until the optimal position in the Y-axis direction is found.

[0056] After adjusting the X and Y axes, the probe is now aligned with the center of the flat-bottomed hole. Adjust the gain of the ultrasonic testing equipment so that the amplitude of the reflected echo from the flat-bottomed hole within the measuring gate precisely reaches a predetermined reference height, such as 80% FSH. Record the gain value used by the ultrasonic testing equipment at this point, as well as the actual acoustic path (corresponding burial depth) of the flat-bottomed hole calculated based on the echo time.

[0057] Step S4: Record the burial depth of the flat-bottomed hole test block and the required reference gain value. Specifically, record the current burial depth of the flat-bottomed hole test block and the gain value required to achieve a predetermined reference amplitude for the reflected echo from the flat-bottomed hole. At the end of step S3, the probe is positioned at the point of maximum amplitude of the reflected echo from the flat-bottomed hole. Based on the position of the ultrasonic echo signal on the time axis at this time (i.e., the propagation time from the interface wave to the reflected wave from the flat-bottomed hole), and combined with the known sound velocity, automatically calculate and record the actual sound path of the current flat-bottomed hole. This sound path value corresponds to the actual burial depth of the flat-bottomed hole relative to the upper surface of the test block. The recorded actual burial depth value may differ slightly from the nominal burial depth of the test block due to manufacturing tolerances or measurement errors; using the actual value improves the accuracy of the curve.

[0058] At the end of step S3, the gain of the ultrasonic testing equipment has been adjusted to achieve a predetermined, uniform reference amplitude for the echo reflected from the flat-bottomed hole (e.g., 80% full-screen height, i.e., 80% FSH). Step S4 explicitly and independently records the final gain value set by the ultrasonic testing equipment to achieve this 80% FSH reference amplitude for the echo. This gain value is typically expressed in decibels.

[0059] Steps S5 and S6 involve traversing the test blocks and generating curves. Specifically, for the remaining flat-bottomed hole test blocks in the calibration sequence, steps S1 to S4 are repeated, and distance-amplitude correction curves are generated based on the recorded burial depth and gain values ​​of the multiple flat-bottomed hole test blocks. More specifically, the controller drives the probe to move sequentially above each of the remaining flat-bottomed hole test blocks on the placement device according to a pre-stored coordinate sequence. For each test block, step S3 is repeated, i.e., the maximum echo is searched along the X / Y axes, and the actual burial depth value and the gain value required to achieve 80% FSH are recorded for each test block.

[0060] After all test blocks are calibrated, the system performs curve fitting on all data points with the burial depth value on the x-axis and the required gain value on the y-axis to automatically generate a distance-amplitude correction curve. The generated correction curve is compared with historically stored correction curves for residual analysis. Anomalies exceeding preset residual ranges are marked, where the preset residual range for burial depth is ±2mm and for gain is ±2dB. Finally, this curve can be stored in the system for direct retrieval during subsequent workpiece inspections, used for quantitative evaluation of echo amplitude at different depths. This invention also provides a flat-bottomed hole test block placement device for implementing this method. This device, used in conjunction with the aforementioned automatic calibration method, rapidly, accurately, and stably positions a series of flat-bottomed hole test blocks of varying heights, but whose upper surfaces must be on the same horizontal plane.

[0061] like Figure 3As shown, the device includes a substrate. The substrate is preferably made of plexiglass, which has good sound transmission and is easy to process. Multiple receiving holes are machined into the substrate. These receiving holes are preferably cylindrical holes and are arranged in a regular array on the substrate, for example, in multiple rows and columns, with a hole spacing of, for example, 5 mm, to facilitate coordinate calibration.

[0062] Each receiving hole is specifically designed to accommodate a flat-bottomed test block of a specific height. Their design dimensions must meet the following relationship to ensure that the top surfaces of all test blocks are flush: The diameter of the cylindrical hole is slightly larger than the outer diameter of the flat-bottomed hole test block to be accommodated, for example, by 1 mm. This ensures that the test block can be inserted smoothly, provides necessary clearance for easy removal, and avoids excessive clearance that could cause the test block to tilt. It should be noted that the diameter of the cylindrical hole is determined based on the 50 mm outer diameter of the flat-bottomed hole test block. The diameter of each cylindrical hole needs to be 1 mm larger than the outer diameter of each flat-bottomed hole test block; therefore, the diameter of the cylindrical hole can be 51 mm to facilitate the removal of the flat-bottomed hole test block from the cylindrical hole.

[0063] The substrate has sufficient thickness below the receiving hole to support the test block. The depth of the receiving hole itself is equal to the height of the flat-bottomed hole test block it accommodates, minus a preset protrusion. This protrusion is, for example, 10mm to 15mm. This means that when the test block is placed in the hole, its top will be higher than the upper surface of the substrate by this protrusion. Taking a standard set of 19 flat-bottomed hole test blocks as an example, based on the maximum height of the test block in the set of 155mm (buried depth 140mm), the height of the flat-bottomed hole test block placement device can be determined to be 155mm. A 15mm gap can be reserved in the plexiglass below the cylindrical hole to support the flat-bottomed hole test block. Therefore, the height of the cylindrical hole can be 15mm shorter than the height of the flat-bottomed hole test block, meaning the flat-bottomed hole test block is higher than the placement device, facilitating the removal of the test block. Simultaneously, all flat-bottomed hole test blocks need to be placed at the same height so that the water distance between each test block does not need to be adjusted during subsequent automatic calibration. The height of each cylindrical hole and the height of the acrylic glass below the cylindrical hole can be determined based on the height of the flat-bottomed hole test block placement device (155mm) and the height of the other flat-bottomed hole test blocks.

[0064] For a set of flat-bottomed hole test blocks with different heights, the depth of the receiving hole for each test block is designed individually, ensuring that "test block height - hole depth = constant protrusion". Therefore, regardless of the height of the test blocks themselves, when they are placed in their respective receiving holes, the portion protruding above the upper surface of the substrate (i.e., the protrusion) is the same. Since the upper surface of the substrate is itself a reference plane, the upper surfaces of all test blocks are naturally within the same horizontal plane. In the embodiment shown in Table 1, the total height of the substrate is determined to be 155mm, based on the maximum test block height of 155mm. For test blocks with smaller heights, the height difference is offset by increasing the thickness of the plexiglass below their receiving holes (i.e., increasing the hole depth), ultimately making the upper surfaces of all test blocks flush with the upper surface of the tallest test block. Based on the number of 19 flat-bottomed hole test blocks in a set, the number of cylindrical holes in the flat-bottomed hole test block placement device is also determined to be 19, thus determining the overall dimensions. The flat-bottomed hole test block placement device is as follows: Figure 3 As shown, the dimensions are 285mm × 229mm × 155mm.

[0065] Table 1 Height values ​​of each flat-bottomed hole test block and each cylindrical hole

[0066] By using this placement device, the operator only needs to place the test block into the corresponding hole once. During automatic calibration, the system only needs to move the probe in the XY plane to above the center of each hole, and the Z-axis height (water distance) does not need to change due to the different heights of the test blocks, which greatly simplifies the complexity of automatic control.

[0067] In summary, the present invention also has the following advantages: Closed-loop feedback control ensures the accuracy of probe alignment and calibration data. In the two key steps of adjusting probe posture (step two) and finding the maximum echo position of the flat-bottomed hole (step three), this invention uses closed-loop control based on the analysis of the amplitude of the real-time acquired ultrasonic echo signal (interface wave or flat-bottomed hole reflection wave). The system automatically determines the current state (e.g., whether the sound beam is vertical, whether the probe is aligned with the center) by comparing the echo amplitude with a preset threshold, and decides whether to continue adjusting the posture / position, adjust the gain, or confirm completion. This perception-judgment-execution closed-loop mechanism replaces the manual alignment process that relies entirely on the operator's experience and eyesight, enabling the probe to automatically and accurately adjust to the optimal position where the sound beam is perpendicular to the test block surface and aligned with the center of the flat-bottomed hole. This obtains a true, repeatable maximum echo amplitude, laying a reliable data foundation for generating a high-precision distance-amplitude correction curve.

[0068] The use of a dedicated placement device ensures uniformity of calibration conditions, simplifies operation, and reduces the skill requirements for personnel. The flat-bottomed hole test block placement device provided by this invention features specially designed depths for its multiple receiving holes, ensuring that the upper surfaces of all flat-bottomed hole test blocks of different heights are at the same height after placement. This eliminates the need to adjust the distance between the probe and the upper surface of each test block individually during automatic calibration, simplifying control logic and accelerating calibration speed. The device integrates a series of dispersed test blocks into a regular, fixed-position whole, facilitating coordinate calibration and path planning by the automated system. This design, combined with a fully automated calibration method, significantly reduces reliance on the professional skills and experience of operators, allowing calibration work to be completed by personnel with basic training, and even integrating it into the equipment's self-test program.

[0069] This invention enhances the intelligence and integration of water immersion ultrasonic testing systems. The method fully utilizes the multi-axis motion and signal acquisition capabilities of existing automated water immersion ultrasonic testing equipment, achieving functional improvements through methodological upgrades. It is not merely an independent calibration process, but can be seamlessly integrated into automated water immersion ultrasonic testing equipment as a core functional module, achieving seamless integration from equipment calibration to workpiece inspection. The generated DAC curve can be directly called by the system for subsequent automated workpiece inspection and evaluation. This promotes the advancement of water immersion ultrasonic testing from semi-automatic to fully automatic and intelligent, aligning with current and future development trends.

[0070] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. An automatic calibration method, characterized in that, The method, applied to a water immersion ultrasonic testing system comprising a multi-axis motion mechanism and a water immersion ultrasonic probe, includes: Control the multi-axis motion mechanism to move the water immersion ultrasonic probe above the first flat-bottomed hole test block; Adjust the orientation of the probe so that the sound beam axis of the probe is perpendicular to the upper surface of the current flat-bottomed hole test block; With the sound beam axis perpendicular to the upper surface, the probe is controlled to move in a plane parallel to the upper surface to find the position where the amplitude of the reflected echo from the flat-bottomed hole is the largest. Record the current burial depth of the flat-bottomed hole test block, as well as the gain value required to make the reflected echo from the flat-bottomed hole reach a predetermined reference amplitude. For the remaining flat-bottomed hole test blocks in the calibration sequence, repeat the entire process of controlling the multi-axis motion mechanism up to the process of recording the current burial depth value of the flat-bottomed hole test block; Based on the recorded burial depth and gain values ​​of multiple flat-bottomed hole test blocks, a distance-amplitude correction curve is generated. The steps of adjusting the probe's attitude and finding the position with the largest reflected echo amplitude from the flat-bottomed hole are both based on closed-loop control through analysis of the ultrasonic echo signal.

2. The automatic calibration method according to claim 1, characterized in that, The adjustment of the probe's attitude includes: The probe is controlled to reciprocate around at least one rotation axis within an angle range including a preset zero position. During the deflection process, the interface echo signal emitted by the probe and reflected by the upper surface of the flat-bottomed hole test block is acquired; Based on the amplitude change of the interface echo signal within the preset gate, the perpendicularity of the current sound beam axis to the upper surface is determined, and the angle of the rotation axis is iteratively adjusted until the amplitude of the interface echo signal meets the preset condition.

3. The automatic calibration method according to claim 2, characterized in that, The step of determining the perpendicularity of the current sound beam axis to the upper surface based on the amplitude change of the interface echo signal within the preset gate, and iteratively adjusting the angle of the rotation axis until the amplitude of the interface echo signal meets the preset condition includes: During the reciprocating deflection process, the amplitude of the interface echo signal at multiple locations is acquired at equal intervals to form a set of amplitude-position sequences, and the maximum amplitude value is determined. The maximum value is compared with a first threshold and a second threshold, wherein the first threshold is less than the second threshold; If the maximum value is greater than or equal to the second threshold, it is determined that the current amplitude is saturated. The probe is then moved to the position where the maximum value is obtained, and the gain of the ultrasonic testing device is reduced. Then the reciprocating deflection and judgment process is repeated. If the maximum value is less than or equal to the first threshold, it is determined that the current amplitude is too low. The probe is then moved to the position where the maximum value is obtained, and the gain of the ultrasonic testing device is increased. Then the reciprocating deflection and judgment process is repeated. If the maximum value is greater than the first threshold and less than the second threshold, the current amplitude is determined to be appropriate. The probe is then moved to the position where the maximum value is obtained. The above process is repeated until the deviation between two consecutive determined maximum value positions is less than the first preset value. This position is then set as the zero position of the rotating axis, and the adjustment of the rotating axis is ended. If the number of times the above process is repeated reaches the first preset upper limit, the adjustment of the rotating axis will end and a prompt message will be issued.

4. The automatic calibration method according to claim 3, characterized in that, The equal interval step size is 0.1°.

5. The automatic calibration method according to claim 3, characterized in that, The first threshold is 40% of the full screen height, and the second threshold is 100% of the full screen height.

6. The automatic calibration method according to claim 3, characterized in that, The step size for reducing or increasing the gain is 6dB.

7. The automatic calibration method according to any one of claims 2 to 6, characterized in that, The reciprocating deflection specifically involves controlling the probe to first deflect from a preset position to a first direction by a fixed angle, and then deflect in the opposite direction by an angle twice the fixed angle.

8. The automatic calibration method according to claim 7, characterized in that, The fixed angle is 5°.

9. The automatic calibration method according to claim 7, characterized in that, Based on the rate of change of the amplitude-angle sequence, the probe is adjusted to deflect a predetermined angle in the first direction next, and then deflected in the opposite direction by an angle twice the predetermined angle.

10. The automatic calibration method according to claim 9, characterized in that, The predetermined deflection angle is controlled between 5° and 10°, and the greater the rate of change of the amplitude-angle sequence, the smaller the deflection angle.

11. The automatic calibration method according to claim 3, characterized in that, The first preset value is 0.2°.

12. The automatic calibration method according to claim 3, characterized in that, The first preset upper limit is 5 times.

13. The automatic calibration method according to claim 1, characterized in that, The step of controlling the probe to move in a plane parallel to the upper surface to find the position with the maximum amplitude of the reflected echo from the flat-bottomed hole, with the sound beam axis perpendicular to the upper surface, includes: The probe is controlled to reciprocate along at least one translation axis within a distance range including a preset center position; During the movement, the echo signal reflected by the flat-bottomed hole is acquired; Based on the amplitude change of the reflected echo from the flat-bottomed hole within the preset gate, it is determined whether the probe is aligned with the center of the flat-bottomed hole, and the position of the translation axis is iteratively adjusted until the amplitude of the reflected echo from the flat-bottomed hole meets the preset conditions.

14. The automatic calibration method according to claim 13, characterized in that, The step of determining whether the probe is aligned with the center of the flat-bottomed hole based on the amplitude change of the reflected echo within the preset gate, and iteratively adjusting the position of the translation axis until the amplitude of the reflected echo from the flat-bottomed hole meets the preset condition includes: During the reciprocating movement, the amplitude of the reflected echo signal from the flat-bottomed hole at multiple locations is collected at equal intervals, and the maximum value is determined. The maximum value is compared with a third threshold and a fourth threshold, wherein the third threshold is less than the fourth threshold; If the maximum value is greater than or equal to the fourth threshold, it is determined that the current amplitude is saturated. The probe is then moved to the position where the maximum value is obtained, and the gain of the ultrasonic testing device is reduced. The reciprocating movement and judgment process is then repeated. If the maximum value is less than or equal to the third threshold, it is determined that the current amplitude is too low. The probe is then moved to the position where the maximum value is obtained, and the gain of the ultrasonic testing device is increased. Then the reciprocating movement and judgment process is repeated. If the maximum value is greater than the third threshold and less than the fourth threshold, the current amplitude is determined to be appropriate. The probe is then moved to the position where the maximum value is obtained. The above process is repeated until the deviation between the positions of the two consecutive determined maximum values ​​is less than the second preset value, and the adjustment of the translation axis is ended. If the number of times the above process is repeated reaches the second preset upper limit, the adjustment of the translation axis will end and a prompt message will be issued.

15. The automatic calibration method according to claim 14, characterized in that, The equal spacing step size is 0.1 mm.

16. The automatic calibration method according to claim 14, characterized in that, The third threshold is 40% of the full screen height, and the fourth threshold is 100% of the full screen height.

17. The automatic calibration method according to claim 14, characterized in that, The step size for reducing or increasing the gain is 6dB.

18. The automatic calibration method according to any one of claims 13 to 17, characterized in that, The reciprocating movement specifically involves controlling the probe to first move a fixed distance from a preset position in a third direction, and then moving in the opposite direction by twice the fixed distance.

19. The automatic calibration method according to claim 18, characterized in that, The fixed distance is 3mm.

20. The automatic calibration method according to claim 14, characterized in that, The second preset value is 0.2mm.

21. The automatic calibration method according to claim 14, characterized in that, The second preset upper limit for the number of repetitions is 5 times.

22. The automatic calibration method according to claim 1, characterized in that, The process of recording the current burial depth of the flat-bottomed hole test block and the gain value required for the reflected echo from the flat-bottomed hole to reach a predetermined reference amplitude, after finding the maximum echo position, further includes: adjusting the gain of the ultrasonic testing equipment so that the amplitude of the reflected echo from the flat-bottomed hole reaches the predetermined reference amplitude, and recording the gain value at this time as the required gain value.

23. The automatic calibration method according to claim 1, characterized in that, The step of generating a distance-amplitude correction curve based on the recorded burial depth and gain values ​​of multiple flat-bottomed hole test blocks includes: fitting multiple data points with the burial depth value as the abscissa and the desired gain value as the ordinate to generate the distance-amplitude correction curve.

24. The automatic calibration method according to claim 23, characterized in that, The generated distance-amplitude correction curve is compared with the historically stored correction curves using residuals, and outliers exceeding the preset residual range are marked.

25. The automatic calibration method according to claim 24, characterized in that, The preset residual range for the burial depth value is ±2mm, and the preset residual range for the gain value is ±2dB.

26. A flat-bottomed hole test block placement device for implementing the method according to any one of claims 1 to 25, characterized in that, include: Matrix; Multiple receiving holes formed on the substrate are used to accommodate multiple flat-bottomed test blocks of different heights; The depth of each of the accommodating holes is configured such that when it accommodates a flat-bottomed hole test block with a corresponding height, the upper surface of the flat-bottomed hole test block is flush with the upper surface of a flat-bottomed hole test block placed in another accommodating hole.

27. The flat-bottomed hole test block placement device according to claim 26, characterized in that, The receiving hole is a cylindrical hole; for any flat-bottomed hole test block, the diameter of the cylindrical hole that receives it is larger than the outer diameter of the flat-bottomed hole test block, and there is a reserved thickness between the bottom of the cylindrical hole and the bottom of the substrate, and the depth of the cylindrical hole is equal to the height of the flat-bottomed hole test block minus a preset protrusion.

28. The flat-bottomed hole test block placement device according to claim 26 or 27, characterized in that, The substrate is made of plexiglass; the plurality of the accommodating holes are arranged in an array on the substrate.

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