An ultrasonic phased array sector scan defect reconstruction method

Abstract

The application discloses a kind of ultrasonic phased array sector scanning defect reconstruction methods, first set the scanning interval of encoder and the sampling interval of carrying ultrasonic phased array equipment are identical, then using encoder carries ultrasonic phased array equipment to the fan-shaped scanning of the test piece along stepping shaft, obtain multiple fan scanning signals and save as text file in order;Then, the A-scan signal of each beam in the text file is extracted and the image is re-synthesized, then the first scanning image is taken as a reference, and the remaining scanning images are all shifted to the right, finally, all images are weighted and summed to obtain the reconstructed defect cross-sectional profile.

Description

Technical Field

[0001] This invention belongs to the field of nondestructive testing technology, and more specifically, relates to a method for defect reconstruction by ultrasonic phased array sector scanning. Background Technology

[0002] Ultrasonic phased array testing technology is an advanced defect detection technique in the field of industrial non-destructive testing. Compared with conventional ultrasonic probes, the advantage of phased arrays is that they can obtain detection signals from multiple beams through beam deflection and focusing without moving the probe, enabling multi-angle scanning and real-time imaging. Sub-fields of this technology include sector scanning imaging, total focusing imaging, and linear scanning imaging.

[0003] This invention relates to sector scanning imaging, the main principle of which is: using an array probe, according to the corresponding emission focusing law and reception focusing law, the excitation time of each array element is controlled to achieve sound beam deflection and focusing, and the received data of each array element is synthesized to obtain the echo detection signal. After processing the signal, a clear image of the acoustic defect can be obtained.

[0004] Among them, the transmission focusing law refers to calculating the time and time difference of the sound wave of each array element to reach the focal point according to the specified focal point when exciting the array elements, and exciting each array element in sequence according to the time difference, so that the sound waves of each array element reach the focal point at the same time, thereby realizing the focusing and deflection of the sound beam; the reception focusing law refers to synthesizing the signals received by each array element according to the specified virtual focal point and the sound wave propagation time difference when receiving the signal, thereby obtaining the echo signal of the beam.

[0005] A significant problem with phased array sector scanning is that at any given moment, only areas where the surface normal of the defect is parallel to the direction of the sector scan beam will have a noticeable echo signal. For example, for a circular defect, phased array sector scanning can only obtain the reflected signal from a very small arc-shaped region on the defect surface; signals from other regions cannot be received. The effective reflection area is as follows: Figure 2 As shown, this signal cannot characterize the true shape and size of the defect, and circular defects of different sizes may have sector scan defect images of the same size, such as... Figure 3 As shown, these issues pose a significant challenge to the defect assessment of sector scan images. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide an ultrasonic phased array fan-shaped scanning defect reconstruction method that can display the surface contour of the defect and thus reflect the size of the defect.

[0007] To achieve the above-mentioned objective, the present invention provides a method for defect reconstruction using ultrasonic phased array sector scanning, characterized by comprising the following steps:

[0008] (1) Scan the test piece to obtain a text file composed of A-scan signals;

[0009] (1.1) Set the encoder's scanning interval to be the same as the sampling interval of the carried ultrasonic phased array device, and satisfy the following:

[0010]

[0011] Where c is the speed of sound propagation in the test piece, Δt is the sampling time interval for each beam, and d is the sampling spacing.

[0012] (1.2) Using an encoder to carry an ultrasonic phased array device to perform a sector scan on the test piece along the stepping axis, a total of n frames of sector scan signals are obtained. Each frame of sector scan signal is composed of the A-scan signals of each beam. Finally, each frame of sector scan signal is saved as a text file in sequence, and a total of n text files are obtained.

[0013] Assume that the fan-shaped scan of the ultrasonic phased array device includes N beams and the scanning angle range is θ1~θ2. p And there is a beam at every degree interval, so each text file contains p lines, each line is the A-scan signal of one beam, and the A-scan signal of each beam includes m sampling points.

[0014] (2) Extract the A-scan signals of each beam from the text file and re-synthesize the image;

[0015] In n text files, extract the A-scan signals from the same line and synthesize p m*n two-dimensional images. Then, perform an affine transformation on each two-dimensional image to obtain scan images corresponding to each scanning angle, for a total of p images.

[0016] (3) Scan image translation;

[0017] Using the first scanned image as a reference, shift all the remaining scanned images to the right by K. i 1 pixel;

[0018]

[0019] Among them, OA i This represents the incident point A from the origin to the i-th beam. i The distance;

[0020] (4) The first scanned image and the remaining translated images are weighted and summed to obtain the reconstructed defect cross-section contour map.

[0021] The objective of this invention is achieved as follows:

[0022] This invention discloses a defect reconstruction method using ultrasonic phased array sector scanning. First, the scanning interval of the encoder is set to be the same as the sampling interval of the ultrasonic phased array device. Then, the encoder carrying the ultrasonic phased array device performs a sector scan on the test piece along the stepping axis, acquiring multiple frames of sector scan signals and saving them sequentially as text files. Next, the A-scan signals of each beam in the text files are extracted and the images are recombined. Then, taking the first scan image as a reference, the remaining scan images are shifted to the right. Finally, all images are weighted and summed to obtain the reconstructed defect cross-sectional contour map.

[0023] This invention provides a method for defect reconstruction using ultrasonic phased array sector scanning.

[0024] Meanwhile, the ultrasonic phased array sector scanning defect reconstruction method of the present invention also has the following beneficial effects:

[0025] (1) The present invention can restore part of the profile of the defect section. Although it is only a small part, it is only the scanning result of a single direction. If the reverse scanning is performed, the profile of the other side can be obtained. The profiles of the two sides can basically reflect the condition of the upper surface of the defect.

[0026] (2) This invention can characterize the basic size of defects. A single-frame sector scan image is difficult to distinguish the true size of a defect because defects of different sizes may have images of the same size, such as... Figure 3 As shown, the present invention can also reflect the basic size of defects because it reconstructs the contour surface.

[0027] (3) This invention can also use arrow diagrams to reflect the normal direction of the defective surface, such as... Figure 11 As shown, this can be used as an auxiliary method for determining the shape of the defect surface contour. Attached Figure Description

[0028] Figure 1 This is a flowchart of a defect reconstruction method for ultrasonic phased array sector scanning according to the present invention;

[0029] Figure 2 This is a schematic diagram of the effective reflection area of ​​a circular defect under sector scanning.

[0030] Figure 3 These are sector scan images comparing defects of different sizes;

[0031] Figure 4 This is a schematic diagram of scanning along the stepper axis;

[0032] Figure 5 This is a schematic diagram of the phased array sampling interval and scanning interval;

[0033] Figure 6 These are examples of reconstituted beam images;

[0034] Figure 7 This is a coordinate diagram for establishing an ultrasonic phased array;

[0035] Figure 8 This is a schematic diagram of the incident points of each beam at the interface;

[0036] Figure 9 This is a schematic diagram of the circular cross-sectional region represented by each beam image;

[0037] Figure 10 This is a schematic diagram of the scanning of each beam image;

[0038] Figure 11 This is the result image after fusing 36-beam images;

[0039] Figure 12 It is an arrow diagram representing the surface normal of the defect. Detailed Implementation

[0040] The specific embodiments of the present invention will now be described with reference to the accompanying drawings to enable those skilled in the art to better understand the invention. It should be particularly noted that in the following description, detailed descriptions of known functions and designs that might obscure the main content of the invention will be omitted here.

[0041] Example

[0042] Figure 1 This is a flowchart of a defect reconstruction method for ultrasonic phased array sector scanning according to the present invention.

[0043] In this embodiment, as Figure 4 As shown, the present invention utilizes an encoder or robotic arm to carry a phased array probe to scan along a direction parallel to the scanning cross section. Then, all sector scanning signals are processed and fused to obtain the contour shape of the defect surface and characterize the size of the defect.

[0044] The following is a detailed description of the ultrasonic phased array sector scanning defect reconstruction method of the present invention, such as... Figure 1 As shown, the specific steps include:

[0045] S1. Scan the test piece to obtain a text file composed of A-scan signals;

[0046] In this embodiment, the encoder typically includes two scanning directions: a scanning axis and a stepping axis. Experimental verification has shown that using an encoder to carry an ultrasonic phased array device to scan the test piece along the stepping axis in a fan-shaped pattern can obtain more information about the defect cross-section.

[0047] In addition, before performing the scan, we must first set the encoder's scanning interval to be the same as the sampling interval d of the carried ultrasonic phased array device, and satisfy the following:

[0048]

[0049] Where c is the speed of sound propagation in the test piece, and Δt is the sampling time interval for each beam;

[0050] The encoder's scanning spacing is the same as the phased array device's sampling spacing, such as... Figure 5 As shown, this ensures that the aspect ratio remains the same during subsequent image processing.

[0051] In this embodiment, we sequentially save each frame of sector scan signal along the step axis as a text file. Each frame of sector scan signal is sequentially saved as a text file. In this embodiment, a total of 1250 text files are obtained. Each frame of sector scan signal consists of A-scan signals of each beam. Taking a sector scan with 36 beams as an example, the scanning angle range is defined as 30° to 65°. There is one beam at every degree interval. Then each text file contains 36 lines, and each line is the A-scan signal of one beam. For example, the first line corresponds to the A-scan signal of the 30° beam, and the last line corresponds to the A-scan signal of the 65° beam. In this embodiment, the A-scan signal of each beam is set to contain 900 sampling points.

[0052] S2. Extract the A-scan signals of each beam and reassemble the image;

[0053] In this embodiment, for the 1250 text files acquired, the A-scan signals of the same line are extracted and synthesized into 36 1250*900 two-dimensional images. For example, the A-scan signal sequence of the same line of each text file is extracted sequentially as each column of the two-dimensional image to obtain the first two-dimensional image, and so on, to obtain 36 two-dimensional images.

[0054] like Figure 6 As shown, an affine transformation is performed on each two-dimensional image to obtain 36 scanned images corresponding to each scanning angle. These scanned images are equivalent to the result of scanning with a beam at a fixed angle. For example, the first scanned image is equivalent to the result of scanning simultaneously with 1250 beams at 30° each. Figure 10 As shown.

[0055] S3. Scan image translation;

[0056] Since the incident points of beams at different angles at the interface between the wedge and the test piece are different, each scanned image needs to be translated to the corresponding position before the 36 scanned images are fused.

[0057] In this embodiment, as Figure 7 As shown, we denote the center of the ultrasonic phased array element as H, and take the intersection point of the interface between the center of the array element and the test piece as the origin O, with the vertical downward direction as the Z-axis and the horizontal direction as the X-axis to construct a coordinate system;

[0058] The incident points of each beam are as follows Figure 8 As shown, taking the first scanned image as a reference, all other scanned images are shifted to the right by K. i 1 pixel;

[0059]

[0060] Among them, OA i This represents the incident point A from the origin to the i-th beam. i The distance;

[0061] S4. Reconstruct the defective section;

[0062] The first scanned image and the remaining translated images are weighted and summed to obtain the reconstructed defect cross-sectional profile.

[0063] In this embodiment, after processing in step S3, these 36 images can respectively characterize different regions of the circular defect cross-section, such as... Figure 9 As shown.

[0064] It is obvious that the strongest reflection signal occurs only when the cross-sectional normal angle is the same as the beam angle. Therefore, these 36 images represent the arc-shaped region of the defect cross-section within the range of 30° to 65°. By directly superimposing these 36 images and dividing by 36, the cross-sectional outline will be delineated, as shown below. Figure 11 As shown.

[0065] As can be seen from the comparison images, the outline of the defect cross-section is basically consistent with the shape of the image. However, due to the limited sector scanning angle (30°–65°), the arc-shaped feature of the image is not particularly obvious. Since the strongest reflection signal occurs only when the cross-section normal angle is the same as the beam angle, and these 36 images represent 36 scanning directions, for the same pixel location, the direction represented by the image with the highest pixel value at that location is essentially the normal direction of the defect cross-section at that point.

[0066] An arrow diagram represents the normal direction of each point, and the size of the arrow represents the pixel value of that point, such as... Figure 12 As shown in the diagram, this yields an arrow diagram representing the normal to the defect section.

[0067] Furthermore, the approximate size of the defect can be directly determined from the synthesized image, which is something that cannot be achieved with a single scanned image.

[0068] Although the illustrative specific embodiments of the present invention have been described above to enable those skilled in the art to understand the invention, it should be understood that the invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of the present invention are protected.

Claims

1. A method for defect reconstruction using ultrasonic phased array sector scanning, characterized in that, Includes the following steps: (1) Scan the test piece to obtain a text file composed of A-scan signals; (1.1) Set the encoder's scanning interval to be the same as the sampling interval d of the carried ultrasonic phased array device, and satisfy the following: Where c is the speed of sound propagation in the test piece, and Δt is the sampling time interval for each beam; (1.2) Using an encoder to carry an ultrasonic phased array device to perform a sector scan on the test piece along the stepping axis, a total of n frames of sector scan signals are obtained. Each frame of sector scan signal is composed of the A-scan signals of each beam. Finally, each frame of sector scan signal is saved in sequence as a text file, and a total of n text files are obtained. Assume that the fan-shaped scan of the ultrasonic phased array device includes N beams and the scanning angle range is θ1~θ2. p And there is a beam at every degree interval, so each text file contains p lines, each line is the A-scan signal of one beam, and the A-scan signal of each beam includes m sampling points. (2) Extract the A-scan signals of each beam from the text file and re-synthesize the image; In n text files, extract the A-scan signals from the same line and synthesize p m*n two-dimensional images. Then, perform an affine transformation on each two-dimensional image to obtain scan images corresponding to each scanning angle, for a total of p images. (3) Scan image translation; Using the first scanned image as a reference, shift all the remaining scanned images to the right by K. i 1 pixel; Among them, OA i This represents the incident point A from the origin to the i-th beam. i The distance; (4) The first scanned image and the remaining translated images are weighted and summed to obtain the reconstructed defect cross-section contour map.

Images