Integrated array type probe facing defects on back face of aircraft panel and application method of integrated array type probe

Abstract

The invention provides an integrated array probe for defects on the back surface of an aircraft panel and an application method. The probe comprises a to-be-detected piece (1), an integrated ultrasonic probe array (2) and a wedge block, the integrated ultrasonic probe array (2) is fixed at the central position of the to-be-tested piece (1) through wedge blocks, the integrated ultrasonic probe array (2) is a square array and consists of 20 ultrasonic probes, each edge is uniformly provided with 5 ultrasonic probes, and the wedge blocks are arranged at four corners of the square array. According to the signal amplitude full-focus imaging acceleration design provided by the invention, on the premise of ensuring that an imaging result is unchanged, 1.206 s before acceleration is improved to 0.334 s, the imaging speed is improved by 2.61 times, and the imaging speed is greatly improved.

Description

Technical Field

[0001] The invention relates to an integrated array probe facing defects on the back side of an aircraft wall panel and an application method thereof, belonging to the technical field of ultrasonic detection. Background Art

[0002] Panels are widely used and extremely important structures on aircraft, and are divided into fuselage panels and wing panels. At present, they are mainly divided into typical panels, composite panels, and integral panels according to their materials and production processes. For typical panels, their most basic structure is a metal sheet structure. During the service of the aircraft, the fuselage is directly subjected to impact and alternating loads, which can easily lead to defects. If left unchecked, it may cause subsequent damage or breakage of the fuselage during flight, seriously threatening the safety of the pilot and the aircraft. Therefore, regular inspection and maintenance of aircraft is an important guarantee for the safety of personnel and national property, and non-destructive testing is an indispensable and important means of aircraft maintenance.

[0003] Lamb waves, surface waves and critical refracted longitudinal waves are generally used to detect defects in metal sheet structures. The acoustic energy of surface waves and critical refracted longitudinal waves is concentrated on the near surface of the medium. Considering that the defects to be detected may be located inside and on the back surface of the detection, it is difficult to detect them using surface waves and critical refracted longitudinal waves; and the vibration mode of Lamb waves is sensitive to defects within the entire thickness range of the propagation distance. Conventional ultrasonic detection methods for defects on wall panel structures have problems such as non-intuitive detection, difficult positioning, and whether defects can be detected depends on the level of the inspectors. Therefore, further research is needed on the visualization, automation and intelligence of defects on the back of aircraft wall panels using Lamb waves.

[0004] There are three common imaging algorithms for ultrasonic imaging at home and abroad: full focusing algorithm, frequency domain full focusing algorithm, and imaging algorithm based on probabilistic damage factor. The full focusing algorithm is based on the ultrasonic reflection signal, and has the advantages of clear imaging, high sensitivity, and flexible signal combination, but the disadvantage is slow imaging speed; the frequency domain full focusing algorithm is based on the ultrasonic reflection signal for focusing imaging in the frequency domain, and the advantage is fast imaging speed, but the disadvantage is narrow application range and inflexible algorithm implementation of complex signal combination; different from the first two algorithms, the imaging algorithm based on probabilistic damage factor is based on ultrasonic transmission signal, and the advantage is fast operation speed and highest sensitivity, but the disadvantage is that it requires a defect-free reference signal. Considering that it is difficult to obtain a defect-free reference signal under actual working conditions, the imaging algorithm based on probabilistic damage factor cannot be used. Summary of the invention

[0005] In order to solve the above problems, the present invention further proposes an integrated array probe for detecting defects on the back side of aircraft wall panels and an application method.

[0006] The technical solution adopted by the present invention to solve the above problems is: the present invention proposes an integrated array probe facing the defects on the back of the aircraft wall panel, comprising:

[0007] A test piece (1), an integrated ultrasonic probe array (2) and a wedge;

[0008] The integrated ultrasonic probe array (2) is fixed at the center position of the test piece (1) via a wedge.

[0009] Optionally, the integrated ultrasonic probe array (2) is a square array, composed of 20 ultrasonic probes, with 5 ultrasonic probes evenly arranged on each side, and wedges are arranged at the four corners of the square array.

[0010] The application method of the integrated array probe for defects on the back of aircraft panels includes:

[0011] Step 1: Collect full matrix signals of the imaging area through five ultrasound probes on each side of the integrated ultrasound probe array (2);

[0012] Step 2: Preprocess the collected full matrix signal;

[0013] Step 3: Using the amplitude full focusing algorithm, the echoes of the pre-processed full matrix signal propagation paths on the four sides of the integrated ultrasonic probe array (2) are delayed and accumulated to obtain the signal amplitude full focusing imaging results.

[0014] Optionally, the step of acquiring the full matrix signal of the imaging area in step 1 includes:

[0015] Step 1.1: Grid the imaging area, use the binary method, and calculate the interpolation index by combining the grid points, ultrasound probe position, signal sampling rate and sampling depth;

[0016] Step 1.2: Select the difference algorithm according to the signal sampling rate and the center frequency of the full matrix signal, and interpolate the full matrix signal in combination with the difference index.

[0017] Optionally, interpolating the full matrix signal in step 1.2 specifically includes:

[0018] When the sampling frequency is greater than the signal center frequency, the nearest neighbor interpolation method is used to interpolate the full matrix signal. When the sampling frequency is less than or equal to the signal center frequency, the piecewise linear interpolation method is used to interpolate the full matrix signal.

[0019] Optionally, the preprocessing of the collected full matrix signal in step 2 specifically includes:

[0020] Perform FIR zero-phase-shift filtering and Lamb wave dispersion compensation on the full matrix signal.

[0021] Optionally, the step of acquiring the signal amplitude full-focus imaging result in step 3 includes:

[0022] Step 3.1: Calculate the distances between the grid point P(x, y) and the excitation array element i and the receiving array element j respectively, where the coordinates of the excitation array element i are (x i ,0), the coordinates of the receiving element j are (x j ,0);

[0023] Step 3.2: Take the full matrix signal as the ultrasonic signal and calculate the propagation time τ of the ultrasonic signal emitted by each ultrasonic probe starting from the excitation array element i, reflected by the grid point P (x, y) and received by the receiving array element j;

[0024] Step 3.3: Based on the propagation time τ, the echoes of the propagation path of the ultrasonic signal of the excitation array element i and the adjacent probe are delayed and accumulated to obtain the image amplitude intensity at the grid point P (x, y);

[0025] Step 3.4: Use CPU parallel computing to traverse each divided grid point to obtain the signal amplitude full focus imaging result;

[0026] The propagation time τ is calculated as:

[0027]

[0028] In formula (1), d i is the distance between the excitation element i and the grid point P(x,y), d j is the distance between receiving array element j and grid point P(x,y), c is the speed of sound;

[0029] The calculation formula of the image amplitude intensity at the grid point P(x,y) is:

[0030]

[0031] In formula (2), I(x, y) is the image amplitude at the coordinate (x, y), Rf is the echo signal, and RfEnv is the envelope of the echo signal.

[0032] The beneficial effects of the present invention are:

[0033] The present invention can meet the requirements of intuitive and intelligent ultrasonic detection. Compared with the traditional full-focusing algorithm with slow imaging speed, the present invention applies the signal amplitude full-focusing imaging algorithm, performs envelope extraction processing on the echo, discards the phase information of the echo signal, and proposes an acceleration method for the real-time requirement of imaging. The acceleration design of the signal amplitude full-focusing imaging proposed by the present invention increases the imaging speed from 1.206s before acceleration to 0.334s while ensuring that the imaging result remains basically unchanged, and the imaging speed is increased by 2.61 times, which greatly improves the imaging speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A structural block diagram of an integrated array probe for defects on the back of an aircraft wall panel provided by the present invention;

[0035] Figure 1 In the figure, 1-test piece, 2-integrated ultrasonic probe array;

[0036] Figure 2 A schematic diagram of the imaging superposition method provided by the present invention;

[0037] Figure 3 A calculation flow chart of the imaging algorithm provided by the present invention;

[0038] Figure 4 This is a diagram of the imaging result using the integrated array probe provided by the present invention;

[0039] Figure 4 In the figure, (a) is the imaging result of the back side of the aircraft wall panel without defects, and (b) is the imaging result of the back side of the aircraft wall panel with groove defects;

[0040] Figure 5 A comparison chart of imaging effects before and after acceleration of the imaging algorithm provided by the present invention;

[0041] Figure 5 In the figure, (a) is the imaging effect diagram before the imaging algorithm is accelerated, and (b) is the imaging effect diagram after the imaging algorithm is accelerated. DETAILED DESCRIPTION

[0042] Specific implementation method 1: Combination Figure 1-2 To illustrate this embodiment, Figure 1 As shown, the structure of the integrated array probe facing the defects on the back of the aircraft wall panel described in this embodiment includes:

[0043] A test piece (1), an integrated ultrasonic probe array (2) and a wedge;

[0044] The integrated ultrasonic probe array (2) is fixed at the center of the test piece (1) through a wedge

[0045] In order to improve the defect detection capability and achieve intuitive detection results, this embodiment adopts an array probe to obtain more echo signals and perform imaging according to the signal processing algorithm. Under normal circumstances, the ultrasonic probe is in a linear array when based on ultrasonic body wave detection, and for detection on the plate, a circumferential probe arrangement can be used to obtain defect information to the greatest extent. In view of the actual needs of detection, this embodiment adopts an array probe with an integrated coupling wedge for signal acquisition, wherein the center frequency of the probe needs to be selected according to the characteristics of the Lamb wave. The function of the integrated coupling wedge is to fix the probe combination together and make the longitudinal wave probe obliquely incident to excite the Lamb wave. The inclination angle of the wedge needs to be determined based on the center frequency of the probe used and the parameters of the material to be tested. The schematic diagram of the detection scheme and the coordinate system established by imaging are shown in the figure. Figure 1 As shown, the upper left corner of the probe layout area is the origin of the imaging area, the horizontal direction is the X-axis, the vertical direction is the Y-axis, and the area surrounded by the probe is the imaging area.

[0046] From the perspective of improving imaging effects, the more probes are arranged, the better. However, the more probes are arranged, the higher the hardware requirements for the ultrasonic excitation and acquisition system, and the larger the size of the array probe, which is not conducive to ultrasonic coupling and scanning. Based on the above considerations, this embodiment decides to use 20 ultrasonic probes to form an array. The probes are combined together by making an integrated wedge block for imaging. The probes are arranged in a circular manner to obtain the most defect amplitude information in the central area. There are two common probe arrangements: circular arrangement and square arrangement. Considering that the square arrangement is convenient for the design of the imaging algorithm, the stitching of the scanned images, and the processing of the integrated wedge block, the square probe arrangement is finally adopted in this embodiment.

[0047] The final imaging result of this embodiment is to collect full matrix signals from the five ultrasonic probes on each side of the square, perform signal processing, and then apply the amplitude full focusing algorithm. The imaging area is selected as the central area where the probes are arranged, and the four imaging results are superimposed. In this way, a good imaging effect can be obtained in both the X and Y directions of the imaging area, and the contrast of the defect area is significantly enhanced. The algorithm superposition schematic diagram is shown in the figure. Figure 2 shown.

[0048] Specific implementation method 2: Combination Figure 2-5 This embodiment is described as follows. Figure 3 As shown, the application method of the integrated array probe for defects on the back of aircraft panels described in this embodiment includes the following steps:

[0049] S1: Use 5 ultrasound probes on each side of the square to collect full matrix signals;

[0050] S101: gridding the imaging area, using a binary method, and calculating an interpolation index by combining the grid points, ultrasound probe position, signal sampling rate, and sampling depth;

[0051] S102: selecting a difference algorithm according to the signal sampling rate and the center frequency of the full matrix signal, and interpolating the full matrix signal in combination with the difference index;

[0052] S103: When the sampling frequency is greater than the signal center frequency, the full matrix signal is interpolated using the nearest neighbor interpolation method; when the sampling frequency is less than or equal to the signal center frequency, the full matrix signal is interpolated using the piecewise linear interpolation method.

[0053] S2: preprocessing the collected full matrix signal;

[0054] S201: Perform FIR zero-phase-shift filtering and Lamb wave dispersion compensation on the collected full-matrix signal.

[0055] S3: Using an amplitude full focusing algorithm, the echoes of the pre-processed full matrix signal propagation paths on the four sides of the integrated ultrasonic probe array (2) are delayed and accumulated to obtain a signal amplitude full focusing imaging result.

[0056] The amplitude full focusing algorithm calculates the imaging by delaying and accumulating the N×N full matrix signal according to the signal arrival time. The steps of the amplitude full focusing algorithm include:

[0057] S1: Calculate the distance between the divided grid and the excitation and receiving array elements;

[0058] S101: Figure 1 Based on the coordinate system established in , the coordinate of the excitation array element i is defined as (x i ,0), the coordinate of receiving element j is (x j ,0), the distance between the excitation array element i and the grid point P(x,y) is calculated to be d i , the distance between the receiving element j and the grid point P(x,y) is d j ;

[0059] S2: Calculate the propagation time τ of the ultrasonic signal;

[0060] The propagation time τ of the ultrasonic signal starting from the i-th array element, reflected by the grid point P(x,y) and received by the j-th array element is:

[0061]

[0062] In formula (1), d i is the distance between the excitation element i and the grid point P(x,y), d j is the distance between receiving array element j and grid point P(x,y), c is the speed of sound;

[0063] S3: Delaying and accumulating the echoes of the ultrasonic signal propagation path according to the propagation time τ can obtain the image amplitude intensity at the grid point P;

[0064] The calculation formula of the image amplitude intensity at the grid point P is:

[0065]

[0066] In formula (2), I(x, y) is the image amplitude at the grid point P, and Rf is the echo signal that needs to be interpolated when used;

[0067] This implementation method takes into account the directivity of the sound field and only extracts the excitation array element itself and the adjacent probes for delayed accumulation imaging. The modified formula (2) is:

[0068]

[0069] In formula (3), I(x, y) is the image amplitude at the coordinate (x, y), Rf is the echo signal, and RfEnv is the envelope of the echo signal.

[0070] Since the echo is subjected to envelope extraction processing, the phase information of the echo signal is discarded. Therefore, there is no need to extract the envelope of I(x, y) in the end. The calculation result of formula (3) directly shows the signal amplitude full-focus imaging result.

[0071] S4: CPU parallel computing is used to traverse each divided grid point to obtain the signal amplitude full focus imaging result;

[0072] like Figure 2 As shown, Figure 2 The solid thin arrow in the middle is the part that needs to be calculated only once after the algorithm is initialized. As long as the imaging parameters remain unchanged, no calculation is required during real-time scanning. The sampling time of the signal theory is calculated using formula (1) according to the input parameters and the divided pixel points. Then, the interpolation index table is established by binary search method with the acquisition time of the hardware AD as the lookup table and stored in the memory; the yellow part is the real-time operation part, which is divided into envelope extraction and pixel value acquisition. The envelopes of each signal are independent of each other and there is no problem of calculation order. Therefore, CPU multi-thread parallel calculation can be used. According to the designed imaging method, the five probes have a total of 5×5=25 echo signals. Considering the sound field directivity mentioned above, only the receiving echoes of the excitation probe itself and the adjacent probes are retained. Finally, 2×2+3×3=13 echo signals are left. Then the envelope information obtained by parallel calculation is stored in the memory.

[0073] Since there is an accumulation operation in the pixel value acquisition part, the same parallelization method as the envelope extraction part will cause different threads to read and write the same variable at the same time, that is, there is a thread-unsafe problem. This implementation method uses parallelization to calculate the image amplitude of different pixel points, while the accumulation operation still uses sequential calculation, that is, formula (3) still uses sequential calculation, and parallel calculation is used for each (x, y) coordinate of formula (3).

[0074] This implementation takes into account the need for real-time on-site scanning, so the imaging frame rate is an issue that cannot be ignored. The imaging speed is increased by considering the acceleration design of the imaging algorithm. The process of the imaging algorithm is as follows: Figure 3 As shown, the imaging speed can be improved from the following three aspects.

[0075] like Figure 4 and Figure 5 As shown, this embodiment uses the same ultrasonic detection data. The acceleration design of the signal amplitude full-focus imaging proposed in this embodiment is improved from 1.206s before acceleration to 0.334s while ensuring that the imaging result remains unchanged. The imaging speed is increased by 2.61 times, which greatly improves the imaging speed.

[0076] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent replacement and improvement made to the above embodiments without departing from the content of the technical solution of the present invention, based on the technical essence of the present invention, within the spirit and principles of the present invention, still fall within the protection scope of the technical solution of the present invention.

Claims

1. An integrated array probe for defects on the back of aircraft panels, characterized in that: The structure of the integrated array probe facing the defects on the back of the aircraft wall panel includes: A test piece (1), an integrated ultrasonic probe array (2) and a wedge; The integrated ultrasonic probe array (2) is fixed at the center of the object to be tested (1) via a wedge.

2. The integrated array probe for detecting defects on the back of an aircraft panel according to claim 1, characterized in that: The integrated ultrasonic probe array (2) is a square array, composed of 20 ultrasonic probes, 5 ultrasonic probes are evenly arranged on each side, and wedge blocks are arranged at the four corners of the square array.

3. An application method of an integrated array probe for defects on the back of an aircraft wall panel, applied to the integrated array probe for defects on the back of an aircraft wall panel as claimed in any one of claims 1 to 2, characterized in that: include: Step 1: Collect full matrix signals of the imaging area through five ultrasound probes on each side of the integrated ultrasound probe array (2); Step 2: Preprocess the collected full matrix signal; Step 3: Using the amplitude full focusing algorithm, the echoes of the pre-processed full matrix signal propagation paths on the four sides of the integrated ultrasonic probe array (2) are delayed and accumulated to obtain the signal amplitude full focusing imaging results.

4. The application method of the integrated array probe for detecting defects on the back side of an aircraft wall panel according to claim 3, characterized in that: The steps of collecting the full matrix signal of the imaging area in step 1 include: Step 1.1: Grid the imaging area, use the binary method, and calculate the interpolation index by combining the grid points, ultrasound probe position, signal sampling rate and sampling depth; Step 1.2: Select the difference algorithm according to the signal sampling rate and the center frequency of the full matrix signal, and interpolate the full matrix signal in combination with the difference index.

5. The application method of the integrated array probe for detecting defects on the back side of aircraft panels according to claim 4, characterized in that: The interpolation of the full matrix signal in step 1.2 specifically includes: When the sampling frequency is greater than the signal center frequency, the nearest neighbor interpolation method is used to interpolate the full matrix signal. When the sampling frequency is less than or equal to the signal center frequency, the piecewise linear interpolation method is used to interpolate the full matrix signal.

6. The application method of the integrated array probe for detecting defects on the back side of an aircraft wall panel according to claim 3, characterized in that: The preprocessing of the collected full matrix signal in step 2 specifically includes: The full matrix signal is subjected to FIR zero-phase-shift filtering and Lamb wave dispersion compensation.

7. The method for applying the integrated array probe for detecting defects on the back side of an aircraft panel according to claim 3, characterized in that: The steps of obtaining the signal amplitude full-focus imaging result in step 3 include: Step 3.1: Calculate the distances between the grid point P(x, y) and the excitation array element i and the receiving array element j respectively, where the coordinates of the excitation array element i are (x i ,0), the coordinates of the receiving element j are (x j ,0); Step 3.2: Take the full matrix signal as the ultrasonic signal and calculate the propagation time τ of the ultrasonic signal emitted by each ultrasonic probe starting from the excitation array element i, reflected by the grid point P (x, y) and received by the receiving array element j; Step 3.3: based on the propagation time τ, delay accumulation is performed on the echoes of the excitation array element i and the adjacent probe ultrasonic signal propagation path to obtain the image amplitude intensity at the grid point P (x, y); Step 3.4: Use CPU parallel computing to traverse each divided grid point to obtain the signal amplitude full focus imaging result; The propagation time τ is calculated as: In formula (1), d i is the distance between the excitation element i and the grid point P(x,y), d j is the distance between receiving array element j and grid point P(x,y), c is the speed of sound; The calculation formula of the image amplitude intensity at the grid point P(x,y) is: In formula (2), I(x, y) is the image amplitude at the coordinate (x, y), Rf is the echo signal, and RfEnv is the envelope of the echo signal.

Images