Honeycomb sandwich structure defect detection system and method based on two-dimensional phased array sensor

Abstract

The invention provides a honeycomb sandwich structure defect detection system and method based on a two-dimensional phased array sensor, and belongs to the technical field of nondestructive testing, the honeycomb sandwich structure defect detection system comprises the two-dimensional phased array sensor, the two-dimensional phased array sensor is a two-dimensional matrix array formed by arranging M * N sub-array elements which can be independently triggered to generate wave sources; the phased array ultrasonic unit is used for transmitting and receiving ultrasonic signals and sequentially exciting part of sub-array elements in the two-dimensional phased array sensor to synthesize electronic scanning sound beams, so that the sequence information of each electronic scanning sound beam corresponds to the spatial position information; and the signal processing and display unit obtains the ultrasonic signal, carries out reverse deduction by combining the sequence information of the electronic scanning sound beam to obtain space position information, and judges whether defects exist or not. Real-time plane imaging detection can be achieved without depending on movement of a mechanical driving sensor, and the method is convenient to use in a narrow space, is particularly applied to a honeycomb structure, can obviously distinguish whether abnormity of ultrasonic signals is caused by changes of the honeycomb structure or defects, improves the defect detection rate and reduces the misjudgment rate.

Description

Technical Field

[0001] This invention belongs to the field of nondestructive testing technology and relates to a defect detection system and method for honeycomb sandwich structures based on a two-dimensional phased array sensor. Background Technology

[0002] Ultrasonic testing is currently the most advanced method for detecting honeycomb sandwich structures (such as...). Figure 2 The main detection method is to determine defects based on the time-domain ultrasonic signals received by the transducer from the honeycomb structure being tested. The amplitude-time display method of the ultrasonic signal is adopted. The amplitude of the ultrasonic reflected signal or the ultrasonic signal transmitted through the sensor is received at various locations. Based on the amplitude of the ultrasonic signal displayed by the instrument, it is determined whether there are defects in the bonding interface inside the honeycomb structure corresponding to the current detection location.

[0003] Ultrasonic waves propagate differently in the honeycomb walls and cells. For example, during reflection testing, ultrasonic waves propagating inside the panel (skin) continue along the honeycomb walls, but are completely reflected at the cells and cannot propagate further. When air gap defects exist inside the honeycomb, the ultrasonic signal is completely reflected, and its acoustic characteristics are similar to those at the cells. This makes it difficult to determine whether the changes in the displayed ultrasonic signal and its amplitude are due to structural changes in the part (honeycomb walls and cells) or the presence of air gap defects when using manual ultrasonic testing, easily leading to misjudgments of defects.

[0004] The invention proposed by Liu Feifei et al. (patent number CN109632954A) discloses a defect identification method for honeycomb sandwich structures based on ultrasonic position signal detection. This method uses a mechanically driven ultrasonic sensor to perform ultrasonic detection, acquiring the positional information corresponding to the ultrasonic signal for imaging detection. By displaying the position-ultrasonic signal information of the entire area scanned by rows or columns on the instrument screen, the changes in ultrasonic signals caused by defects can be clearly and intuitively determined, improving the defect detection rate. However, this method has significant drawbacks: ① The system includes a mechanical scanning unit, resulting in a large overall size, making it difficult to deploy in confined spaces, such as narrow openings; ② Acquiring ultrasonic signal positional information through mechanical drive requires the sensor to move within a certain range, which is not feasible in environments with restricted movement, such as in-service aircraft inspection or assembly part inspection; ③ The image resolution obtained through mechanical drive is related to the positioning accuracy of the mechanical system, generally resulting in low resolution, and the mechanical system is prone to failure; ④ The positioning accuracy of the mechanical structure needs to be periodically verified, otherwise the positioning accuracy and reliability cannot be guaranteed; ⑤ Mechanical movement takes time, resulting in poor real-time performance. Summary of the Invention

[0005] This invention provides a cellular sandwich structure defect detection system and method based on a two-dimensional phased array sensor. The two-dimensional phased array sensor is placed in the area to be inspected in the cellular sandwich structure to acquire the sequence information corresponding to the ultrasonic signal. The position information is inferred from the sequence information to achieve rapid real-time display of the ultrasonic signal and its spatial positioning. Imaging detection is achieved without the need for synchronous mechanical movement of the sensor, and defect identification can be performed intuitively. This solves the problem that the original method cannot be implemented in confined spaces or environments where sensor movement is restricted. At the same time, it improves imaging resolution and ensures reliability and accuracy.

[0006] The technical solution adopted in this invention is as follows:

[0007] A defect detection system for honeycomb sandwich structures based on a two-dimensional phased array sensor includes a two-dimensional phased array sensor 100, a phased array ultrasonic unit 200, and a signal processing and display unit 300.

[0008] The two-dimensional phased array sensor 100 consists of a two-dimensional matrix array composed of M×N array elements that can be independently triggered to generate wave sources. It is used to transmit and receive ultrasonic signals. The size of the two-dimensional phased array sensor 100, i.e. the number of array elements, is selected according to the surface curvature of the honeycomb sandwich structure being detected and the size of the opening at the location.

[0009] The phased array ultrasonic unit 200 is used to transmit and receive ultrasonic signals. It is matched and connected to the two-dimensional phased array sensor 100. Its effective digitization frequency is not less than 100MHz, its sampling frequency is not less than 200MHz, and its synchronization accuracy is high. The phased array ultrasonic unit 200 sets the size of the subarray according to the detection requirements. The subarray is a two-dimensional array composed of m×n array elements in the two-dimensional phased array sensor 100. By adjusting the transmission time difference of each array element in the subarray, the sound waves are superimposed in phase at the target focal point to synthesize an enhanced sound beam, i.e., an electronic scanning sound beam. The phased array ultrasonic unit 200 excites the subarray sequentially with a constant phase according to a certain time delay law, synthesizing a total of K electronic scanning sound beams. The sequence information of each electronic scanning sound beam corresponds to the spatial position information. The spatial position information can be deduced from the sequence information of the electronic scanning sound beam using a delay algorithm.

[0010] The signal processing and display unit 300 is connected to the two-dimensional phased array sensor 100 and the phased array ultrasonic unit 200. Its acquisition frame rate is 50 frames / second. It is used to acquire the ultrasonic signal u(t) and its amplitude signal A(t) of each electronic scanning sound beam. Combined with the sequence information of the electronic scanning sound beam, it inversely infers the corresponding spatial position information P(x,y), where (x,y) represents the position coordinates of the detected cellular sandwich structure in the aircraft coordinate system. It displays the position information P(x,y) and the amplitude A(t) of the ultrasonic signal u(t), i.e., P(x,y)-A(t). At the same time, the signal processing and display unit 300 determines whether there are defects in the detected cellular sandwich structure and finally forms an image of the detected cellular sandwich structure for display. The defective parts are distinguished by color in the image.

[0011] A method for detecting defects in honeycomb sandwich structures based on a two-dimensional phased array sensor, implemented using the aforementioned honeycomb sandwich structure defect detection system, includes the following steps:

[0012] The first step is to obtain the location information P(x,y) and the amplitude signal A(t) of the ultrasonic signal u(t):

[0013] 1.1 Connect the detection system and place the two-dimensional phased array sensor 100 on the surface of the location to be measured, ensuring good acoustic coupling. Through the phased array ultrasonic unit 200, set parameters such as element size, subarray overlap length, time-delay focusing rule, ultrasonic signal, gain, and electronic gate to control the elements in the two-dimensional phased array sensor 100 to synthesize K electronic scanning sound beams that conform to a certain time delay rule. The sequence information of each electronic scanning sound beam is denoted as S. k (x * ,y * ), k = 1, 2, ..., K, (x * ,y * The coordinates of the electronic scanning acoustic beam are the position coordinates in the coordinate system established with the two-dimensional phased array sensor 100 as the reference.

[0014] 1.2 The signal processing and display unit 300 can clearly observe the ultrasonic signal u(t) from the position to be measured, adjust the gain so that its amplitude A(t) is not less than 40% of the display screen in the signal processing and display unit 300, and adjust the electronic gate so that the ultrasonic signal u(t) is located within the set gate.

[0015] 1.3 K electron scanning acoustic beams are sequentially excited until all elements in the two-dimensional phased array sensor 100 are traversed. The signal processing and display unit 300 acquires the ultrasonic signal characteristics and records and stores the corresponding sequence information S. k (x * ,y * ) and its corresponding ultrasound signal u k The amplitude signal A of (t)k (t):

[0016]

[0017] Among them, S k (x * ,y * )-A k (t) represents the sequence information S of the ultrasound signal from the k-th electronic scanning beam. k (x * ,y * ) and amplitude information A k (t) Correspondence.

[0018] Based on the time delay algorithm, the spatial location information P of the area to be tested is obtained by inversely deducing the sequence information of the electronic scanning acoustic beam. k (x,y):

[0019] P k (x,y)=αS k (x*,y*) (2)

[0020] Wherein, α is the inverse coefficient, determined by the relevant parameters and delay algorithm of the two-dimensional phased array sensor 100. Furthermore, by combining equation (1), the correspondence between the spatial location information P(x,y) and the amplitude information A(t) of the area to be measured is obtained, namely the P(x,y)-A(t) image.

[0021] The second step is to characterize the defect-free structure using ultrasonic signals:

[0022] A defect-free test piece identical to the honeycomb sandwich structure being tested is fabricated. A two-dimensional phased array sensor 100 is placed on the test piece, and the process in the first step is performed to acquire ultrasonic signal features, resulting in a waveform P(x,y)-A(t) image.

[0023] Based on equations (1) and (2), the defect-free structure P is obtained. w and P l , where P w P is the maximum width of two adjacent positive peaks of P(x,y)-A(t); l Let P(x,y)-A(t) be the maximum width of two adjacent negative peaks.

[0024] The third step is to obtain the alarm threshold:

[0025] Determine the defect alarm thresholds N1 and N2 according to equations (3) and (4):

[0026] N1=γ×P w (3)

[0027] N2=γ×P l (4)

[0028] Where γ is an empirical constant.

[0029] Step 4, Defect Identification:

[0030] The two-dimensional phased array sensor 100 is placed on the surface of the first test area of ​​the honeycomb sandwich structure to be tested. The process in the first step is performed to acquire ultrasonic signal features. The signal processing and display unit 300 obtains Np and Nm according to P(x,y)-A(t). Np is the width of two adjacent positive peaks in the P(x,y)-A(t) image, and Nm is the width of two adjacent negative peaks in the P(x,y)-A(t) image. When Np>N1 and Nm>N2, it is determined that there is a defect in the corresponding area, and the defect location is determined by combining the spatial location information. Otherwise, it is determined that there is no defect. The defective area is distinguished from the non-defective area with different colors and displayed by the signal processing and display unit 300.

[0031] Fifth, place the two-dimensional phased array sensor 100 on the surface of the next test area of ​​the honeycomb sandwich structure being tested, and repeat the fourth step to determine whether there are defects in the next test area.

[0032] The beneficial effects of this invention are:

[0033] 1. This invention does not rely on mechanical drive. Based on the sequence information of the linear scanning sound beam of a two-dimensional phased array sensor, it realizes spatial point positioning transmission and reception. It can realize real-time planar imaging detection without moving the sensor, which is convenient for imaging detection in narrow spaces or environments where it is not suitable to install mechanical drive systems.

[0034] 2. This invention utilizes a sound beam formed by a two-dimensional phased array sensor for electronic linear scanning, which provides high spatial positioning accuracy, high real-time imaging performance, and signal-to-noise ratio and resolution unaffected by mechanical systems.

[0035] 3. This invention can realize the intuitive display of defects within the sensor coverage area, and can clearly distinguish whether the abnormality of the ultrasonic signal is caused by changes in the honeycomb structure or by defects, thereby improving the defect detection rate and reducing the false judgment rate. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the detection system of the present invention;

[0037] Figure 2 This is a schematic diagram of a honeycomb sandwich structure;

[0038] The figure shows: 2D phased array sensor 100, phased array ultrasonic unit 200, and signal processing and display unit 300. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] This embodiment uses a narrow-aperture, deep U-shaped honeycomb structure as an example to further illustrate the present invention. The honeycomb structure has a titanium metal skin thickness of 1.0 mm, a TC4 titanium honeycomb core, and a honeycomb core height of 10 mm.

[0041] A defect detection system based on a two-dimensional phased array sensor includes a two-dimensional phased array sensor 100, a phased array ultrasonic unit 200, and a signal processing and display unit 300, such as... Figure 1 As shown.

[0042] The two-dimensional phased array sensor 100 consists of a two-dimensional matrix array composed of M×N array elements that can be independently triggered to generate wave sources. It is used to transmit and receive ultrasonic signals. According to the material, thickness and opening size of the honeycomb structure being detected, the two-dimensional phased array sensor 100 selected in this embodiment adopts a 5MHz array with 64×64 array elements that can be independently triggered to generate wave sources, and the array element size is 0.5mm×0.5mm.

[0043] The phased array ultrasonic unit 200 uses an Olympus OmniScan X3 phased array detector for transmitting and receiving ultrasonic signals. It is matched and connected to the two-dimensional phased array sensor 100. Its effective digitization frequency is not less than 100MHz, its sampling frequency is not less than 200MHz, and its synchronization accuracy is high. The phased array ultrasonic unit 200 sets the subarray size according to the detection requirements. The subarray is a two-dimensional array composed of m×n array elements in the two-dimensional phased array sensor 100. By adjusting the transmission time difference of each array element in the subarray, the sound waves are superimposed in phase at the target focal point to synthesize an enhanced sound beam, i.e., an electronic scanning sound beam. The phased array ultrasonic unit 200 excites the subarray sequentially with a constant phase according to a certain time delay rule, synthesizing a total of K electronic scanning sound beams. The sequence information of each electronic scanning sound beam corresponds to the spatial position information. The spatial position information can be deduced from the sequence information of the electronic scanning sound beam using a time delay algorithm.

[0044] The signal processing and display unit 300 is connected to the two-dimensional phased array sensor 100 and the phased array ultrasonic unit 200. Its acquisition frame rate is 50 frames / second. It is used to acquire the ultrasonic signal u(t) and its amplitude signal A(t) of each electronic scanning sound beam. Combined with the sequence information of the electronic scanning sound beam, the spatial position information P(x,y) is obtained. Here, (x,y) represents the position coordinates of the U-shaped honeycomb structure in the aircraft coordinate system. The position information P(x,y) and the amplitude A(t) of the ultrasonic signal u(t) are displayed, i.e., P(x,y)-A(t). The system determines whether there is a defect in the U-shaped honeycomb structure and finally forms an image of the U-shaped honeycomb structure for display. The defective parts are distinguished by color in the image.

[0045] A defect detection method based on a two-dimensional phased array sensor, implemented using the aforementioned defect detection system, includes the following steps:

[0046] The first step is to obtain the location information P(x,y) and the amplitude signal A(t) of the ultrasonic signal u(t):

[0047] 1.1 Connect the detection system and place the two-dimensional phased array sensor 100 on the surface of the location to be measured, ensuring good acoustic coupling. Through the phased array ultrasonic unit 200, set parameters such as element size, subarray overlap length, time-delay focusing rule, ultrasonic signal, gain, and electronic gate to control the elements in the two-dimensional phased array sensor 100 to synthesize K electronic scanning sound beams that conform to a certain time delay rule. The sequence information of each electronic scanning sound beam is denoted as S. k (x * ,y * ), k = 1, 2, ..., K, (x * ,y * The coordinates of the electronic scanning acoustic beam are the position coordinates in the coordinate system established with the two-dimensional phased array sensor 100 as the reference.

[0048] In this embodiment, the parameters are set as follows: in the 64×64 array of the two-dimensional phased array sensor 100, the subarray size is 16×16, and the overlap length between subarrays is 2 array elements as the step size. When performing electronic linear scanning, the subarrays are first excited one by one along the y-axis to form an electronic scanning sound beam. Then, after moving one step along the x-axis, the subarrays are excited one by one along the y-axis to form an electronic scanning sound beam. This process is repeated until all array elements of the two-dimensional phased array sensor 100 are traversed, forming a total of 576 electronic scanning sound beams.

[0049] 1.2 The signal processing and display unit 300 can clearly observe the ultrasonic signal u(t) from the position to be measured, adjust the gain so that its amplitude A(t) is not less than 40% of the display screen in the signal processing and display unit 300, and adjust the electronic gate so that the ultrasonic signal u(t) is located within the set gate.

[0050] 1.3 K (K=576) electron scanning acoustic beams are sequentially excited until all elements in the two-dimensional phased array sensor 100 are traversed. The signal processing and display unit 300 acquires the ultrasonic signal characteristics and records and stores the corresponding sequence information S. k (x * ,y * ) and its corresponding ultrasound signal u k The amplitude signal A of (t) k (t):

[0051]

[0052] Among them, S k (x * ,y * )-A k (t) represents the sequence information S of the ultrasound signal from the k-th electronic scanning beam. k (x * ,y * ) and amplitude information A k (t) Correspondence.

[0053] Based on the time delay algorithm, the spatial location information P of the area to be tested is obtained by inversely deducing the sequence information of the electronic scanning acoustic beam. k (x,y):

[0054] P k (x,y)=αS k (x*,y*) (2)

[0055] Wherein, α is the inverse coefficient, determined by the relevant parameters and delay algorithm of the two-dimensional phased array sensor 100. Furthermore, by combining equation (1), the correspondence between the spatial location information P(x,y) and the amplitude information A(t) of the area to be measured is obtained, namely the P(x,y)-A(t) image.

[0056] The second step is to characterize the defect-free structure using ultrasonic signals:

[0057] A defect-free test piece identical to the U-shaped honeycomb structure was fabricated. A two-dimensional phased array sensor 100 was placed on the test piece, and the process in the first step was performed to acquire ultrasonic signal features, resulting in a waveform P(x,y)-A(t) image.

[0058] Based on equations (1) and (2), the defect-free structure P is obtained. w and Pl , where P w P is the maximum width of two adjacent positive peaks of P(x,y)-A(t); l Let P(x,y)-A(t) be the maximum width of two adjacent negative peaks. In this embodiment, considering the characteristic that the honeycomb structure includes honeycomb walls and honeycomb cells with different ultrasonic signals, and combining the position information, P corresponding to the honeycomb walls and honeycomb cells are obtained respectively. w and P l .

[0059] The third step is to obtain the alarm threshold:

[0060] Determine the defect alarm thresholds N1 and N2 according to equations (3) and (4):

[0061] N1=γ×P w (3)

[0062] N2=γ×P l (4)

[0063] Wherein, γ is an empirical constant. In this embodiment, γ is taken as 3, that is, the separation of three consecutive honeycomb cells from the skin is used as the standard for evaluating debonding defects.

[0064] Step 4, Defect Identification:

[0065] The two-dimensional phased array sensor 100 is placed on the surface of the first test area of ​​the honeycomb sandwich structure to be tested. The process in the first step is performed to acquire ultrasonic signal features. The signal processing and display unit 300 obtains Np and Nm according to P(x,y)-A(t). Np is the width of two adjacent positive peaks in the P(x,y)-A(t) image, and Nm is the width of two adjacent negative peaks in the P(x,y)-A(t) image. When Np>N1 and Nm>N2, it is determined that there is a defect in the corresponding area, and the defect location is determined by combining the spatial location information. Otherwise, it is determined that there is no defect. The defective area is distinguished from the non-defective area with different colors and displayed by the signal processing and display unit 300.

[0066] Fifth, place the two-dimensional phased array sensor 100 on the surface of the next test area of ​​the U-shaped honeycomb structure, repeat the fourth step, and determine whether there are defects in the next test area.

[0067] Application results show that the two-dimensional phased array sensor 100 can perform real-time imaging when placed in any area of ​​the U-shaped honeycomb structure, provided that good acoustic coupling is ensured. When three or more adjacent honeycomb cores in the U-shaped honeycomb structure debond, it can be identified very accurately and intuitively.

[0068] The above description is only a partial embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A defect detection system for honeycomb sandwich structures based on a two-dimensional phased array sensor, characterized in that, The system includes a two-dimensional phased array sensor (100) for transmitting and receiving ultrasonic signals, which is composed of M×N array elements that can be independently triggered to generate wave sources. The phased array ultrasonic unit (200) sequentially excites some array elements in the two-dimensional phased array sensor (100) to synthesize several electronic scanning sound beams with sequence information. The signal processing and display unit (300) is used to acquire and display ultrasonic signals and determine whether there are defects based on sequence information and ultrasonic signals.

2. The honeycomb sandwich structure defect detection system based on a two-dimensional phased array sensor according to claim 1, characterized in that, The number of array elements of the two-dimensional phased array sensor (100) is selected according to the surface curvature of the honeycomb sandwich structure being detected and the size of the opening at the location.

3. The honeycomb sandwich structure defect detection system based on a two-dimensional phased array sensor according to claim 1, characterized in that, The phased array ultrasonic unit (200) sets the size of the subarray according to the detection requirements. The subarray is a two-dimensional array composed of m×n array elements in the two-dimensional phased array sensor (100) and is used to synthesize electronic scanning sound beams. The phased array ultrasonic unit (200) excites the subarrays in sequence with an unchanged phase according to a certain time delay law to synthesize several electronic scanning sound beams that conform to a certain law. The sequence information of each electronic scanning sound beam corresponds to the spatial position information.

4. The honeycomb sandwich structure defect detection system based on a two-dimensional phased array sensor according to claim 1, characterized in that, The phased array ultrasonic unit (200) has an effective digitization frequency of not less than 100MHz and a sampling frequency of not less than 200MHz.

5. The honeycomb sandwich structure defect detection system based on a two-dimensional phased array sensor according to claim 1, characterized in that, The signal processing and display unit (300) is used to acquire the ultrasonic signal u(t) and its amplitude signal A(t) of each electronic scanning acoustic beam, and to reverse-engineer the spatial position information P(x,y) by combining the sequence information of the electronic scanning acoustic beam. The unit displays the position information P(x,y) and the amplitude A(t) of the ultrasonic signal u(t), i.e., P(x,y)-A(t), to determine whether there are defects in the detected honeycomb sandwich structure, and finally to form an image of the detected honeycomb sandwich structure for display.

6. The honeycomb sandwich structure defect detection system based on a two-dimensional phased array sensor according to claim 5, characterized in that, The signal processing and display unit (300) distinguishes defect locations in the image by color.

7. A honeycomb sandwich structure defect detection system based on a two-dimensional phased array sensor according to claim 1, characterized in that, The signal processing and display unit (300) has a frame rate of 50 frames per second.

8. A method for detecting defects in a honeycomb sandwich structure based on a two-dimensional phased array sensor, implemented using the defect detection system described in any one of claims 1-7, characterized in that, Includes the following steps: The first step is to obtain the location information P(x,y) and the amplitude signal A(t) of the ultrasonic signal u(t): 1.1 Connect the detection system and place the two-dimensional phased array sensor (100) on the surface of the position to be measured, ensuring good acoustic coupling; set the parameters through the phased array ultrasonic unit (200) to control the array elements in the two-dimensional phased array sensor (100) to synthesize K electronic scanning sound beams, and denote the sequence information of each electronic scanning sound beam as S. k (x * ,y * ), k = 1, 2, ..., K; 1.2 Adjust the gain so that its amplitude A(t) is not less than 40% of the display screen in the signal processing and display unit (300), and adjust the electronic gate so that the ultrasonic signal u(t) is within the set gate; 1.3 K electron scanning acoustic beams are sequentially excited until all elements in the two-dimensional phased array sensor (100) are traversed. The signal processing and display unit (300) acquires the ultrasonic signal characteristics and records and stores the corresponding sequence information S. k (x * ,y * ) and its corresponding ultrasound signal u k The amplitude signal A of (t) k (t): Among them, S k (x * ,y * )-A k (t) represents the sequence information S of the ultrasound signal from the k-th electronic scanning beam. k (x * ,y * ) and amplitude information A k (t) Correspondence; Based on the delay algorithm, the spatial location information P of the area to be tested is obtained by back-calculating the sequence information of the electronic scanning acoustic beam. k (x,y), and then, combined with equation (1), the P(x,y)-A(t) image of the region to be measured is obtained; The second step is to characterize the defect-free structure using ultrasonic signals: A defect-free test piece identical to the honeycomb sandwich structure being tested was fabricated. A two-dimensional phased array sensor (100) was placed on the test piece, and the ultrasonic signal feature acquisition process in the first step was performed to obtain the P of the defect-free structure. w and P l , where P w P is the maximum width of two adjacent positive peaks of P(x,y)-A(t); l The maximum width of two adjacent negative peaks of P(x,y)-A(t); The third step is to obtain the alarm threshold: Determine the defect alarm thresholds N1 and N2 according to equations (3) and (4): N1=γ×P w (3) N2=γ×P l (4) Where γ is an empirical constant; Step 4, Defect Identification: A two-dimensional phased array sensor (100) is placed on the surface of the test area of ​​the honeycomb sandwich structure to be tested. The process in the first step is performed to acquire ultrasonic signal features. The signal processing and display unit (300) obtains Np and Nm according to P(x,y)-A(t). Np is the width of two adjacent positive peaks in the P(x,y)-A(t) image, and Nm is the width of two adjacent negative peaks in the P(x,y)-A(t) image. When Np>N1 and Nm>N2, it is determined that there is a defect in the corresponding area, and the defect location is determined by combining the spatial location information. Otherwise, it is determined to be defect-free. The defective area is distinguished from the defect-free area by different colors and displayed by the signal processing and display unit 300.

9. The method for detecting defects in a honeycomb sandwich structure based on a two-dimensional phased array sensor according to claim 8, characterized in that, In section 1.3, the formula for back-calculating the spatial location information of the test area based on the sequence information of the electronic scanning acoustic beam using a time-delay algorithm is as follows: P k (x,y)=αS k (x*,y*) (2) Where α is the inverse coefficient.

10. The method for detecting defects in a honeycomb sandwich structure based on a two-dimensional phased array sensor according to claim 8, characterized in that, For a large-area honeycomb sandwich structure, a two-dimensional phased array sensor (100) is placed on the surface of the next test area of ​​the honeycomb sandwich structure being tested, and the fourth step is repeated to determine whether there is a defect in the next test area.

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