Phased array ultrasonic interface debonding detection method for multilayer curved surface bonding structure

Abstract

The invention provides a phased array ultrasonic interface debonding detection method for a multilayer curved surface bonding structure, which comprises the following steps of: accurately calculating delay time of each array element in a phased array ultrasonic probe to a target focus by designing a delay block attached to a solid engine and aiming at a cylindrical special structure; therefore, in-phase superposition of sound waves at the target focus is achieved, focusing of sound beams is achieved, the problem of delay time calculation of sound waves emitted by all array elements of a phased array probe of a cylindrical structure is solved, and the problem of control over the deflection angle and the focusing depth of the sound beams synthesized after the sound waves pass through a plurality of curved surface interfaces is solved. Accurate positioning and visual representation of the debonding defect of the deep interface are realized. The technology provides a new technical means for accurately judging the interface debonding defect, and has important significance for guaranteeing the structural integrity and the use safety of the interface debonding defect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of multi-layer structure damage detection, and particularly relates to a phased array ultrasonic interface debonding detection method for a multi-layer curved surface bonding structure. BACKGROUND

[0002] With the increasing demand for high-reliability composite structures in the fields of aerospace, energy and chemical industry, the interface damage detection of multi-layer curved surface structures (especially cylindrical laminated structures) has become an important topic in the field of industrial nondestructive testing. Taking a solid rocket engine as an example, the combustion chamber of the wall-adhered cast solid rocket engine adopts a multi-layer bonding structure: the outer layer is a metal or composite shell, the middle layer is an ethylene-propylene-diene rubber (EPDM) thermal insulation layer, and the inner layer is an HTPB propellant. When such multi-layer curved surface structures are in service under complex conditions for a long time, stress concentration is easily generated at the interface of each layer due to the difference in thermodynamic properties, leading to debonding, delamination and other damages. Deep interface defects often have the characteristics of strong concealment and rapid expansion, which seriously threaten the safety of the structure. Therefore, it is of great significance to accurately and reliably evaluate the bonding interface damage.

[0003] The current mainstream debonding detection technologies include X-ray, industrial CT and conventional ultrasonic detection. X-ray detection and industrial CT technology use high-energy rays to penetrate materials and form images through density differences, but they need to be equipped with a lead shielding room that meets the GBZ 117-2015 standard, and the equipment is bulky, which cannot meet the needs of on-site detection. Industrial CT technology reconstructs three-dimensional tomographic images through multi-angle projection, but a single scan takes more than 30 minutes, and the detection efficiency is low for full-size engines with a diameter greater than 1.5 m. In addition, the artifacts produced by carbon fiber shells can cause a gray scale deviation of more than 15%, which seriously affects the accuracy of defect interpretation. Conventional ultrasonic detection usually uses a single probe for detection. For the measured ultrasonic time domain signals, only manual experience can be relied on to determine whether debonding damage occurs, and it is difficult to perform visual detection.

[0004] The ultrasonic phased array technology can realize visual detection. The technology controls multiple array element chips in a probe to emit sound waves through a time delay method to form a synthetic sound beam with a specific deflection angle and a focusing depth, thereby simplifying the internal defect detection process of a complex structure. However, the current ultrasonic phased array is mainly used for detecting internal defects in a single medium, such as cracks, welds and the like. For debonding detection of a multilayer adhesive medium, the application of the ultrasonic phased array in deep interface detection is relatively less, and is mainly applied to flat plate test pieces, and less to curved surface multilayer structures such as cylinders. This is mainly due to the following technical bottlenecks: first, the cylinder structure causes the probe to be difficult to closely adhere to the surface, the coupling efficiency is low, the signal is seriously attenuated, and the detection accuracy is affected. Secondly, the acoustic impedance mismatch between the multilayer medium and the distortion effect of the curved surface structure will distort the sound wave propagation path, causing the focusing algorithm under the traditional plane assumption to fail, and the deep interface echo signal is difficult to accurately capture. Although the existing phased array method (literature: Zhou Zhenggan, Wang Jun, Li Yang, Wang Fei, Xi Qiang. New method of array ultrasonic detection and evaluation of multilayer adhesive structure [J]. Journal of Beijing University of Aeronautics and Astronautics, 2022, 32(06): 190-198) has made progress in debonding detection of a polyurethane-rubber-titanium alloy multilayer structure, but its sound beam path calculation method depends on three-dimensional geometric modeling, and a CAD three-dimensional geometric model of the multilayer structure needs to be constructed in advance. The calculation method is complex, the calculation time is long, the real-time performance is poor, and the like, which is difficult to meet the rapid detection demand of the engineering site. SUMMARY

[0005] In view of the problems existing in the prior art, the present application provides a phased array ultrasonic interface debonding detection method for a multilayer curved surface adhesive structure, which solves the problem of calculating the delay time of the sound waves emitted by each array element of the phased array probe for a cylindrical structure, and solves the problem of controlling the deflection angle and focusing depth of the synthetic sound beam after the sound waves pass through multiple curved surface interfaces.

[0006] The technical scheme of the present application is as follows:

[0007] The phased array ultrasonic interface debonding detection method for a multilayer curved surface adhesive structure comprises the following steps:

[0008] Step 1: measuring the geometric parameters of the solid rocket engine, determining the size of the delay block that fits the solid rocket engine, and installing the delay block on the phased array ultrasonic probe; the delay block has a planar end face and an arc surface structure, wherein the planar part is arranged on the phased array ultrasonic probe, and the arc surface part is fitted to the outer surface of the solid rocket engine shell;

[0009] Step 2: establishing a coordinate system and discretizing each layer of interface:

[0010] The phased array ultrasonic probe with delay block is attached to the position to be tested on the engine housing. A rectangular coordinate system is established with the center of the first array element of the probe as the origin. The array elements are linearly arranged along the y-axis and the x-axis is perpendicular to the plane of the delay block.

[0011] The three-layer interface is discretized to obtain a sequence of discrete coordinate points. in This is a discrete point sequence at the interface I between the delay block and the shell. This represents a discrete point sequence at the interface II between the shell and the insulation layer. This is a discrete point sequence at interface III between the insulation layer and the propellant.

[0012] Step 3: For each element of the phased array ultrasonic probe, the acoustic time required for the ultrasonic wave to propagate from the element to the target focal point is obtained through the following steps:

[0013] For the i-th element, the coordinates are (0, b) i ):

[0014] Step 3.1: Calculate the beam deflection angle θ of array element i. i The search interval [θ] i,start ,θ i,end ];

[0015] Step 3.2: In the search interval [θ] i,start ,θ i,end [Select initial deflection angle θ] i,1 Establish the propagation path equation of the sound beam emitted by array element i in the delay block; thus, calculate the intersection point of the sound beam and interface I.

[0016] Step 3.3: Based on the intersection of the sound beam and interface I Establish the propagation path equation of the sound beam emitted by array element i in the shell;

[0017] Step 3.4: Calculate the intersection point of the sound beam and interface II based on the propagation path equation of the sound beam emitted by array element i in the shell.

[0018] Step 3.5: Based on the intersection of the sound beam and interface II Establish the propagation path equation of the sound beam emitted by array element i in the insulation layer;

[0019] Step 3.6: Calculate the intersection point of the sound beam and interface III based on the propagation path equation of the sound beam emitted by array element i in the insulation layer.

[0020] Step 3.7: Construct the objective function in The y-axis coordinates of the intersection point between the sound beam and interface III, calculated from the sound beam deflection angle θ, are given for the target focus. Located on interface III, its coordinates are In the interval [θ i,start ,θ i,end Solving for f(θ) = 0 within the array element, we obtain the beam deflection angle of the sound beam emitted by array element i that can pass through the target focus.

[0021] Step 3.8: Based on the beam deflection angle obtained in Step 3.7 The array element i was calculated according to the beam deflection angle. The intersection point P of the emitted sound beam and interfaces I, II, and III I (x i,I ,y i,I ), P II (x i,II ,y i,II ), P III (x i,III ,y i,III ), and the deflection angle in the shell and insulation layer. Then, the acoustic time t required for the ultrasonic wave to propagate from array element i to the target focus is calculated. i ;

[0022] Step 4: Calculate the maximum acoustic time max(t) required for the ultrasonic wave to propagate from each array element to the target focus, as obtained in Step 3; based on t i,delay =max(t)-t i The delay time t of array element i with respect to the target focus was calculated. i,delay ;

[0023] Step 5: Using the resonant frequency of the solid rocket motor insulation layer as the excitation signal frequency, control each element of the ultrasonic phased array probe to excite ultrasonic waves according to the corresponding delay time, so that the sound waves are superimposed in phase at the target focus, and the sound beam is focused; the echo signals received by each element are superimposed, and the damage index of the target focus is calculated.

[0024] Step 6: Update the target focus coordinates, and repeat steps 3 to 5 to obtain damage indices at multiple target focuses.

[0025] Step 7: Move the ultrasonic phased array probe and repeat steps 3 to 6 to obtain damage indicators at different detection locations.

[0026] Furthermore, in step 3.1, the beam deflection angle θ of array element i i The search interval [θ] i,start ,θ i,end ]for:

[0027]

[0028] The beam deflection angle is the angle between the beam and the central axis of the array element. and These are the coordinates of the first and last points of the discrete point sequence of interface I.

[0029] Furthermore, in step 3.2, the intersection point of the sound beam and interface I is calculated. The specific process is as follows:

[0030] Establish the propagation path equation y = tanθ of the sound beam emitted by array element i in the delay block. i,1 x+b i ; Traverse the sequence of discrete points on interface I, for each discrete point Calculate the distance between discrete points and the sound beam. Find two objects that are closest to the sound beam and simultaneously satisfy... Nearby point and

[0031] like Then take Otherwise, solve the system of equations.

[0032]

[0033] Obtain the intersection point of the sound beam and interface I.

[0034] Furthermore, in step 3.3, based on the intersection of the sound beam and interface I... The propagation path equation of the sound beam emitted by the i-th element in the shell is established as follows: Where θ i,2 The angle of the sound beam after passing through interface I is given by the formula. in Let be the angle of the interface tangent at the intersection of the sound beam and interface I, according to the formula Calculations show that Let be the refraction angle at the intersection of the sound beam and interface I, according to the formula Calculations show that Let be the incident angle at the intersection of the sound beam and interface I, according to the formula Calculated.

[0035] Furthermore, in step 3.4, the intersection point of the sound beam and interface II is calculated. The specific process is as follows: traverse the discrete point sequence of interface II, and for each discrete point... By calculating the distance between discrete points and the sound beam Find two objects that are closest to the sound beam and simultaneously satisfy... Nearby point and

[0036] like Then take Otherwise, solve the system of equations.

[0037]

[0038] Obtain the intersection point of the sound beam and interface II.

[0039] Furthermore, in step 3.5, based on the intersection of the sound beam and interface II... The propagation path equation of the sound beam emitted by the i-th element in the adiabatic layer is established as follows: Where θ i,3 The angle of the sound beam after passing through interface II is given by the formula. in The angle of the interface tangent at the intersection of the sound beam and interface II is given by the formula. Calculations show that The angle of refraction at the intersection of the sound beam and interface II is given by the formula. Calculations show that Let be the incident angle at the intersection of the sound beam and interface II, according to the formula Calculated.

[0040] Furthermore, in step 3.6, the intersection point of the sound beam and interface III is calculated. The specific process is as follows: traverse the discrete point sequence of interface III, and for each discrete point... By calculating the distance between discrete points and the sound beam Find two objects that are closest to the sound beam and simultaneously satisfy... Nearby point and

[0041] like Then take Otherwise, solve the system of equations.

[0042]

[0043] Obtain the intersection point of the sound beam and interface III.

[0044] Furthermore, in step 3.7, the Brent algorithm is used in the interval [θ] i,start ,θ i,end Solving for f(θ) = 0 within the array element, we obtain the beam deflection angle of the sound beam emitted by array element i that can pass through the target focus.

[0045] Furthermore, in step 3.8, according to the formula

[0046]

[0047] The acoustic time t required for the ultrasonic wave to propagate from array element i to the target focal point is calculated. i .

[0048] Furthermore, in step 5, the damage index of the target focus is... Where S i Let N be the echo data sequence received by array element i, and N be the number of array elements.

[0049] Beneficial effects

[0050] This invention innovatively proposes a method for detecting interface debonding in cylindrical multilayer adhesive structures based on phased array ultrasonic technology. This method, tailored to the special cylindrical structure, enables high-precision imaging of the adhesive interface between different media, achieving accurate localization and visual characterization of deep interface debonding defects. This technology provides a new technical means for accurately determining interface debonding defects, and is of great significance for ensuring the structural integrity and safety of the structure.

[0051] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0052] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0053] Figure 1 Schematic diagram of the propagation of the sound beam emitted by the array element in the solid rocket motor;

[0054] Figure 2 : Schematic diagram of sound beam refraction at the interface;

[0055] Figure 3 Multi-layer surface delay algorithm flow;

[0056] Figure 4 Schematic diagram of ultrasonic array focusing in a solid rocket motor;

[0057] Figure 5 Simulated solid rocket motor test specimen;

[0058] Figure 6 : Deadlock detection results of simulated engine; (a) Imaging results, (b) Thresholding results. Detailed Implementation

[0059] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0060] In this embodiment, a 16-element probe is used. A simulated solid rocket motor specimen with an outer diameter of 180mm and a carbon fiber wound composite shell, containing a shell and insulation layer, is used as the test object. A phased array ultrasonic interface debonding detection method for cylindrical multilayer bonded structures is proposed. The solid rocket motor interface debonding detection is performed on the test object, specifically including the following steps:

[0061] Step 1: Deploy the detection system:

[0062] The geometric parameters of the solid rocket motor were measured to determine the size of the delay block that fits the curved surface of the solid rocket motor, and the delay block was then mounted onto the phased array ultrasonic probe.

[0063] The geometric parameters of the solid rocket motor include: the shell thickness d2 and radius r2, and the insulation layer thickness d3 and radius r3.

[0064] The delay block has a flat surface on one end and an arc surface on the other end. The flat part is arranged on the phased array ultrasonic probe, and the arc surface is attached to the outer surface of the housing. The center thickness of the delay block is d1.

[0065] The sound velocities of the delay block, shell, and insulation layer materials are c1, c2, and c3, respectively.

[0066] The interfaces between the delay block, the shell, the insulation layer, and the propellant are defined as follows: the interface between the delay block and the shell is interface I, the interface between the shell and the insulation layer is interface II, and the interface between the insulation layer and the propellant is interface III.

[0067] Step 2: Establish a coordinate system and discretize each interface layer:

[0068] The phased array ultrasonic probe with a delay block is attached to the position to be tested on the engine housing. A rectangular coordinate system is established with the center of the first array element of the probe as the origin. The array elements are linearly arranged along the y-axis and the x-axis is perpendicular to the plane of the delay block.

[0069] The three-layer interface is discretized to obtain a high-density discrete coordinate point sequence. in Let I be the discrete point sequence of interface I. For the discrete point sequence of interface II, This is the discrete point sequence of interface III.

[0070] Step 3: For each element of the phased array ultrasonic probe, the acoustic time required for the ultrasonic wave to propagate from the element to the target focal point is obtained through the following steps:

[0071] For the i-th array element:

[0072] Step 3.1: Calculate the beam deflection angle θ of array element i. i The search interval [θ] i,start ,θ i,end ]:

[0073]

[0074] The beam deflection angle is the angle between the beam and the central axis of the array element, and the coordinates of array element i are (0, b). i ), and These are the coordinates of the first and last points of the discrete point sequence of interface I.

[0075] Step 3.2: Calculate the intersection point of the sound beam and interface I.

[0076] In the search interval [θ i,start ,θ i,end [Select initial deflection angle θ] i,1 The propagation path equation of the sound beam emitted by the i-th element in the delay block is y = tanθ. i,1 x+b i ;

[0077] Traverse the sequence of discrete points of interface I, for each discrete point By calculating the distance between discrete points and the sound beam Find two objects that are closest to the sound beam and simultaneously satisfy... Nearby point and

[0078] like Then take Otherwise, solve the system of equations.

[0079]

[0080] Obtain the intersection point of the sound beam and interface I.

[0081] Step 3.3: Based on the intersection of the sound beam and interface I The propagation path equation of the sound beam emitted by the i-th element in the shell is established as follows: Where θ i,2 The angle of the sound beam after passing through interface I is given by the formula. in Let be the angle of the interface tangent at the intersection of the sound beam and interface I, according to the formula Calculations show that Let be the refraction angle at the intersection of the sound beam and interface I, according to the formula Calculations show that Let be the incident angle at the intersection of the sound beam and interface I, according to the formula Calculated.

[0082] Step 3.4: Calculate the intersection of the sound beam and interface II.

[0083] Traverse the discrete point sequence of interface II, for each discrete point By calculating the distance between discrete points and the sound beam Find two objects that are closest to the sound beam and simultaneously satisfy... Nearby point and

[0084] like Then take Otherwise, solve the system of equations.

[0085]

[0086] Obtain the intersection point of the sound beam and interface II.

[0087] Step 3.5: Based on the intersection of the sound beam and interface II The propagation path equation of the sound beam emitted by the i-th element in the adiabatic layer is established as follows: Where θ i,3 The angle of the sound beam after passing through interface II is given by the formula. in The angle of the interface tangent at the intersection of the sound beam and interface II is given by the formula. Calculations show that The angle of refraction at the intersection of the sound beam and interface II is given by the formula. Calculations show that Let be the incident angle at the intersection of the sound beam and interface II, according to the formula Calculated.

[0088] Step 3.6: Calculate the intersection of the sound beam and interface III.

[0089] Traverse the discrete point sequence of interface III, for each discrete point By calculating the distance between discrete points and the sound beam Find two objects that are closest to the sound beam and simultaneously satisfy... Nearby point and

[0090] like Then take Otherwise, solve the system of equations.

[0091]

[0092] Obtain the intersection point of the sound beam and interface III.

[0093] Step 3.7: Construct the objective function in The y-axis coordinates of the intersection point between the sound beam and interface III, calculated from the sound beam deflection angle θ, are given for the target focus. Located on interface III, its coordinates are Using Brent's algorithm in the interval [θ i,start ,θ i,end Solving for f(θ) = 0 within the array element, we obtain the beam deflection angle of the sound beam emitted by array element i that can pass through the target focus.

[0094] Step 3.8: Based on the beam deflection angle obtained in Step 3.7 The array element i was calculated according to the beam deflection angle. The intersection point P of the emitted sound beam and interfaces I, II, and III I (x i,I ,y i,I ), P II (x i,II ,y i,II ), P III (x i,III ,y i,III ), and the deflection angle in the shell and insulation layer. Then according to the formula

[0095]

[0096] The acoustic time t required for the ultrasonic wave to propagate from array element i to the target focal point is calculated. i .

[0097] Step 4: Calculate the maximum acoustic time max(t) required for the ultrasonic wave to propagate from each array element to the target focus, as obtained in Step 3; based on t i,delay =max(t)-t i The delay time t of array element i with respect to the target focus was calculated. i,delay .

[0098] Step 5: Using the resonant frequency of the solid rocket motor insulation layer as the excitation signal frequency, control each element of the ultrasonic phased array probe to excite ultrasonic waves according to the corresponding delay time, so that the sound waves are superimposed in phase at the target focal point, thereby achieving the focusing of the sound beam.

[0099] The echo signals received by each array element are superimposed, and the damage index of the target focus is calculated. Where S i Let N be the echo data sequence received by array element i, and N be the number of array elements.

[0100] Step 6: Update the target focus coordinates, and repeat steps 3 to 5 to obtain damage indices at multiple target focuses.

[0101] Step 7: Move the ultrasonic phased array probe and repeat steps 3 to 6 to obtain damage indicators at different detection locations.

[0102] Finally, a damage imaging map of the interface is drawn based on the damage index values ​​of each focal point at each location of the insulation layer / propellant interface.

[0103] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A phased array ultrasonic interface debonding detection method for multilayer curved surface bonded structures, characterized in that: Includes the following steps: Step 1: Measure the geometric parameters of the solid rocket motor, determine the size of the delay block that fits the solid rocket motor, and install the delay block onto the phased array ultrasonic probe; the delay block has a flat end face and an arc surface structure, wherein the flat part is arranged on the phased array ultrasonic probe, and the arc surface part is attached to the outer surface of the solid rocket motor housing. Step 2: Establish a coordinate system and discretize each interface layer: The phased array ultrasonic probe with delay block is attached to the position to be tested on the engine housing. A rectangular coordinate system is established with the center of the first array element of the probe as the origin. The array elements are linearly arranged along the y-axis and the x-axis is perpendicular to the plane of the delay block. The three-layer interface is discretized to obtain a sequence of discrete coordinate points. in This is a discrete point sequence at the interface I between the delay block and the shell. This represents a discrete point sequence at the interface II between the shell and the insulation layer. This is a discrete point sequence at interface III between the insulation layer and the propellant. Step 3: For each element of the phased array ultrasonic probe, the acoustic time required for the ultrasonic wave to propagate from the element to the target focal point is obtained through the following steps: For the i-th array element, the coordinates are (0, b) i ): Step 3.1: Calculate the beam deflection angle θ of array element i. i The search interval [θ] i,start ,θ i,end ]; Step 3.2: In the search interval [θ] i,start ,θ i,end [Select initial deflection angle θ] i,1 Establish the propagation path equation of the sound beam emitted by array element i in the delay block; thus, calculate the intersection point of the sound beam and interface I. Step 3.3: Based on the intersection of the sound beam and interface I Establish the propagation path equation of the sound beam emitted by array element i in the shell; Step 3.4: Calculate the intersection point of the sound beam and interface II based on the propagation path equation of the sound beam emitted by array element i in the shell. Step 3.5: Based on the intersection of the sound beam and interface II Establish the propagation path equation of the sound beam emitted by array element i in the adiabatic layer; Step 3.6: Calculate the intersection point of the sound beam and interface III based on the propagation path equation of the sound beam emitted by array element i in the insulation layer. Step 3.7: Construct the objective function in The y-axis coordinates of the intersection point between the sound beam and interface III, calculated from the sound beam deflection angle θ, are given for the target focus. Located on interface III, its coordinates are In the interval [θ i,start ,θ i,end Solving for f(θ) = 0 within the array element, we obtain the beam deflection angle of the sound beam emitted by array element i that can pass through the target focus. Step 3.8: Based on the beam deflection angle obtained in Step 3.7 The array element i was calculated according to the beam deflection angle. The intersection point P of the emitted sound beam and interfaces I, II, and III I (x i,I ,y i,I ), P II (x i,II ,y i,II ), P III (x i,III ,y i,III ), and the deflection angle in the shell and insulation layer. Then, the acoustic time t required for the ultrasonic wave to propagate from array element i to the target focus is calculated. i ; Step 4: Calculate the maximum acoustic time max(t) required for the ultrasonic wave to propagate from each array element to the target focus, as obtained in Step 3; based on t i,delay =max(t)-t i The delay time t of array element i with respect to the target focus was calculated. i,delay ; Step 5: Using the resonant frequency of the solid rocket motor insulation layer as the excitation signal frequency, control each element of the ultrasonic phased array probe to excite ultrasonic waves according to the corresponding delay time, so that the sound waves are superimposed in phase at the target focus, and the sound beam is focused; the echo signals received by each element are superimposed, and the damage index of the target focus is calculated. Step 6: Update the target focus coordinates, and repeat steps 3 to 5 to obtain damage indices at multiple target focuses. Step 7: Move the ultrasonic phased array probe and repeat steps 3 to 6 to obtain damage indicators at different detection locations.

2. The phased array ultrasonic interface debonding detection method for multilayer curved surface bonded structures according to claim 1, characterized in that: In step 3.1, the beam deflection angle θ of array element i i The search interval [θ] i,start ,θ i,end ]for: The beam deflection angle is the angle between the beam and the central axis of the array element. and These are the coordinates of the first and last points of the discrete point sequence of interface I.

3. The phased array ultrasonic interface debonding detection method for multilayer curved surface bonded structures according to claim 1, characterized in that: In step 3.2, the intersection point of the sound beam and interface I is calculated. The specific process is as follows: Establish the propagation path equation y = tanθ of the sound beam emitted by array element i in the delay block. i,1 x+b i ; Traverse the discrete point sequence of interface I, for each discrete point (x Ik ,y Ik ), calculate the distance between discrete points and the sound beam. Find two objects that are closest to the sound beam and simultaneously satisfy... Nearby point and like Then take Otherwise, solve the system of equations. Obtain the intersection point of the sound beam and interface I.

4. The phased array ultrasonic interface debonding detection method for multilayer curved surface bonded structures according to claim 1, characterized in that: In step 3.3, based on the intersection of the sound beam and interface I... The propagation path equation of the sound beam emitted by the i-th element in the shell is established as follows: Where θ i,2 The angle of the sound beam after passing through interface I is given by the formula. in Let be the angle of the interface tangent at the intersection of the sound beam and interface I, according to the formula Calculations show that Let be the refraction angle at the intersection of the sound beam and interface I, according to the formula Calculations show that Let be the incident angle at the intersection of the sound beam and interface I, according to the formula Calculated.

5. The phased array ultrasonic interface debonding detection method for multilayer curved surface bonded structures according to claim 4, characterized in that: In step 3.4, the intersection point of the sound beam and interface II is calculated. The specific process is as follows: traverse the discrete point sequence of interface II, and for each discrete point... By calculating the distance between discrete points and the sound beam Find two objects that are closest to the sound beam and simultaneously satisfy... Nearby point and like Then take Otherwise, solve the system of equations. Obtain the intersection point of the sound beam and interface II.

6. The phased array ultrasonic interface debonding detection method for multilayer curved surface bonded structures according to claim 1, characterized in that: In step 3.5, based on the intersection of the sound beam and interface II... The propagation path equation of the sound beam emitted by the i-th element in the adiabatic layer is established as follows: Where θ i,3 The angle of the sound beam after passing through interface II is given by the formula. in The angle of the interface tangent at the intersection of the sound beam and interface II is given by the formula. Calculations show that The angle of refraction at the intersection of the sound beam and interface II is given by the formula. Calculations show that Let be the incident angle at the intersection of the sound beam and interface II, according to the formula Calculated.

7. The phased array ultrasonic interface debonding detection method for multilayer curved surface bonded structures according to claim 6, characterized in that: In step 3.6, the intersection point of the sound beam and interface III is calculated. The specific process is as follows: traverse the discrete point sequence of interface III, and for each discrete point... By calculating the distance between discrete points and the sound beam Find two objects that are closest to the sound beam and simultaneously satisfy... Nearby point and like Then take Otherwise, solve the system of equations. Obtain the intersection of the sound beam and interface III.

8. The phased array ultrasonic interface debonding detection method for multilayer curved surface bonded structures according to claim 1, characterized in that: In step 3.7, the Brent algorithm is used in the interval [θ] i,start ,θ i,end Solving for f(θ) = 0 within the array element, we obtain the beam deflection angle of the sound beam emitted by array element i that can pass through the target focus.

9. The phased array ultrasonic interface debonding detection method for multilayer curved surface bonded structures according to claim 1, characterized in that: In step 3.8, according to the formula The acoustic time t required for the ultrasonic wave to propagate from array element i to the target focal point is calculated. i .

10. The phased array ultrasonic interface debonding detection method for multilayer curved surface bonded structures according to claim 1, characterized in that: In step 5, the damage index of the target focus is: Where S i Let N be the echo data sequence received by array element i, and N be the number of array elements.

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