Ultrasonic guided wave damage ellipse imaging positioning method and equipment for layering decreasing composite material laminated plate

Abstract

The invention discloses an ultrasonic guided wave damage ellipse imaging positioning method and equipment for a layer decreasing composite material laminated plate. The method comprises the following steps: S1, acquiring thickness change direction information of the laminated plate and position coordinates of an excitation transducer and a receiving transducer; s2, according to the material characteristic parameters, simulating and calculating the propagation time of ultrasonic guided waves transmitted from an excitation transducer to any point to generate a first theoretical propagation time map, and simulating and calculating the propagation time of the ultrasonic guided waves transmitted from any point to a receiving transducer to generate a second theoretical propagation time map to generate a second theoretical propagation time map; coupling influence of thickness change and material anisotropy on guided wave propagation is considered in the simulation process; s3, transmitting an ultrasonic guided wave signal, and extracting the actual flight time of a damaged wave packet; s4, calculating theoretical total propagation time, and determining a candidate area where damage exists; and S5, on the basis of repeated operation of the multiple groups of transducer pairs, taking a plurality of candidate region intersections to determine a final damage position. The objective of the invention is to solve the positioning error problem caused by the structural characteristics of a laminated plate in a traditional algorithm, and to realize more accurate damage detection and positioning.

Description

Technical Field

[0001] This invention relates to the field of damage detection, specifically to an ultrasonic guided wave damage elliptic imaging localization method and device for ply reduction composite laminates. Background Technology

[0002] Composite materials, with their high specific strength, specific stiffness, good wear and corrosion resistance, and strong design flexibility, are widely used in aerospace, wind power, and other industrial fields. However, uniform thickness composite structures have certain limitations in weight reduction, optimizing stiffness distribution, and achieving lightweighting. Therefore, composite components with continuous thickness variations are often used in practical engineering. For example, key components such as aircraft wing skin, center wing box, fuselage tail, engine nacelles and air intakes, satellite supports, and wind turbine blades are usually variable thickness carbon fiber reinforced polymer (CFRP) components. Since composite laminates are usually made by curing multiple layers of fiber composite materials with a resin matrix in a certain layup sequence, variable thickness designs are typically achieved in industry using reduction layup manufacturing technology. Reduction layup composite laminates refer to composite laminates in which the layup of certain layers is terminated in a planned, stepwise manner, thereby achieving a gradual and continuous change in component thickness. The gradual and continuous reduction in layer thickness avoids stress concentration caused by abrupt changes in thickness, while also ensuring that the smooth external shape of the component is not affected while realizing changes in the internal structure of the laminate, thus meeting the aerodynamic shape requirements of components such as wings and blades.

[0003] However, during the layup process of decreasing layup composite laminates, localized resin aggregation is prone to occur, leading to reduced carbon fiber volume dispersion in these areas. Furthermore, the curing shrinkage rate of the resin during composite curing is much higher than that of the carbon fiber, causing lateral expansion or longitudinal depression in these areas, resulting in increased or decreased thickness and defects in the resin-rich region. In addition, the inclusion of foreign matter, such as release paper fragments or residual release film, between the fiber composite layers during manufacturing will further increase the thickness in these areas. Moreover, decreasing layup composite laminates inevitably suffer structural damage during service, ultimately leading to overall component performance degradation and failure, and potentially causing safety accidents. Therefore, effective damage and health monitoring of decreasing layup composite laminates is crucial for ensuring the safe operation of equipment.

[0004] Ultrasonic guided wave testing technology is widely used for non-destructive testing of composite material structures due to its high detection efficiency and damage sensitivity. Elliptic imaging is a classic, effective, and widely applied damage imaging method: the ultrasonic guided wave is excited by an excitation transducer, propagates through the laminate, and is reflected at the damage location. The reflected wave is ultimately received by a receiving transducer. By analyzing the damage echo signal of the ultrasonic guided wave in the received signal, the flight time of the guided wave during this process can be obtained. Based on the known flight time, the damage location can be determined to lie on an ellipse with the excitation and receiving transducers as foci. By arranging multiple pairs of excitation and receiving transducers, focusing can be achieved on the damage location. However, in decreasing layup composite laminates, the thickness variation of the laminate structure caused by decreasing layup manufacturing, as well as the anisotropic properties of the composite material, will jointly affect the propagation behavior of ultrasonic guided waves. Ultrasonic guided waves in this type of plate exhibit velocity anisotropy, tilting effect, and plate thickness variation modulating wave velocity changes, which leads to significant positioning errors and low damage detection accuracy in traditional elliptic positioning algorithms. Therefore, they cannot be applied to ultrasonic guided wave damage detection and damage localization in decreasing layup composite laminates. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides an elliptical imaging method and device for ultrasonic guided wave damage localization of decreasing layup composite laminates. The purpose is to solve the problem that traditional elliptical localization algorithms suffer from positioning errors and low damage detection accuracy in decreasing layup composite laminates due to variations in laminate thickness and the anisotropic properties of the material affecting ultrasonic guided wave propagation behavior. This makes them unsuitable for ultrasonic guided wave damage detection and localization of such laminates, thus achieving more accurate damage detection and localization for decreasing layup composite laminates.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution: According to a first aspect of the present invention, a method for elliptic imaging localization of ultrasonic guided wave damage in a ply reduction composite laminate is provided, comprising: S1. Obtain the thickness change direction information of the detected reduction layup composite laminate, as well as the position coordinates of at least one set of excitation transducers and receiving transducers arranged on the laminate. S2. Based on the pre-acquired material property parameters of the laminate, simulate and calculate the propagation time of ultrasonic guided waves emitted from the excitation transducer in different directions to any point in the laminate, generating a first theoretical propagation time spectrum; and simulate and calculate the propagation time from any point in the laminate to the receiving transducer, generating a second theoretical propagation time spectrum. The simulation process considers the coupling effect of the thickness variation and material anisotropy of the laminate on the propagation path and propagation speed of the guided waves. S3. An ultrasonic guided wave signal is emitted into the laminate through the excitation transducer, and the guided wave signal after damage modulation is received by the receiving transducer. The actual flight time of the damage wave packet caused by the damage is extracted from the received guided wave signal. S4. Based on the first theoretical propagation time spectrum and the second theoretical propagation time spectrum, calculate the theoretical total propagation time of the ultrasonic guided wave from the excitation transducer to the receiving transducer after being reflected by any point in the laminate, and determine the set of spatial points where the theoretical total propagation time is equal to the actual flight time as the candidate region for the corresponding damage of the transducer pair. S5. Based on multiple sets of excitation-receiver transducer pairs arranged at different positions on the laminate, repeat S2 to S4 to obtain multiple candidate regions for the existence of the damage, and determine the intersection of the multiple candidate regions as the final location of the damage.

[0007] In one possible implementation of the first aspect, the simulation and calculation of the propagation time of ultrasonic guided waves emitted from the excitation transducer in different directions to any point in the laminate specifically includes: Traverse all possible launch directions with a preset angle step size; For each emission direction, the bending propagation path of the ultrasonic guided wave in that emission direction is determined based on the thickness variation of the laminate and the anisotropic properties of the material. Integrating the local propagation velocity along the curved propagation path in the emission direction yields the propagation time at each point along the curved propagation path in the emission direction.

[0008] In one possible implementation of the first aspect, determining the bending propagation path of the ultrasonic guided wave in the emission direction based on the thickness variation and anisotropic properties of the laminate specifically includes: The laminate is discretized into multiple continuous equal-thickness segments along its own thickness variation direction; Within each of the equal thickness sections, the local propagation direction and local propagation speed of the ultrasonic guided wave when it passes through the section are determined based on the thickness and material anisotropy parameters of the section. The local propagation paths within each of the equal thickness sections are connected sequentially to form a complete curved propagation path.

[0009] In one possible implementation of the first aspect, when traversing all possible emission directions with a preset angular step size, the size of the angular step size is set to ensure that at least one simulated waveguide propagation path passes through any point in the laminate.

[0010] In one possible implementation of the first aspect, extracting the actual flight time of the damage wave packet caused by the damage from the received guided wave signal includes: Pre-acquire reference signals in a non-destructive state; Acquire comparison signals while in detection mode; The comparison signal and the reference signal are differentially processed to obtain a damage signal containing damage information; The damage wave packet and the corresponding actual flight time are identified and extracted from the damage signal.

[0011] In one possible implementation of the first aspect, the total theoretical propagation time is equal to the sum of a first theoretical propagation time from the excitation transducer to any point in the laminate and a second theoretical propagation time from that point to the receiving transducer.

[0012] In one possible implementation of the first aspect, the material property parameters include at least: the phase velocity and group velocity of the laminate at different thickness locations and in different waveguide propagation directions, and the tilt angle of the group velocity propagation direction relative to the phase velocity propagation direction.

[0013] According to a second aspect of the present invention, a computer device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the aforementioned ultrasonic guided wave damage elliptic imaging localization method for a ply reduction composite laminate.

[0014] According to a third aspect of the present invention, a computer-readable storage medium is provided, the computer-readable storage medium storing a computer program, which, when executed by a processor, implements the aforementioned method for ultrasonic guided wave damage elliptic imaging localization of a ply reduction composite laminate.

[0015] According to a fourth aspect of the present invention, a computer program product is provided, which, when executed by a processor, implements the aforementioned ultrasonic guided wave damage elliptic imaging localization method for a ply reduction composite laminate.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects: The thickness of a decreasing layup composite laminate varies continuously along a certain direction, while the composite material itself exhibits anisotropy. These two factors coupled together cause the ultrasonic guided wave to propagate neither in a straight line nor at a constant velocity. Traditional methods ignore these factors, assuming a straight path and a constant velocity. Therefore, the propagation time calculated for variable thickness laminates deviates significantly from the actual situation, leading to positioning errors. This invention provides an elliptic imaging method for ultrasonic guided wave damage localization in decreasing layup composite laminates. By using pre-acquired material property parameters, it simultaneously considers the coupled effects of thickness variation and anisotropy on the path and velocity during simulated guided wave propagation. In other words, when calculating the propagation time from the excitation point to any point in the laminate, a curved path and varying velocity consistent with the actual physical process are used, rather than an idealized straight line and constant velocity. The generated first and second theoretical propagation time maps more accurately reflect the actual propagation law of the guided wave in anisotropic plates with variable thickness. By extracting the actual flight time of the damage wave packet, the actual flight time objectively reflects the true location of the damage. The actual flight time is matched with the theoretical total propagation time to identify points where the theoretical total propagation time coincides with the actual flight time, which are considered potential locations of damage. Since the calculation of the theoretical total propagation time is based on real physical processes, the matched candidate regions are inherently closer to the true location of the damage than traditional methods. This process is repeated using multiple sets of sensors at different locations to obtain multiple candidate regions; the intersection of these regions is the final location of the damage. The fusion of multiple sets of data further eliminates potential ambiguity in localization due to a single sensor, making the final determined damage location more reliable. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings used in the description of the specific embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a flowchart of an ultrasonic guided wave damage elliptic imaging localization method for a layered decreasing composite laminate according to the present invention.

[0019] Figure 2 (a) in the figure represents the traditional elliptical positioning algorithm, which treats the guided wave propagation path as a straight line, calculates the guided wave propagation time, and draws the damage ellipse. Figure 2 (b) in the figure represents the positioning method of the present invention, which considers the bending propagation path of the guided wave, calculates the propagation time of the guided wave, and plots the range of the damage.

[0020] Figure 3The diagram shows the propagation time from any point in the plate to the transducer calculated using the elliptical imaging positioning method of the present invention. In this diagram, (a) represents the propagation time of the ultrasonic guided wave from the excitation transducer to any point in the plate; (b) represents the propagation time of the ultrasonic guided wave from any point in the plate to the receiving transducer; and (c) represents the propagation time of the ultrasonic guided wave from the excitation transducer to any point in the plate, and then reflected to the receiving transducer.

[0021] Figure 4 A schematic diagram of a variable thickness composite panel manufactured using a reduction layup technique.

[0022] Figure 5 This is a flowchart of an ultrasonic guided wave damage elliptic imaging localization method for a layered decreasing composite laminate according to an embodiment of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0024] Combination Figure 1 and Figure 5 As shown, this invention provides a method for elliptical imaging localization of ultrasonic guided wave damage in a ply-reduction composite laminate, specifically including the following steps: S1. Obtain the thickness change direction information of the detected reduction layup composite laminate, as well as the position coordinates of at least one set of excitation transducers and receiving transducers arranged on the laminate.

[0025] Specifically, the first step is preparatory work before testing. At least one set of excitation and receiving transducers should be arranged on the reduction layup composite laminate to be tested. It should be understood that the transducers can be piezoelectric ceramic sheets, piezoelectric fiber composite sheets, or other sensors capable of exciting and receiving ultrasonic guided waves. The operator needs to clearly define the direction of thickness change in the laminate, i.e., the direction in which the thickness continuously changes during the reduction layup manufacturing process. For ease of description and calculation, the direction of thickness change in the reduction layup composite laminate is defined as... y Direction, with equal thickness as x Direction. Record the position coordinates of each transducer on the board, such as the coordinates of the excitation transducer ( At the same time, the scope of the area to be detected is determined, i.e. , The thickness of the laminate varies within the range of... .

[0026] S2. Based on the pre-acquired material property parameters of the laminate, simulate and calculate the propagation time of ultrasonic guided waves emitted from the excitation transducer in different directions to any point in the laminate, generating a first theoretical propagation time spectrum, and simulate and calculate the propagation time from any point in the laminate to the receiving transducer, generating a second theoretical propagation time spectrum, wherein the simulation process considers the coupling effect of the thickness variation and material anisotropy of the laminate on the propagation path and propagation speed of the guided waves.

[0027] In other words, after completing the preparatory work, the next stage is to construct the theoretical propagation time map. Based on the material property parameters of the laminate obtained in advance through theoretical calculations or experimental tests, the propagation process of ultrasonic guided waves in the plate is simulated, and the propagation of guided waves emitted from the excitation transducer in different directions to any point in the ply reduction plate is calculated. The required propagation time is used to generate the first theoretical propagation time map. Simultaneously, simulations were performed to calculate the ultrasonic guided wave from any point in the ply reduction plate. The propagation time required to reach the receiving transducer is used to generate a second theoretical propagation time map. It should be understood that the method for generating the second theory propagation time map is similar to that of the first theory propagation time map, the difference being that the source point is set as any point on the board. The target point is set as the receiving transducer.

[0028] It is important to note that during the simulation, the coupled effects of two key factors on guided wave propagation must be considered simultaneously: first, the continuous change in plate thickness caused by ply reduction; and second, the anisotropic properties of the composite material itself. These two factors work together to cause the actual propagation path of the guided wave to bend, and the propagation speed to vary with position and direction, rather than the straight-line propagation and constant speed assumed by traditional methods. Figure 2 As shown, Figure 2 In (a), the traditional method treats the path as a straight line, while... Figure 2 (b) in the figure represents the method of the present invention taking into account the actual bending path.

[0029] S3. An ultrasonic guided wave signal is emitted into the laminate through the excitation transducer, and the guided wave signal after damage modulation is received by the receiving transducer. The actual flight time of the damage wave packet caused by the damage is extracted from the received guided wave signal.

[0030] Specifically, an ultrasonic guided wave signal is emitted into the laminate by an excitation transducer. The ultrasonic guided wave signal propagates within the laminate and is scattered when it encounters damage (such as delamination, debonding, glue-rich areas, foreign object inclusions, or impact damage). The scattered wave carrying damage information is ultimately received by a receiving transducer. From the received guided wave signal, the actual flight time corresponding to the damage wave packet caused by the damage needs to be extracted. It should be understood that the actual flight time refers to the time elapsed from the moment of excitation to the arrival of the damage packet at the receiving transducer.

[0031] S4. Based on the first theoretical propagation time spectrum and the second theoretical propagation time spectrum, calculate the theoretical total propagation time of the ultrasonic guided wave from the excitation transducer to the receiving transducer after reflection from any point in the laminate, and determine the set of spatial points where the theoretical total propagation time is equal to the actual flight time as the candidate region for the corresponding damage of the transducer pair.

[0032] Specifically, this step involves determining the candidate damage region. Based on the previously generated first and second theoretical propagation time maps, for any point on the plate... It is possible to calculate the distance the ultrasonic guided wave travels from the excitation transducer to that point. Then pass through that point Theoretical total propagation time to the receiving transducer after reflection .

[0033] In other words, for any point in the plate Theoretical total propagation time It consists of two parts: Part 1 Propagation from the excitation transducer to the point The required time can be directly obtained from the first theoretical propagation time map, which already includes the time it takes for the excitation transducer to propagate along the curved path to any point in the plate. Part Two From point The time required for the ultrasonic guided wave to propagate to the receiving transducer can be obtained from the second theoretical propagation time spectrum. Adding these two times together gives the time it takes for the ultrasonic guided wave to travel from the point... Theoretical total propagation time from excitation end to receiver end after reflection The calculation process applies to all possible points in the plate. This process is performed to obtain the theoretical total propagation time distribution across the entire plate surface.

[0034] The total propagation time of this theory Compared with the actual flight time extracted from the experiment Compare and find all that meet the requirements. Spatial points, the set of these points is determined as the candidate region for the corresponding damage of the transducer pair. That is, if This indicates that the guided wave travels from the excitation transducer to the location point. If the propagation time required for the waveguide to travel from the excitation transducer to the damage location and then back to the receiving transducer is consistent with the propagation time of the guided wave from the excitation transducer to the damage location and then back to the receiving transducer, then that location is considered a potential location of the damage. Because of the consideration of curved paths and variable wave speeds, this candidate region is no longer a standard ellipse in traditional elliptic imaging methods, but rather an irregular closed curve. Figure 3 A schematic diagram illustrating this calculation process is shown. Figure 3 (a) in the diagram represents the propagation timeline of the first theory. Figure 3 (b) in the diagram represents the propagation timeline of the second theory. Figure 3 (c) in the figure represents the theoretical total propagation time distribution obtained by adding the two.

[0035] S5. Based on multiple sets of excitation-receiver transducer pairs arranged at different positions on the laminate, repeat S2 to S4 to obtain multiple candidate regions for the existence of the damage, and determine the intersection of the multiple candidate regions as the final location of the damage.

[0036] In other words, to achieve accurate localization, multiple sets of excitation-receiver transducer pairs at different locations need to be arranged on the laminate. For each transducer pair, the above-mentioned steps of theoretical spectrum generation, signal acquisition and time extraction, and candidate region determination are repeated to obtain the corresponding candidate regions for damage. These candidate regions are plotted on the same coordinate system, and their intersection area is the final location of the damage. By fusing multi-angle information, the uncertainty of localization from a single sensor can be effectively eliminated, improving localization accuracy.

[0037] In one possible implementation, the simulation and calculation of the propagation time of ultrasonic guided waves emitted from the excitation transducer in different directions to any point in the laminate specifically includes: First, all possible launch directions are traversed using a preset angle step size. For example, using a preset angle step size... (For example =1°) Traverse all possible emission directions, that is, starting from 0°, and successively take the incident direction of the ultrasonic guided wave. That is, the direction of waveguide excitation The initial excitation direction of the ultrasonic guided wave , The traversal range is [0°, 360°).

[0038] It should be noted that when traversing all possible launch directions with a preset angle step size, the angle step size... The angle step size needs to be set appropriately. Theoretically, the angle step size should be small enough to ensure that for any point in the laminate, at least one simulated waveguide propagation path passes through that point. If the angle step size is too large, some spatial points may not have any traversed paths, resulting in voids in the generated first theoretical propagation time map and affecting damage localization. In practice, the angle step size can be determined based on the size of the plate, the thickness variation gradient, and the required localization accuracy. The general principle is that the path family generated after angle traversal should uniformly cover the entire area to be detected, ensuring that each location has at least one associated path.

[0039] Next, for each emission direction, the bending propagation path of the ultrasonic guided wave in that emission direction is determined based on the thickness variation of the laminate and the anisotropic properties of the material.

[0040] Specifically, for each guided wave excitation direction Based on the thickness variation characteristics and anisotropic properties of the laminate, the bending propagation path of the ultrasonic guided wave in this direction is determined. Due to the continuous change in thickness, the propagation direction of the guided wave will gradually deflect during propagation, forming a smooth curve rather than a straight line.

[0041] Finally, the local propagation velocity is integrated along the curved propagation path in the launch direction to obtain the propagation time at each point on the curved propagation path in the launch direction.

[0042] In other words, after determining the curved propagation path, the local propagation velocity is integrated along this path to obtain the propagation time at each point on the path. Specifically, the curved path is divided into countless tiny path segments, each corresponding to a local propagation direction and a local plate thickness. The propagation time is then determined based on the group velocity under these local conditions. By calculating the time required to traverse this tiny segment and summing up the times of all the tiny segments, the total propagation time from the starting point to any point on the path can be obtained. In this way, for each guided wave excitation direction (i.e., incident angle)... Each of these methods yields a curved path and the propagation time for all points along that path. Save this... The propagation time at any point on the path of the incident guided wave It is used to generate a complete propagation time map.

[0043] For a given angle of incidence Calculate the propagation path of the ultrasonic guided wave in this propagation direction, and the distance of the guided wave from the transducer to any point on this propagation path. transmission time The following integral formula can be used:

[0044] In the formula: For ultrasonic guided waves at points along the propagation path The tilt angle at that point, and its relationship with the incident direction of the guided wave at that point. and plate thickness related; The ultrasonic guided wave propagation group velocity at that point is related to the plate thickness at that point. incident direction and tilt angle This is relevant. The physical meaning of this integral is: decomposing the curved path into countless tiny arc segments, each arc segment corresponding to... y Incremental direction The length of the arc segment is Divide the time by the local group velocity on the arc segment to obtain the time to pass through the arc segment, then integrate and sum to obtain the total time.

[0045] In one feasible approach, combining Figure 4 As shown, the bending propagation path of the ultrasonic guided wave in the emission direction is determined based on the thickness variation and anisotropic properties of the laminate, as detailed below: First, the laminate is discretized into multiple continuous equal-thickness segments along its own thickness variation direction.

[0046] Specifically, the laminate is placed along its thickness variation direction (i.e. y The plate thickness is discretized into multiple continuous segments of equal thickness along the direction of thickness variation. Divide the plate into equal parts according to the step length. A sub-plate of equal thickness, along the direction where the plate thickness remains constant ( x (direction) The plate is discretized using a step size. The thickness within each sub-plate is approximately constant.

[0047] Then, within each of the equal-thickness sections, the local propagation direction and local propagation speed of the ultrasonic guided wave as it passes through the section are determined based on the thickness and material anisotropy parameters of that section.

[0048] Specifically, when a guided wave moves from one segment to the next adjacent segment, its propagation direction changes due to the change in thickness, and the amount of change is determined by the tilt angle. Determine the tilt angle It is the angle between the direction of the guided wave phase velocity propagation and the direction of the group velocity propagation, which is a function of the incident direction of the guided wave and the plate thickness, i.e. With varying thickness, the tilt angle also depends on the incident direction at the current point. and the plate thickness at that point ,Right now Meanwhile, the local group velocity within this section... It also depends on the thickness of the section. and direction of dissemination .

[0049] Finally, the local propagation paths within each equal-thickness section are connected sequentially, that is, the straight-line propagation segments of the guided wave within each section are connected end to end to form a complete curved propagation path. The finer the segment division (i.e., The smaller the value, the closer the resulting bending path will be to the actual continuous bending situation.

[0050] In one possible implementation, the extraction of the actual flight time of the damage wave packet caused by the damage from the received guided wave signal is specifically carried out as follows: 1) Acquire reference signals in advance under non-destructive conditions.

[0051] In other words, a signal acquisition is performed when the laminate is in an undamaged state to obtain a reference signal. For example, an ultrasonic guided wave damage detection experimental platform is established, and ultrasonic guided waves are excited in an undamaged reduction layup laminate. The ultrasonic guided wave signal is received by a receiving transducer and used as the reference signal. This step can be performed in the initial state after the laminate is manufactured, or it can be performed during service when the structure is considered to be in good condition.

[0052] 2) Acquire comparison signals while in detection mode.

[0053] In other words, when damage detection is required, signal acquisition is performed again to obtain a comparison signal. At this time, actual damage may exist in the laminate, or to simulate damage, a mass block can be attached to the undamaged laminate to simulate scattering caused by the added mass. Alternatively, irreversible damage can be created in the undamaged ply reduction plate to obtain a comparison plate with damage.

[0054] 3) The comparison signal and the reference signal are differentially processed to obtain a damage signal containing damage information. Specifically, the acquired comparison signal is subtracted point by point from the pre-stored reference signal to obtain the difference signal, i.e., the damage signal.

[0055] 4) Identify and extract the damage wave packet and the actual flight time corresponding to the damage wave packet from the damage signal.

[0056] For example, damage packets are identified from damage signals. Typically, a damage packet appears as a distinct pulse or packet in the time-domain waveform. By setting a threshold or using methods such as envelope analysis, the arrival time of the packet can be determined. This arrival time minus the excitation time (i.e., the start time of the excitation signal) gives the actual flight time. .

[0057] In one possible implementation, the material property parameters include at least: Wave velocity parameters, i.e., phase velocity, at different thicknesses of the laminate. Group speed With plate thickness y The relationship curve of the change. Due to the continuous change in plate thickness caused by the decreasing ply count, the ply sequence and ply ratio may change at different thicknesses, and therefore the wave velocity will also change accordingly, which needs to be obtained in advance through experimental testing.

[0058] Wave velocity parameters, i.e., phase velocity, at different thicknesses and in different waveguide propagation directions of the laminate. ) and group velocity With thickness h and direction of dissemination The changing functional relationship reflects the anisotropic characteristics of composite materials; even at the same thickness, the guided wave velocity propagating in different directions is different.

[0059] The tilt angle parameter is the angle between the group velocity propagation direction and the phase velocity propagation direction. With thickness h and incident direction Changing functional relationship .

[0060] For unidirectional ultrasonic guided waves, given their initial incident angle, considering the anisotropy of wave velocity, tilting effect, and wave velocity variation with thickness, the wave propagation path becomes curved. This renders the traditional elliptic imaging method for calculating propagation time unsuitable for decreasing layup composite laminates. This invention optimizes the propagation time algorithm in the traditional elliptic imaging method to obtain the propagation path and propagation time of the guided wave at the given incident angle. Then, it performs traversal calculations for any incident angle to obtain the propagation time of the ultrasonic guided wave from the transducer to any point in the laminate. By acquiring a reference damage signal, the damage wave packet and its actual flight time are extracted, locating the damage location within the laminate. Multiple sensors are used to locate the damage in the decreasing layup composite laminate. This invention systematically considers the coupling effect of structural thickness variations caused by decreasing layup and composite material anisotropy on ultrasonic guided wave propagation, improves the traditional elliptic positioning algorithm, and optimizes the propagation time calculation algorithm, thus achieving the detection and location of damage in decreasing layup composite laminates.

[0061] In another embodiment of the present invention, a computer device is provided, comprising a processor and a memory. The memory stores a computer program, which includes program instructions. The processor executes the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions in the computer storage medium to achieve a corresponding method flow or corresponding function. The processor described in this embodiment of the present invention can be used in the operation of an ultrasonic guided wave damage elliptic imaging localization method for a layered decreasing composite laminate.

[0062] In another embodiment of the present invention, a storage medium is provided, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device used to store programs and data. It is understood that the computer-readable storage medium here can include both the built-in storage medium in the computer device and extended storage media supported by the computer device. The computer-readable storage medium provides storage space that stores the terminal's operating system. Furthermore, the storage space also stores one or more instructions suitable for loading and execution by a processor. These instructions can be one or more computer programs (including program code). It should be noted that the computer-readable storage medium here can be Random Access Memory (RAM) or non-volatile memory, such as at least one disk storage device. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the corresponding steps of the ultrasonic guided wave damage elliptic imaging localization method for a layered decreasing composite laminate in the above embodiments.

[0063] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, optical storage, etc.) containing computer-usable program code.

[0064] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0065] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0066] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0067] This invention also provides a computer program product, which is used to execute any of the above-described methods for elliptic imaging localization of ultrasonic guided wave damage in decreasing layup composite laminates. Since the computer program product provided by this invention and the above-described method for elliptic imaging localization of ultrasonic guided wave damage in decreasing layup composite laminates belong to the same inventive concept, the computer program product provided by this invention possesses all the advantages of the above-described method for elliptic imaging localization of ultrasonic guided wave damage in decreasing layup composite laminates. Therefore, the beneficial effects of the computer program product provided by this invention will not be elaborated upon here.

[0068] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0069] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit them. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the scope of the technology disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention.

Claims

1. A method for elliptic imaging localization of ultrasonic guided wave damage in a decreasing layup composite laminate, characterized in that, include: S1. Obtain the thickness change direction information of the detected reduction layup composite laminate, as well as the position coordinates of at least one set of excitation transducers and receiving transducers arranged on the laminate. S2. Based on the pre-acquired material property parameters of the laminate, simulate and calculate the propagation time of ultrasonic guided waves emitted from the excitation transducer in different directions to any point in the laminate, generating a first theoretical propagation time spectrum; and simulate and calculate the propagation time from any point in the laminate to the receiving transducer, generating a second theoretical propagation time spectrum. The simulation process considers the coupling effect of the thickness variation and material anisotropy of the laminate on the propagation path and propagation speed of the guided waves. S3. An ultrasonic guided wave signal is emitted into the laminate through the excitation transducer, and the guided wave signal after damage modulation is received by the receiving transducer. The actual flight time of the damage wave packet caused by the damage is extracted from the received guided wave signal. S4. Based on the first theoretical propagation time spectrum and the second theoretical propagation time spectrum, calculate the theoretical total propagation time of the ultrasonic guided wave from the excitation transducer to the receiving transducer after being reflected by any point in the laminate, and determine the set of spatial points where the theoretical total propagation time is equal to the actual flight time as the candidate region for the corresponding damage of the transducer pair. S5. Based on multiple sets of excitation-receiver transducer pairs arranged at different positions on the laminate, repeat S2 to S4 to obtain multiple candidate regions for the existence of the damage, and determine the intersection of the multiple candidate regions as the final location of the damage.

2. The ultrasonic guided wave damage elliptic imaging localization method for a layered decreasing composite laminate according to claim 1, characterized in that, The simulation and calculation of the propagation time of ultrasonic guided waves emitted from the excitation transducer in different directions to any point in the laminate are as follows: Traverse all possible launch directions with a preset angle step size; For each emission direction, the bending propagation path of the ultrasonic guided wave in that emission direction is determined based on the thickness variation of the laminate and the anisotropic properties of the material. Integrating the local propagation velocity along the curved propagation path in the emission direction yields the propagation time at each point along the curved propagation path in the emission direction.

3. The ultrasonic guided wave damage elliptic imaging localization method for a layered decreasing composite laminate according to claim 2, characterized in that, The determination of the bending propagation path of the ultrasonic guided wave in the emission direction based on the thickness variation and anisotropic properties of the laminate specifically includes: The laminate is discretized into multiple continuous equal-thickness segments along its own thickness variation direction; Within each of the equal thickness sections, the local propagation direction and local propagation speed of the ultrasonic guided wave when it passes through the section are determined based on the thickness and material anisotropy parameters of the section. The local propagation paths within each of the equal thickness sections are connected sequentially to form a complete curved propagation path.

4. The ultrasonic guided wave damage elliptic imaging localization method for a layered decreasing composite laminate according to claim 2, characterized in that, When traversing all possible emission directions with a preset angle step size, the angle step size is set to ensure that at least one simulated waveguide propagation path passes through any point in the laminate.

5. The ultrasonic guided wave damage elliptic imaging localization method for a layered decreasing composite laminate according to claim 1, characterized in that, Extracting the actual flight time of the damage wave packet caused by the damage from the received guided wave signal includes: Pre-acquire reference signals in a non-destructive state; Acquire comparison signals while in detection mode; The comparison signal and the reference signal are differentially processed to obtain a damage signal containing damage information; The damage wave packet and the corresponding actual flight time are identified and extracted from the damage signal.

6. The ultrasonic guided wave damage elliptic imaging localization method for a layered decreasing composite laminate according to claim 1, characterized in that, The total theoretical propagation time is equal to the sum of the first theoretical propagation time from the excitation transducer to any point in the laminate and the second theoretical propagation time from that point to the receiving transducer.

7. The ultrasonic guided wave damage elliptic imaging localization method for a layered decreasing composite laminate according to claim 1, characterized in that, The material property parameters include at least the phase velocity and group velocity of the laminate at different thicknesses and in different waveguide propagation directions, as well as the tilt angle of the group velocity propagation direction relative to the phase velocity propagation direction.

8. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the ultrasonic guided wave damage elliptic imaging localization method for a layered decreasing composite laminate as described in any one of claims 1 to 7.

9. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the ultrasonic guided wave damage elliptic imaging localization method for a layered decreasing composite laminate as described in any one of claims 1 to 7.

10. A computer program product, characterized in that, When executed by a processor, the computer program product implements an ultrasonic guided wave damage elliptic imaging localization method for a layered decreasing composite laminate as described in any one of claims 1 to 7.

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