Laser ultrasonic crack size quantitative characterization method and system based on energy spectrum analysis

Abstract

The application discloses a kind of laser ultrasonic crack size quantitative characterization method and system based on energy spectrum analysis, crack defect is manufactured on the surface of measured object;Subsequently excite ultrasonic wave, obtain laser ultrasonic signal;Realize scanning detection to defect, obtain ultrasonic wave field near defect simultaneously;By reconstructing ultrasonic wave field at different times, the propagation process of ultrasonic wave and the process of action with defect are judged;Subsequently, energy spectrum is extracted from ultrasonic wave field diagram at different times, obtain the influence of defect on energy spectrum at different times;Determine energy redistribution of energy spectrum, judge whether there is defect and further judge whether through defect;When passing through defect, the attenuation of energy spectrum energy is analyzed, and a single corresponding relationship with the depth of defect is established, the quantitative characterization of defect is realized, and the characterization of defect is realized using artificial intelligence algorithm to extract other parameters;The application improves the detection ability and characterization ability of laser ultrasonic.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of crack characterization detection, and particularly relates to a laser ultrasonic crack size quantitative characterization method and system based on energy spectrum analysis. BACKGROUND

[0002] In the manufacturing engineering and service stage, cracks and other defects are easily generated on the surface and inside of metal and other materials due to the influence of various working environments. If not detected in time, failure such as fracture is likely to occur, thereby causing great personnel and property losses. Therefore, timely detection is required. There are many detection methods for cracks and other defects at present, including ultrasonic detection, ray detection, eddy current detection and the like. Laser ultrasonic detection is widely concerned due to its non-contact and wide frequency band, and is often used for qualitative, positioning and quantitative characterization of defects. However, quantitative characterization has always been a difficulty and focus of defect detection characterization. Through research, it is found that due to the closing effect of cracks, when laser ultrasonic generated by thermal elastic effect or ablation effect propagates to the vicinity of defects, the cracks will cause mode conversion to ultrasonic and also affect the energy redistribution of laser ultrasonic. More importantly, the closing of cracks will also consume part of the energy.

[0003] The reflection coefficient mainly considers the amplitude of laser ultrasonic, and its calculation method is to use the ratio of reflected wave peak value to incident wave or direct wave peak value as a damage sensitive characteristic parameter for quantitative characterization of cracks and other defects. However, generally speaking, many factors will affect the size of the amplitude, including laser energy, laser spot diameter, material properties, excitation point and receiving point position and the like. Moreover, as mentioned before, the reflection coefficient is calculated by using the peak value, which means that this algorithm cannot consider other waveforms except the peak value. However, for laser ultrasonic signals with wide frequency band characteristics, it is easy to ignore other related important information, so that the required results cannot be obtained.

[0004] Because the reflection coefficient has many problems, relevant scholars propose a reflection energy coefficient algorithm, that is, the ratio of reflected wave energy to direct wave energy is used. Although this algorithm can solve the problem of only considering the peak value, because the energy of direct wave and reflected wave needs to be calculated respectively, the direct wave and reflected wave signals need to be obtained first. However, for many small defects, it is very difficult to accurately extract the reflected wave from the laser ultrasonic signal, so this algorithm can only be used for large defects, which greatly limits the application scenarios of this algorithm. Moreover, in the on-site signal collection, the reflected wave may not be obvious due to the interference of many other signals, so there are certain difficulties in actual operation. SUMMARY

[0005] The technical problems to be solved by the present application are to provide a laser ultrasonic crack size quantitative characterization method and system based on energy spectrum analysis to solve the technical problem of insufficient quantitative characterization capability of existing laser ultrasonic.

[0006] The present application adopts the following technical solutions:

[0007] A laser ultrasonic crack size quantitative characterization method based on energy spectrum analysis comprises the following steps:

[0008] S1, taking the crack depth as the size to be characterized, processing a crack on the surface of the measured object;

[0009] S2, exciting ultrasonic waves on the surface and inside of the measured object obtained in step S1 by using a high-power pulsed laser;

[0010] S3, moving the measured object or the laser beam to realize the movement of the laser spot, completing the laser ultrasonic scanning detection of the defect, and reconstructing the laser ultrasonic wave field based on the data collected by the laser ultrasonic scanning;

[0011] S4, solving the energy spectrum of the laser ultrasonic wave field obtained in step S3, and judging the defect position according to the energy spectrum;

[0012] S5, determining the moment when the laser ultrasonic wave passes through the defect according to the defect position obtained in step S4, and analyzing the wave field energy spectrum of the laser ultrasonic wave passing through the defect at multiple moments to obtain the energy spectrum change of the laser ultrasonic wave passing through the defect;

[0013] S6, determining the energy spectrum energy attenuation when passing through the defect based on the energy spectrum change obtained in step S5, establishing a single correspondence between the energy spectrum and the defect depth, and realizing the quantitative characterization of the crack size.

[0014] Specifically, in step S1, the depth of the crack is 0.1mm, 0.3mm, 0.5mm, 0.7mm and 0.9mm.

[0015] Further, the length of the crack is 5mm, and the width is 0.5mm.

[0016] Specifically, in step S2, the thermal elastic effect or the ablation effect is used to excite ultrasonic waves on the surface and inside of the measured object.

[0017] Specifically, in step S3, an ultrasonic probe or an optical interference method is used to collect the corresponding signals to obtain the laser ultrasonic time-frequency domain signals.

[0018] Specifically, in step S4, a scanning interval is set, the laser ultrasonic wave field diagram of the defect is obtained through the scanning detection of the light spot, and then the energy spectrum algorithm is used to obtain the laser ultrasonic wave field energy spectrum at different moments.

[0019] Specifically, in step S5, the energy spectrum change of the laser ultrasonic wave in the process of passing through the defect includes the redistribution characteristics of the defect to the laser ultrasonic energy.

[0020] Specifically, step S6 is specifically:

[0021] The energy of all energy spectrums of the wave field passing through the defect and the wave field not passing through the defect is summed up, and the energy difference and the energy ratio are calculated, and the corresponding relationship between the energy spectrum and the defect depth is established to realize quantitative characterization of the defect depth.

[0022] Further, the corresponding parameters are extracted from the energy spectrum by using an artificial intelligence method to realize characterization of the defect.

[0023] In a second aspect, an embodiment of the present application provides a laser ultrasonic crack size quantitative characterization system based on energy spectrum analysis, comprising:

[0024] A machining module, taking the crack depth as the size to be characterized, machining a crack on the surface of the measured object;

[0025] An excitation module, exciting ultrasonic waves on the surface and inside of the measured object obtained by the machining module by using high-power pulsed laser;

[0026] A scanning module, moving the measured object or the laser beam to realize movement of the laser spot, completing laser ultrasonic scanning detection of the defect, and reconstructing the laser ultrasonic wave field based on the data collected by the laser ultrasonic scanning;

[0027] A calculation module, solving the energy spectrum of the laser ultrasonic wave field obtained by the scanning module, and determining the defect position according to the energy spectrum;

[0028] A characterization module, determining the moment when the laser ultrasonic wave passes through the defect according to the defect position obtained by the calculation module, analyzing the wave field energy spectrum of the laser ultrasonic wave passing through the defect at multiple moments, obtaining the energy spectrum change of the laser ultrasonic wave in the process of passing through the defect, determining the energy spectrum energy attenuation in the process of passing through the defect based on the energy spectrum change, establishing a single corresponding relationship between the energy spectrum and the defect depth, and realizing quantitative characterization of the crack size.

[0029] Compared with the prior art, the present application has at least the following beneficial effects:

[0030] A laser ultrasonic crack size quantitative characterization method based on energy spectrum analysis, from the perspective of energy spectrum, combined with the closing effect of cracks and other defects, the damage of the material and the position of the defect can be judged. At the same time, the energy spectrum of the sound wave at different times when passing through the defect can be analyzed, the interaction between the defect and the sound wave can be obtained, and the redistribution of the defect to the sound wave energy can be analyzed. At the same time, different energy values through the defect and not through the defect can be analyzed, and the quantitative characterization of the crack and other defects can be realized through the energy difference or energy ratio. Compared with many damage sensitive feature algorithms before, the amplitude of different frequencies can be fully considered, so the signal information of different frequencies of laser ultrasonic can be considered in more detail. Because we only care about the energy spectrum information in the calculation process, we do not need to extract the direct wave and reflected wave, so it has strong anti-interference ability, and it can also detect micro-cracks and other micro-defects.

[0031] Further, in order to subsequent defect detection, considering that the pulse width of the laser we use is 8nm, we set the defect depth to be 0.1mm, 0.3mm, 0.5mm, 0.7mm, 0.9mm. The advantage is not only to detect defects, but also to basically reflect the superiority of the patent in detecting micro-cracks and other defects.

[0032] Further, since the processing method adopted is wire cutting processing, the crack width is set to 0.5mm, considering the aspect ratio of the crack, and the scanning range is 1cm, so the crack length is set to 5mm.

[0033] Further, the laser can excite different types of sound waves on the surface and inside of the measured object according to the actual situation, for example, it can excite acoustic surface waves through thermal elastic effect, and it can excite longitudinal waves through ablation effect. Therefore, in this patent, different excitation methods can be used according to different needs to obtain different types of sound waves, thereby expanding its application range.

[0034] Further, the same can be done according to the actual situation to perform different types of receiving methods. If only acoustic surface waves are studied, an ultrasonic probe can be used to receive sound waves. If all waveforms need to be studied, an optical interferometer can be used, and the optical interferometer is also not affected by the surface of the measured object.

[0035] Further, considering the precision limit of the experimental platform, we set the scanning step to be 1mm, but a more precise motion platform can be used to realize a smaller scanning step, and then a more detailed and clear imaging map can be obtained. Then energy spectrum is used for analysis, by analyzing the energy spectrum at different times, the process of the defect acting on the sound wave can be obtained, which is beneficial to analyze the energy redistribution process of the defect to the sound wave, especially the energy proportion change of different frequency components in the sound wave.

[0036] Further, since the crack closure effect is more sensitive to the size of the defect, and the sound wave carries the defect information after interacting with the defect, the most intuitive is the change of energy, so the energy spectrum analysis is used for quantitative characterization of the defect, so as to more easily and more accurately realize the characterization of the defect, because the closure effect of the crack and other defects causes the change of energy, and the change of energy is not as single as the change of amplitude, so the energy spectrum analysis can more comprehensively obtain the size and other information of the defect.

[0037] Further, through the previous analysis, when the sound wave passes through the defect, the defect redistributes the energy of the sound wave. At the same time, due to the closure effect of the defect, when the sound wave passes through the defect, it will cause the attenuation of the energy and other changes, and the attenuation condition has a close relationship with the defect depth. Therefore, we realize the quantitative characterization of the defect depth by calculating the energy difference and ratio before and after passing through the defect. Through the previous research, the defect has an extremely obvious influence on the energy proportion of different frequency components in addition to the redistribution influence on the overall energy of the sound wave, so the quantitative characterization of the defect depth can also be realized by analyzing the energy proportion of different frequency components.

[0038] Further, by introducing an artificial intelligence algorithm, the characterization accuracy of laser ultrasonic can be effectively improved.

[0039] It can be understood that the beneficial effects of the above-mentioned second aspect can be referred to the related description in the above-mentioned first aspect, which will not be repeated here.

[0040] In summary, the application utilizes the advantages of laser ultrasonic detection, further improves the quantitative characterization ability of laser ultrasonic technology, expands the application range of laser ultrasonic, effectively improves the quantitative characterization ability of laser ultrasonic, and realizes the size characterization of crack-type defects.

[0041] The technical solutions of the application will be further described in detail below with the help of the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 is a schematic diagram of laser ultrasonic scanning for a defect;

[0043] Figure 2 is a time-frequency domain graph of a defect with a depth of 0.7mm;

[0044] Figure 3 is a laser ultrasonic wave field graph at different times, wherein (a) is not through the defect, (b) is in contact with the defect, and (c) is through the defect;

[0045] Figure 4 is an energy spectrum graph of laser ultrasonic wave field at different times, wherein (a) is not through the defect, and (b) is through the defect;

[0046] Figure 5wavefield energy spectra at different times near the defect. DETAILED DESCRIPTION

[0047] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application but not all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of the present application.

[0048] In the description of the present application, it should be understood that the terms "comprising" and "including" indicate the presence of described features, integers, steps, operations, elements, and / or components, but do not exclude one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0049] It should also be understood that the terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in the specification and the appended claims of the present application, unless otherwise clearly indicated by the context, the singular forms "a", "an" and "the" are intended to include the plural forms as well.

[0050] It should be further understood that the term "and / or" used in the specification and the appended claims of the present application means any combination of one or more of the associated listed items and all possible combinations, and includes these combinations, for example, A and / or B can represent three cases of A alone, A and B together, and B alone. In addition, the character " / " in this paper generally represents that the front and rear associated objects are in an "or" relationship.

[0051] It should be understood that although the terms first, second, third, etc. may be used in the embodiments of the present application to describe the preset ranges, etc., these preset ranges should not be limited to these terms. These terms are only used to distinguish the preset ranges from each other. For example, the first preset range can also be referred to as the second preset range, and similarly, the second preset range can also be referred to as the first preset range without departing from the scope of the embodiments of the present application.

[0052] Depending on the context, the word "if" as used herein can be interpreted as meaning "when" or "while" or "in response to determining" or "in response to detecting". Similarly, depending on the context, the phrase "if determined" or "if detecting (a stated condition or event)" can be interpreted as meaning "when determined" or "in response to determining" or "when detecting (a stated condition or event)" or "in response to detecting (a stated condition or event)".

[0053] Various structural diagrams according to the disclosed embodiments of the present application are shown in the drawings. These diagrams are not drawn to scale, in which certain details are exaggerated for clarity of presentation and may be omitted, for example. The shapes of various regions, layers, and the relative sizes and positional relationships among them shown in the drawings are merely exemplary and may deviate in actuality due to manufacturing tolerances or technical limitations, and regions / layers having different shapes, sizes, and relative positions can be additionally designed according to actual needs by those skilled in the art.

[0054] The present application provides a laser ultrasonic crack size quantitative characterization method based on energy spectrum analysis, artificially manufacturing a crack defect on the surface of the measured object; then using a high-power pulsed laser to excite ultrasonic waves on the surface and inside of the measured object, obtaining laser ultrasonic signals; and using a motion platform to realize scanning detection of the defect and simultaneously obtaining the ultrasonic wave field near the defect; by reconstructing the ultrasonic wave field at different times, the propagation process of the ultrasonic wave and the interaction process with the defect are judged; then the energy spectrum of the ultrasonic wave field at different times is extracted to obtain the influence of the defect on the energy spectrum at different times; first, the energy redistribution of the energy spectrum is judged to judge whether there is a defect and whether it has passed through the defect; then the energy spectrum of the ultrasonic wave field is further analyzed to analyze the energy attenuation of the energy spectrum when passing through the defect, and a single corresponding relationship between the energy attenuation and the defect depth is established, so as to realize the quantitative characterization of the crack and other defects, and other parameters can also be extracted using artificial intelligence algorithms to realize the characterization of the defect. The present application realizes the characterization of the defect based on the energy spectrum of the ultrasonic wave field, and improves the detection and characterization capabilities of laser ultrasonic.

[0055] The present application takes the crack closure effect as the starting point of quantitative characterization, analyzes the laser ultrasonic energy spectrum, analyzes the propagation process of the ultrasonic wave and the interaction process with the defect, and analyzes the energy attenuation of the ultrasonic wave, and finally realizes the detection and quantitative characterization of the crack and other defects.

[0056] Whether the defect is passed through can be judged by the energy redistribution characteristics in the energy spectrum analysis. Generally, when the sound wave does not pass through the defect, the sound wave has a main peak energy. However, when the sound wave passes through the defect, the main peak energy gradually disappears, and energy is transferred to other frequencies. Based on this, it can be judged whether the defect is passed through, and whether the defect exists and the position of the defect can be determined. After judging that the defect exists, the energy spectrum of the wave field near the defect at different times is analyzed comprehensively to obtain the interaction between the crack and other defects and laser ultrasonic, and to obtain the energy redistribution characteristics of the defect on the sound wave. Moreover, the energy difference or ratio between the energy passing through the defect and the energy not passing through the defect can be calculated to judge the size of the crack and other defects, including the depth, length, and width, so as to realize the existence judgment and quantitative characterization of the crack and other defects.

[0057] The energy spectrum analysis includes energy redistribution characteristics and energy loss value. The energy loss value characterization method is different from the existing characterization methods, including reflection coefficient (maximum amplitude of reflected wave to maximum amplitude of direct wave ratio) and reflection energy coefficient.

[0058] The quantitative characterization method of the energy spectrum analysis has the following advantages:

[0059] First, the analysis is made from the energy angle, and the characteristics of laser ultrasonic, such as multi-band and multi-amplitude, are fully considered.

[0060] Second, the energy spectrum analysis is directly used, and the direct wave and the reflected wave are not considered simply, so that the method can be applied to micro-defects and the application of laser ultrasonic in micro-defects is expanded.

[0061] If the energy of the signal is limited 0<E<∞, it is called energy-limited signal, simply referred to as energy signal, such as trigonometric function, gate function, etc.

[0062]

[0063] That is:

[0064]

[0065] The above formula is called Parseval formula or energy equation, and F(jω) is the energy on the unit frequency in the frequency domain.

[0066] For energy signals, energy spectrum is commonly used to describe. The so-called energy spectrum, also known as energy spectrum density, refers to the distribution of signal energy at each frequency point by using the concept of density. The integral of energy spectrum in the frequency domain can obtain the energy of the signal. The energy spectrum is the square of the modulus of the signal amplitude spectrum, and its dimension is joule / hertz.

[0067] E(ω)=|F(ω)| 2 (3)

[0068]

[0069]

[0070]

[0071] Wherein, E1 is the energy spectrum energy sum without defect, E2 is the energy spectrum energy sum with defect, the difference between the two is expressed by the energy attenuation value D, and the energy ratio M can also be used for characterization.

[0072] Please refer to Figure 1 The laser ultrasonic crack size quantitative characterization method based on energy spectrum analysis includes the following steps:

[0073] S1, pretreating the measured object to process a crack with a certain length, width and depth on the surface thereof, wherein the depth is taken as the dimension to be characterized for quantitative characterization;

[0074] S2, exciting ultrasonic waves on the surface and inside of the material by using a thermal elastic effect or an ablation effect of a high-power pulsed laser;

[0075] The ultrasonic signals are collected in a contact or non-contact manner.

[0076] Considering that the laser ultrasonic usually adopts a nanometer laser, and the detection accuracy and other requirements, and more importantly, the wave field near the crack and other defects needs to be reconstructed, when the crack size is set, the length of the crack is set to 5 mm, the width is set to 0.5 mm, and the depth is set to 0.1 mm, 0.3 mm, 0.5 mm, 0.7 mm and 0.9 mm. Since the scale is sub-millimeter, the processing method is wire cutting molybdenum wire discharge.

[0077] S3, moving the laser spot by moving the measured object or the laser beam to realize laser ultrasonic scanning detection of the defect, combining the collected data, and performing laser ultrasonic wave field reconstruction according to the acoustic reciprocity principle;

[0078] The high-power pulsed laser is used to excite ultrasonic waves on the surface of the material, and the corresponding signals are collected by using an ultrasonic probe or an optical interference method to obtain laser ultrasonic time-frequency domain signals. Generally, a high-power laser excites ultrasonic waves on the surface and inside of the material by a thermal elastic effect or an ablation effect, and different laser parameters are set according to different effects. Due to the equipment, an ultrasonic probe combined with a precision motion platform is used. Therefore, in addition to the laser, a collimating and expanding mirror and a focusing lens or a cylindrical lens are needed to process the light beam, and an attenuation sheet is also needed when necessary. In order to verify the present application and require nondestructive testing, the laser power is set to 30 Mj in the experiment.

[0079] S4, solving the energy spectrum of the laser ultrasonic wave field to realize the judgment of the defect position;

[0080] Because it is necessary to judge whether there is a defect, the energy spectrum is solved in two cases of not passing through the defect and passing through the defect. When not passing through the defect, the energy spectrum shows that the energy of the main peak frequency is high, but after passing through the defect, the main peak energy attenuates and transfers energy to other frequencies, and there is energy redistribution. Based on this, the judgment of the defect position is realized.

[0081] After obtaining the time-frequency domain of single-point excitation and single-point reception, a precision motion platform is used to realize the movement of the measured object, and due to the relativity of the movement, the movement of the light spot is realized, and the laser ultrasonic field map near the defect is obtained through the scanning detection based on the reciprocity of acoustics, in order to improve the scanning accuracy, the scanning interval is 1mm, and after obtaining the laser ultrasonic field, the energy spectrum algorithm is used to obtain the energy spectrum of the laser ultrasonic field at different times.

[0082] S5, when the position of the defect is obtained, the time when the sound wave passes through the defect is judged, the ultrasonic wave field energy spectrum at multiple times when passing through the defect is analyzed at the same time, the change of the energy spectrum of the laser ultrasonic wave in the process of passing through the defect is obtained, so as to analyze the interaction between the defect and the laser ultrasonic, including the redistribution characteristics of the defect to the laser ultrasonic energy;

[0083] Due to the propagation of the sound wave to the defect, the closing effect of the defect will redistribute the energy of the sound wave, and the distribution rule of the energy of the sound wave will be changed. Through the energy redistribution of the sound wave, it can be judged whether the defect exists.

[0084] S6, after obtaining the energy spectrum, the existence of the defect is determined, and the laser ultrasonic field with the defect is further analyzed to quantitatively characterize the defect;

[0085] The energy of the energy spectrum of the wave field passing through the defect and the energy of the energy spectrum of the wave field not passing through the defect are summed up, and the energy difference and the energy ratio are calculated, and the corresponding relationship between the energy difference and the energy ratio and the defect depth is established, so as to realize the quantitative characterization of the defect depth.

[0086] Due to the closing effect of the defect, when the sound wave transmits to the defect, the opening and closing of the defect will consume part of the energy, so that the energy of the sound wave before and after passing through the defect appears to be attenuated, and the energy consumed by different defects in opening and closing is different, based on which the characterization of the defect depth can be realized.

[0087] S7, in addition to using the energy difference or the energy ratio, an artificial intelligence method is used to extract related parameters from the energy spectrum to realize the characterization of the defect.

[0088] When the sound wave passes through the defect, due to the influence of the crack defect, the energy of the sound wave passing through the defect will be attenuated, and the energy attenuation values of different depths are different, based on which the quantitative characterization of the defect can be realized.

[0089] When the sound wave passes through the defect, due to the influence of the crack defect, the energy of the sound wave passing through the defect will be attenuated, and the energy attenuation values of different depths are different, based on which the quantitative characterization of the defect can be realized.

[0090] The relevant parameters mainly refer to the change of the energy spectrum after the defect, for example, the overall energy difference or energy ratio, and the energy proportion of different frequency components.

[0091] The specific artificial intelligence method includes machine learning, deep learning, neural network, etc.

[0092] In another embodiment of the present application, a laser ultrasonic crack size quantitative characterization system based on energy spectrum analysis is provided, which can be used to realize the above-mentioned laser ultrasonic crack size quantitative characterization method based on energy spectrum analysis.

[0093] The machining module is used to machine a crack on the surface of the measured object with the crack depth as the size to be characterized.

[0094] The excitation module is used to excite ultrasonic waves on the surface and inside of the measured object machined by the machining module by using high-power pulsed laser.

[0095] The scanning module is used to realize the movement of the laser spot by moving the measured object or the laser beam, complete the laser ultrasonic scanning detection of the defect, and reconstruct the laser ultrasonic wave field based on the data collected by the laser ultrasonic scanning.

[0096] The calculation module is used to solve the energy spectrum of the laser ultrasonic wave field obtained by the scanning module, and determine the defect position according to the energy spectrum.

[0097] The characterization module is used to determine the moment when the laser ultrasonic wave passes through the defect according to the defect position obtained by the calculation module, analyze the wave field energy spectrum of the laser ultrasonic wave passing through the defect at multiple moments, obtain the energy spectrum change of the laser ultrasonic wave passing through the defect, determine the energy spectrum energy attenuation when passing through the defect based on the energy spectrum change, establish a single corresponding relationship between the energy spectrum and the defect depth, and realize the quantitative characterization of the crack size.

[0098] In still another embodiment of the present application, a terminal device is provided, which comprises a processor and a memory, the memory being configured to store a computer program, the computer program comprising program instructions, and the processor being configured to execute the program instructions stored in the computer storage medium. The processor can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic, discrete hardware components, etc., which are the computing core and control core of the terminal, and are suitable for implementing one or more instructions, and are specifically suitable for loading and executing one or more instructions to implement a corresponding method flow or a corresponding function; the processor in the embodiments of the present application can be used for the operation of the laser ultrasonic crack size quantitative characterization method based on energy spectrum analysis, comprising:

[0099] Taking the crack depth as the size to be characterized, a crack is processed on the surface of the measured object; high-power pulsed laser is used to excite ultrasonic waves on the surface and inside of the measured object respectively; the movement of the laser spot is realized by moving the measured object or the laser beam, and the laser ultrasonic scanning detection of the defect is completed; the laser ultrasonic wave field reconstruction is performed based on the data collected by the laser ultrasonic scanning; the energy spectrum of the laser ultrasonic wave field is solved, and the defect position is determined according to the energy spectrum; the moment when the laser ultrasonic wave passes through the defect is determined according to the obtained defect position, and the wave field energy spectrum of the laser ultrasonic wave passing through the defect at multiple moments is analyzed, so as to obtain the energy spectrum change of the laser ultrasonic wave in the process of passing through the defect; the energy spectrum energy attenuation in the process of passing through the defect is determined based on the energy spectrum change, a single corresponding relationship between the energy spectrum and the defect depth is established, and the quantitative characterization of the crack size is realized.

[0100] In another embodiment of the present application, the present application also provides a storage medium, specifically a computer readable storage medium (Memory), which is a memory device in the terminal device, used for storing programs and data. It can be understood that the computer readable storage medium herein can include the built-in storage medium in the terminal device, and of course can also include the expansion storage medium supported by the terminal device. The computer readable storage medium provides a storage space, which stores the operating system of the terminal. Moreover, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space, and these instructions can be one or more computer programs (including program codes). It should be noted that the computer readable storage medium herein can be a high-speed RAM memory, or a non-volatile memory such as at least one disk memory.

[0101] The one or more instructions stored in the computer readable storage medium can be loaded and executed by the processor to realize the corresponding steps of the laser ultrasonic crack size quantitative characterization method based on energy spectrum analysis in the above-mentioned embodiments; the one or more instructions in the computer readable storage medium are loaded and executed by the processor to realize the following steps:

[0102] Taking the crack depth as the size to be characterized, a crack is processed on the surface of the measured object; high-power pulsed laser is used to excite ultrasonic waves on the surface and inside of the measured object respectively; the movement of the laser spot is realized by moving the measured object or the laser beam, and the laser ultrasonic scanning detection of the defect is completed; the laser ultrasonic wave field reconstruction is carried out based on the data collected by the laser ultrasonic scanning; the energy spectrum of the laser ultrasonic wave field is solved, and the defect position is determined according to the energy spectrum; the moment when the laser ultrasonic wave passes through the defect is determined according to the obtained defect position, and the wave field energy spectrum of the laser ultrasonic wave passing through the defect at multiple moments is analyzed to obtain the energy spectrum change of the laser ultrasonic wave in the process of passing through the defect; the energy spectrum energy attenuation in the process of passing through the defect is determined based on the energy spectrum change, a single corresponding relationship between the energy spectrum and the defect depth is established, and the quantitative characterization of the crack size is realized.

[0103] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0104] A preliminary verification experiment of the present application is carried out through relevant experiments with pure aluminum as the measured object, an aluminum plate with a length of 200 mm, a width of 50 mm and a thickness of 10 mm, a crack depth of 0.1 mm, 0.3 mm, 0.5 mm, 0.7 mm and 0.9 mm, a width of 0.5 mm and a length of 5 mm. Then, a high-power pulsed laser is used to excite ultrasonic waves on the surface and inside of the aluminum plate through thermal elastic effect, a motion platform is used for laser ultrasonic scanning detection of defects, then an ultrasonic field map near the defects is obtained, the scanning interval is set to 1 mm according to the size of the defects and the position of the ultrasonic probe, the scanning range is 30 mm*20 mm, and a total of 600 points are obtained.

[0105] Through an energy spectrum analysis algorithm, the energy spectrum corresponding to the wave field map is extracted, then whether a defect exists and the position of the defect are determined by analyzing the main peak energy redistribution of the energy spectrum. At the same time, the energy spectra at different times when passing through the defect are analyzed, the propagation process of the ultrasonic waves and the interaction process with the defect can be analyzed. Finally, by analyzing the energy difference or ratio before and after passing through the defect, and combining the different depths of the defect, the detection and characterization of the crack-type defect are realized.

[0106] Through analysis, a corresponding relationship between the crack size is established, and part of the experimental results are as follows:

[0107] First, a point not passing through the defect is selected from the 600 scanning point data, and its time-frequency domain data is obtained, which is used to analyze the time domain and frequency domain signals of the sound waves when not passing through the defect. Since the time-frequency domain data of each point changes when passing through the defect, it can be used as a basis for judging whether the sound waves pass through the defect. The 0.7 mm deep defect is taken as the analysis object. Its time-frequency domain signal is as shown in Figure 2 .

[0108] For the 600 collected scanning point data, we reconstruct the laser ultrasonic wave field at different times through the acoustic mutual incompatibility, and divide it into two cases of not passing through the defect, contact defect and passing through the defect, as shown in Figure 3 .

[0109] Through the propagation process of the sound wave, we can judge whether the defect exists or not, and further obtain the position of the defect. Through the above preliminary experiment, the preliminary position of the defect is judged to be 15mm in the scanning range.

[0110] Through the propagation process of the ultrasonic wave before, the preliminary position of the defect is obtained, and then the energy spectrum of the laser ultrasonic wave field at different times near the defect is obtained. Thus, the interaction process of the defect and the ultrasonic wave field is analyzed, and the energy redistribution characteristics of the defect on the laser ultrasonic wave field are emphasized, as shown in Figure 4 , wherein A and B are the energy spectrum of the wave field not passing through the defect and the energy spectrum of the wave field passing through the defect respectively.

[0111] In addition to analyzing the energy spectrum passing through the defect and not passing through the defect, the energy spectrum near the defect is emphasized, so as to obtain the interaction process of the defect and the sound wave. The energy spectrum near the defect is shown in Figure 5 .

[0112] Through the analysis of the wave field energy spectrum at different times near the defect, the interaction of the defect and the defect is obtained, including the energy redistribution of the defect on the sound wave.

[0113] Finally, the quantitative characterization of the defect is realized by calculating the energy difference passing through the defect and not passing through the defect. In addition to directly using the energy difference to realize the quantitative characterization of the defect, the AI algorithm can be used for artificial intelligence learning, so as to realize more accurate defect characterization.

[0114] Finally, through the energy spectrum analysis of the laser ultrasonic wave field, the detection of the defect is realized, including the position detection, the interaction analysis of the defect and the sound wave and the quantitative characterization.

[0115] The present application analyzes from the energy angle, which can effectively reduce the influence of laser ultrasonic with wide frequency band on the result compared with other characterization methods.

[0116] At the same time, the energy spectrum is extracted from the ultrasonic wave field diagram instead of the energy spectrum of a single excitation point, which can consider the case of multiple excitation points to further reduce the influence of single signal, and greatly ensure the calculation accuracy of the final result.

[0117] At the same time, the crack closure effect is fully considered, and through the present application, the quantitative characterization and detection ability of laser ultrasonic can be improved, and the application and research of the crack closure effect can be promoted.

[0118] In summary, the laser ultrasonic crack size quantitative characterization method and system based on energy spectrum analysis in the application, a groove with a certain width, length and depth is processed on the surface of the measured object as a crack by linear cutting, and the depth is taken as the characterization object; high-power pulsed laser is used to excite ultrasonic waves on the surface and inside of the measured object, and laser ultrasonic time-frequency domain signals are obtained; surface wave signals are collected by using a surface acoustic probe or an optical interference method, and the movement scanning of the light spot or the measured object is realized through a two-dimensional galvanometer or a precision motion platform, and according to the acoustic reciprocity, the reconstruction of the laser ultrasonic wave field near the defect is realized. The energy spectrum of the wave field is obtained from the laser ultrasonic wave field by the energy spectrum algorithm, and whether the defect exists and the positioning of the defect are determined according to the energy change of the main peak of the energy spectrum. The propagation process of the acoustic wave and the interaction process with the defect are obtained by analyzing the energy redistribution characteristics of the energy spectrum, and finally the characterization of the defect is realized through the energy difference or ratio. In addition, other parameters can be extracted by artificial intelligence and other methods to realize higher-precision defect characterization. The application fully considers the interaction between the crack and the defect, including the redistribution characteristics of the acoustic wave energy, and improves the detection and characterization capabilities of the laser ultrasonic.

[0119] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the division of the above functional units and modules is exemplified, and in actual application, the above functions can be completed by different functional units and modules according to needs, that is, the internal structure of the device is divided into different functional units or modules to complete all or part of the functions described above. Each functional unit and module in the embodiment can be integrated in one processing unit, or each unit can exist physically, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware or software. In addition, the specific names of each functional unit and module are only for easy distinction, and do not limit the protection scope of the application. The specific working process of the units and modules in the system can refer to the corresponding process in the foregoing method embodiments, which will not be repeated here.

[0120] In the above embodiments, the description of each embodiment has its own emphasis, and the parts not described or recorded in detail in a certain embodiment can be referred to the relevant description of other embodiments.

[0121] Those skilled in the art can understand that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be realized by electronic hardware or a combination of computer software and electronic hardware. Whether the functions are realized in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0122] In the embodiments provided by the present application, it should be understood that the disclosed apparatus / terminal and method can be implemented in other ways. For example, the apparatus / terminal embodiments described above are merely schematic. For example, the division of the modules or units is merely a logical function division, and there can be another division manner in actual implementation. For example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the displayed or discussed coupling or direct coupling or communication connection between the units can be indirect coupling or communication connection through some interface, device or unit, and can be electrical, mechanical or in other forms.

[0123] The units described as separate components can or can not be physically separate, and the components shown as units can or can not be physical units, i.e. they can be located in one place, or distributed on a plurality of network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the embodiments.

[0124] In addition, each functional unit in each embodiment of the present application can be integrated into a processing unit, or each unit can exist physically independently, or two or more units can be integrated into one unit. The integrated unit can be realized in the form of hardware or in the form of a software functional unit.

[0125] The integrated module / unit, if realized in the form of a software function unit and sold or used as an independent product, can be stored in a computer-readable storage medium. Based on such understanding, all or part of the processes in the above-mentioned embodiment methods can also be completed by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of each method embodiment when executed by a processor. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or some intermediate forms, etc. The computer-readable medium can include any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal, and software distribution medium, etc. It should be noted that the computer-readable medium can include or exclude contents according to the requirements of legislation and patent practice in the jurisdiction, for example, in some jurisdictions, according to legislation and patent practice, the computer-readable medium does not include electrical carrier signals and telecommunication signals.

[0126] The present application is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of flows and / or blocks in the flowcharts 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, a special-purpose computer, an embedded processor, or other programmable data processing apparatus to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing apparatus generate a means for implementing the functions specified in the flowcharts and / or block diagrams. Figure 1 The means for implementing the functions specified in one or more flows and / or blocks. Figure 1 The means for implementing the functions specified in one or more flows and / or blocks.

[0127] These computer program instructions can also be stored in a computer-readable memory capable of instructing the computer or other programmable data processing apparatus to work in a specific manner, so that the instructions stored in the computer-readable memory produce a manufactured product including instruction means, which implements the functions specified in the flowcharts and / or block diagrams. Figure 1 The means for implementing the functions specified in one or more flows and / or blocks. Figure 1 The means for implementing the functions specified in one or more flows and / or blocks.

[0128] These computer program instructions can also be loaded into a computer or other programmable data processing devices, so that a series of operational steps are performed on the computer or other programmable data processing devices to generate a computer implemented process, so that the instructions executed on the computer or other programmable data processing devices provide a process for implementing the flowchart Figure 1 one flowchart or multiple flowcharts and / or blocks Figure 1 one flowchart or multiple flowcharts and / or blocks

[0129] The above is only to illustrate the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical scheme falls within the protection scope of the claims of the present application.

Claims

1. A method for laser ultrasonic crack size quantitative characterization based on energy spectrum analysis, characterized in that, The method comprises the following steps: S1, taking the crack depth as a to-be-characterized dimension, processing a crack on the surface of the measured object; S2, exciting ultrasonic waves on the surface and inside of the measured object obtained in step S1 by using high-power pulsed laser respectively; S3, moving the measured object or the laser beam to realize the movement of the laser spot, completing laser ultrasonic scanning detection of the defect, and reconstructing the laser ultrasonic wave field based on the data collected by laser ultrasonic scanning; S4, solving the energy spectrum of the laser ultrasonic wave field obtained in step S3, judging the defect position according to the energy spectrum, setting a scanning interval, obtaining the laser ultrasonic wave field map of the defect through scanning detection of the spot, and then obtaining the energy spectrum of the laser ultrasonic wave field at different times by using the energy spectrum algorithm; S5, determining the time when the laser ultrasonic wave passes through the defect according to the defect position obtained in step S4, analyzing the wave field energy spectrum of the laser ultrasonic wave passing through the defect at multiple times, and obtaining the energy spectrum change of the laser ultrasonic wave in the process of passing through the defect, wherein the energy spectrum change of the laser ultrasonic wave in the process of passing through the defect includes the redistribution characteristics of the defect to the laser ultrasonic energy; S6, determining the energy attenuation of the energy spectrum when passing through the defect based on the energy spectrum change obtained in step S5, establishing a single correspondence between the energy spectrum and the defect depth, and realizing quantitative characterization of the crack size, specifically: summing all energies of the energy spectrum of the wave field passing through the defect and the wave field not passing through the defect, calculating the energy difference and the energy ratio, establishing a correspondence between the energy spectrum and the defect depth, realizing quantitative characterization of the defect depth, and extracting corresponding parameters from the energy spectrum by using an artificial intelligence method to realize characterization of the defect.

2. The laser ultrasonic crack size quantitative characterization method based on energy spectrum analysis according to claim 1, characterized in that, In step S1, the depth of the crack is 0.1 mm, 0.3 mm, 0.5 mm, 0.7 mm and 0.9 mm.

3. The laser ultrasonic crack size quantitative characterization method based on energy spectrum analysis according to claim 2, characterized in that, The length of the crack is 5 mm, and the width is 0.5 mm.

4. The laser ultrasonic crack size quantitative characterization method based on energy spectrum analysis according to claim 1, characterized in that, In step S2, the ultrasonic waves are excited on the surface and inside of the measured object by using thermal elastic effect or ablation effect.

5. The laser ultrasonic crack size quantitative characterization method based on energy spectrum analysis according to claim 1, characterized in that, In step S3, the corresponding signals are collected by using an ultrasonic probe or an optical interference method to obtain laser ultrasonic time-frequency domain signals.

6. A laser ultrasonic crack size quantitative characterization system based on energy spectrum analysis, characterized in that, The method comprises: a processing module, which processes a crack on the surface of the measured object by taking the crack depth as a to-be-characterized dimension; an exciting module, which excites ultrasonic waves on the surface and inside of the measured object obtained by the processing module by using high-power pulsed laser; a scanning module, which moves the measured object or the laser beam to realize the movement of the laser spot, completes laser ultrasonic scanning detection of the defect, and reconstructs the laser ultrasonic wave field based on the data collected by laser ultrasonic scanning; a calculation module, which solves the energy spectrum of the laser ultrasonic wave field obtained by the scanning module, judges the defect position according to the energy spectrum, sets a scanning interval, obtains the laser ultrasonic wave field map of the defect through scanning detection of the spot, and then obtains the energy spectrum of the laser ultrasonic wave field at different times by using the energy spectrum algorithm; and The characterization module determines the time when the laser ultrasonic wave passes through the defect according to the defect position obtained by the calculation module, analyzes the wave field energy spectrum of the laser ultrasonic wave passing through the defect at multiple times, obtains the energy spectrum change of the laser ultrasonic wave in the process of passing through the defect, and the energy spectrum change of the laser ultrasonic wave in the process of passing through the defect includes the redistribution characteristics of the defect to the laser ultrasonic energy; based on the energy spectrum change, the attenuation of the energy spectrum energy when passing through the defect is determined, a single corresponding relationship between the energy spectrum and the defect depth is established, and quantitative characterization of the crack size is realized, specifically as follows: The energy of the energy spectrum of the wave field passing through the defect and the energy spectrum of the wave field not passing through the defect is summed, and the energy difference and the energy ratio are calculated, the corresponding relationship between the energy spectrum and the defect depth is established, the quantitative characterization of the defect depth is realized, and the corresponding parameters are extracted from the energy spectrum by using an artificial intelligence method to realize the characterization of the defect.

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