Waveguide device and method based on nonlinear characteristics of component R zone

Abstract

The present invention provides a nonlinear characteristic waveguide device and method based on the R zone of a component, and aims at the detection and evaluation of the R zone of a complex-shaped component of a composite material, through a single-mode narrow-band flexible electromagnetic ultrasonic transducer for exciting characteristic waveguide, and a multi-mode broadband flexible electromagnetic ultrasonic transducer for receiving the nonlinear effect of the characteristic waveguide, to achieve rapid and long-distance detection and evaluation of the stress in the unreachable R zone. The present invention adopts non-contact flexible electromagnetic ultrasonic detection technology, excites the characteristic waveguide mode according to the geometric size of the structural area, performs data processing on the received signal to obtain the relative nonlinear parameters in the structural area, that is, uses the relative nonlinear parameters as coefficient factors to achieve effective characterization of the overall stress of the structural area, increases convenience, and improves detection efficiency.

Description

Technical Field

[0001] The present invention discloses a nonlinear characteristic waveguide device and method for evaluating the stress concentration degree of the R zone of a composite material component with a complex shape. According to the International Patent Classification (IPC), the device belongs to the field of nondestructive testing. Specifically, the device uses nonlinear ultrasonic waveguide to evaluate the stress concentration degree of the R zone of a composite material component with a complex shape. Background Art

[0002] With the development of industrial technology and the continuous improvement of structural design requirements, the geometric shapes of composite engineering components are becoming more and more complex, and corner areas, namely R areas, are common. R areas are important connections and geometric transition areas in the structure, which play a role in bearing and transmitting force. During processing and service, stress concentration is easily formed, resulting in defects. In order to ensure the manufacturing quality and service safety of complex-shaped composite components, it is necessary to develop reliable non-destructive testing technology for complex-shaped R areas of composite materials.

[0003] At present, the non-destructive testing of the complex shape R zone of composite materials is mainly linear ultrasonic testing, which mainly uses the reflection and transmission principle of waves to measure acoustic parameters such as sound velocity, attenuation, spectrum, amplitude, etc. However, linear ultrasonic testing technology has limitations. In the early stage of material damage, when the damage is relatively small, the changes in acoustic parameters such as wave velocity and first wave amplitude are small, and it is not sensitive to stress damage in the early stage of the material. Compared with linear ultrasonic testing, nonlinear ultrasonic testing has higher detection sensitivity. By using the nonlinear response of ultrasonic waves that is sensitive to early stress damage of materials, relative nonlinear parameters can be used as coefficient factors to effectively characterize the overall stress of the structural area. Nonlinear ultrasonic guided wave technology is one of the current research hotspots in the field of non-destructive testing. It uses the nonlinear effect of stress in the material and ultrasonic waveguide to effectively detect stress concentration in the material.

[0004] At present, ultrasonic testing of R-zone of complex-shaped composite components is mainly carried out by phased array ultrasonic testing, such as the ultrasonic testing method of R-zone component defects and stress based on synthetic aperture dynamic focusing with application number CN202111037507. Its main shortcomings include:

[0005] (1) The front end of the probe is larger, so the blind area is also larger. Most methods require the use of wedges and coupling agents to achieve detection, which increases the influence of human factors on the results, resulting in low quality of R zone detection.

[0006] (2) The detection efficiency is low and the detection accuracy is not high. At present, the main phased array detection method is point-to-point scanning. For large and long-distance components, multiple inspections are required, and the detection efficiency is low. In addition, for some composite materials with complex shapes, the R area is a closed inner cavity and the middle is an inaccessible area, so this method cannot be used for inspection.

[0007] In addition, the phased array detection method is more expensive than traditional ultrasonic sensors and can only detect late damage in the complex shape R zone of the composite material, when the damage is more serious. Therefore, it is of great significance to detect stress concentration in the complex shape R zone of the composite material at an early stage. Summary of the invention

[0008] A brief summary of embodiments of the present invention is provided below to provide a basic understanding of certain aspects of the present invention. It should be understood that the following summary is not an exhaustive summary of the present invention. It is not intended to identify key or important parts of the present invention, nor is it intended to limit the scope of the present invention. Its purpose is merely to provide certain concepts in a simplified form as a prelude to a more detailed description discussed later.

[0009] In view of the shortcomings of the above-mentioned prior art, the present invention provides a nonlinear characteristic waveguide method and device for evaluating the stress concentration degree of the R zone of complex-shaped components of composite materials. The technology of R-zone stress detection by exciting characteristic waveguide with nonlinear ultrasonic method and electromagnetic resonance technology solves the problems of high detection cost, poor detection accuracy and low detection efficiency of R zone of complex-shaped components of composite materials.

[0010] To achieve the above-mentioned purpose, on the one hand, the present invention provides a nonlinear characteristic waveguide device based on the R zone of a component, comprising: an ultrasonic signal generator, a single-mode narrowband flexible electromagnetic ultrasonic transducer (excitation probe), a multi-mode broadband flexible electromagnetic ultrasonic transducer (receiving probe), a first signal generator, a second signal generator, an oscilloscope, a first signal amplifier (power amplifier), a second signal amplifier, a bandpass filter and a computer; the ultrasonic signal generator is interconnected with the computer and the oscilloscope; the ultrasonic signal generator has an excitation end and a receiving end, and the excitation end of the ultrasonic signal generator The first end is connected to the first bandpass filter and the first signal amplifier in sequence, and then connected to the single-mode narrow-band flexible electromagnetic ultrasonic transducer; the receiving end of the ultrasonic signal generator is connected to the second bandpass filter and the second signal amplifier in sequence, and then connected to the multi-mode broadband flexible electromagnetic ultrasonic transducer; the multi-mode broadband flexible electromagnetic ultrasonic transducer and the single-mode narrow-band flexible electromagnetic ultrasonic transducer are respectively placed on both sides of the R zone of the measured component; the single-mode narrow-band flexible electromagnetic ultrasonic transducer is narrow-band and can only excite a single modal characteristic waveguide signal, and the multi-mode broadband flexible electromagnetic ultrasonic transducer is broadband and can receive multiple modes.

[0011] Among them, the ultrasonic signal generator sends out an ultrasonic signal with an excitation frequency of f0, which is filtered and amplified by the first bandpass filter and the first signal amplifier, and then the single-mode narrow-band flexible electromagnetic ultrasonic transducer induces a characteristic guided wave on one side of the R zone of the measured component, and the characteristic guided wave propagates axially along the R zone of the measured component. The multi-mode broadband flexible electromagnetic ultrasonic transducer located on the other side of the R zone of the measured component receives the ultrasonic signal with an excitation frequency of 3f0, and sends it to the computer for signal analysis and processing after amplification and filtering by the second signal amplifier and the second bandpass filter; the received ultrasonic signal of the R zone of the measured component under stress concentration conditions is tested, and the ultrasonic signal under stress concentration conditions is Fourier transformed to obtain the corresponding frequency spectrum, and then the ultrasonic signal amplitude α1 of the excitation frequency f0 and the ultrasonic signal amplitude α3 of the excitation frequency 3f0 are obtained, and the nonlinear parameter β1 under stress concentration conditions is obtained from the ultrasonic signal amplitude α1 and the ultrasonic signal amplitude α3. The received ultrasonic signal in the R zone of the tested component under stress-free conditions is tested, and the ultrasonic signal under stress-free conditions is Fourier transformed to obtain the corresponding frequency spectrum, and then the ultrasonic signal amplitude of the excitation frequency f0 and the ultrasonic signal amplitude of the excitation frequency 3f0 under stress-free conditions are obtained, and the nonlinear parameter β0 is also obtained. The nonlinear parameters β1 and β0 can be used to characterize stress.

[0012] Among them, the excitation frequency of the ultrasonic signal received by the multi-mode broadband flexible electromagnetic ultrasonic transducer located on the other side of the R zone of the measured component is 3f0, because a slight change in stress in the R zone can lead to obvious differences in the nonlinear response of the guided wave, especially the third harmonic of the wave is more sensitive to the stress information in the material. The principle is as follows: When ultrasonic waves propagate in a medium material containing stress concentration, waveform distortion occurs, generating double-frequency second harmonics, triple-frequency third harmonics, etc., which are called nonlinear responses of ultrasonic waves. Generally speaking, the greater the concentrated stress, the more microscopic defects (dislocations, slips, microcracks), and the more obvious the nonlinear response of ultrasonic waves. The method based on electromagnetic ultrasonic resonance can measure the nonlinear response of the material while increasing the signal strength. According to the measured ultrasonic nonlinear response, the corresponding parameters can be constructed to characterize the internal structure of the material.

[0013] The nonlinear parameter β1 is obtained by filtering the received ultrasonic signal with a bandpass filter, averaging the data multiple times, and observing, extracting, and processing with an oscilloscope.

[0014] In order to better adapt to the semi-analytical finite element method of the present application, the cross section of the R zone of the measured component remains unchanged in the axial direction. The present invention is a single-mode narrow-band flexible electromagnetic ultrasonic transducer and a multi-mode broadband flexible electromagnetic ultrasonic transducer that are matched with each other under curvature.

[0015] Furthermore, the ultrasonic signal of the excitation frequency f0 is an ultrasonic excitation frequency selected based on a characteristic waveguide dispersion curve of the acoustic energy localized in the R region of the tested component calculated according to the geometric shape of the tested test piece.

[0016] The single-mode narrowband flexible electromagnetic ultrasonic transducer and the multi-mode broadband flexible electromagnetic ultrasonic transducer have the same structure, both are arc-shaped structures, and both include a racetrack-shaped coil and trapezoidal permanent magnets with opposite polarities arranged on the racetrack-shaped coil to provide magnetic flux for the coil and arranged periodically, and the curvature of the arc-shaped structure is the same as the curvature of the R zone of the measured component. The spacing of the racetrack-shaped coil is half the wavelength of the excited characteristic guided wave.

[0017] Furthermore, the mode narrowband flexible electromagnetic ultrasonic transducer and the multi-mode broadband flexible electromagnetic ultrasonic transducer and the test piece are fixed during detection, and the centers of the narrowband flexible electromagnetic ultrasonic transducer and the multi-mode broadband flexible electromagnetic ultrasonic transducer are aligned with the center of the test piece.

[0018] Furthermore, the phase velocity v0 of the characteristic waveguide at the excitation frequency f0 is obtained from the characteristic waveguide dispersion curve of the R region of the measured component, and then the wavelength λ0 is calculated, λ0=v0 / f0, thereby obtaining the coil spacing d of the racetrack coil, d=λ0 / 2.

[0019] Furthermore, the propagation direction of the characteristic guided wave is the vertical direction of the structural cross section of the R zone of the measured component, and the wavelength λ0 of the characteristic guided wave is greater than or equal to the cross-sectional width of the R zone.

[0020] Furthermore, the coil of the single-mode narrowband flexible electromagnetic ultrasonic transducer and the coil of the multi-mode broadband flexible electromagnetic ultrasonic transducer are both racetrack-shaped coils, and the arc structure of the racetrack-shaped coil has the same curvature as the R zone of the measured component.

[0021] On the one hand, the present invention provides a nonlinear characteristic waveguide method based on the R zone of a component, comprising: exciting a characteristic waveguide mode according to the geometric dimensions of the R zone of a measured component under stress concentration conditions and stress-free conditions, performing data processing on the received ultrasonic signal, obtaining a relative nonlinear parameter of the R zone of the measured component, and using the relative nonlinear parameter as a coefficient factor to achieve effective characterization of the overall stress of the structural area.

[0022] Specifically, the method includes the following steps:

[0023] According to the geometric shape of the R region of the tested component (R region of the tested composite material complex shape component), the characteristic guided wave dispersion curve of the acoustic energy localized in the R region is obtained, and the frequency f0, phase velocity v0 and wavelength λ0 of the excited characteristic guided wave are determined;

[0024] The ultrasonic signal received in the R zone of the tested component under stress concentration conditions is tested, and the ultrasonic signal under stress concentration conditions is Fourier transformed to obtain the corresponding spectrum, and then the ultrasonic signal amplitude α1 of the excitation frequency f0 and the ultrasonic signal amplitude α3 of the triple excitation frequency 3f0 are obtained. The nonlinear parameter β1 under stress concentration conditions is obtained from the ultrasonic signal amplitude α1 and the ultrasonic signal amplitude α3.

[0025] The ultrasonic signal received in the R region of the tested component under stress-free conditions is tested, and the ultrasonic signal under stress-free conditions is Fourier transformed to obtain the corresponding frequency spectrum, and then the ultrasonic signal amplitude of the excitation frequency f0 and the ultrasonic signal amplitude of the excitation frequency 3f0 under stress-free conditions are obtained, and the nonlinear parameter β0 is also obtained;

[0026] The relative nonlinear parameter β is calculated from the nonlinear parameters β1 and β0. The relative nonlinear parameter β is the ratio of the nonlinear parameters under stress concentration state and under stress-free state. According to the size of the relative nonlinear parameter β, the stress concentration degree of the R zone of the complex-shaped component of the composite material can be qualitatively and quantitatively evaluated.

[0027] Furthermore, the characteristic waveguide dispersion curve can be obtained by using the semi-analytical finite element method combined with the perfect matching layer technology. The specific process includes:

[0028] Consider a wave propagating in a solid waveguide with a constant cross section. Its displacement vector can be written as:

[0029]

[0030] Where k is the complex wave number, ω = 2πf is the angular frequency, t is the time variable, and the subscript i = 1, 2, 3 represents the coordinate axis direction number (x3 is the axial direction). For anisotropic materials, the dynamic equilibrium equation is:

[0031]

[0032] Among them C ikjl is the stiffness tensor, and ρ is the mass density. Substituting the displacement vector into the dynamic equilibrium equation, we can obtain the problem of solving the eigenvalue of the partial differential motion equation:

[0033]

[0034] δ ij is the Kronecker function (when i=j, δ ij =1, otherwise δ ij =0), V j =kU j .

[0035] Then, the perfect matching layer technology is combined to expand the real coordinates of the physical equation into complex coordinates through analytical methods to realize the infinite width plate. The coordinate expansion function is defined as:

[0036]

[0037] in:

[0038]

[0039] Finally, the partial differential motion equation is obtained:

[0040]

[0041] in:

[0042]

[0043] This equation can be solved to obtain the characteristic waveguide frequency with the help of the eigenvalue solver in the commercial finite element software COMSOL.

[0044] The present invention realizes a nonlinear characteristic waveguide method and device for evaluating the stress concentration degree of the R zone of a composite material complex shape component through the above scheme. The characteristic waveguide is excited on one side of the R zone of the composite material complex shape component by using a narrowband flexible electromagnetic ultrasonic transducer and a multi-mode broadband flexible electromagnetic ultrasonic transducer, and the amplitude α1 of the excitation frequency and the amplitude α3 of the triple excitation frequency are received on the other side to obtain the nonlinear parameters characterizing the stress concentration degree in the R zone of the composite material complex shape component. The nonlinear parameters under stress-free conditions are used as the standard, and the nonlinear parameters of the R zone of other composite material complex shape components in the comparison test can be used to determine the stress concentration degree of the R zone of the composite material complex shape component.

[0045] The present invention adopts the above scheme, and aims at the detection and evaluation of the R zone of the complex-shaped components of composite materials, through a single-mode narrow-band flexible electromagnetic ultrasonic transducer for exciting characteristic waveguides, and a multi-mode broadband flexible electromagnetic ultrasonic transducer for receiving the nonlinear effect of the characteristic waveguides, to achieve rapid and long-distance detection and evaluation of the stress in the unreachable R zone. The present invention adopts non-contact flexible electromagnetic ultrasonic detection technology, excites the characteristic waveguide mode according to the geometric dimensions of the structural area, and performs data processing on the received signal to obtain the relative nonlinear parameters in the structural area, that is, the relative nonlinear parameters are used as coefficient factors to achieve effective characterization of the overall stress of the structural area. The present invention effectively reduces the system error and condition cost of traditional ultrasonic detection, increases convenience, and improves detection efficiency. At the same time, the characteristics of characteristic waveguides can be used to detect from any side, simplifying the difficulty of R zone detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The present invention may be better understood by referring to the following description given in conjunction with the accompanying drawings, wherein the same or similar reference numerals are used throughout the drawings to represent the same or similar components. The accompanying drawings, together with the following detailed description, are included in and form a part of this specification and are used to further illustrate the preferred embodiments of the present invention and to explain the principles and advantages of the present invention. In the drawings:

[0047] Figure 1 is a wiring diagram of a detection device according to an embodiment of the present invention;

[0048] Figure 2 It is a schematic diagram of the arc structure of the single-mode narrow-band flexible electromagnetic ultrasonic transducer and the R zone of the measured component in the present invention;

[0049] Figure 3 A top view of a single-mode narrow-band flexible electromagnetic ultrasonic transducer according to an embodiment of the present invention;

[0050] Figure 4 1 is a top view of a multi-mode broadband flexible electromagnetic ultrasonic transducer according to an embodiment of the present invention. DETAILED DESCRIPTION

[0051] Embodiments of the present invention will be described below with reference to the accompanying drawings. Elements and features described in one drawing or one embodiment of the present invention may be combined with elements and features shown in one or more other drawings or embodiments. It should be noted that for the purpose of clarity, the representation and description of components and processes that are not related to the present invention and are known to those of ordinary skill in the art are omitted in the drawings and descriptions.

[0052] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0053] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0054] Example 1

[0055] This embodiment provides a nonlinear characteristic waveguide device for evaluating the stress concentration degree of the R zone of a complex-shaped composite component. Figure 1-Figure 4 , including an ultrasonic signal generator 1, a first bandpass filter 22, a second bandpass filter 21, a first signal amplifier 32, a second signal amplifier 31, a single-mode narrowband flexible electromagnetic ultrasonic transducer 4, a multi-mode broadband flexible electromagnetic ultrasonic transducer 5, a composite material complex shape component R zone specimen 6, an oscilloscope 7 and a computer 8. The ultrasonic signal generator 1 is connected to the computer 8, and the oscilloscope 7 is connected to the ultrasonic signal generator 1 to display the waveform. One end of the ultrasonic signal generator 1 is an excitation end, and the other end is a receiving end. The excitation end of the ultrasonic signal generator 1 is connected to the first bandpass filter 22, the first bandpass filter 22 is connected to the second signal amplifier 32, and the second signal amplifier 32 is connected to the single-mode narrowband flexible electromagnetic ultrasonic transducer 4; the receiving end of the ultrasonic signal generator 1 is connected to the second bandpass filter 21, the second bandpass filter 21 is connected to the second signal amplifier 31, and the second signal amplifier 31 is connected to the multi-mode broadband flexible electromagnetic ultrasonic transducer 5; the single-mode narrowband flexible electromagnetic ultrasonic transducer 4 and the multi-mode broadband flexible electromagnetic ultrasonic transducer 5 are placed on both sides of the R zone of the composite material complex shape component R zone specimen 6 to perform non-destructive testing on the R zone of the tested component.

[0056] During detection, the single-mode narrow-band flexible electromagnetic ultrasonic transducer 4 receives an ultrasonic signal with an excitation frequency of f0 emitted by the ultrasonic signal generator 1 and filtered by the band-pass filter 2, and induces a characteristic guided wave on one side of the composite material complex shape component R zone specimen 6. The characteristic guided wave propagates axially along the R zone of the composite material complex shape component. On the other side of the composite material complex shape component R zone specimen 6, the multi-mode broadband flexible electromagnetic ultrasonic transducer 5 is used to receive an ultrasonic signal with a frequency of 3f0. After the signal is amplified by the signal amplifier 3 and filtered by the band-pass filter, it is input into the computer 8 for signal analysis and processing, and the received waveform is displayed by the oscilloscope 7.

[0057] Nonlinear characteristic waveguide device for evaluating stress concentration degree in R zone of complex shape composite components Figure 2As shown, 11 is a permanent magnet, and adjacent permanent magnets have opposite magnetic properties. 12 is a coil, and 13 is a measured object. The arrow direction is the magnetic direction.

[0058] The detection steps of the above nonlinear characteristic waveguide device are as follows:

[0059] A single-mode narrowband flexible electromagnetic ultrasonic transducer and a multi-mode broadband flexible electromagnetic ultrasonic transducer are used as the excitation and receiving probes respectively, and the center of the R zone specimen of the complex-shaped composite component is aligned and fixed with the center of the probe;

[0060] According to the geometric shape of the test piece, the characteristic waveguide dispersion curve of the acoustic energy localized in the R region is calculated by using the semi-analytical finite element method combined with the perfect matching layer technology, and the appropriate waveguide mode and ultrasonic excitation frequency f0 are selected;

[0061] A single-mode narrowband flexible electromagnetic ultrasonic transducer is used as an excitation end, and a multi-mode broadband flexible electromagnetic ultrasonic transducer is used as a receiving end, close to both ends of the test piece;

[0062] The single-mode narrow-band flexible electromagnetic ultrasonic transducer excites a characteristic guided wave with a frequency of f0 on one side, and the multi-mode broadband flexible electromagnetic ultrasonic transducer receives a signal with a characteristic guided wave with a frequency of 3f0 on the other side;

[0063] The phase velocity v0 of the characteristic guided wave at the frequency f0 is obtained, and then the wavelength λ0 is calculated to obtain the coil spacing d of the excitation coil; the calculation formula for the wavelength of the excited characteristic guided wave is: λ0=v0 / f0. The coil of the single-mode narrow-band flexible electromagnetic ultrasonic transducer is a racetrack coil, and the coil spacing formula is: d=λ0 / 2;

[0064] The received signal is filtered and averaged a certain number of times. An appropriate and wide signal interval is selected for windowed Fourier time-frequency transform. The frequency domain amplitude α1 of the excitation frequency f0 and the frequency domain amplitude α3 of the triple excitation frequency 3f0 in the corresponding spectrum are extracted. The nonlinear parameter β1 is calculated as follows:

[0065] The same method as above was used to test under stress-free conditions to obtain the nonlinear parameter β0;

[0066] Based on the value of the nonlinear parameter obtained under stress-free conditions as the evaluation benchmark, the relative nonlinear parameter β is obtained by comparing and testing specimens with other different stress concentration levels. The calculation formula is:

[0067] Among them, β0 is the nonlinear parameter obtained under stress-free conditions, and β1 is the nonlinear parameter under other stress concentration conditions.

[0068] Based on the obtained relative nonlinear parameters, the stress concentration degree in the R zone of complex-shaped components of composite materials can be qualitatively and quantitatively evaluated.

[0069] Among them, a single-mode narrow-band flexible electromagnetic ultrasonic transducer excites a single-mode characteristic guided wave below the excitation end. Due to the energy trapping effect, the characteristic guided wave propagates axially in the R region, and the broadband ultrasonic signal is received by the multi-mode broadband flexible electromagnetic ultrasonic transducer at the receiving end; the stress change in the material will cause the wave velocity to change, resulting in waveform distortion, gradually evolving from a simple harmonic wave to a sawtooth wave-like wave, resulting in the appearance of harmonic components higher than the fundamental frequency in the signal's spectrum.

[0070] The single-mode narrowband flexible electromagnetic ultrasonic transducer and the multi-mode broadband flexible electromagnetic ultrasonic transducer and the test piece are fixed during the test, and the center of the narrowband flexible electromagnetic ultrasonic transducer and the multi-mode broadband flexible electromagnetic ultrasonic transducer are aligned with the center of the test piece. The single-mode narrowband flexible electromagnetic ultrasonic transducer is narrow-band and can only excite a single-mode characteristic waveguide signal, and the multi-mode broadband flexible electromagnetic ultrasonic transducer is broadband and can receive multiple modes.

[0071] Both the single-mode narrowband flexible electromagnetic ultrasonic transducer and the multi-mode broadband flexible electromagnetic ultrasonic transducer are arc-shaped structures, and the curvature of the arc-shaped structure is the same as the curvature of the R zone of the complex-shaped component of the composite material. The single-mode narrowband flexible electromagnetic ultrasonic transducer and the multi-mode broadband flexible electromagnetic ultrasonic transducer include a racetrack-shaped coil of a flexible printed circuit board process and a periodically arranged trapezoidal permanent magnet with opposite polarities arranged on the racetrack-shaped coil. The coil spacing of the racetrack-shaped coil is half the wavelength of the characteristic waveguide of the excitation, and the single-mode narrowband flexible electromagnetic ultrasonic transducer coil performs good impedance matching.

[0072] Among them, the permanent magnet design of the single-mode narrowband flexible electromagnetic ultrasonic transducer and the multi-mode broadband flexible electromagnetic ultrasonic transducer are the same, but the coil design is different. The number of coils of the single-mode narrowband flexible electromagnetic ultrasonic transducer is half of that of the multi-mode broadband flexible electromagnetic ultrasonic transducer, and the coil spacing of the single-mode narrowband flexible electromagnetic ultrasonic transducer is twice that of the multi-mode broadband flexible electromagnetic ultrasonic transducer. The top view of the structure of the single-mode narrowband flexible electromagnetic ultrasonic transducer is shown in the figure. Figure 3 As shown in Figure 1, the coil spacing is λ / 2. Figure 4 As shown, the coil spacing is λ / 6.

[0073] The trapezoidal permanent magnets with opposite polarities arranged periodically on the racetrack-shaped coil of the single-mode narrowband flexible electromagnetic ultrasonic transducer and the multi-mode broadband flexible electromagnetic ultrasonic transducer refer to the trapezoidal permanent magnets with opposite polarities being adjacent to each other.

[0074] The single-mode narrow-band flexible electromagnetic ultrasonic transducer and the multi-mode broadband flexible electromagnetic ultrasonic transducer coils are special flexible coils. The trapezoidal permanent magnet is mainly used to form an approximate arc shape by arranging multiple magnets at the wide head, and is combined with the flexible coil to generate guided waves according to the electromagnetic effect.

[0075] The wavelength of the characteristic guided wave is greater than or equal to the cross-sectional width of the R zone in order to generate ultrasonic guided waves, and the specific wavelength can be set according to actual conditions.

[0076] The cross section of the R zone of the composite material complex shape component remains unchanged in the axial direction. The propagation direction of the excited characteristic guided wave is the vertical direction of the structural cross section of the R zone and the wavelength λ0 of the characteristic guided wave is greater than or equal to the cross section width of the R zone.

[0077] The nonlinear characteristic waveguide device for evaluating the stress concentration degree of the R zone of a composite material complex shape component of the present invention uses a narrowband flexible electromagnetic ultrasonic transducer and a multi-mode broadband flexible electromagnetic ultrasonic transducer to excite characteristic waveguides on one side of the R zone of the composite material complex shape component, and receives the amplitude α1 of the excitation frequency and the amplitude α3 of the triple excitation frequency on the other side, so as to obtain the nonlinear parameters characterizing the stress concentration degree in the R zone of the composite material complex shape component. The nonlinear parameters under stress-free conditions are used as the standard, and the nonlinear parameters of the R zone of other composite material complex shape components in the test can be compared to determine the stress concentration degree of the R zone of the composite material complex shape component.

[0078] The R zone of a complex-shaped composite component is usually a structure with a constant cross-section and a long axial extension. Due to the particularity of its structure, stress concentration is prone to occur, and existing methods cannot achieve rapid and effective evaluation of stress concentration in such inaccessible areas. This patent uses the above-mentioned single-mode narrow-band flexible electromagnetic ultrasonic transducer for detecting and evaluating the R zone of a complex-shaped composite component to excite characteristic guided waves; and a multi-mode broadband flexible electromagnetic ultrasonic transducer for receiving the nonlinear effect of the characteristic guided waves, to achieve rapid and long-distance detection and evaluation of stress in the inaccessible R zone. The present invention adopts non-contact flexible electromagnetic ultrasonic detection technology, excites characteristic guided wave modes according to the geometric dimensions of the structural area, and performs data processing on the received signals to obtain relative nonlinear parameters in the structural area, that is, using relative nonlinear parameters as coefficient factors to achieve effective characterization of the overall stress of the structural area. The present invention effectively reduces the system error and condition cost of traditional ultrasonic detection, increases convenience, and improves detection efficiency. At the same time, the characteristics of characteristic guided waves can be used to detect from any side, simplifying the difficulty of R zone detection.

[0079] Example 2

[0080] The present embodiment provides a nonlinear characteristic waveguide method for evaluating the stress concentration degree of the R zone of a composite material component with a complex shape, including the following process: according to the geometric structure of the R zone of the composite material component with a complex shape, the characteristic waveguide dispersion curve of the acoustic energy localized in the R zone is calculated in combination with the semi-analytical finite element method and the perfect matching layer technology, and the target waveguide mode and the ultrasonic excitation frequency f0 are selected; the target characteristic waveguide is excited, and an ultrasonic signal with a receiving frequency of 3f0 is received. The corresponding frequency spectrum is obtained by Fourier transforming the received signal of the composite material component with a complex shape under stress concentration conditions and the received signal under stress-free conditions, and then the ultrasonic signal amplitude α1 of the excitation frequency f0 and the ultrasonic signal amplitude α3 of three times the excitation frequency 3f0 are obtained, and the nonlinear parameters β1 and β0 are calculated. The ratio of the nonlinear parameters under stress concentration state and stress-free state is the relative nonlinear parameter β, where According to the size of the relative nonlinear parameters, the stress concentration degree of the R zone of the complex-shaped composite material component can be qualitatively and quantitatively evaluated.

[0081] This method is based on the R-zone stress detection technology of exciting characteristic guided waves using nonlinear ultrasonic methods and electromagnetic resonance technology, which solves the problems of high R-zone detection cost, poor detection accuracy and low detection efficiency for complex-shaped composite components.

[0082] Among them, the semi-analytical finite element method is combined with the perfect matching layer technology, specifically including:

[0083] Consider a wave propagating in a solid waveguide with a constant cross section. Its displacement vector can be written as:

[0084]

[0085] Where k is the complex wave number, ω = 2πf is the angular frequency, t is the time variable, and the subscript i = 1, 2, 3 represents the coordinate axis direction number (x3 is the axial direction). For anisotropic materials, the dynamic equilibrium equation is:

[0086]

[0087] Among them C ikjl is the stiffness tensor, and ρ is the mass density. Substituting the displacement vector into the dynamic equilibrium equation, we can obtain the problem of solving the eigenvalue of the partial differential motion equation:

[0088]

[0089] δ ij is the Kronecker function (when i=j, δ ij =1, otherwise δ ij =0), V j =kU j .

[0090] Then, the perfect matching layer technology is combined to expand the real coordinates of the physical equation into complex coordinates through analytical methods to realize the infinite width plate. The coordinate expansion function is defined as:

[0091]

[0092] in:

[0093]

[0094] Finally, the partial differential motion equation is obtained:

[0095]

[0096] in:

[0097]

[0098] This equation can be solved with the help of the eigenvalue solver in the commercial finite element software COMSOL to obtain the characteristic waveguide frequency.

[0099] According to the size of the relative nonlinear parameters, the stress concentration degree of the R zone of the complex-shaped composite material component can be qualitatively and quantitatively evaluated. This method is based on: (1) small stress changes in the R zone of the complex-shaped composite material component can lead to different nonlinear responses of the sound wave; (2) ultrasonic guided waves will produce energy concentration in the R zone of the complex-shaped composite material component, resulting in the generation of characteristic guided waves, which will propagate axially in the R zone of the complex-shaped composite material component; (3) the single-mode narrow-band flexible electromagnetic ultrasonic transducer has a narrow center frequency after good impedance matching. (4) The multi-mode broadband flexible electromagnetic ultrasonic transducer has no impedance matching and can accept broadband models. (5) The single-mode narrow-band flexible electromagnetic ultrasonic transducer and the multi-mode broadband flexible electromagnetic ultrasonic transducer are used as receiving and excitation probes, and the center is aligned and fixed with the center of the R zone of the complex-shaped composite material component.

[0100] The present invention solves the problem of poor stress detection accuracy and low detection efficiency in the R zone of a composite material component with complex shape based on the interaction relationship between the nonlinear ultrasound of characteristic guided waves and stress. A single-mode narrowband flexible electromagnetic ultrasonic transducer and a multi-mode broadband flexible electromagnetic ultrasonic transducer matching the R zone of a composite material component with complex shape are designed to ensure the stability of the coupling state in the detection, reduce the system error and condition cost of the detection, increase convenience, and improve the detection efficiency. At the same time, the characteristics of characteristic guided waves can be used to detect from any side, simplifying the difficulty of R zone detection, and can be used for on-site, real-time, and rapid detection and evaluation of the stress concentration degree in the R zone of a composite material component with complex shape.

[0101] In addition, the method of the present invention is not limited to being executed in the time sequence described in the specification, and may also be executed in other time sequences, in parallel or independently. Therefore, the execution order of the method described in this specification does not limit the technical scope of the present invention.

[0102] Although the present invention has been disclosed above by describing specific embodiments of the present invention, it should be understood that all the above embodiments and examples are exemplary rather than restrictive. Those skilled in the art may design various modifications, improvements or equivalents of the present invention within the spirit and scope of the appended claims. These modifications, improvements or equivalents should also be considered to be included in the protection scope of the present invention.

Claims

1. A nonlinear characteristic waveguide device based on the R zone of a component, characterized in that: include: An ultrasonic signal generator, a single-mode narrow-band flexible electromagnetic ultrasonic transducer, a multi-mode broadband flexible electromagnetic ultrasonic transducer, a first signal generator, a second signal generator, an oscilloscope, a first signal amplifier, a second signal amplifier, a bandpass filter and a computer; the ultrasonic signal generator is connected to the computer and the oscilloscope; the ultrasonic signal generator has an excitation end and a receiving end, the excitation end of the ultrasonic signal generator is sequentially connected to the first bandpass filter and the first signal amplifier, and then connected to the single-mode narrow-band flexible electromagnetic ultrasonic transducer; the receiving end of the ultrasonic signal generator is sequentially connected to the second bandpass filter and the second signal amplifier, and then connected to the multi-mode broadband flexible electromagnetic ultrasonic transducer; The multi-mode broadband flexible electromagnetic ultrasonic transducer and the single-mode narrow-band flexible electromagnetic ultrasonic transducer are respectively placed on both sides of the R zone of the measured component; the single-mode narrow-band flexible electromagnetic ultrasonic transducer is narrow-band and can only excite a single-mode characteristic waveguide signal, and the multi-mode broadband flexible electromagnetic ultrasonic transducer is broadband and can receive multiple modes; The ultrasonic signal generator sends out an ultrasonic signal with an excitation frequency of f0, and after filtering and amplification by the first bandpass filter and the first signal amplifier, the single-mode narrowband flexible electromagnetic ultrasonic transducer induces a characteristic guided wave on one side of the R zone of the measured component, and the characteristic guided wave propagates axially along the R zone of the measured component. The multi-mode broadband flexible electromagnetic ultrasonic transducer located on the other side of the R zone of the measured component receives the ultrasonic signal with an excitation frequency of 3f0, and after amplification and filtering by the second signal amplifier and the second bandpass filter, sends it to the computer for signal analysis and processing; the received ultrasonic signal of the R zone of the measured component under stress concentration conditions is tested, and the ultrasonic signal under stress concentration conditions is Fourier transformed to obtain a corresponding frequency spectrum, and then the ultrasonic signal amplitude α1 of the excitation frequency f0 and the ultrasonic signal amplitude α3 of the excitation frequency 3f0 are obtained, and the nonlinear parameter β1 under stress concentration conditions is obtained from the ultrasonic signal amplitude α1 and the ultrasonic signal amplitude α3. The ultrasonic signal received in the R region of the tested component under stress-free conditions is tested, and the ultrasonic signal under stress-free conditions is Fourier transformed to obtain the corresponding frequency spectrum, and then the ultrasonic signal amplitude of the excitation frequency f0 and the ultrasonic signal amplitude of the excitation frequency 3f0 under stress-free conditions are obtained, and the nonlinear parameter β0 is also obtained. The nonlinear parameters β1 and β0 can be used to characterize stress; Among them, the nonlinear parameter β1 is obtained by filtering the received ultrasonic signal with a bandpass filter and averaging the data multiple times, and finally observing, extracting and processing it with an oscilloscope; The single-mode narrow-band flexible electromagnetic ultrasonic transducer and the multi-mode broadband flexible electromagnetic ultrasonic transducer have the same structure, both are arc-shaped structures, and both include a racetrack-shaped coil and trapezoidal permanent magnets with opposite polarities arranged on the racetrack-shaped coil to provide magnetic flux therefor and arranged periodically, and the curvature of the arc-shaped structure is the same as the curvature of the R zone of the measured component; The single-mode narrowband flexible electromagnetic ultrasonic transducer, the multi-mode broadband flexible electromagnetic ultrasonic transducer and the component under test are fixed during testing, and the centers of the single-mode narrowband flexible electromagnetic ultrasonic transducer and the multi-mode broadband flexible electromagnetic ultrasonic transducer are aligned with the center of the component under test.

2. A waveguide device based on the nonlinear characteristics of the component R zone according to claim 1, characterized in that: The ultrasonic signal of the excitation frequency f0 is an ultrasonic excitation frequency selected based on a characteristic waveguide dispersion curve of the acoustic energy localized in the R region of the measured component calculated according to the geometric shape of the measured component.

3. A nonlinear characteristic waveguide device based on the R zone of a component according to claim 1, characterized in that: The phase velocity v0 of the characteristic waveguide at the excitation frequency f0 is obtained from the characteristic waveguide dispersion curve of the R region of the measured component, and the wavelength λ0=v0 / f0 is obtained, thereby obtaining the coil spacing d=λ0 / 2 of the racetrack type coil.

4. A waveguide device based on the nonlinear characteristics of the component R zone according to claim 1, characterized in that: The propagation direction of the characteristic guided wave is the vertical direction of the structural cross section of the R zone of the measured component, and the wavelength λ0 of the characteristic guided wave is greater than or equal to the cross-sectional width of the R zone.

5. A nonlinear characteristic waveguide method based on the R zone of a component, applied to the nonlinear characteristic waveguide device according to any one of claims 1 to 4, characterized in that: include: Under stress concentration conditions and stress-free conditions, characteristic guided wave modes are excited according to the geometric dimensions of the R zone of the measured component, and the received ultrasonic signals are processed to obtain the relative nonlinear parameters of the R zone of the measured component. The relative nonlinear parameters are used as coefficient factors to effectively characterize the overall stress of the structural area. The method specifically includes the following processes: According to the geometric shape of the R region of the measured component, the characteristic guided wave dispersion curve where the acoustic energy is localized in the R region is obtained, and the frequency f0, phase velocity v0 and wavelength λ0 of the excited characteristic guided wave are determined; The ultrasonic signal received in the R zone of the tested component under stress concentration conditions is tested, and the ultrasonic signal under stress concentration conditions is Fourier transformed to obtain the corresponding spectrum, and then the ultrasonic signal amplitude α1 of the excitation frequency f0 and the ultrasonic signal amplitude α3 of the triple excitation frequency 3f0 are obtained. The nonlinear parameter β1 under stress concentration conditions is obtained from the ultrasonic signal amplitude α1 and the ultrasonic signal amplitude α3. The ultrasonic signal received in the R region of the tested component under stress-free conditions is tested, and the ultrasonic signal under stress-free conditions is Fourier transformed to obtain the corresponding frequency spectrum, and then the ultrasonic signal amplitude of the excitation frequency f0 and the ultrasonic signal amplitude of the excitation frequency 3f0 under stress-free conditions are obtained, and the nonlinear parameter β0 is also obtained; The relative nonlinear parameter β is calculated from the nonlinear parameters β1 and β0. The relative nonlinear parameter β is the ratio of the nonlinear parameters under stress concentration state and under stress-free state. According to the size of the relative nonlinear parameter β, the stress concentration degree in the R zone of a complex-shaped composite component can be qualitatively and quantitatively evaluated.

6. A nonlinear characteristic waveguide method based on the R zone of a component according to claim 5, characterized in that: Characteristic guided wave The specific process of obtaining the dispersion curve includes the following steps: A wave propagates in a solid waveguide with a constant cross section, and its displacement vector is recorded as: Where k is the complex wave number, ω = 2πf is the angular frequency, t is the time variable, the subscript i = 1, 2, 3 represents the coordinate axis direction number, and x3 is the axial direction; for anisotropic materials, the dynamic equilibrium equation is: Among them C ikjl is the stiffness tensor, ρ is the mass density; bringing the displacement vector into the dynamic equilibrium equation, we get the problem of solving the eigenvalue of the partial differential motion equation: δ ij is the Kronecker function, when i=j,δ ij =1, otherwise δ ij =0, V j =kU j ; Then, the perfect matching layer technology is combined to expand the real coordinates of the physical equation into complex coordinates through analytical methods to realize the infinite width plate; the coordinate expansion function is defined as: in: Finally, the partial differential motion equation is obtained: in: This equation can be solved to obtain the characteristic waveguide frequency with the help of the eigenvalue solver in the commercial finite element software COMSOL.

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