An ultrasonic guided wave mode precision regulation device for a railway steel rail component and a method thereof

Abstract

This invention discloses a device and method for precise control of ultrasonic guided wave modes in railway rail components. The device includes a rail component, a multi-channel ultrasonic guided wave transducer array, a multi-channel control unit, and a processing module. The multi-channel ultrasonic guided wave transducer array is disposed on the outer surface of the rail component. The multi-channel ultrasonic guided wave transducer array is electrically connected to the multi-channel control unit and the processing module. The method includes acquiring information about the rail component and determining the target displacement field, establishing a guided wave mode analysis model of the rail component cross-section, screening target modes and determining the displacement extreme value region, determining the excitation complex weight of each transducer unit, and achieving target mode excitation, target region energy focusing, and target wave field synthesis through independent multi-channel control. This invention improves the ability to control the guided wave modes of railway rail components with complex cross-sections, reduces mode aliasing during the detection process, and enhances the distinguishability of target mode components, thereby providing support for the detection and monitoring of railway rail components.

Description

Technical Field

[0001] This invention belongs to the field of nondestructive testing (NDT) and structural health monitoring (SHM) technology, specifically relating to an ultrasonic guided wave monitoring technology applied to railway infrastructure; more specifically, this invention relates to an ultrasonic guided wave mode precision control device and method for railway rail components. Background Technology

[0002] Rail components (including stock rails, switch rails, and frog rails) are the core load-bearing parts of railway track systems. During train operation, these components are subjected to a complex service environment, including high-intensity wheel-rail impacts, alternating loads, and thermal stresses caused by temperature changes. With increasing service time, micro-cracks (such as rolling contact fatigue cracks and core defects) are highly likely to initiate and propagate inside the rails. If these early damages are not detected in time, they can easily develop into macroscopic fractures, especially in critical variable cross-section areas such as switch rails or frog rails. Failure in these areas can directly lead to catastrophic accidents such as train derailments. Therefore, efficient and accurate defect detection and monitoring of rail components are of paramount importance for ensuring railway transportation safety.

[0003] Among numerous non-destructive testing (NDT) technologies, ultrasonic guided wave technology has attracted significant attention due to its unique propagation characteristics. Compared to traditional NDT techniques, ultrasonic guided waves offer advantages such as low attenuation, long propagation distance, and the ability to cover the entire cross-section of long-distance components with a single-point excitation. This makes them particularly suitable for rapid screening of inaccessible or covered areas (such as the rail base). By using transducers installed on the rail surface to excite and receive guided waves, the effect of "one-point installation, full-line inspection" can be achieved, making it a current research hotspot in the field of railway structural health monitoring.

[0004] Ultrasonic guided waves are mechanoelastic waves constrained by the geometric boundaries of the propagation medium. As they propagate within the waveguide, they are formed by the continuous reflection, superposition, and mode conversion of body waves at the boundaries. This results in significant dispersion and multimodal characteristics in guided waves. Dispersion characteristics refer to the variation of the ultrasonic guided wave propagation velocity with frequency. Multimodal characteristics refer to the ability of multiple different guided wave vibration modes to coexist and propagate simultaneously within the waveguide structure under the same excitation frequency. This is particularly true for irregular, complex cross-sectional components like rails, and components with variable cross-sections along the longitudinal direction, such as turnout switch rails, where waveguide characteristics are especially complex. Within commonly used detection frequency bands, dozens of propagable modes often coexist in rails.

[0005] In existing technologies, single-channel transducers or simple conventional arrays are typically used to excite guided waves in rails. Due to the lack of detailed modeling and utilization of the spatial distribution characteristics of the displacement fields of each guided wave mode within the rail cross-section, existing excitation methods often excite multiple propagable modes simultaneously in practical applications. This results in the received echo signal containing multiple wave packets with different propagation velocities and waveform characteristics, leading to mode superposition in the time and frequency domains. This increases the complexity of signal analysis and adversely affects the identification and quantitative analysis of echoes from minor defects. Particularly in rail components with complex or variable cross-sectional characteristics, such as turnout switch rails and frog rails, existing technologies lack effective means for multi-channel active control of different modes, making it difficult to achieve selective excitation of specific modes or effective concentration of guided wave energy within specific regions of the cross-section. This limits further improvements in the detection signal-to-noise ratio and defect identification accuracy. Summary of the Invention

[0006] The main objective of this invention is to provide a method and apparatus for precise control of ultrasonic guided wave modes in railway rail components. In particular, it relates to sensor array optimization, pure mode excitation, and multi-mode energy focusing control technology based on the characteristics of cross-sectional modal displacement fields. By establishing an accurate cross-sectional numerical model, the geometric dimensions and arrangement of the multi-channel transducer array units are matched with the modal shape. By utilizing the active control of multi-channel time delay and phase, the excitation of specific pure modes or energy focusing in specific regions can be directly achieved during the physical excitation stage, thereby significantly reducing the difficulty of signal processing and improving the sensitivity of defect detection.

[0007] The core idea of ​​this invention does not lie in complex post-processing or algorithm optimization of the guided wave signal, but in introducing a physical constraint mechanism based on the distribution characteristics of the modal displacement field during the guided wave excitation stage. By matching the arrangement position and geometry of each transducer unit in the transducer array with the spatial distribution characteristics of the target guided wave mode in the coupling region of the rail section, such as the displacement extreme value region and the in-phase displacement region, and combining this with the independent control of the excitation complex weights of each channel, it is difficult for non-target modes to achieve effective coupling during the source-end excitation stage, thereby realizing selective excitation of the target guided wave mode, energy focusing in the target region, and synthesis of the target wave field.

[0008] This invention provides the following technical solution: A device for precise control of ultrasonic guided wave modes for railway rail components includes a rail component, a multi-channel ultrasonic guided wave transducer array, a multi-channel control unit, and a processing module. The multi-channel ultrasonic guided wave transducer array is disposed on the outer surface of the rail component. The multi-channel ultrasonic guided wave transducer array is electrically connected to the multi-channel control unit and the processing module.

[0009] The multi-channel ultrasonic guided wave transducer array includes multiple transducer units, which are arranged sequentially on the surface of the rail component along the outer contour of the rail component cross section. Each transducer unit is electrically connected to a multi-channel control unit.

[0010] The transducer unit is one of a piezoelectric transducer or a magnetostrictive transducer.

[0011] When the transducer unit adopts a piezoelectric transducer, the multi-channel control unit outputs a modulated voltage excitation signal; when the transducer unit adopts a magnetostrictive transducer, the multi-channel control unit outputs a modulated current excitation signal to drive an alternating magnetic field.

[0012] The rail component is one or more of the following: base rail, AT rail, switch rail, and center rail; the transducer unit is arranged along the cross-section of the rail component, and the cross-section of the rail component is one or more of the following: the heel end cross-section, the standard cross-section, and any cross-section selected along the longitudinal direction.

[0013] A method for modal control of railway rail components using an ultrasonic guided wave mode precision control device, comprising the following steps: S1. Parameter Input: Detect and acquire the basic information and target displacement field of the rail component; S2. Model Construction and Solution: Using the aforementioned basic information, a guided wave mode analysis model of the rail component cross section is established, and the set of propagable modes of the rail component cross section within the target frequency band and the displacement field function corresponding to each mode are obtained. Based on the target displacement field, target modes are selected from the set of propagable modes, and the displacement extreme value region is determined based on the displacement field function. S3. Array optimization arrangement: Based on the displacement extreme value region and spatial distribution characteristics of the target mode in the cross section of the rail component, determine the arrangement position and size of the transducer unit, and discretize the multi-channel ultrasonic guided wave transducer array in the coupling region of the cross section of the rail component. S4. Modal modulation excitation: Based on the coupling relationship between the target mode and the multi-channel ultrasonic guided wave transducer array, the excitation complex weight of each transducer unit is determined, and a driving signal corresponding to the excitation complex weight is applied to each transducer unit respectively. Then, the target wave field is synthesized inside the rail component. S5. Signal reception and post-processing: The multi-channel control unit receives the echo signal formed by the target wave field propagating in the rail component, and performs spatial filtering and mode decomposition processing on the echo signal according to the spatial distribution characteristics of the target mode, extracts the energy component of the target mode in the echo signal, and reconstructs one or more target mode signals reflecting the state characteristics and / or damage characteristics of the rail component.

[0014] In step S1, the basic information is one or more of the following: detection frequency, rail component material parameters, and rail component geometric parameters; the target displacement field is determined based on the energy focusing requirements or displacement distribution requirements within the preset area of ​​the rail component.

[0015] In step S2, the rail component cross-section is a rail component cross-section equipped with a multi-channel ultrasonic guided wave transducer array; the target frequency band is 30 kHz to 90 kHz. The guided wave modal analysis model is one or more combinations of a semi-analytical finite element model, a finite element model, and a wave finite element model.

[0016] In step S3, the arrangement position and size of the transducer unit are determined based on the distribution of the extreme displacement region and the characteristic length of the target mode in the coupling region of the rail component section, so that the arrangement position of the transducer unit matches the distribution position of the extreme displacement region of the target mode on the profile of the rail component section, and the size of the transducer unit matches the characteristic length; the characteristic length is the spatial variation scale of the target mode displacement field along the array arrangement direction in the coupling region, used to characterize the spatial distance of the displacement field changing from one extreme value to an adjacent extreme value or from in-phase to out-of-phase; the characteristic length is one or more combinations of the in-phase displacement region width and the equivalent width of the displacement extreme region.

[0017] Specifically, the characteristic length of the transducer unit is matched with the characteristic length of the displacement extreme region of the target mode, meaning that the effective excitation width of the transducer unit in the array arrangement direction is not greater than the width of the in-phase displacement region corresponding to the characteristic length.

[0018] In step S4, the synthesized target wavefield specifically refers to: Based on the energy distribution characteristics of different modes within a preset area of ​​the rail component cross section, the target mode and its multi-mode linear combination weights are determined, and a target mode vector is constructed. Then, based on the coupling relationship between the transducer channel and the modal response, the excitation complex weights of each transducer unit are calculated, and a driving signal with corresponding amplitude, phase, and time delay is applied to each transducer unit according to the excitation complex weights, thereby realizing target mode excitation, target region energy focusing, and target wave field synthesis within the rail component.

[0019] In step S5, the echo signal is one or more of the following combinations: echo signal formed by the target wave field propagating in the rail component through the boundary, end face, structural discontinuity area, echo signal formed by defect reflection, and echo signal formed by scattering. Each transducer unit receives the echo signal and transmits it to the multi-channel control unit.

[0020] Compared with the prior art, the present invention has the following beneficial effects: This invention does not primarily rely on complex signal post-processing or numerical separation algorithms. Instead, it introduces physical constraints and channel control mechanisms during the guided wave excitation stage based on the spatial distribution characteristics of the target modal displacement field. By matching the arrangement and geometry of each transducer unit in the transducer array with the extreme displacement region, in-phase displacement region, and spatial variation characteristics of the target mode on the rail cross section, and by applying excitation complex weights corresponding to the target mode to each channel, the excitation selectivity of the target mode can be improved, and the coupling response of non-target modes can be suppressed. This results in a target wave field with stronger modal selectivity within the structure, which is beneficial for the extraction and analysis of target modal features in the subsequent response signal.

[0021] Furthermore, by limiting the effective excitation width of the transducer unit in the array arrangement direction to the characteristic length range corresponding to the extreme value region of the target modal displacement, the spatial averaging effect caused by excessive transducer size can be reduced, and the excitation inefficiency caused by transducer arrangement near modal nodes or in the antiphase region can be avoided. This improves the consistency and effectiveness of excitation and reception of target modes of different orders, and enhances the applicability of this method in rail component condition assessment, local anomaly identification, and damage detection.

[0022] This invention can improve the ability to control the guided wave modes of railway rail components with complex cross sections, reduce mode aliasing during the detection process, and enhance the distinguishability of target mode components, thereby providing support for the detection and monitoring of railway rail components.

[0023] Under the premise of achieving array physical matching, this invention can adjust the multi-channel excitation parameters within a limited and controllable excitation degree of freedom, thereby enhancing the guided wave energy of the target mode within a preset region of the rail cross section and forming a target wave field with mode selectivity. By adjusting the excitation complex weights of each transducer unit, the energy concentration of the target mode in selected areas such as the rail head, rail web, and rail bottom can be achieved, which is beneficial to improving the guided wave response intensity and mode identification in key areas. This method is applicable to various complex rail cross-sectional structures such as stock rails, AT rails, switch rails, and frog rails, and has good structural adaptability and engineering application potential.

[0024] Since the modal selectivity and regional energy regulation capabilities originate from the physical matching relationship between the transducer array and the target modal displacement field, this invention can be used in both online monitoring and offline detection or condition assessment scenarios. In online applications, transducers can be deployed in non-working contact areas such as the rail web and rail base, and modal regulation can enhance the response and sensing capabilities of key areas such as the rail head. In offline applications, target modal excitation and response analysis can be performed on different cross-sectional areas of the rail, thereby providing support for the condition characterization, local anomaly identification, and damage detection of rail components. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall architecture of an ultrasonic guided wave mode precision control device for railway rail components provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the multi-channel transducer array arrangement for the cross-section of a rail component provided in an embodiment of the present invention; Figure 3 The dispersion curve of the rail component is calculated by the semi-analytical finite element (SAFE) model provided in the embodiment of the present invention. Figure 4 This is a typical modal displacement field cloud map and a schematic diagram of a multi-channel transducer array at 64kHz for a rail cross section provided in an embodiment of the present invention. (a) Wavenumber is 157.5m -1 Typical modal displacement field contour plots and corresponding multi-channel transducer array excitation diagrams are shown, with transducer channels 6, 7, 8, and 9 being the main activated channels. (b) Wavenumber is 156.0m -1 Typical modal displacement field contour plots and corresponding multi-channel transducer array excitation diagrams are shown, with transducer channels 12, 13, 14, and 15 being the main activated channels. (c) represents a wave number of 137.6 m. -1 Typical modal displacement field contour plots and corresponding multi-channel transducer array excitation diagrams are shown, with transducer channels 22, 23, 26, and 27 being the main activated channels. (d) represents a wave number of 141.0 m. -1 Typical modal displacement field contour plots and corresponding multi-channel transducer array excitation diagrams are shown, with transducer channels 18, 19, 20, and 21 being the main activated channels. (e) represents a wave number of 134.6 m. -1 Typical modal displacement field contour plots and corresponding multi-channel transducer array excitation diagrams are shown, with the main activated transducer channels being 16, 18, 23, 25, and 26. (f) represents a wave number of 133.6 m. -1 Typical modal displacement field contour plots and corresponding multi-channel transducer array excitation diagrams are shown, with the main activated transducer channels being channels 12, 13, 17, 22, and 24. (g) represents a wavenumber of 127.4 m. -1 Typical modal displacement field contour plots and corresponding multi-channel transducer array excitation diagrams are shown, with transducer channels 24, 25, 26, and 27 being the main activated channels. (h) represents a wave number of 126.0 m. -1Typical modal displacement field cloud diagrams and corresponding multi-channel transducer array excitation diagrams are shown, with the main activated transducer channels being 10, 12, 18, 19, 20, 21 and 24. Figure 5 This is a schematic flowchart of the ultrasonic guided wave multi-channel modal modulation method provided in an embodiment of the present invention; Figure 6 These are schematic diagrams of transducer array arrangement under different engineering application modes provided in the embodiments of the present invention, wherein (a) is a schematic diagram of transducer arrangement under full array working mode, and (b) is a schematic diagram of subarray working mode under partial transducer shutdown condition.

[0026] In the figure: 1. Rail component; 2. Multi-channel transducer unit; 3. Multi-channel transducer array; 4. Multi-channel control unit; 5. Processing module; 6-27. Each transducer unit in this example. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0029] An ultrasonic guided wave mode precision control device for railway rail components includes: The rail component 1 comprises a multi-channel ultrasonic guided wave transducer array 3, a multi-channel control unit 4, and a processing module 5. The outer surface of the rail component 1 is provided with a multi-channel ultrasonic guided wave transducer array 3. The multi-channel ultrasonic guided wave transducer array 3 is electrically connected to the multi-channel control unit 4 and the processing module 5. The multi-channel ultrasonic guided wave transducer array 3 includes multiple transducer units 2. The transducer units 2 are arranged sequentially along the outer surface contour of the cross section of the rail component 1 and in the coupling area on the surface of the rail component 1 to form a multi-channel transducer array. Each transducer unit 2 is electrically connected to the multi-channel control unit 4.

[0030] Specifically, the ultrasonic guided wave mode precision control device for railway rail components includes the following components: Processing module 5 is configured to use a semi-analytical finite element model based on the cross section of the rail component to determine the set of propagable guided wave modes in the target frequency band and the displacement field function corresponding to each mode. Based on the spatial distribution characteristics of the modal displacement field of the target mode, it generates excitation complex weights for each transducer unit 2 in the multi-channel transducer array 3. The excitation control parameters include at least amplitude weights, phase compensation amounts, and time delay amounts. The multi-channel control unit 4 is used to output corresponding drive signals to each transducer unit 2 according to the excitation complex weight, and to receive the echo signals returned by each transducer unit 2.

[0031] The multi-channel ultrasonic guided wave transducer array 3 includes several independent and controllable transducer units, which are arranged in the coupling area on the surface of the rail component. The multi-channel control unit 4 is connected to each transducer unit and is configured to receive excitation control parameters, modulate the excitation signal of each channel, and receive echo signals.

[0032] The transducer unit 2 is one of a piezoelectric transducer or a magnetostrictive transducer; When the transducer unit 2 uses a piezoelectric transducer, the multi-channel control unit 4 outputs a modulated voltage excitation signal; when the transducer unit 2 uses a magnetostrictive transducer, the multi-channel control unit 4 outputs a modulated current excitation signal to drive the alternating magnetic field.

[0033] The rail component 1 is a combination of one or more of the following: base rail, AT rail, switch rail, and frog rail; the transducer unit 2 is arranged along the cross section of the rail component 1, and the cross section of the rail component 1 is one or more of the following: the heel end cross section, the standard cross section, or any cross section selected along the longitudinal direction.

[0034] Specifically, in some embodiments, the arrangement of the multi-channel ultrasonic guided wave transducer array 3 includes: online monitoring mode, in which the transducer unit 2 is arranged in the rail web and rail bottom areas of the rail component 1 to avoid the wheel-rail contact area; and offline detection mode, in which the transducer unit 2 is arranged in the full cross-sectional area of ​​the rail component 1, including the rail head.

[0035] The modal control method for railway rail components using an ultrasonic guided wave mode precision control device includes the following steps: S1. Parameter input: Detect and acquire the basic information of rail component 1, and determine the target displacement field according to the energy focusing requirements or displacement distribution requirements within the preset area of ​​rail component 1. S2. Model Construction and Solution: Using the basic information of rail component 1, a semi-analytical finite element model of the cross section of rail component 1 is established, and the set of propagable modes of the cross section of rail component 1 in the target frequency band and the displacement field function corresponding to each mode are obtained by solving the model. According to the target displacement field, the target mode is selected from the set of propagable modes, and the displacement extreme value region is determined based on the displacement field function corresponding to the target mode.

[0036] S3. Array optimization arrangement: Based on the displacement extreme value region and spatial distribution characteristics of the target mode in the cross section of the rail component 1, determine the arrangement position and size of the transducer unit 2, and discretize the multi-channel ultrasonic guided wave transducer array 3 in the coupling region. S4. Modal modulation excitation: Based on the coupling relationship between the target mode and the multi-channel ultrasonic guided wave transducer array 3, the excitation complex weight of each transducer unit 2 is determined, and a driving signal corresponding to the excitation complex weight is applied to each transducer unit 2 to synthesize the target wave field inside the rail component 1. The modal modulation excitation step is carried out on the premise of completing the array optimization arrangement. The adjustment range of the multi-channel excitation parameters is limited by the physical matching relationship between the transducer array and the target modal displacement field. When the physical matching condition is not met, the modal modulation excitation is difficult to effectively enhance the target mode.

[0037] S5. Signal reception and post-processing: The multi-channel control unit (4) receives the echo signal formed by the propagation of the target wave field in the rail component through the multi-channel ultrasonic guided wave transducer array 3, and performs spatial filtering and mode decomposition processing on the echo signal according to the spatial distribution characteristics of the target mode, extracts the energy component of the target mode in the echo signal, and reconstructs one or more target mode signals that reflect the state characteristics and / or damage characteristics of the rail component.

[0038] In step S1, the basic information is one or more combinations of basic information such as detection frequency, rail component material parameters, and rail component geometric parameters.

[0039] In step S2, the rail component 1 section adopts a rail component 1 section equipped with a multi-channel ultrasonic guided wave transducer array 3; the target frequency band is 30 kHz to 90 kHz; the guided wave modal analysis model is one or more combinations of semi-analytical finite element model, finite element model, and wave finite element model.

[0040] In step S3, the arrangement position and size of transducer unit 2 are determined based on the distribution of the displacement extremum region and the characteristic length of the target mode within the coupling region of the rail component 1 section. This ensures that the arrangement position of transducer unit 2 matches the distribution position of the target mode displacement extremum region on the profile of the rail component 1 section, and that the size of transducer unit 2 matches the characteristic length. The characteristic length is the spatial variation scale of the target mode displacement field along the array arrangement direction within the coupling region, used to characterize the spatial distance of the displacement field changing from one extremum to an adjacent extremum or from in-phase to out-of-phase. The characteristic length can be one or more of the in-phase displacement region width and the equivalent width of the displacement extremum region. The transducer units 2 of the multi-channel ultrasonic guided wave transducer array 3 are arranged in the following ways: in online monitoring mode, the transducer units are arranged in the rail web and / or rail bottom area to avoid the wheel-rail contact area; in offline detection mode, the transducer units are arranged in the full cross-section area including the rail head.

[0041] The geometric dimensions of transducer unit 2 are matched with the spatial distribution characteristics of the modal displacement field of the target mode in the coupling region. The effective excitation width of transducer unit 2 in the array arrangement direction is preferably limited to the in-phase displacement region corresponding to the extreme value region of the target modal displacement, so as to reduce the excitation response cancellation caused by covering the out-of-phase displacement region and improve the excitation efficiency of the target mode.

[0042] The characteristic length of transducer unit 2 is matched with the characteristic length of the displacement extreme region of the target mode. Specifically, the effective excitation width of transducer unit 2 in the array arrangement direction is not greater than the width of the in-phase displacement region corresponding to the characteristic length, thereby reducing the response cancellation caused by the transducer being too large and crossing the out-of-phase displacement region.

[0043] In step S4, based on the energy distribution characteristics of different modes within a preset area of ​​the rail component cross section, the target mode and its multi-mode linear combination weights are determined, and a target mode vector is constructed. Then, based on the coupling relationship between the transducer channel and the modal response, the excitation complex weights of each transducer unit 2 are calculated, and a driving signal with corresponding amplitude, phase, and / or time delay is applied to each transducer unit 2 according to the excitation complex weights, so as to realize the excitation of the target mode, the energy focusing of the target region, and / or the synthesis of the target wave field inside the rail component 1.

[0044] The multi-channel control unit 4 can independently adjust the drive signals of each independent channel to coordinate the excitation amplitude, phase and timing relationships between each transducer unit 2, thereby improving the synthesis effect of the target mode and reducing the non-target mode components.

[0045] In step S5, the echo signal is the echo signal formed by the target wave field propagating in the rail component 1 and being reflected and / or scattered by the boundary, end face, structural discontinuity area and / or defect. Each transducer unit 2 receives the echo signal and transmits it to the multi-channel control unit 4.

[0046] This invention belongs to the field of non-destructive testing technology and is applicable to railway rail components such as main rail, AT rail, switch rail, and frog rail. By establishing a guided wave mode analysis model of the cross-section of the turnout rail component, the dispersion characteristics and cross-sectional displacement field distribution features of the propagable guided wave modes within the target frequency band are obtained. Based on the target displacement field, target modes are selected from the set of propagable modes. Furthermore, the size parameters and arrangement of the transducer array are matched and designed based on the spatial distribution characteristics of the target mode displacement field. The device includes a multi-channel ultrasonic guided wave transducer array 3, a multi-channel control unit 4, and a processing module 5. The multi-channel control unit 4 determines the excitation complex weights corresponding to each transducer channel based on the coupling relationship between the target modes and the multi-channel ultrasonic guided wave transducer array 3, and applies corresponding excitation amplitude, phase, and / or time delay control to achieve target mode excitation, target region energy focusing, and / or target wave field synthesis. Through the synergistic effect of the method and the device, this invention can improve the ability to control the guided wave modes of complex cross-section turnout rail components, help reduce mode aliasing during the detection process, and improve the distinguishability of target mode components in the echo signal, thereby providing support for the detection and monitoring of railway rail components.

[0047] Example 1: System Hardware Architecture and Sensor Layout This embodiment uses the rail components in railway turnouts as the inspection object, such as typical cross-sectional areas of the turnout switch rail or frog rail (e.g., the switch rail heel end cross-section). Figure 1 As shown, the system of the present invention mainly includes: a multi-channel ultrasonic guided wave transducer array, a multi-channel control unit, and a processing module.

[0048] Within a predetermined operating frequency band (e.g., approximately 64 kHz), a multi-channel, independently controllable ultrasonic guided wave transducer array is constructed, taking into account the asymmetric geometric characteristics of the rail cross-section and the displacement field distribution characteristics of the propagable modes within this frequency band. The array includes several transducer channels (e.g., 22), each electrically connected to a multi-channel control unit 4 and capable of independently outputting a drive signal according to its corresponding excitation complex weight, to meet the requirements of target mode excitation, target region energy focusing, and / or target wave field synthesis.

[0049] like Figure 2 As shown, the transducer array is discretely arranged in the coupling region of the outer contour surface of the rail component cross-section, specifically in the rail head region, rail web region, and rail bottom region. The transducers in each region are distributed according to the structural characteristics of the outer contour surface of the rail cross-section to achieve effective coverage of the entire rail cross-section. Wherein: Several transducer channels are arranged in the rail head area to cover the rail head tread, sides and lower jaw area; The transducer channels are symmetrically arranged on both sides of the web in the rail waist region. Multi-channel transducers are arranged on the upper, side and lower surfaces of the rail base to enhance the detection capability of the rail base and key stress areas.

[0050] For online monitoring scenarios, the transducer unit can preferably be arranged in the rail web and rail bottom areas to avoid the wheel-rail contact area; for offline detection scenarios, the transducer unit can be arranged in more areas of the outer contour surface of the rail component cross section, including the rail head area.

[0051] The transducer unit can be a piezoelectric transducer, a magnetostrictive transducer, or other transducer types suitable for ultrasonic guided wave excitation and reception. Each transducer is fixed to the surface of the rail with a rigid coupling agent (e.g., high-strength epoxy resin) to ensure efficient coupling of guided wave energy.

[0052] To match the spatial displacement distribution characteristics of the target mode, the effective excitation width of the transducer unit 2 in the array arrangement direction is designed according to the characteristic length of the target mode in the corresponding coupling region, and preferably not greater than the width of the in-phase displacement region corresponding to the characteristic length, thereby reducing the response cancellation caused by the transducer being too large and crossing the out-of-phase displacement region, and improving the excitation effect of the target mode.

[0053] It should be noted that this embodiment uses a 22-channel transducer array as an example, namely transducer units 6-27. However, the present invention is not limited to 22 channels. The number of transducer channels can be adjusted according to the cross-sectional dimensions of the rail component, the distribution characteristics of the target modal displacement field, and the actual detection requirements.

[0054] Example 2: Modal Analysis and Multi-channel Controlled Excitation Method This embodiment uses 64kHz as the typical operating frequency band and takes the switch rail, a typical component in a turnout, as an example to illustrate the modal control and excitation method described in this invention.

[0055] Step S1: Obtain the basic information required for detection, including the detection frequency band, rail material parameters, and geometric parameters of rail components, and determine the target displacement field according to the energy focusing requirements or displacement distribution requirements of the preset detection area; the preset detection area can be the rail bottom area, rail head area, or rail web area.

[0056] Step S2: Model construction and solution.

[0057] Based on the aforementioned fundamental information, a semi-analytical finite element model of the rail cross section is established. Since the wave propagation problem of the rail cross section can be expressed as a generalized eigenvalue problem: , Where, in the formula A and B This is a system matrix constructed from the cross-sectional geometry and material parameters of rail components. ξ The wave number is the propagation constant (wave number) of the guided wave in the component. Q This is the corresponding modal feature vector.

[0058] By solving the aforementioned generalized eigenvalue problem, the corresponding modal eigenvectors can be obtained, including both right and left eigenvectors. The right eigenvector can be used to determine the modal displacement field distribution, while the left eigenvector describes the mode response characteristics under external load. The propagable modes of the rail component in the target frequency band are analyzed to obtain the dispersion characteristics and displacement field distribution of each mode.

[0059] Figure 3 The dispersion curve of the rail component calculated by the semi-analytical finite element (SAFE) model provided in the embodiment of the present invention is shown.

[0060] By solving the model, a set of propagable modes within the target frequency band can be obtained, and the displacement distribution characteristics of each mode in different regions of the rail cross section can be extracted. Based on the target displacement field, target modes are selected from the set of propagable modes, and their displacement extremum regions are determined based on the displacement field function corresponding to the target modes.

[0061] Figure 4 The cross-sectional displacement field distribution of several representative propagable modes at the target frequency of 64 kHz is shown.

[0062] Depend on Figure 4 It is evident that the displacement field distribution of different modes on the rail component cross-section varies significantly. Specifically, the displacement or energy of modes (c) and (g) is mainly concentrated in the rail head region, the displacement or energy of modes (a) and (b) is mainly concentrated in the rail bottom region, and the displacement or energy of modes (d) and (h) is mainly concentrated in the rail web region. Therefore, based on the energy focusing or displacement distribution requirements of the preset detection area, the corresponding target mode can be selected from the set of propagable modes. For example, when the detection requirement is to enhance the guided wave response in the rail head region, the mode whose displacement field is mainly concentrated in the rail head region can be preferentially selected as the target mode; similarly, when the detection requirement is to enhance the guided wave response in the rail bottom region, the mode whose displacement field is mainly concentrated in the rail bottom region can be preferentially selected as the target mode.

[0063] Based on the spatial distribution characteristics of the cross-sectional displacement field of the selected target mode, the arrangement position and size parameters of the transducer array in the corresponding coupling region can be further determined, so that the transducer array can be effectively coupled with the in-phase extreme region of the target mode displacement field at the physical level, and reduce the excitation contribution to non-target modes, thereby providing a limited and controllable excitation degree of freedom for subsequent multi-channel modal control.

[0064] Step S3: Array Optimization and Layout Based on the displacement extremum region distribution and spatial distribution characteristics of the target mode within the coupling region of the switch section, the arrangement position, number of channels, and size parameters of each transducer unit in the transducer array are determined, and the transducer array is discretely arranged in the corresponding coupling region. Specifically, the effective excitation width of the transducer unit in the array arrangement direction is designed to match the characteristic length of the target mode within the corresponding coupling region, and preferably is not greater than the width of the in-phase displacement region corresponding to the characteristic length. This ensures that the transducer array preferentially forms effective coupling with the in-phase extremum region of the target mode displacement field at the physical level, reducing response cancellation caused by crossing the out-of-phase displacement region, and forming prior suppression of non-target modes.

[0065] Example 3: Multi-channel modal modulation excitation process Step S4: Modal modulation excitation This step is crucial for achieving modal modulation in this invention. Based on the principle of wave superposition, the system uses a multi-channel control unit to precisely control the transducer array. The specific process is as follows: Step S41 Calculate the channel excitation weights.

[0066] It should be noted that the method of constructing the excitation influence matrix and solving the channel weights in this embodiment is only used to illustrate a feasible calculation implementation of multi-channel excitation parameters under the condition that the array physical matching has been completed.

[0067] Without departing from the core idea of ​​this invention for physical-level control based on modal displacement field matching, those skilled in the art can use other numerical solution methods or empirical optimization methods to obtain equivalent excitation parameters, all of which should fall within the protection scope of this invention.

[0068] For the target frequency band within the rail cross section M One propagable mode, combined with the number of channels determined in step S3. N Extract the excitation response (displacement amplitude and direction) of each transducer unit 2 to each mode under unit excitation, and construct... M × N dimensional incentive influence matrix C Matrix elements C mn The contribution of the nth transducer channel to the excitation of the mth mode is quantified and can be determined by the following formula:

[0069] in, Let be the left-hand eigenvector of the equation. For the nth The generalized force vector of a transducer represents the normalization coefficient of the mode.

[0070] Based on the modal response results under individual channel excitation, a linear mapping matrix from the channel domain to the modal domain is established. C ,set up Let be the complex weight vector of each channel of the array. Given the target mode vector, based on the principle of linear superposition, the channel weights and modal responses satisfy the following:

[0071] in, T The value in the middle represents the expected complex amplitude of the target mode, which is constructed according to the detection requirements. dimensional target vector .

[0072] Assuming a single-mode excitation is used, the preferred excitation mode is the first mode that focuses on the energy concentration in the target region. i If the first-order mode is taken as the objective, then the first-order mode in the objective vector is set as the target mode. i The elements are 1 (i.e.) Alternatively, the target vector elements corresponding to multiple modes can be set to their respective weights, while the remaining elements are all 0, in order to achieve target mode excitation, target region energy focusing, and / or target wave field synthesis.

[0073] Assuming multimodal excitation is used, the preferred approach is to achieve partial or full energy coverage of the target region. k Each mode is taken as the target mode, and in the target mode vector T The elements corresponding to these modes are assigned the desired complex amplitude value, and the remaining elements are all 0, in order to realize the excitation of target modes, energy focusing of target regions and / or synthesis of target wave fields.

[0074] Since the number of modes M and the number of channels N are usually not equal, this inverse problem involves solving an overdetermined or underdetermined system of equations. Therefore, a least squares method with Tikhonov regularization is used to solve for the complex weight vector. W Pass:

[0075] In the formula, (*) H This indicates the conjugate transpose. For regularization parameters, I It is the identity matrix, used to improve the numerical stability of the inversion process and obtain a stable and realizable control solution.

[0076] It should be noted that the weight vector varies depending on the number of excitation channels, transducer placement, and target mode selection. W This is not the only solution. The solution form given in this embodiment is only for illustrative purposes. Any equivalent solution that satisfies the conditions of target mode enhancement and non-target mode suppression can achieve the purpose of this invention.

[0077] Step S42: Multi-channel weighted stimulus.

[0078] The calculated complex weight vector W Include N complex elements The multi-channel control unit parses it into the following physical drive commands.

[0079] (1) Amplitude control: Extracting complex modulus The linear mapping is the first n The amplitude of the drive signal of the road signal generator.

[0080] (2) Phase and / or time delay control: Extract complex argument And convert it into the time domain launch delay. ,in f The excitation frequency.

[0081] In this example, the system utilizes the high-precision timing function of the FPGA to apply corresponding amplitude and time delay control to multiple channels, thereby driving the transducer array.

[0082] like Figure 4 As shown, rectangles represent transducer units, and black-filled units represent transducer units participating in the excitation of the target mode modulation; the size and arrangement of the array units correspond to the modal displacement extreme region to achieve target mode excitation or energy focusing. Figure 4 Figures (a)-(h) show schematic diagrams of the displacement field distribution of several typical modes on the rail cross section within the target frequency band. It can be seen that different modes exhibit significantly different extreme displacement distribution characteristics in the rail head, rail web, and rail bottom regions, thus allowing for precise control of the target mode.

[0083] Example 4: Signal Reception and Post-processing Step S5: Signal Post-processing After the target wavefield propagates within the rail component 1, it is reflected and / or scattered by boundaries, end faces, structural discontinuities, and / or defects to form echo signals. These echo signals are received by each transducer unit 2 in the multi-channel ultrasonic guided wave transducer array 3 and then transmitted to the multi-channel control unit 4. Based on the spatial distribution characteristics of the target modes, the multi-channel control unit 4 performs spatial filtering and mode decomposition processing on the echo signals, extracting the energy components of the target modes in the echo signals and reconstructing one or more target mode signals reflecting the state characteristics and / or damage characteristics of the rail component 1.

[0084] This invention introduces array physical matching constraints based on the spatial distribution characteristics of the modal displacement field during the guided wave excitation stage, making it difficult for non-target modes to form effective excitation at the source end. This reduces the degree of mode aliasing in the received signal and improves the distinguishability of target mode components. Compared to methods that mainly rely on complex post-processing algorithms for mode separation, this invention simplifies the composition of the echo signal through the synergistic effect of the physical excitation end and the signal processing end, which helps to improve the stability and engineering repeatability of the detection results.

[0085] After completing one inspection process, the system can enter standby mode according to a preset strategy, or continue to execute the next round of inspection, so as to realize periodic inspection or long-term online monitoring of rail components.

[0086] Figure 5 A schematic flowchart of the ultrasonic guided wave multi-channel modal modulation method provided in an embodiment of the present invention is shown.

[0087] Example 5: Engineering Application Mode and Extensibility Description In practical engineering applications, the system of this invention can flexibly switch working modes according to the operating environment and testing requirements. For example: In offline precision detection mode, a full array channel can be enabled, and the array can be arranged in more areas on the outer contour surface of the rail component 1 section. These areas may include the rail head region, to achieve target mode excitation, target region energy focusing, and / or target wavefield synthesis, such as... Figure 6 As shown in (a) of the diagram.

[0088] In long-term online monitoring mode, some transducer channels located in the wheel-rail contact area can be shut down, and only the sub-arrays in the rail web and rail base areas can be activated. Continuous monitoring of key areas can be achieved through multi-channel control, such as... Figure 6 As shown in (b) of the diagram.

[0089] It should be noted that the number of transducer channels, array arrangement, and number of target modes described in this embodiment are merely examples. The array arrangement and multi-channel modal control method based on the spatial distribution characteristics of the modal displacement field proposed in this invention are also applicable to detection and monitoring needs under different frequency bands, different cross-sectional geometries, and different combinations of guided wave modes. Those skilled in the art can adjust or expand the number of transducer channels, array density, and control parameters according to the dimensions of the rail components, the distribution characteristics of the target modal displacement field, and actual engineering requirements. All such adjustments should fall within the protection scope of this invention without departing from its spirit and essence.

[0090] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Equivalent substitutions or modifications made by those skilled in the art to the technical solutions of the present invention without departing from the spirit and substance of the present invention should all fall within the scope of protection of the present invention. The terminology used in the specification and claims is only used to describe specific embodiments and should not be construed as limiting the present invention.

Claims

1. A method for modal control of railway rail components using an ultrasonic guided wave mode precision control device, characterized in that, The method employs an ultrasonic guided wave mode precision control device for railway rail components. The device includes a rail component (1), a multi-channel ultrasonic guided wave transducer array (3), a multi-channel control unit (4), and a processing module (5). The outer surface of the rail component (1) is provided with a multi-channel ultrasonic guided wave transducer array (3). The multi-channel ultrasonic guided wave transducer array (3) is electrically connected to the multi-channel control unit (4) and the processing module (5). The multi-channel ultrasonic guided wave transducer array (3) includes multiple transducer units (2). The transducer units (2) are arranged sequentially on the surface of the rail member (1) along the outer contour of the cross section of the rail member (1). Each transducer unit (2) is electrically connected to the multi-channel control unit (4). The method includes the following steps: S1, Parameter Input: Detect and acquire the basic information and target displacement field of the rail component (1); S2. Model Construction and Solution: Using the basic information, a waveguide mode analysis model of the rail component (1) section is established, and the set of propagable modes and displacement field function of the rail component (1) section in the target frequency band are obtained by solving the model. According to the target displacement field, the target mode is selected from the set of propagable modes, and the displacement extreme value region is determined based on the displacement field function. S3. Array optimization arrangement: Based on the displacement extreme value region and spatial distribution characteristics of the target mode in the cross section of the rail component (1), the multi-channel ultrasonic waveguide transducer array (3) is discretized and arranged in the coupling region of the rail component (1). In step S3, the arrangement position and size of the transducer unit (2) are determined according to the distribution of the extreme displacement region and the characteristic length of the target mode in the coupling region of the rail member (1) section, so that the arrangement position of the transducer unit (2) matches the distribution position of the extreme displacement region of the target mode on the profile of the rail member (1) section, and the size of the transducer unit (2) matches the characteristic length; the characteristic length adopts the spatial variation scale of the target mode displacement field along the array arrangement direction in the coupling region; the characteristic length is one or more of the following combinations: the width of the in-phase displacement region and the equivalent width of the displacement extreme region; S4. Modal modulation excitation: Based on the coupling relationship between the target mode and the multi-channel ultrasonic guided wave transducer array (3), the excitation complex weight of each transducer unit (2) is determined, and the driving signal corresponding to the excitation complex weight is applied to each transducer unit (2) respectively. Then, the target wave field is synthesized inside the rail component (1). S5. Signal reception and post-processing: The multi-channel control unit (4) receives the echo signal formed by the propagation of the target wave field in the rail component, and performs spatial filtering and mode decomposition processing on the echo signal according to the spatial distribution characteristics of the target mode, extracts the energy component of the target mode in the echo signal, and reconstructs one or more target mode signals that reflect the state characteristics and / or damage characteristics of the rail component.

2. The method for modal control of rail components using an ultrasonic guided wave mode precision control device for railway rail components according to claim 1, characterized in that, In step S1, the basic information is one or more of the following: detection frequency, rail component material parameters, and rail component geometric parameters; the target displacement field is determined based on the energy focusing requirements or displacement distribution requirements within the preset area of ​​the rail component (1).

3. The method for modal control of rail components using an ultrasonic guided wave mode precision control device for railway rail components according to claim 1, characterized in that, In step S2, the cross section of the rail component (1) is a rail component (1) with a multi-channel ultrasonic waveguide transducer array (3); the target frequency band is 30 kHz to 90 kHz. In step S2, the guided wave mode analysis model is one or more of the following: a semi-analytical finite element model, a finite element model, and a wave finite element model.

4. The method for modal control of rail components using an ultrasonic guided wave mode precision control device for railway rail components according to claim 1, characterized in that, The characteristic length of the transducer unit (2) is matched with the characteristic length of the displacement extreme region of the target mode, specifically: the effective excitation width of the transducer unit (2) in the array arrangement direction is not greater than the width of the in-phase displacement region corresponding to the characteristic length.

5. The method for modal control of rail components using an ultrasonic guided wave mode precision control device for railway rail components according to claim 1, characterized in that, In step S4, the synthesized target wavefield specifically refers to: Based on the energy distribution characteristics of different modes within a preset area of ​​the rail component section, the target mode and its multi-mode linear combination weights are determined, and the target mode vector is constructed. Then, based on the coupling relationship between the transducer channel and the modal response, the excitation complex weights of each transducer unit (2) are calculated, and driving signals with corresponding amplitude, phase, and time delay are applied to each transducer unit (2) according to the excitation complex weights, thereby realizing target mode excitation, target region energy focusing, and target wave field synthesis within the rail component (1).

6. The method for modal control of rail components using an ultrasonic guided wave mode precision control device for railway rail components according to claim 1, characterized in that, In step S5, the echo signal is one or more of the following combinations: the echo signal formed by the target wave field after propagation in the rail component (1) through the boundary, end face, structural discontinuity area, the echo signal formed by defect reflection, and the echo signal formed by scattering. Each transducer unit (2) receives the echo signal and transmits it to the multi-channel control unit (4).

7. The method for modal control of rail components using an ultrasonic guided wave mode precision control device for railway rail components according to claim 1, characterized in that, The transducer unit (2) is one of a piezoelectric transducer or a magnetostrictive transducer; When the transducer unit (2) adopts a piezoelectric transducer, the multi-channel control unit (4) outputs a modulated voltage excitation signal; when the transducer unit (2) adopts a magnetostrictive transducer, the multi-channel control unit (4) outputs a modulated current excitation signal to drive the alternating magnetic field.

8. The method for modal control of rail components using an ultrasonic guided wave mode precision control device for railway rail components according to claim 1, characterized in that, The rail component (1) is one or more of the following: base rail, AT rail, switch rail, and center rail; the transducer unit (2) is arranged along the cross section of the rail component (1), and the cross section of the rail component (1) is one or more of the following: the heel end cross section, the standard cross section, and any cross section selected along the longitudinal direction.

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