Air-coupled medium mechanical property detection device and method

Abstract

This invention discloses a device and method for detecting the mechanical properties of a medium based on air coupling, belonging to the field of non-destructive testing technology in engineering geophysics. The device utilizes the leakage effect of seismic waves at the solid-gas interface, acquiring the coupling signal through a receiving device positioned in the air above the medium being tested, thus achieving non-contact detection of the medium's mechanical properties. The device includes a mobile carrier, an air coupling receiving unit, an excitation unit, a time synchronization unit, and a control and processing unit, supporting continuous detection while in motion. The detection method includes exciting vibrations in the medium being tested, receiving the signal via air coupling, mobile detection, and data processing and parameter estimation. This invention eliminates the constraints of the coupling link on data quality, achieving a technological leap from "contact point measurement" to "non-contact continuous scanning," and is suitable for non-destructive testing of the mechanical properties of various infrastructures.

Description

Technical Field

[0001] This invention relates to the field of engineering geophysical nondestructive testing technology, and in particular to a device and method for detecting the mechanical properties of a medium based on air coupling. Background Technology

[0002] Mechanical property testing of infrastructure such as roads, bridges, airports, dams, and mines is a crucial aspect of ensuring public safety. Existing testing technologies are mainly divided into two categories: the first is destructive testing. Core drilling directly damages the medium structure, resulting in high costs, long processing times, inability to achieve dynamic monitoring, and limited sampling points, making it difficult to reflect the overall condition. The second category is non-destructive testing, including ground-penetrating radar, ultrasonic testing, and seismic surface wave methods.

[0003] The seismic surface wave method (MASW / SASW) estimates wave propagation velocity by measuring the dispersion characteristics of surface waves, making it an effective means of evaluating the mechanical properties of a medium. However, existing seismic methods and ultrasonic testing have limitations, namely the coupling dependency problem. Whether it's inserting the geophone into the ground, applying coupling agent to the piezoelectric transducer, or forcefully pressing the accelerometer, existing seismic methods require a good solid-solid coupling with the ground surface, and the coupling quality directly determines the reliability of the data. This necessitates the point-to-point deployment of equipment and coupling operations, limiting efficiency and making it difficult to meet the needs of large-scale rapid detection; it also suffers from poor repeatability, failing to adapt to the rapid detection needs of complex scenarios such as urban areas, and has limited adaptability to different surface conditions. While ground-penetrating radar can acquire high-precision structural information about a medium, it struggles to obtain its mechanical properties.

[0004] Earthquake air coupling signals are the energy components of surface waves that leak into the air during propagation and can propagate in the air. This physical phenomenon provides a theoretical basis for completely non-contact seismic detection. However, current research is still at the stage of low speed and artificial excitation, and there are technical challenges in engineering applications: (1) lack of adaptive adjustment mechanism, signal consistency is difficult to guarantee under complex working conditions; (2) fixed array shape, which cannot solve the problem of detection in anisotropic media; (3) single source form, which is difficult to adapt to complex terrain and active frequency scanning requirements; (4) incomplete technical closed loop, and multi-scenario engineering verification has not been realized. Summary of the Invention

[0005] The purpose of this invention is to provide a medium mechanical property detection device and method based on air coupling, which can adapt to different road conditions and calculate anisotropic parameters through air coupling. This solves the application limitation of existing technologies that are only applicable to ideal smooth road surfaces, and forms a complete technical closed loop from "signal excitation - array adaptive configuration - anti-terrain interference reception - anisotropic parameter inversion".

[0006] To achieve the above objectives, the present invention provides a medium mechanical property detection device based on air coupling, comprising: A mobile carrier is used to support the entire detection device for continuous detection in a mobile state. An air-coupled receiving unit is suspended in the air layer above the measured medium and has no physical contact with the medium. It receives elastic wave signals coupled from the medium interface into the air using an air coupling method. The air-coupled receiving unit includes an array of sound pressure sensitive elements, an array shape control structure, and a height adjustment module. The excitation unit applies periodic excitation to the measured medium by utilizing either the kinetic energy of the mobile carrier or the on-board energy while moving with the mobile carrier. The time synchronization unit is used to record the excitation time to achieve multi-channel signal synchronization; The control processing unit is connected to the air-coupled receiving unit via a high-speed transmission unit. It has a built-in computing and display unit and an RTK positioning unit. The control processing unit is used for control data acquisition and management.

[0007] Preferably, the shape of the acoustic pressure sensing element array is adaptively configured according to the detection requirements, including linear arrays and T-shaped arrays; the linear array consists of several acoustic pressure sensing elements arranged along a straight line, which is suitable for longitudinal profile detection of roads; the T-shaped array consists of several acoustic pressure sensing elements arranged along two perpendicular intersecting straight lines, which is suitable for simultaneously acquiring wave fields in orthogonal directions.

[0008] Preferably, the sound pressure sensing element array is maintained at a predetermined height above the ground, and the frequency response of the sound pressure sensing element covers 1kHz-500kHz; The array morphology control structure is used to adjust the spatial distribution of acoustic pressure sensitive elements to adapt to different detection requirements.

[0009] Preferably, the height adjustment module is an adjustable bracket used to dynamically control the vertical distance between the air coupling receiving unit and the medium according to the road surface undulations, maintaining a constant detection spacing; the height adjustment module includes a laser ranging feedback device and a servo motor, the laser ranging feedback device monitors the distance between the sound pressure sensitive element array and the ground surface in real time, and the servo motor adjusts the length of the bracket according to the monitoring results, so that the sound pressure sensitive element array maintains a constant suspension height under different road surface conditions.

[0010] Preferably, the excitation method of the excitation unit includes two types: A mechanical inertial vibration source specifically utilizes either the dragging inertia of the carrier or the interaction between wheels and rails to drive a hammer mechanism to periodically strike the ground. The electromagnetically driven seismic source specifically utilizes the power supply of a mobile carrier to generate an alternating electromagnetic field, which drives the hammer mechanism to periodically strike the ground. The excitation frequency is controllable within the range of 1-100Hz, and different depths of layered detection can be achieved by changing the power supply frequency.

[0011] Preferably, the time synchronization unit performs time calibration for excitation and reception, and the time synchronization accuracy meets the requirements of signal coherence analysis, ensuring signal time consistency.

[0012] Preferably, the transmission method of the time synchronization unit includes several of the following: wired transmission, wireless radio frequency transmission, satellite time synchronization, and physical triggering. The physical triggering is based on the detection of physical field changes generated by the excitation event.

[0013] Based on the above-mentioned detection device, the present invention also provides a method for detecting the mechanical properties of a medium based on air coupling, comprising the following steps: S1. Excite the tested medium to generate vibration: During the movement of the mobile carrier, the tested medium is periodically excited to generate vibration by using one of the kinetic energy of the mobile carrier and the on-board energy through the excitation unit installed on the mobile carrier. S2. Air-coupled signal reception: The air-coupled receiving unit, suspended in the air layer above the measured medium, receives the elastic wave signal coupled from the medium to the air in a non-contact state. The air-coupled receiving unit maintains an effective detection distance from the measured medium in a non-contact state. The distance between the sound pressure sensitive element array and the ground surface is adjusted in real time by the height adjustment module to maintain a constant detection distance. S3. Mobile Detection: While receiving signals, the mobile carrier maintains its driving state to achieve continuous mobile detection; S4. Data Processing and Parameter Estimation: Based on the received elastic wave signal in the air, perform signal processing and parameter estimation to obtain the elastic wave propagation speed; S5. Based on the estimated wave propagation velocity of the medium, calculate the mechanical parameters of the underground medium. The calculation formula is as follows: G= pV s 2 E d =2 pV s 2 (1+ v ); Where G is the shear stiffness parameter. p For density, V s E is the propagation speed of elastic waves. d For dynamic elastic modulus, v Poisson's ratio; used to evaluate the mechanical state of a medium based on mechanical parameters.

[0014] Preferably, S4 includes: performing domain transformation on the received multichannel signal to extract dispersion characteristics and extracting dispersion feature information; performing parameter identification based on the dispersion feature information; and estimating the distribution of medium parameters with depth based on the dispersion features.

[0015] Therefore, the present invention employs the above-mentioned device and method for detecting the mechanical properties of a medium based on air coupling, which has the following beneficial effects: (1) By utilizing the leakage effect of elastic waves at the solid-gas interface, signals are collected through a suspended air coupling receiving unit, eliminating the limiting factors of contact detection and improving data quality and consistency. (2) To address the limitation of existing technologies that can only obtain one-dimensional velocity structures, a T-array configuration is proposed, which can obtain the Rayleigh wave phase velocities in two orthogonal directions of the medium through a single travel measurement and calculate the anisotropy coefficient. (3) Since the air-coupled receiving unit maintains a fixed suspended height above the ground, it has good adaptability to different working conditions and ensures the consistency of data acquisition conditions. (4) By using the height adjustment module to dynamically control the distance between the array and the medium according to the road surface undulations, a constant detection spacing is maintained, which solves the problem of signal consistency under complex working conditions and realizes the leap from smooth roads to non-smooth engineering scenarios; (5) By using a dual-mode switchable design of mechanical inertial source and electromagnetic drive source, the problem of uncontrollable frequency of passive source is solved, and the excitation mode can be flexibly selected according to road conditions and detection depth requirements. (6) Its non-contact nature enables it to perform detection without interrupting traffic, reducing interference with normal traffic flow and reducing the need for manual operation.

[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of the detection device according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the array configuration of the air-coupled receiving unit according to an embodiment of the present invention (a. linear array, b. T-type array); Figure 3 This is a dispersion characteristic analysis diagram of an embodiment of the present invention; Figure 4 These are elastic modulus diagrams estimated in embodiments of the present invention (a. elastic modulus profile along the road direction, b. elastic modulus profile perpendicular to the road direction). Detailed Implementation

[0018] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0019] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0020] Example 1 This invention provides a medium mechanical property detection device based on air coupling, used for rapid detection of the mechanical properties of infrastructure such as roads, railways, mines, dams, and airports. The overall structure is as follows: Figure 1 As shown, it includes a mobile carrier, an air coupling receiving unit, an excitation unit, a time synchronization unit, and a control processing unit. The functions of each unit are as follows.

[0021] A mobile carrier is used to carry the entire detection device for continuous detection in a mobile state; for example, a car trailer chassis is used, which is connected to the detection vehicle through a standard trailer hitch, and can be quickly changed to a handcart or electric vehicle towed type.

[0022] The air-coupled receiving unit comprises an array of acoustic pressure sensors, an array shape control structure, and a height adjustment module. The entire air-coupled receiving unit is suspended from the moving carrier by the height adjustment module, located in the air layer above the measured medium, and has no physical contact with the medium. The air-coupled receiving unit uses air coupling to receive elastic wave signals coupled from the medium interface into the air. The height adjustment module is specifically an adjustable bracket used to dynamically control the vertical distance between the air-coupled receiving unit and the medium according to road surface undulations, maintaining a constant detection interval. The height adjustment module also includes a laser ranging feedback device and a servo motor. The laser ranging feedback device monitors the distance between the acoustic pressure sensors array and the ground surface in real time, and the servo motor adjusts the bracket length according to the monitoring results, ensuring that the acoustic pressure sensors array maintains a constant suspension height under different road surface conditions.

[0023] The acoustic pressure sensing element array is maintained at a predetermined height above the ground surface. The specific distance is determined based on road conditions and required detection depth; in this embodiment, the height is set to 5-30 cm. The frequency response of the acoustic pressure sensing element covers 1 kHz to 100 kHz. The array configuration can be adaptively configured according to the different detection targets. Figure 2The array configuration allows for rapid adjustment of the spatial distribution of sound pressure sensitive elements to adapt to different detection targets.

[0024] The array configuration is selected based on the specific target being detected, and the selection principles for each configuration are as follows: Linear array ( Figure 2 a): Multiple sound pressure sensing elements are arranged in a straight line, which is suitable for longitudinal profile detection of roads to obtain one-dimensional velocity structure.

[0025] T-array ( Figure 2 b): Multiple acoustic pressure sensing elements are arranged along two perpendicular intersecting straight lines, which is suitable for simultaneously acquiring wave fields in orthogonal directions to solve the anisotropic parameters of the medium.

[0026] It should also be noted that Figure 2 The two configurations shown are just examples. In actual applications, other array configurations can be used according to detection requirements, such as three-dimensional area arrays, semi-circular arrays, circular arrays, spiral arrays, etc.

[0027] The excitation unit, while moving with the mobile carrier, utilizes the kinetic energy of the carrier or onboard energy to apply periodic excitation to the measured medium; specific methods include motion inertia, mechanical linkage, and power-driven operation by the mobile carrier. The excitation unit can employ a mechanical inertial vibration source or an electromagnetically driven vibration source. Mechanical inertial vibration source: Utilizing the dragging inertia generated when the carrier moves or the interaction between wheels and rails, the hammer mechanism is driven to periodically strike the ground without the need for external power supply; Electromagnetic drive source: The alternating electromagnetic field generated by the power supply of the mobile carrier drives the hammer mechanism to periodically strike the ground. The excitation energy is controllable, and the excitation frequency is controllable within the range of 1-100Hz. Different depths of layered detection can be achieved by changing the power supply frequency.

[0028] The time synchronization unit is used to record the excitation time to achieve multi-channel signal synchronization. The time synchronization unit realizes the time calibration of excitation and reception, and the time synchronization accuracy meets the requirements of signal coherence analysis to ensure signal time consistency. The transmission methods of the time synchronization unit include several of the following: wired transmission, wireless radio frequency transmission, satellite time synchronization, and physical triggering. Physical triggering is based on the detection of physical field changes generated by the excitation event.

[0029] The control processing unit is connected to the air-coupled receiving unit via a high-speed transmission unit. It has a built-in computing and display unit and an RTK positioning unit. The control processing unit is used for control data acquisition and management.

[0030] This embodiment, using the detection of a certain city's expressway as an example, further illustrates the implementation steps of this method: S1. Excite the measured medium to generate vibration: During the movement of the mobile carrier, the excitation unit installed on the mobile carrier periodically excites the measured medium to generate vibration by utilizing the dragging inertia of the mobile carrier, the interaction between the wheels and rails, and the power supply of the mobile carrier.

[0031] This embodiment selects a car trailer-type mobile carrier, configures an array of sound pressure sensitive elements, employs a mechanical inertial source, and connects to a control and processing unit. Based on the detection depth and scenario, a T-shaped array is used (a linear array can be considered a type of T-shaped array; therefore, this embodiment only describes the T-shaped array).

[0032] S2. Air-coupled signal reception: The air-coupled receiving unit, suspended in the air layer above the measured medium, receives the elastic wave signal coupled from the medium to the air in a zero-contact state. The air-coupled receiving unit maintains a predetermined distance from the measured medium in a non-contact state.

[0033] S3. Motion Detection: While receiving signals, the moving vehicle maintains its driving state to achieve continuous motion detection.

[0034] In this embodiment, the vehicle accelerates to a predetermined speed and maintains a constant speed, at which point the control processing unit begins continuous recording. A mechanical inertial vibration source continuously impacts the road surface while being dragged by the vehicle, and an array of sound pressure sensitive elements receives the coupled signals propagating in the air while suspended in mid-air.

[0035] S4. Data Processing and Parameter Estimation: Based on the received elastic wave signals in the air, signal processing and parameter extraction are performed. Specifically, the received multichannel signals are subjected to domain transformation to extract dispersion feature information, and the distribution of medium parameters with depth is estimated based on the dispersion features.

[0036] In this embodiment, the acquisition parameters are first set according to the detection requirements. The acquired raw data is preprocessed, including filtering to eliminate interference components. Domain transformation analysis is performed using the τ-p transform dispersion analysis method to generate a dispersion feature map. Figure 3 As can be seen from the figure, the fundamental-order surface wave dispersion energy acquired by the device has good focusing, showing an overall trend of low velocity at the low-frequency end and gradual stabilization at the high-frequency end, with a clean background. This indicates that the quality of the air-coupled signal acquired by the device meets the analysis requirements, and the dispersion characteristics are obvious. Further, dispersion characteristic curves are extracted from the energy map, and an optimized algorithm is used to estimate the distribution of medium parameters.

[0037] S5. Based on the estimated wave propagation velocity of the medium, calculate the mechanical parameters of the underground medium using the following formula: G= pV s 2 E d =2 pV s 2(1+ v ); Where G is the shear stiffness parameter. p For density, V s E is the propagation speed of elastic waves. d For dynamic elastic modulus, v Poisson's ratio is used to evaluate the mechanical state of the medium based on mechanical parameters. In this embodiment, the mechanical properties of the pavement structure layer are evaluated based on information such as shear stiffness parameters and dynamic elastic modulus. Figure 4 The obtained pavement layer elastic modulus diagram shows a significant difference in elastic modulus along the road direction and perpendicular to the road direction, which to some extent reflects the differences in the mechanical properties of the road in different directions. This coincides with the location of local settlement and damage in this section of the pavement.

[0038] Therefore, this invention employs the aforementioned device and method for detecting the mechanical properties of a medium based on air coupling. Utilizing the leakage effect of seismic waves at the solid-gas interface, signals are acquired through a suspended air coupling receiving unit. This eliminates the constraint of ground coupling quality on data reliability and avoids signal attenuation, distortion, and poor repeatability caused by poor ground coupling. The detection system is carried by a mobile carrier, enabling continuous dynamic detection while in motion, achieving a continuous "detection while moving" operation mode. Because the air coupling receiving unit maintains a fixed suspension height above the ground surface, it is unaffected by changes in road surface smoothness, humidity, looseness, or material, ensuring highly consistent signal reception conditions and improving data repeatability and comparability. Simultaneously, its non-contact nature allows for detection without interrupting traffic, reducing interference with normal passage and eliminating the need for manual sensor placement, significantly reducing labor intensity.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A medium mechanical property detection device based on air coupling, characterized in that, include: A mobile carrier is used to support the entire detection device for continuous detection in a mobile state. An air-coupled receiving unit is suspended in the air layer above the measured medium and has no physical contact with the medium. It receives elastic wave signals coupled from the medium interface into the air using an air coupling method. The air-coupled receiving unit includes an array of sound pressure sensitive elements, an array shape control structure, and a height adjustment module. The excitation unit applies periodic excitation to the measured medium by utilizing either the kinetic energy of the mobile carrier or the on-board energy while moving with the mobile carrier. The time synchronization unit is used to record the excitation time to achieve multi-channel signal synchronization; The control processing unit is connected to the air-coupled receiving unit via a high-speed transmission unit. It has a built-in computing and display unit and an RTK positioning unit. The control processing unit is used for control data acquisition and management.

2. The medium mechanical property detection device based on air coupling according to claim 1, characterized in that, The shape of the acoustic pressure sensing element array is adaptively configured according to the detection requirements, including linear arrays and T-shaped arrays; the linear array consists of several acoustic pressure sensing elements arranged along a straight line, which is suitable for longitudinal profile detection of roads; the T-shaped array consists of several acoustic pressure sensing elements arranged along two perpendicular intersecting straight lines, which is suitable for simultaneously acquiring wave fields in orthogonal directions.

3. The medium mechanical property detection device based on air coupling according to claim 2, characterized in that, The sound pressure sensing element array is maintained at a predetermined height above the ground surface, and the frequency response of the sound pressure sensing element covers 1kHz-500kHz. The array morphology control structure is used to adjust the spatial distribution of acoustic pressure sensitive elements to adapt to different detection requirements.

4. The medium mechanical property detection device based on air coupling according to claim 1, characterized in that, The height adjustment module is an adjustable bracket used to dynamically control the vertical distance between the air coupling receiving unit and the medium according to the road surface undulations, maintaining a constant detection spacing. The height adjustment module includes a laser ranging feedback device and a servo motor. The laser ranging feedback device monitors the distance between the sound pressure sensing element array and the ground surface in real time. The servo motor adjusts the length of the bracket according to the monitoring results, so that the sound pressure sensing element array maintains a constant suspension height under different road surface conditions.

5. The medium mechanical property detection device based on air coupling according to claim 1, characterized in that, The excitation method of the excitation unit includes two types: A mechanical inertial vibration source specifically utilizes either the dragging inertia of the carrier or the interaction between wheels and rails to drive a hammer mechanism to periodically strike the ground. The electromagnetically driven seismic source specifically utilizes the power supply of a mobile carrier to generate an alternating electromagnetic field, which drives the hammer mechanism to periodically strike the ground. The excitation frequency is controllable within the range of 1-100Hz, and different depths of layered detection can be achieved by changing the power supply frequency.

6. The medium mechanical property detection device based on air coupling according to claim 1, characterized in that, The time synchronization unit realizes the time calibration of excitation and reception, and the time synchronization accuracy meets the requirements of signal coherence analysis, ensuring signal time consistency.

7. The medium mechanical property detection device based on air coupling according to claim 6, characterized in that, The time synchronization unit can transmit data in several ways, including wired transmission, wireless radio frequency transmission, satellite time synchronization, and physical triggering. The physical triggering is based on detecting changes in the physical field generated by the excitation event.

8. The detection method using the medium mechanical property detection device based on air coupling as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Excite the tested medium to generate vibration: During the movement of the mobile carrier, the tested medium is periodically excited to generate vibration by using one of the kinetic energy of the mobile carrier and the on-board energy through the excitation unit installed on the mobile carrier. S2, Air-coupled signal reception: The elastic wave signal coupled from the medium to the air is received in a non-contact state by an air-coupled receiving unit suspended in the air layer above the measured medium. The air-coupled receiving unit maintains an effective detection distance from the measured medium in a non-contact state. The distance between the sound pressure sensitive element array and the ground surface is adjusted in real time by the height adjustment module to maintain a constant detection spacing. S3. Mobile Detection: While receiving signals, the mobile carrier maintains its driving state to achieve continuous mobile detection; S4. Data Processing and Parameter Estimation: Based on the received elastic wave signal in the air, perform signal processing and parameter estimation to obtain the elastic wave propagation speed; S5. Based on the estimated wave propagation velocity of the medium, calculate the mechanical parameters of the underground medium. The calculation formula is as follows: G= ρV s 2 ； E d =2 ρV s 2 (1+ ν )； Where G is the shear stiffness parameter. ρ For density, V s E is the propagation speed of elastic waves. d For dynamic elastic modulus, ν Poisson's ratio; used to evaluate the mechanical state of a medium based on mechanical parameters.

9. The detection method according to claim 8, characterized in that, S4 includes: performing domain transformation on the received multichannel signal to extract dispersion characteristics and extracting dispersion feature information; performing parameter identification based on the dispersion feature information; and estimating the distribution of medium parameters with depth based on the dispersion features.

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