Air coupled impact-echo porous array physical enhancement method
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA UNIV OF MINING & TECH
- Filing Date
- 2026-06-17
- Publication Date
- 2026-08-07
AI Technical Summary
但由于混凝土与空气的声阻抗差异较大，应力波从固体耦合到空气时能量会急剧衰减，导致接收信号幅值极低、信噪比差，检测深度和可靠性受到严重限制
[0023]This invention, through the combination of equal-length channels and a spherical converging structure, ensures that leakage waves from the concrete surface have completely consistent sound paths when propagating to the microphone. This achieves phase synchronization and coherent superposition of multiple signals, effectively enhancing the amplitude of air-coupled impact echo signals. The invention employs physical coherent superposition to enhance signals, eliminating the need for electronic amplification equipment such as preamplifiers, thus avoiding additional noise introduced during electronic amplification and improving the signal-to-noise ratio and reliability of the detected signal. The entire device is integrally molded using 3D printing technology, resulting in a simple structure, lightweight design, and excellent portability and field applicability, adaptable to the testing needs of various complex scenarios. The base surface of this invention undergoes precision machining to ensure a tight fit with the concrete surface being tested, reducing sound wave reflection losses at the interface. The inner walls of the channels are polished to reduce energy loss during sound wave propagation within the channels, further enhancing the signal enhancement effect. The microphone is installed at the center of the virtual sphere, ensuring that the distance between the microphone and the exit points of all channels is strictly equal, guaranteeing the accuracy and stability of signal superposition.
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Figure CN122524967A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of non-destructive testing technology for concrete structures, specifically to a physical enhancement method for air-coupled impact echo multi-hole array. Background Technology
[0002] Concrete structures such as bridges and tunnels are prone to internal defects such as voids and cracks during construction and operation. If these defects are not detected and repaired in a timely manner, they can seriously affect the safety and service life of the structure. Therefore, there is an urgent need for efficient and reliable non-destructive testing (NDT) technologies to conduct regular inspections and assessments of concrete structures. The traditional contact impact-echo method is currently a widely used concrete defect detection technology. This method uses a coupling agent to attach sensors to the concrete surface and receives stress wave reflection signals to determine internal defects. However, contact testing requires the deployment of sensors at each detection point, resulting in low detection efficiency. Furthermore, in high-altitude and complex surface environments such as tunnel arches and bridge bases, sensor deployment is extremely difficult, making it difficult to meet the engineering requirements for large-scale, rapid detection.
[0003] Air-coupled impact echo method achieves non-contact detection by receiving leakage waves radiated from the concrete surface, effectively solving the problems of low efficiency and difficult deployment of contact detection. However, due to the large difference in acoustic impedance between concrete and air, the energy of the stress wave attenuates sharply when coupled from the solid to the air, resulting in extremely low received signal amplitude and poor signal-to-noise ratio, severely limiting the detection depth and reliability. To address this issue, existing technologies have proposed various signal enhancement schemes. Among them, parabolic acoustic reflectors enhance the signal by reflecting and converging sound waves, but their bulky structure and complex calibration severely reduce the flexibility of non-contact detection. Dynamic microphones have low sensitivity and narrow frequency response range, making it difficult to capture low-frequency characteristic signals corresponding to deep defects. Although array sensor designs can improve signal strength through multi-channel signal superposition, they do not systematically solve the phase synchronization problem of multi-channel signals. Differences in the propagation path of sound waves in different channels lead to phase mismatch, resulting in poor coherent superposition effects. Furthermore, existing array devices do not take into account portability and field applicability. Summary of the Invention
[0004] To address the aforementioned technical shortcomings, the purpose of this invention is to provide a physical enhancement method for air-coupled impulse echo multi-aperture arrays that can achieve physical signal enhancement without electronic amplification.
[0005] To achieve the above objectives, the present invention adopts the following technical solution:
[0006] A method for physical enhancement of air-coupled shock echo using a porous array includes the following steps:
[0007] Step 1: Fabricate an air-coupled impulse echo multi-aperture physical signal amplifier, which includes a base, multiple equal-length channels, a spherical converging structure, and a microphone mounting position;
[0008] Step 2: Attach the base of the amplifier to the concrete surface to be tested;
[0009] Step 3: Place the microphone at the microphone mounting location;
[0010] Step 4: Use a striking device to strike the concrete surface to be tested to generate stress waves;
[0011] Step 5: The stress wave propagates to the interface between the concrete and the air, radiating a leakage wave.
[0012] Step six: The leakage wave enters each equal-length channel of the amplifier and propagates along the channel to the spherical converging structure;
[0013] Step 7: Leakage waves from all channels simultaneously reach the microphone located at the center of the virtual sphere, achieving coherent superposition of multiple signals.
[0014] Preferably, the amplifier prepared in step one has multiple equal-length channels evenly distributed on the circumference of the base, and the physical length of each channel is completely equal.
[0015] Preferably, in the amplifier prepared in step one, all channels extend upward and converge, with the ends of the channels terminating at the same virtual sphere, and the axes of each channel intersecting at the center of the virtual sphere.
[0016] Preferably, the amplifier prepared in step one has its microphone mounting position set at the center of the virtual sphere, and the distance between the microphone and the end outlet of all channels is strictly equal.
[0017] Preferably, in step one, the amplifier is fabricated in one piece using polylactic acid material through 3D printing technology.
[0018] Preferably, the amplifier prepared in step one has its channel inner wall polished.
[0019] Preferably, the amplifier prepared in step one has a disc-shaped base, and the bottom surface of the base has been precision machined.
[0020] Preferably, the microphone placed in step three is a MEMS omnidirectional microphone.
[0021] Preferably, the striking device used in step four is a steel ball striking hammer.
[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0023] This invention, through the combination of equal-length channels and a spherical converging structure, ensures that leakage waves from the concrete surface have completely consistent sound paths when propagating to the microphone. This achieves phase synchronization and coherent superposition of multiple signals, effectively enhancing the amplitude of air-coupled impact echo signals. The invention employs physical coherent superposition to enhance signals, eliminating the need for electronic amplification equipment such as preamplifiers, thus avoiding additional noise introduced during electronic amplification and improving the signal-to-noise ratio and reliability of the detected signal. The entire device is integrally molded using 3D printing technology, resulting in a simple structure, lightweight design, and excellent portability and field applicability, adaptable to the testing needs of various complex scenarios. The base surface of this invention undergoes precision machining to ensure a tight fit with the concrete surface being tested, reducing sound wave reflection losses at the interface. The inner walls of the channels are polished to reduce energy loss during sound wave propagation within the channels, further enhancing the signal enhancement effect. The microphone is installed at the center of the virtual sphere, ensuring that the distance between the microphone and the exit points of all channels is strictly equal, guaranteeing the accuracy and stability of signal superposition. Attached Figure Description
[0024] Figure 1 This is a schematic diagram of the physical enhancement amplifier model for the multi-hole array of air-coupled impulse echo signals in this invention;
[0025] Figure 2 In the diagram, (a) is a schematic diagram of the air component, and (b) is a schematic diagram of the C50 concrete component;
[0026] Figure 3 The sound pressure cloud map of the multi-hole array physical signal amplifier model at 0.7ms;
[0027] Figure 4 The above are the time-domain and spectrum diagrams of the enhanced and unenhanced signals of the defect-free model, where (a) is the time-domain diagram of the enhanced signal, (b) is the spectrum diagram of the enhanced signal, (c) is the time-domain diagram of the unenhanced signal, and (d) is the spectrum diagram of the unenhanced signal.
[0028] Figure 5 This is a schematic diagram of the defect model;
[0029] Figure 6 The time-domain and spectrum diagrams of the enhanced and unenhanced signals of the defect model are shown, where (a) is the time-domain diagram of the enhanced signal, (b) is the spectrum diagram of the enhanced signal, (c) is the time-domain diagram of the unenhanced signal, and (d) is the spectrum diagram of the unenhanced signal.
[0030] Figure 7 The figures are time-domain plots and spectrum plots under different operating conditions in the experiment. (a) is the time-domain plot of the enhanced signal, (b) is the spectrum plot of the enhanced signal, (c) is the time-domain plot of the unenhanced signal, and (d) is the spectrum plot of the unenhanced signal. Detailed Implementation
[0031] A physical enhancement method for air-coupled impulse echo signals using a multi-aperture array is disclosed. This method achieves the enhancement effect of air-coupled impulse echo signals by designing a physical signal amplifier for the multi-aperture array. The technical solution is described below with reference to the accompanying drawings.
[0032] Signal enhancement mechanism:
[0033] The core of this invention lies in utilizing the Huygens-Fresnel principle to achieve coherent superposition of signals through equal-length sound path design.
[0034] When a steel ball strikes a concrete surface and generates an impact echo, the stress wave propagates to the concrete-air interface and radiates a leakage wave.
[0035] For the channel path and phase synchronization conditions, let the physical length of the channel be *l*, and the speed of sound in air be *v*. For a sound wave emitted from the microphone (center) and propagating along any channel to the end of the sphere, then reflected by the concrete surface and returning along the same path, its total path is:
[0036] in, Let be the radius of the upper sphere. For each channel, a tiny air path from the end of the channel to the concrete surface and back, under ideal normal incidence conditions... Equal. To ensure that multiple signals from the same wavefront are superimposed in phase at the receiving point, the path difference between each channel must be much smaller than the wavelength of the sound wave, i.e. This design, through the arrangement of equal-length channels and the center of the sphere, theoretically achieves... The coherence condition is met.
[0037] Suppose there is a plane sound wave originating from a concrete surface and incident perpendicularly onto the opening of the device. Let the incident sound pressure at the entrance of the channel be denoted as... The sound wave entered at a length of... After passing through the channel, the sound waves propagate to the microphone located at the center of the sphere. The distance the sound waves travel in the air through the channel is... Attenuation will occur, determined by the attenuation coefficient. The description is frequency-dependent. Sound waves propagate at grazing incidence through the inner wall of an ideal, rigid, smooth channel, theoretically with no energy loss, and the reflection coefficient... In practice, due to the influence of material acoustic impedance and surface roughness, the reflection coefficient... Therefore, for an inner wall with a reflection coefficient of... , length is The channel through which the sound pressure is transmitted to the microphone. It can be represented as:
[0038]
[0039] When the sound path is equal, the signals from each channel arrive at the microphone at exactly the same time, with zero phase difference. According to the principle of vector superposition of sound pressure levels, the total sound pressure received at the microphone... yes The magnitude of the vector superposition of the signals from each channel. Considering that the sound wave is a simple harmonic oscillation, we use complex number representation and let the sound pressure level of a single channel be... ,in For the first If the phase of the channel signal relative to the reference point is given, then the total sound pressure level is... The vector sum of all phasors:
[0040] Its amplitude is the modulus of the sum of the complex numbers: The amplification factor is defined as the ratio of the signal voltage (proportional to the sound pressure level) received by the microphone after using the amplification device to the signal voltage received by an ideal omnidirectional single-point microphone at the same location. The latter can be considered as the microphone being placed directly in the incident sound field at the center of the sphere, with the measured sound pressure level being... The formula for the magnification factor is:
[0041] Structural relationships:
[0042] like Figure 1 As shown, the device is made of PLA (polylactic acid) material and is integrally formed by 3D printing. The specific structural parameters and connection relationships of each component are as follows:
[0043] Base: Located at the bottom of the device, it is a disc-shaped structure. It has a diameter of 10cm and a thickness of 0.1cm. The bottom surface is finely machined to ensure flatness. It is used to support and fix the channel structure above and to ensure that it can fit tightly against the concrete surface to be tested during testing.
[0044] Equal-length channels: A total of 12 cylindrical channels are provided, evenly distributed on the circumference of the base. Each channel has a physical length of 5.5cm and a wall thickness of 0.1cm. To ensure low sound wave loss during propagation, the inner walls of the channels are polished.
[0045] Spherical Converging Structure: Twelve channels extend upwards and converge, ending on a virtual sphere with a diameter of 2cm. The axes (center lines) of all channels intersect at the center of this virtual sphere, forming a focusing structure.
[0046] Microphone mounting location: Located at the center of the virtual sphere. Used to place the MEMS omnidirectional microphone, ensuring that the distance between the microphone and the end outlet of all 12 channels is strictly equal (error ≤ 0.1mm).
[0047] Main functions and implementation process:
[0048] 1. Impact echo enhancement effect of defect-free model
[0049] Simulations were performed using the ABAQUS / Explicit explicit dynamics solver. The model was established as follows: Figure 2 As shown, a coupling model of a C50 concrete slab (100×100×20cm) and air (100×100×10cm) is established. A multi-hole array physical signal amplifier model is imported, with the base attached to the concrete surface and the microphone located at the center of the sphere. Material parameters are set as follows: C50 concrete density 2420kg / m³. 3 Elastic modulus 3.45×10 10 Pa; air density 1.29 kg / m³ 3 Elastic modulus 1.42×10 5 Pa; PLA material density 1250 kg / m³ 3 Elastic modulus 3×10 9 Pa.
[0050] like Figure 3 As shown, the stress waves generated by the impact converge at the center of the sphere through various channels, forming a high sound pressure zone. Two finite element analysis models were established, differing only in whether or not an amplifier was included.
[0051] like Figure 4 The image shows the time-domain and frequency-domain plots of the enhanced and unenhanced signals of the defect-free model. Using MATLAB software, the received signal was transformed from a time-domain signal to a frequency-domain signal through FFT. The time-domain plot of the unenhanced signal is quite cluttered, with a peak-to-peak value of approximately 3.2 × 10⁻⁶. -8 The time-domain plot of the enhanced signal is relatively clear, with a peak-to-peak value of approximately 7.2 × 10⁻⁶. -8 The ratio between the two operating conditions is approximately 2, which indicates that the multi-hole array physical amplifier has a signal amplification function, i.e., an amplification factor. In addition to amplitude changes, frequency changes also need to be considered: as shown in the figure above, the main frequency is 9301.12Hz in both operating conditions. The peak frequency of the main frequency with the multi-aperture array physical signal amplifier is larger, which is more prominent in the spectrum diagram, approximately twice the peak frequency of the main frequency without the multi-aperture array physical signal amplifier, and is consistent with the amplification factor mentioned above. To maintain consistency. The thickness frequency of this model is 9600Hz, which has an error of 3% compared to the actual measured peak frequency of 9301.12Hz.
[0052] 2. Impact echo enhancement effect of defect model
[0053] like Figure 5As shown, a defect model including a porous array physical signal amplifier was established. The blue area represents the air region, and the remaining part is C50 concrete. A 15cm × 15cm × 1cm air layer was preset in a C50 concrete slab of the same size to simulate a void defect, with the air layer 2cm away from the top. A comparative model without the porous array physical signal amplifier was established: all conditions of this comparative model, including geometric dimensions, material parameters, impact load, and the 1cm air layer defect at the bottom, are the same as those of the model with the signal amplifier. The difference is that this model removes the signal amplifier structure, retaining only the free-field air domain. The coordinates of the sound pressure signal receiving point in three-dimensional space are consistent with the position of the microphone's center in the signal amplifier model to ensure that the collected sound field signal originates from the same point in space.
[0054] like Figure 6 The figure shows the time-domain and frequency-domain plots of the enhanced and unenhanced signals of the defective model. In the time domain, the device achieves an enhancement and amplification effect, reducing the signal peak-to-peak value from approximately 7.9 × 10⁻⁶ without an amplifier. -9 Increased to approximately 16.5 × 10 -9 The enhancement is approximately 2.1 times, i.e., the magnification factor. Focusing on the frequency domain, the enhanced signal's spectrum shows a maximum dominant frequency of 3539.93Hz, with a second dominant frequency of 11519.8Hz, and amplitudes of approximately 4.5 × 10⁻⁶. -10 and 2.1×10 -10 These correspond to the defect layer information frequency and thickness frequency of the defect model, respectively. The unenhanced signal spectrum shows two characteristic frequencies: 3499.65Hz and 11498.9Hz, but with relatively small amplitudes, each around 2.53 × 10⁻⁶. -10 and 1.9×10 -10 Compared to the characteristic frequency errors of 2% and 1% when the multi-aperture array physical signal amplifier is configured, it proves that when the structure is placed in the same position, the characteristic frequency results obtained by configuring the multi-aperture array physical signal amplifier are not changed, and the amplitudes are increased to 177% and 110% of the original, respectively.
[0055] 3. Physical preparation and field test verification
[0056] 3D Printing: The physical object was fabricated using a Topzhu P1S 3D printer. PLA material was selected, with a layer thickness of 0.2mm and an infill density of 80%. After printing, the inner walls of the channels and the spherical convergence area were finely polished to ensure that the inner wall roughness R meets the design requirements for a high reflectivity. The finished product weighs only 185g, offering excellent portability.
[0057] Experimental setup: The test object was a 100cm×100cm×30cm C50 concrete slab. The testing system consisted of three parts: a 20mm steel ball hammer, an amplifier with a fixed MEMS microphone, and a PicoScope4824 eight-channel oscilloscope. The control group consisted of a microphone placed in a free field at the same height.
[0058] Data processing and results: such as Figure 7 As shown, the acquired signal was processed by bandpass filtering (500Hz-1.5kHz). The peak-to-peak value of the enhanced signal in the time domain was 0.31, while that of the unenhanced signal was 0.16. The measured amplification factor was approximately 1.93, which is in high agreement with the numerical simulation results. Spectral analysis showed that the dominant frequency of the enhanced signal was 7111.1Hz, while that of the unenhanced signal was 7592.6Hz, with an average error of approximately 6% compared to the theoretical thickness frequency (7000Hz). This experiment fully verifies the signal enhancement effect and frequency fidelity capability of this invention in a real physical environment.
Claims
1. A method for physical enhancement of air-coupled impact echo using a multi-aperture array, characterized in that, Includes the following steps: Step 1: Fabricate an air-coupled impulse echo multi-aperture physical signal amplifier, which includes a base, multiple equal-length channels, a spherical converging structure, and a microphone mounting position; Step 2: Attach the base of the amplifier to the concrete surface to be tested; Step 3: Place the microphone at the microphone mounting location; Step 4: Use a striking device to strike the concrete surface to be tested to generate stress waves; Step 5: The stress wave propagates to the interface between the concrete and the air, radiating a leakage wave. Step six: The leakage wave enters each equal-length channel of the amplifier and propagates along the channel to the spherical converging structure; Step 7: Leakage waves from all channels simultaneously reach the microphone located at the center of the virtual sphere, achieving coherent superposition of multiple signals.
2. The method for physical enhancement of air-coupled impact echo multi-aperture array as described in claim 1, characterized in that, The amplifier prepared in step one has multiple equal-length channels evenly distributed on the circumference of the base, and the physical length of each channel is completely equal.
3. The method for physical enhancement of air-coupled impact echo via a multi-aperture array as described in claim 1, characterized in that, The amplifier prepared in step one has all its channels extending upwards and converging, with the ends of the channels all terminating at the same virtual sphere, and the axes of each channel intersecting at the center of the virtual sphere.
4. The method for physical enhancement of air-coupled impact echo via a multi-aperture array as described in claim 1, characterized in that, The amplifier prepared in step one has its microphone mounting position set at the center of the virtual sphere, and the distance between the microphone and the end outlet of all channels is strictly equal.
5. The method for physical enhancement of air-coupled impact echo via a multi-aperture array as described in claim 1, characterized in that, In step one, the amplifier is fabricated in one piece using polylactic acid material through 3D printing technology.
6. The method for physical enhancement of air-coupled impact echo via a multi-aperture array as described in claim 1, characterized in that, The amplifier prepared in step one has its channel inner wall polished.
7. The method for physical enhancement of air-coupled impact echo via a multi-aperture array as described in claim 1, characterized in that, The amplifier prepared in step one has a disc-shaped base, and the bottom surface of the base has been precision machined.
8. The method for physical enhancement of air-coupled impact echo via a multi-aperture array as described in claim 1, characterized in that, The microphone placed in step three is a MEMS omnidirectional microphone.
9. The method for physical enhancement of air-coupled impact echo via a multi-aperture array as described in claim 1, characterized in that, The striking device used in step four is a steel ball hammer.