Concrete Internal Crack Detection System Based on Focusing Piezoelectric Ceramic Array

Abstract

The present invention discloses a concrete internal crack detection system based on a focused piezoelectric ceramic array, which includes a driving end and a receiving end respectively implanted at both ends of the concrete structure to be detected. The driving end is connected to a multi-channel signal generator, and the receiving end is connected to a multi-channel signal collector. Both the multi-channel signal generator and the multi-channel signal collector are connected to a workstation. Among them, the driving end uses a focused piezoelectric ceramic array sensor, and the receiving end uses one of a focused piezoelectric ceramic array sensor, a unidirectional sensing piezoelectric ceramic array sensor, or a spherical piezoelectric ceramic array sensor. The present invention makes full use of the self-focusing characteristic of the focused piezoelectric ceramic array, can realize the self-amplification of the signal amplitude at the driving end, effectively extend the transmission distance of ultrasonic waves, improve the signal-to-noise ratio of the detection signal, and enhance the detection effect.

Description

Technical Field

[0001] The present invention relates to the technical field of nondestructive testing and monitoring of civil engineering structures, and particularly relates to an implantable concrete internal crack detection system based on a focused piezoelectric ceramic array. Background Art

[0002] The ultrasonic detection technology based on stress waves is widely used in the nondestructive testing of reinforced concrete structures. However, the existing technology is difficult to meet the efficient testing of internal cracks in completed concrete structures. The signal trigger frequency of traditional ultrasonic detection equipment is a fixed value, which is not convenient for real-time adjustment of the center frequency of the excitation signal, and it is difficult to achieve accurate identification of defects of different scales.

[0003] The detection of internal cracks in concrete structures generally uses implantable PZT piezoelectric sensors to achieve long-term monitoring during the use of the structure. Commonly used implantable sensors generally use circular and rectangular PZT piezoelectric ceramic sheets as the core sensing elements, and are encapsulated with a concrete shell outside to play the roles of protection, insulation and waterproofing. However, this kind of PZT ceramic can generally only sense stress waves in a specific direction and can only achieve the induction of 2D stress waves.

[0004] In order to achieve the detection and monitoring of internal cracks in concrete with the ability to sense 3D stress waves and at the same time achieve wearable modularization, the applicant's team once proposed Figure 1 the cuboid sensing module shown, and made corresponding sensor elements and carried out relevant experimental studies. However, Figure 1 the sensing module and method shown have the following four technical drawbacks:

[0005] 1) In terms of shape, a cubic module is used for packaging. It is difficult to open a rectangular hole and it is difficult to accurately control the accuracy of the hole shape and the surface roughness. The rough surface will increase the interface reflection and reduce the propagation efficiency of the stress wave. 2) This method uses a copper tube as the positioning rod of the spherical PZT. The existence of the positioning rod has greatly changed the vibration form of the PZT ball and the propagation of the stress wave it excites. 3) In addition, the PZT ball uses black rubber as an insulating and protective layer. Because the rubber material is soft and has strong wave absorption ability, it greatly weakens the signal energy and frequency of the stress wave excited by the PZT ball, which is very unfavorable for the propagation of weak stress wave signals in concrete structures. The stress wave energy received by the sensor will be significantly reduced and the frequency will have a large error with the preset excitation frequency. 4) This scheme adopts a diamond arrangement scheme of four spherical sensors on a plane. The original purpose is to hope that the four spherical sensors may achieve the focusing and superposition of stress waves after propagating a certain distance to achieve self-enhancement of stress wave signals. However, since this scheme uses spherical rods, rubber sheaths, etc. as auxiliary processes, it greatly disrupts the formation mechanism of stress waves. 5) Since the stress excited by the signal excitation end is relatively disordered, the sensing end cannot effectively sense vertical cracks when using the same PZT ball arrangement. This arrangement scheme cannot be used to identify cracks in the longitudinal or other directions.

[0006] In addition, since the propagation attenuation of high-frequency stress waves in concrete is significant, there is an urgent need to develop ultrasonic detection technology with self-focusing capability to increase the amplitude of the stress wave at the driving end, improve the signal-to-noise ratio of the detection signal and the accuracy of damage identification. Summary of the invention

[0007] In view of the above problems, the purpose of the present invention is to provide a concrete internal crack detection system based on a focusing piezoelectric ceramic array. Based on the focusing piezoelectric ceramic linear array, the energy focusing of the stress wave is improved to carry out scanning testing; based on the focusing piezoelectric ceramic annular array, the secondary focusing of the stress wave is realized, the amplitude of the stress wave is significantly improved, the effective test distance is extended, and the damage detection of large concrete structures is realized; a cylindrical concrete matrix is ​​used as a wearable module, the auxiliary positioning device is eliminated, the quality of the excited stress wave is improved, and the crack identification effect is improved; the cylindrical sensing module is arranged horizontally and vertically, which can realize the identification and monitoring of cracks in different directions.

[0008] To solve the above technical problems, the embodiments of the present invention provide the following solutions:

[0009] A concrete internal crack detection system based on a focused piezoelectric ceramic array, comprising a driving end and a receiving end respectively implanted at both ends of the concrete structure to be detected. The driving end is connected to a multi-channel signal generator, the receiving end is connected to a multi-channel signal collector, and both the multi-channel signal generator and the multi-channel signal collector are connected to a workstation;

[0010] Wherein, the driving end adopts a focused piezoelectric ceramic array sensor, and the receiving end adopts one of a focused piezoelectric ceramic array sensor, a unidirectional sensing piezoelectric ceramic array sensor, or a spherical piezoelectric ceramic array sensor;

[0011] The focused piezoelectric ceramic array sensor is a cylindrical module, with a plurality of arc-shaped focused piezoelectric ceramics uniformly arranged inside. The plurality of arc-shaped focused piezoelectric ceramics are connected to a multi-hole connector through shielded wires, and the multi-hole connector is connected to the multi-channel signal generator or the multi-channel signal collector;

[0012] The unidirectional sensing piezoelectric ceramic array sensor is a cylindrical module, with a plurality of rectangular sheet-shaped piezoelectric ceramics uniformly arranged inside. The plurality of rectangular sheet-shaped piezoelectric ceramics are connected to a multi-hole connector through shielded wires, and the multi-hole connector is connected to the multi-channel signal collector;

[0013] The spherical piezoelectric ceramic array sensor is a cylindrical module, with a plurality of spherical piezoelectric ceramics uniformly arranged inside. The plurality of spherical piezoelectric ceramics are connected to a multi-hole connector through shielded wires, and the multi-hole connector is connected to the multi-channel signal collector.

[0014] Preferably, the focused piezoelectric ceramic array sensor includes a bottom semi-cylinder and a top semi-cylinder. The bottom semi-cylinder and the top semi-cylinder are respectively provided with a plurality of arc-shaped grooves for accommodating half of the arc-shaped focused piezoelectric ceramics. The positions of the arc-shaped grooves are used to position the arc-shaped focused piezoelectric ceramics. The bottom semi-cylinder and the top semi-cylinder are buckled to form a cylindrical module, and a plurality of the arc-shaped focused piezoelectric ceramics are accommodated inside.

[0015] Preferably, the unidirectional sensing piezoelectric ceramic array sensor includes a bottom semi-cylinder and a top semi-cylinder. The bottom semi-cylinder and the top semi-cylinder are respectively provided with a plurality of rectangular grooves for accommodating half of the rectangular sheet-shaped piezoelectric ceramics. The positions of the rectangular grooves are used to position the rectangular sheet-shaped piezoelectric ceramics. The bottom semi-cylinder and the top semi-cylinder are buckled to form a cylindrical module, and a plurality of the rectangular sheet-shaped piezoelectric ceramics are accommodated inside.

[0016] Preferably, the spherical piezoelectric ceramic array sensor includes a bottom semi-cylinder and a top semi-cylinder. The bottom semi-cylinder and the top semi-cylinder are respectively provided with a plurality of spherical grooves for accommodating one half of the spherical piezoelectric ceramics. The positions of the spherical grooves are used to position the spherical piezoelectric ceramics. The bottom semi-cylinder and the top semi-cylinder are buckled to form a cylindrical module, which internally accommodates a plurality of the spherical piezoelectric ceramics.

[0017] Preferably, the bottom semi-cylinder and the top semi-cylinder are made of a high-strength and low-shrinkage concrete matrix and are prepared by 3D printing technology. After the two are buckled, they are encapsulated with epoxy resin.

[0018] Preferably, in the focusing piezoelectric ceramic array sensor, the arrangement of the plurality of arc-shaped focusing piezoelectric ceramics includes the following three types:

[0019] Parallel array enhancement type, a plurality of the arc-shaped focusing piezoelectric ceramics are arranged in a straight line at uniform intervals, and the focusing directions of the respective arc-shaped focusing piezoelectric ceramics are parallel;

[0020] Linear array enhancement type, a plurality of the arc-shaped focusing piezoelectric ceramics are arranged in a straight line at uniform intervals, and the focusing directions of the respective arc-shaped focusing piezoelectric ceramics converge at a first convergence point, and the first convergence point is the center of a circle passing through the focusing points of the first and last arc-shaped focusing piezoelectric ceramics in the array;

[0021] Annular array enhancement type, the focusing points of a plurality of the arc-shaped focusing piezoelectric ceramics are located on the same circle and are arranged at uniform intervals, and the focusing directions of the respective arc-shaped focusing piezoelectric ceramics converge at a second convergence point, and the second convergence point is the center of the circle.

[0022] Preferably, the number of arc-shaped focusing piezoelectric ceramics at the driving end is not less than 5, and the number of arc-shaped focusing piezoelectric ceramics or rectangular sheet piezoelectric ceramics or spherical piezoelectric ceramics at the receiving end corresponds to the number of arc-shaped focusing piezoelectric ceramics at the driving end.

[0023] Preferably, the focusing piezoelectric ceramic array sensor and the unidirectional sensing piezoelectric ceramic array sensor are bonded to the implanted concrete structure through epoxy resin.

[0024] Preferably, the detection system further includes an oscilloscope and a voltage signal amplifier. The oscilloscope is connected to the multi-channel signal generator. The input end of the voltage signal amplifier is connected to the multi-channel signal generator, and the output end of the voltage signal amplifier is connected to the driving end.

[0025] Preferably, the installation methods of the driving end and the receiving end are as follows:

[0026] Measurement of the size of the concrete structure to be detected; for large-sized concrete structures, a focused piezoelectric ceramic array sensor with an annular array enhancement arrangement is used; for small-sized concrete structures, a focused piezoelectric ceramic array sensor with a parallel array enhancement or linear array enhancement arrangement is used;

[0027] Locate the specific position of the circular-arc focused piezoelectric ceramic at the driving end according to the size and test area of the concrete structure to be detected;

[0028] Select the type of piezoelectric ceramic sensor as the receiving end according to the test accuracy requirements, including one of a focused piezoelectric ceramic array sensor, a unidirectional sensing piezoelectric ceramic array sensor, and a spherical piezoelectric ceramic array sensor;

[0029] Locate the specific position of the circular-arc focused piezoelectric ceramic or rectangular sheet piezoelectric ceramic or spherical piezoelectric ceramic at the receiving end according to the size and test area of the structure to be detected;

[0030] Use high-strength low-shrinkage concrete as the matrix to fabricate the driving end and the receiving end respectively;

[0031] Open holes at both ends of the concrete structure to be detected, implant the driving end and the receiving end respectively, pour low-shrinkage epoxy resin, and let it stand and cure for more than 24 hours;

[0032] Connect external equipment for debugging.

[0033] Preferably, the detection method of the detection system is as follows:

[0034] The computer of the workstation sends a trigger signal to the multi-channel signal generator;

[0035] The multi-channel signal generator generates waveforms and checks the waveforms through an oscilloscope;

[0036] If the waveform check is normal, input the signal to the voltage signal amplifier; if the waveform check is abnormal, check the circuit and send a trigger signal again;

[0037] The voltage signal amplifier inputs the amplified signal to the driving end, and the driving end generates high-frequency stress waves;

[0038] The receiving end senses the high-frequency stress waves, generates an induced signal and transmits it to the multi-channel signal acquisition instrument;

[0039] The multi-channel signal acquisition instrument sends the collected induced signal to the computer of the workstation for storage and analysis;

[0040] The computer of the workstation performs signal time-domain / frequency-domain analysis based on the collected induced signals, and uses parameters including signal energy, first-wave acoustic time, signal frequency, and amplitude as crack identification indicators at the same time to achieve multi-parameter crack identification.

[0041] The beneficial effects brought by the technical solutions provided in the embodiments of the present invention at least include:

[0042] The present invention breaks through the technical bottlenecks of the existing detection methods in pre-buried installation and signal amplification, and can be widely applied to the crack detection and health monitoring of large concrete structures. The present invention makes full use of the self-focusing characteristics of the focused piezoelectric ceramic array to achieve self-amplification of the signal amplitude at the driving end, extend the transmission distance of ultrasonic waves, and improve the signal-to-noise ratio of the detection signal. The focused piezoelectric ceramic array has large signal energy and strong directivity; the linear array can achieve scanning tests, breaking through the limitation that point-to-point tests cannot form images; the annular array can achieve signal amplification, thereby realizing long-distance tests on cracks and internal damages. The cylindrical sensing modules are arranged horizontally and vertically, which can identify and monitor cracks in different directions, and have broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0044] Figure 1 is a schematic diagram of an existing implantable sensor;

[0045] Figure 2 is a schematic structural diagram of a concrete internal crack detection system based on a focused piezoelectric ceramic array provided in an embodiment of the present invention;

[0046] Figure 3 is a schematic diagram of the focusing principle of an arc-shaped focused piezoelectric ceramic provided in an embodiment of the present invention;

[0047] Figure 4 is a schematic diagram of the internal structure of an arc-shaped focused piezoelectric ceramic provided in an embodiment of the present invention;

[0048] Figure 5 is a schematic diagram of the internal structure of a focused piezoelectric ceramic array sensor provided in an embodiment of the present invention;

[0049] Figure 6 is a schematic assembly diagram of a focused piezoelectric ceramic array sensor provided in an embodiment of the present invention;

[0050] Figure 7 is a schematic diagram of the internal structure of a rectangular sheet-shaped piezoelectric ceramic provided in an embodiment of the present invention;

[0051] Figure 8It is a schematic diagram of the internal structure of a unidirectional sensing piezoelectric ceramic array sensor provided by an embodiment of the present invention;

[0052] Figure 9 It is a schematic diagram of assembling a unidirectional sensing piezoelectric ceramic array sensor provided by an embodiment of the present invention;

[0053] Figure 10a , Figure 10b , Figure 10c Schematic diagrams of three arrangements of arc-shaped focusing piezoelectric ceramic arrays provided in embodiments of the present invention;

[0054] Figure 11a , Figure 11b , Figure 11c It is a schematic diagram of the three arrangement modes of arc-shaped focusing piezoelectric ceramic arrays provided in the embodiment of the present invention as the driving end and the unidirectional sensing type piezoelectric ceramic linear array as the receiving end;

[0055] Figure 12a , Figure 12b , Figure 12c It is a schematic diagram of three arrangements of arc-shaped focusing piezoelectric ceramic arrays provided in an embodiment of the present invention as a driving end and a spherical piezoelectric ceramic array as a receiving end;

[0056] Figure 13 is a schematic diagram of a sensor selection and installation method provided by an embodiment of the present invention;

[0057] Figure 14 is a schematic diagram of a detection method of a detection system provided by an embodiment of the present invention;

[0058] Figure 15a and Figure 15b It is a schematic diagram of the perception principle without cracks and with cracks;

[0059] Figure 16 It is a schematic diagram of the detection process provided by an embodiment of the present invention.

[0060] As shown in the figure, in order to clearly implement the structure of the embodiment of the present invention, specific structures and devices are marked in the figure, but this is only for illustrative purposes and is not intended to limit the present invention to the specific structure, device and environment. According to specific needs, ordinary technicians in this field can adjust or modify these devices and environments, and the adjustments or modifications made are still included in the scope of protection of the present invention. DETAILED DESCRIPTION

[0061] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0062] An embodiment of the present invention provides a concrete internal crack detection system based on a focused piezoelectric ceramic array, as Figure 2 shown. The detection system includes a driving end 1 and a receiving end 2 respectively implanted at both ends of the concrete structure to be detected. The driving end 1 is connected to a multi-channel signal generator 3, and the receiving end 2 is connected to a multi-channel signal collector 4. Both the multi-channel signal generator 3 and the multi-channel signal collector 4 are connected to a workstation 5; the workstation here includes at least one high-performance computer.

[0063] To improve the detection accuracy, the detection system further includes an oscilloscope 6 and a voltage signal amplifier 7. The oscilloscope 6 is connected to the multi-channel signal generator 3. The input end of the voltage signal amplifier 7 is connected to the multi-channel signal generator 3, and the output end of the voltage signal amplifier 7 is connected to the driving end 1.

[0064] Among them, the driving end 1 uses a focused piezoelectric ceramic array sensor, and the receiving end 2 uses one of a focused piezoelectric ceramic array sensor, a unidirectional sensing piezoelectric ceramic array sensor, or a spherical piezoelectric ceramic array sensor.

[0065] As Figures 3 - 6 shown, it is a structural and assembly schematic diagram of a focused piezoelectric ceramic array sensor. The focused piezoelectric ceramic array sensor is a cylindrical module, and a plurality of arc-shaped focused piezoelectric ceramics 13 are uniformly arranged inside. The plurality of arc-shaped focused piezoelectric ceramics 13 are connected to a multi-hole connector 9 through a shielded wire 8, and the multi-hole connector 9 is connected to the multi-channel signal generator 3 or the multi-channel signal collector 4.

[0066] In the embodiment of the present invention, the focused piezoelectric ceramic array sensor includes a bottom semi-cylinder 10 and a top semi-cylinder 11. The bottom semi-cylinder 10 and the top semi-cylinder 11 are respectively provided with a plurality of arc-shaped grooves 12 for accommodating half of the arc-shaped focused piezoelectric ceramics 13. The positions of the arc-shaped grooves 12 are used to position the arc-shaped focused piezoelectric ceramics 13. The bottom semi-cylinder 10 and the top semi-cylinder 11 are buckled to form a cylindrical module, and a plurality of arc-shaped focused piezoelectric ceramics 13 are accommodated inside.

[0067] The present invention makes full use of the self-focusing characteristic of the focused piezoelectric ceramic array to realize the self-amplification of the signal amplitude at the driving end, extend the transmission distance of ultrasonic waves and the signal-to-noise ratio of the detection signal.

[0068] AsFigures 7 - 9 As shown, it is a schematic diagram of the structure and assembly of a unidirectional sensing piezoelectric ceramic array sensor. The unidirectional sensing piezoelectric ceramic array sensor is a cylindrical module, with a plurality of rectangular sheet-shaped piezoelectric ceramics 14 evenly arranged inside. The plurality of rectangular sheet-shaped piezoelectric ceramics 14 are connected to a porous connector 9 through shielded wires 8, and the porous connector 9 is connected to a multi-channel signal acquisition instrument 4.

[0069] Correspondingly, the unidirectional sensing piezoelectric ceramic array sensor includes a bottom semi-cylinder 10 and a top semi-cylinder 11. The bottom semi-cylinder 10 and the top semi-cylinder 11 are respectively provided with a plurality of rectangular grooves 15 for accommodating half of the rectangular sheet-shaped piezoelectric ceramics 14. The positions of the rectangular grooves 15 are used to position the rectangular sheet-shaped piezoelectric ceramics 14. The bottom semi-cylinder 10 and the top semi-cylinder 11 are buckled to form a cylindrical module, and a plurality of rectangular sheet-shaped piezoelectric ceramics 14 are accommodated inside.

[0070] The structure and assembly of the spherical piezoelectric ceramic array sensor are similar to those of the unidirectional sensing piezoelectric ceramic array sensor. It is a cylindrical module, with a plurality of spherical piezoelectric ceramics evenly arranged inside. The plurality of spherical piezoelectric ceramics are connected to a porous connector through shielded wires, and the porous connector is connected to a multi-channel signal acquisition instrument.

[0071] Similarly, the spherical piezoelectric ceramic array sensor includes a bottom semi-cylinder and a top semi-cylinder. The bottom semi-cylinder and the top semi-cylinder are respectively provided with a plurality of spherical grooves for accommodating half of the spherical piezoelectric ceramics. The positions of the spherical grooves are used to position the spherical piezoelectric ceramics. The bottom semi-cylinder and the top semi-cylinder are buckled to form a cylindrical module, and a plurality of spherical piezoelectric ceramics are accommodated inside.

[0072] As a preferred embodiment of the present invention, the bottom semi-cylinder 10 and the top semi-cylinder 11 are made of a high-strength and low-shrinkage concrete matrix, prepared by 3D printing technology. After the two are buckled, they are encapsulated with epoxy resin to avoid damage to the piezoelectric ceramics during the pouring and hardening processes of the concrete matrix, and play a role in waterproofing and insulation. The method of 3D printing semi-cylinders and then assembling effectively avoids the disturbance of the positioning rods and additional devices to the stress wave, and solves the problem of the influence of the traditional rubber layer on the reduction of the stress wave energy.

[0073] In the embodiments of the present invention, the geometric dimensions of the implantable sensor can be adjusted according to the dimensions of the structure to be detected. To ensure the detection accuracy, the number of arc-shaped focused piezoelectric ceramics at the driving end is not less than 5, and the number of arc-shaped focused piezoelectric ceramics or rectangular sheet-shaped piezoelectric ceramics or spherical piezoelectric ceramics at the receiving end corresponds to the number of arc-shaped focused piezoelectric ceramics at the driving end.

[0074] Furthermore, as Figures 10a - 10cAs shown in the figure, in a focused piezoelectric ceramic array sensor, the arrangement of multiple arc-shaped focused piezoelectric ceramics includes the following three types:

[0075] Parallel array enhanced type, where multiple arc-shaped focused piezoelectric ceramics are arranged in a straight line at uniform intervals, and the focusing directions of each arc-shaped focused piezoelectric ceramic are parallel;

[0076] Linear array enhanced type, where multiple arc-shaped focused piezoelectric ceramics are arranged in a straight line at uniform intervals, and the focusing directions of each arc-shaped focused piezoelectric ceramic converge at a first convergence point, and the first convergence point is the center of the circle passing through the focusing points of the first and the last arc-shaped focused piezoelectric ceramics in the array;

[0077] Annular array enhanced type, where the focusing points of multiple arc-shaped focused piezoelectric ceramics are located on the same circle and arranged at uniform intervals, and the focusing directions of each arc-shaped focused piezoelectric ceramic converge at a second convergence point, and the second convergence point is the center of this circle.

[0078] Correspondingly, a detection system with an arc-shaped focused piezoelectric ceramic array arranged in the above three ways as the driving end and a unidirectional sensing piezoelectric ceramic linear array as the receiving end is as Figures 11a - 11c shown; a detection system with an arc-shaped focused piezoelectric ceramic array arranged in the above three ways as the driving end and a spherical piezoelectric ceramic array as the receiving end is as Figures 12a - 12c shown.

[0079] The focused piezoelectric ceramic array has a large signal energy and strong directivity; the linear array can achieve scanning tests, breaking through the limitation that point-to-point tests cannot form images; the annular array can achieve signal amplification, thus realizing long-distance tests for cracks and internal damages.

[0080] In the embodiments of the present invention, the installation method of the driving end and the receiving end is as Figure 13 shown, including the following steps:

[0081] Measuring the size of the concrete structure to be detected; for a large-sized concrete structure, a focused piezoelectric ceramic array sensor with an annular array enhanced type arrangement is used; for a small-sized concrete structure, a focused piezoelectric ceramic array sensor with a parallel array enhanced type or a linear array enhanced type arrangement is used;

[0082] Positioning the specific positions of the arc-shaped focused piezoelectric ceramics at the driving end according to the size and test area of the concrete structure to be detected;

[0083] Selecting the type of piezoelectric ceramic sensor as the receiving end according to the test accuracy requirements, including one of a focused piezoelectric ceramic array sensor, a unidirectional sensing piezoelectric ceramic array sensor, and a spherical piezoelectric ceramic array sensor;

[0084] Locate the specific positions of the arc-shaped focused piezoelectric ceramics, rectangular sheet piezoelectric ceramics, or spherical piezoelectric ceramics at the receiving end according to the dimensions of the structure to be detected and the test area;

[0085] Use high-strength low-shrinkage concrete as the matrix to fabricate the driving end and the receiving end respectively;

[0086] Open holes at both ends of the concrete structure to be detected, implant the driving end and the receiving end respectively, pour low-shrinkage epoxy resin, and let it stand for curing for more than 24 hours; here, the driving end and the receiving end are bonded to the implanted concrete structure through epoxy resin, and this method causes minimal damage to the structure itself and is convenient for installation;

[0087] Connect external devices for debugging.

[0088] Furthermore, the detection method of the detection system is as Figure 14 shown, and it includes the following steps:

[0089] The computer of the workstation sends a trigger signal to the multi-channel signal generator;

[0090] The multi-channel signal generator generates waveforms and checks the waveforms through an oscilloscope;

[0091] If the waveform check is normal, input the signal into the voltage signal amplifier; if the waveform check is abnormal, check the circuit and send a trigger signal again;

[0092] The voltage signal amplifier inputs the amplified signal into the driving end, and the driving end generates high-frequency stress waves;

[0093] The receiving end senses the high-frequency stress waves, generates induced signals and transmits them to the multi-channel signal acquisition instrument;

[0094] The multi-channel signal acquisition instrument sends the acquired induced signals to the computer of the workstation for storage and analysis;

[0095] The computer of the workstation performs signal time-domain / frequency-domain analysis based on the acquired induced signals, and uses parameters including signal energy, first-wave arrival time, signal frequency, and amplitude as crack identification indicators at the same time to achieve multi-parameter crack identification.

[0096] Figure 15a and Figure 15b are schematic diagrams of the sensing principle of the detection system described in the present invention. It can be seen that when there are cracks, the vibration amplitude sensed at the position of the piezoelectric ceramics is significantly reduced. Figure 16It is a schematic diagram of the detection process of the detection system of the present invention. The present invention can simultaneously use parameters such as signal energy, first arrival time, signal frequency, and amplitude as indicators for damage assessment, realizing multi-parameter damage assessment, avoiding misjudgment caused by traditional single-parameter or single-index assessment methods, and improving the test accuracy.

[0097] The internal structure of the present invention is simple. By making full use of the self-focusing characteristics of the focused piezoelectric ceramic array, it realizes the self-amplification of the signal amplitude at the driving end, extends the transmission distance of ultrasonic waves, and improves the signal-to-noise ratio of the detection signal. The focused piezoelectric ceramic array has large signal energy and strong directivity; the linear array can realize scanning tests, breaking through the limitation that point-to-point tests cannot form images; the circular array can realize signal amplification, thereby realizing long-distance tests for cracks and internal damages. The cylindrical sensing modules are arranged horizontally and vertically, which can realize the identification and monitoring of cracks in different directions.

[0098] It should be noted that in this article, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or terminal device. Without more limitations, an element defined by the statement "including one..." does not exclude the existence of additional identical elements in the process, method, article or terminal device including the said element.

[0099] When referring to "an embodiment", "embodiment", "exemplary embodiment", "some embodiments", etc. in the specification, it indicates that the said embodiment may include specific features, structures or characteristics, but not necessarily every embodiment includes such specific features, structures or characteristics. Additionally, when combining an embodiment to describe a specific feature, structure or characteristic, implementing such feature, structure or characteristic in combination with other embodiments (whether explicitly described or not) should be within the knowledge of those skilled in the relevant art.

[0100] Generally, the terms can be understood at least in part from their use in the context. For example, at least in part depending on the context, the term "one or more" used herein can be used to describe any feature, structure or characteristic in a singular sense, or can be used to describe a combination of features, structures or characteristics in a plural sense. Additionally, the term "based on" can be understood as not necessarily aiming to convey a set of exclusive factors, but rather, at least in part depending on the context, allowing for the existence of other factors that may not be explicitly described.

[0101] It is understood that the meanings of "on", "above", and "over" in this disclosure should be interpreted in the broadest manner, such that "on" not only means "directly on" something, but also includes the meaning of being "on" something with intervening features or layers therebetween, and "above" or "over" not only means "above" or "over" something, but may also include the meaning of being "above" or "over" something with no intervening features or layers therebetween.

[0102] In addition, spatial relative terms such as "under", "below", "lower", "above", "upper", etc. may be used herein for convenience of description to describe the relationship of one element or feature to another or other elements or features, as shown in the drawings. The spatial relative terms are intended to cover different orientations in the use or operation of the device in addition to the orientation depicted in the drawings. The device may be oriented in other ways, and the spatial relative descriptors used herein may be interpreted accordingly.

[0103] The present invention encompasses any substitutions, modifications, equivalent methods, and solutions made to the essence and scope of the present invention. For the public to have a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention, and those skilled in the art can fully understand the present invention without the description of these details. Additionally, well-known methods, processes, procedures, elements, and circuits, etc. are not described in detail to avoid unnecessary confusion to the essence of the present invention.

[0104] Those of ordinary skill in the art can understand that all or part of the steps in the methods of the above embodiments can be completed by instructing relevant hardware through a program, and the program can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disks, optical disks, etc.

[0105] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A concrete internal crack detection system based on a focused piezoelectric ceramic array, characterized in that, it includes a driving end and a receiving end respectively implanted at both ends of the concrete structure to be detected. The driving end is connected to a multi-channel signal generator, the receiving end is connected to a multi-channel signal collector, and both the multi-channel signal generator and the multi-channel signal collector are connected to a workstation; wherein, the driving end uses a focused piezoelectric ceramic array sensor, and the receiving end uses one of a focused piezoelectric ceramic array sensor, a unidirectional sensing piezoelectric ceramic array sensor, or a spherical piezoelectric ceramic array sensor; The focused piezoelectric ceramic array sensor is a cylindrical module, with multiple arc-shaped focused piezoelectric ceramics uniformly arranged inside. The multiple arc-shaped focused piezoelectric ceramics are connected to a porous connector through shielded wires, and the porous connector is connected to the multi-channel signal generator or the multi-channel signal collector; The unidirectional sensing piezoelectric ceramic array sensor is a cylindrical module, with multiple rectangular sheet-shaped piezoelectric ceramics uniformly arranged inside. The multiple rectangular sheet-shaped piezoelectric ceramics are connected to a porous connector through shielded wires, and the porous connector is connected to the multi-channel signal collector; The spherical piezoelectric ceramic array sensor is a cylindrical module, with multiple spherical piezoelectric ceramics uniformly arranged inside. The multiple spherical piezoelectric ceramics are connected to a porous connector through shielded wires, and the porous connector is connected to the multi-channel signal collector; The focused piezoelectric ceramic array sensor includes a bottom semi-cylinder and a top semi-cylinder. The bottom semi-cylinder and the top semi-cylinder are respectively provided with multiple arc-shaped grooves for accommodating half of the arc-shaped focused piezoelectric ceramics. The positions of the arc-shaped grooves are used to position the arc-shaped focused piezoelectric ceramics. The bottom semi-cylinder and the top semi-cylinder are buckled to form a cylindrical module, and multiple arc-shaped focused piezoelectric ceramics are accommodated inside; The bottom semi-cylinder and the top semi-cylinder are made of a high-strength and low-shrinkage concrete matrix and prepared by 3D printing technology. After being buckled, they are encapsulated with epoxy resin; In the focused piezoelectric ceramic array sensor, the arrangement methods of the multiple arc-shaped focused piezoelectric ceramics include the following three types: Parallel array enhancement type, where multiple arc-shaped focused piezoelectric ceramics are arranged in a straight line at equal intervals, and the focusing directions of the arc-shaped focused piezoelectric ceramics are parallel; Linear array enhancement type, where multiple arc-shaped focused piezoelectric ceramics are arranged in a straight line at equal intervals, and the focusing directions of the arc-shaped focused piezoelectric ceramics converge at a first convergence point, and the first convergence point is the center of the circle passing through the focusing points of the first and last arc-shaped focused piezoelectric ceramics in the array; Annular array enhancement type, where the focusing points of multiple arc-shaped focused piezoelectric ceramics are located on the same circle and arranged at equal intervals, and the focusing directions of the arc-shaped focused piezoelectric ceramics converge at a second convergence point, and the second convergence point is the center of the circle; The number of arc-shaped focused piezoelectric ceramics located at the driving end is not less than 5, and the number of arc-shaped focused piezoelectric ceramics or rectangular sheet-shaped piezoelectric ceramics or spherical piezoelectric ceramics located at the receiving end corresponds to the number of arc-shaped focused piezoelectric ceramics at the driving end.

2. The internal concrete crack detection system based on a focused piezoelectric ceramic array according to claim 1, wherein, the unidirectional sensing piezoelectric ceramic array sensor includes a bottom semi-cylinder and a top semi-cylinder. The bottom semi-cylinder and the top semi-cylinder are respectively provided with a plurality of rectangular grooves for accommodating half of the rectangular sheet-shaped piezoelectric ceramics. The positions of the rectangular grooves are used to position the rectangular sheet-shaped piezoelectric ceramics. The bottom semi-cylinder and the top semi-cylinder are buckled to form a cylindrical module, and a plurality of the rectangular sheet-shaped piezoelectric ceramics are accommodated inside.

3. The internal concrete crack detection system based on a focused piezoelectric ceramic array according to claim 1, wherein, the spherical piezoelectric ceramic array sensor includes a bottom semi-cylinder and a top semi-cylinder. The bottom semi-cylinder and the top semi-cylinder are respectively provided with a plurality of spherical grooves for accommodating half of the spherical piezoelectric ceramics. The positions of the spherical grooves are used to position the spherical piezoelectric ceramics. The bottom semi-cylinder and the top semi-cylinder are buckled to form a cylindrical module, and a plurality of the spherical piezoelectric ceramics are accommodated inside.

4. The internal concrete crack detection system based on a focused piezoelectric ceramic array according to claim 1, wherein, the detection system further includes an oscilloscope and a voltage signal amplifier. The oscilloscope is connected to the multi-channel signal generator. The input end of the voltage signal amplifier is connected to the multi-channel signal generator, and the output end of the voltage signal amplifier is connected to the driving end.

5. The internal concrete crack detection system based on a focused piezoelectric ceramic array according to claim 1, wherein, the installation method of the driving end and the receiving end is as follows: Measuring the size of the concrete structure to be detected; for a large-sized concrete structure, a focused piezoelectric ceramic array sensor with an annular array enhanced arrangement is used; for a small-sized concrete structure, a focused piezoelectric ceramic array sensor with a parallel array enhanced or linear array enhanced arrangement is used; Locating the specific positions of the arc-shaped focused piezoelectric ceramics at the driving end according to the size of the concrete structure to be detected and the test area; Selecting the type of piezoelectric ceramic sensor as the receiving end according to the test accuracy requirements, including one of a focused piezoelectric ceramic array sensor, a unidirectional sensing piezoelectric ceramic array sensor, and a spherical piezoelectric ceramic array sensor; Locating the specific positions of the arc-shaped focused piezoelectric ceramics or rectangular sheet-shaped piezoelectric ceramics or spherical piezoelectric ceramics at the receiving end according to the size of the structure to be detected and the test area; Using high-strength low-shrinkage concrete as the matrix to fabricate the driving end and the receiving end respectively; Drilling holes at both ends of the concrete structure to be detected, implanting the driving end and the receiving end respectively, pouring low-shrinkage epoxy resin, and standing for curing for more than 24 hours; Connecting external equipment for debugging.

6. The concrete internal crack detection system based on a focused piezoelectric ceramic array according to claim 1, characterized in that, the detection method of the detection system is as follows: The computer of the workstation sends a trigger signal to the multi-channel signal generator; The multi-channel signal generator generates a waveform and checks the waveform through an oscilloscope; If the waveform check is normal, the signal is input into the voltage signal amplifier; If the waveform check is abnormal, the circuit is checked and the trigger signal is sent again; The voltage signal amplifier inputs the amplified signal into the driving end, and the driving end generates high-frequency stress waves; The receiving end senses the high-frequency stress waves, generates an induced signal and transmits it to the multi-channel signal acquisition instrument; The multi-channel signal acquisition instrument sends the acquired induced signal to the computer of the workstation for storage and analysis; The computer of the workstation performs signal time-domain / frequency-domain analysis based on the acquired induced signal, and realizes multi-parameter crack identification by using parameters including signal energy, first-wave arrival time, signal frequency, and amplitude as crack identification indicators at the same time.

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