Prestressed reinforcement nondestructive testing method and system based on ultrasonic waves
By arranging ultrasonic transmitters and receivers on the surface of the concrete structure, the stress of prestressed steel bars is calculated and identified by energy entropy spectrum, the problem of non-destructive detection of prestressed steel bars is solved, and efficient and accurate non-destructive detection is achieved.
Patent Information
- Application Number
- CN202510515952.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-23
- Publication Date
- 2025-08-29
AI Technical Summary
The prior art is difficult to non-destructively detect the types of prestressed steel bars in concrete structures, and the method of chiseling and removing concrete will lead to an increase in construction costs.
Ultrasonic transmitters and receivers are arranged at intervals on the surface of the concrete structure, and the energy entropy spectrum is detected and calculated through ultrasonic signals, and combined with the correspondence between identification indicators and stress, the stress of prestressed steel bars is identified.
The prestressed steel bars in the concrete structure are realized without the increase in construction costs and the accuracy and efficiency of inspection are improved.
Smart Images
Figure CN120559079A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of bridge engineering detection, and in particular to an ultrasonic-based non-destructive detection method and system for prestressed steel bars. Background Art
[0002] In bridge construction, to increase the strength of concrete components, steel bars or cold-drawn prestressed steel bars are often installed within the concrete structure. Cold-drawn prestressed steel bars apply a certain amount of prestressing force according to design requirements, thereby providing higher structural strength to the concrete components. However, it is difficult to detect the stress of prestressed steel bars at the construction site. Even if the surface concrete is chiseled off to expose the steel bars, it is difficult to visually distinguish whether the steel bars used inside are cold-drawn prestressed steel bars or ordinary steel bars. Chiseling off the concrete to expose the steel bars also damages the concrete components, increasing construction costs. Therefore, a non-destructive testing solution is urgently needed. Summary of the Invention
[0003] The purpose of the present invention is to overcome the defects of the prior art and provide a method and system for non-destructive testing of prestressed steel bars based on ultrasound, so as to solve the problem that the existing method of removing concrete to expose steel bars for testing cannot identify the type of steel bars by the naked eye, causes damage to the components, and increases construction costs.
[0004] The technical solution to achieve the above purpose is:
[0005] The present invention provides a non-destructive testing method for prestressed steel bars based on ultrasonic waves, comprising the following steps:
[0006] Providing an ultrasonic transmitter and an ultrasonic receiver, and arranging the ultrasonic transmitter and the ultrasonic receiver at intervals on the surface of the concrete structure to be inspected along the arrangement direction of the steel bars in the concrete structure to be inspected;
[0007] The ultrasonic transmitter transmits an ultrasonic signal at a set angle into the concrete structure to be inspected, and the ultrasonic receiver receives the ultrasonic signal reflected by the steel bars in the concrete structure to be inspected to obtain a detection signal;
[0008] Performing energy entropy spectrum calculation on the obtained detection signal to obtain the measured index;
[0009] Provide the corresponding relationship between identification indicators and stress;
[0010] According to the measured index, the corresponding stress is found from the corresponding relationship between the identification index and the stress, and is used as the stress of the steel bar, thereby completing the detection.
[0011] A further improvement of the ultrasonic-based nondestructive testing method for prestressed steel bars of the present invention is to provide a corresponding relationship between identification indicators and stress:
[0012] Provide multiple sets of test steel bars, and attach strain gauges to each test steel bar;
[0013] Apply different prestresses to multiple groups of test steel bars and make corresponding concrete test components;
[0014] Using the strain gauge to detect the actual stress in the corresponding test steel bar;
[0015] Arranging an ultrasonic transmitter and an ultrasonic receiver on the concrete test member to perform ultrasonic detection on the test steel bars in the concrete test member to obtain a test signal;
[0016] Calculating the energy entropy spectrum of the test signal, calculating the distance between the characteristic vector of the energy entropy spectrum and the set reference vector according to the set reference vector, and using the calculated distance as the recognition index;
[0017] The obtained identification index is associated with the actual stress, thereby obtaining a corresponding relationship between the identification index and the stress.
[0018] A further improvement of the ultrasonic-based nondestructive testing method for prestressed steel bars of the present invention is that, when calculating the energy entropy spectrum of the detection signal, the distance between the characteristic vector of the energy entropy spectrum of the detection signal and the set reference vector is calculated according to the set reference vector and recorded as the measured index.
[0019] The ultrasonic-based nondestructive testing method for prestressed steel bars of the present invention is further improved in that it further comprises: obtaining a sonic velocity temperature coefficient through experimental calibration;
[0020] The propagation velocity in the detection signal is corrected using the calibrated sound velocity temperature coefficient, and the energy entropy spectrum is calculated after the correction.
[0021] A further improvement of the ultrasonic-based nondestructive testing method for prestressed steel bars of the present invention is that, when arranging the ultrasonic transmitter and the ultrasonic receiver, the interval between the ultrasonic transmitter and the ultrasonic receiver is arranged to be 1.5 to 2 times the thickness of the steel bar protective layer on the concrete structure to be tested.
[0022] The present invention also provides an ultrasonic-based nondestructive testing system for prestressed steel bars, comprising:
[0023] An ultrasonic transmitter is arranged on the surface of the concrete structure to be inspected, and is used to transmit ultrasonic signals into the concrete structure to be inspected;
[0024] an ultrasonic receiver arranged on a surface of the concrete structure to be inspected, the ultrasonic receiver and the ultrasonic transmitter being arranged spaced apart along an arrangement direction of the steel bars in the concrete structure to be inspected, the ultrasonic receiver being configured to receive ultrasonic signals reflected by the steel bars in the concrete structure to be inspected to obtain a detection signal;
[0025] a signal processing unit connected to the ultrasonic receiver and configured to calculate the energy entropy spectrum of the detection signal received by the ultrasonic receiver to obtain a measured index;
[0026] A storage unit, used for storing the corresponding relationship between the identification index and the stress;
[0027] A stress calculation unit is connected to the signal processing unit and the storage unit. The stress calculation unit is used to find the corresponding stress from the corresponding relationship between the identification index and the stress according to the measured index, as the stress of the steel bar.
[0028] A further improvement of the ultrasonic nondestructive detection system for prestressed steel bars of the present invention is that the corresponding relationship between the identification index and the stress stored in the storage unit is obtained through experiments.
[0029] A further improvement of the ultrasonic nondestructive testing system for prestressed steel bars of the present invention is that the signal processing unit is also used to calculate the distance between the characteristic vector of the energy entropy spectrum of the detection signal and the set reference vector based on the set reference vector, and record it as a measured indicator.
[0030] A further improvement of the ultrasonic nondestructive testing system for prestressed steel bars of the present invention is that the signal processing unit is further used to correct the propagation speed of the detection signal according to a calibrated sound speed temperature system.
[0031] A further improvement of the ultrasonic nondestructive testing system for prestressed steel bars of the present invention is that the interval between the ultrasonic transmitter and the ultrasonic receiver is 1.5 to 2 times the thickness of the steel bar protective layer on the concrete structure to be tested.
[0032] The beneficial effects of the ultrasonic nondestructive testing method and system for prestressed steel bars of the present invention are:
[0033] The detection method and system of the present invention utilizes ultrasound to detect stress in steel bars within concrete structures, thereby distinguishing between prestressed and conventional steel bars based on the stress. This method does not damage the concrete structure, does not increase construction costs, and offers the advantages of high detection efficiency. Furthermore, the present invention utilizes guided wave energy entropy, a method with strong noise immunity, to analyze detection signals, thereby improving the accuracy of stress detection. BRIEF DESCRIPTION OF THE DRAWINGS
[0034] Figure 1The present invention is a flowchart of the ultrasonic-based nondestructive testing method for prestressed steel bars.
[0035] Figure 2 This is a system diagram of the ultrasonic-based nondestructive testing system for prestressed steel bars of the present invention.
[0036] Figure 3 The present invention is a schematic structural diagram of an ultrasonic transmitter and an ultrasonic receiver in a nondestructive testing method and system for prestressed steel bars based on ultrasonic waves, in which the ultrasonic transmitter and the ultrasonic receiver are arranged on a concrete structure to be tested. DETAILED DESCRIPTION
[0037] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.
[0038] See Figure 1 The present invention provides an ultrasonic-based nondestructive testing method and system for prestressed steel bars. This method aims to accurately and rapidly identify the stress of steel bars in concrete, thereby achieving the purpose of identifying prestressed steel bars. Furthermore, the present invention is a nondestructive testing method that only requires placing an ultrasonic transmitter and an ultrasonic receiver on the concrete structure to be tested, without destroying the concrete structure, thus avoiding increased construction costs. The present invention's ultrasonic-based nondestructive testing method and system for prestressed steel bars are described below with reference to the accompanying drawings.
[0039] See Figure 2 , which shows the system diagram of the ultrasonic-based nondestructive testing system for prestressed steel bars of the present invention. Figure 3 , shows a schematic diagram of the structure of the ultrasonic transmitter and ultrasonic receiver arranged on the concrete structure to be detected in the ultrasonic non-destructive testing method of prestressed steel bars and the system of the present invention. Figure 2 and Figure 3 , the ultrasonic-based nondestructive testing system for prestressed steel bars of the present invention is described.
[0040] like Figure 2 and Figure 3As shown, the ultrasonic-based nondestructive testing system for prestressed steel bars of the present invention includes an ultrasonic transmitter 21, an ultrasonic receiver 22, a signal processing unit 23, a storage unit 24, and a stress calculation unit 25, wherein the ultrasonic transmitter 21 and the ultrasonic receiver 22 are both arranged on the surface of the concrete structure 10 to be inspected, and the ultrasonic transmitter 21 and the ultrasonic receiver 22 are arranged at intervals along the arrangement direction of the steel bars 11 in the concrete structure 10 to be inspected, that is, the line connecting the arrangement positions of the ultrasonic transmitter 21 and the ultrasonic receiver 22 is parallel to the arrangement direction of the steel bars 11, the ultrasonic transmitter 21 is used to transmit ultrasonic signals into the concrete structure 10 to be inspected; the ultrasonic receiver 22 is used to receive ultrasonic signals reflected by the steel bars 11 in the concrete structure 10 to be inspected to obtain detection signals.
[0041] Specifically, if there are design drawings of the concrete structure to be inspected, the layout of the internal steel bars can be obtained based on the design drawings, and the layout positions of the ultrasonic transmitter 21 and the ultrasonic receiver 22 can be determined. If there are no design drawings of the concrete structure to be inspected, the ultrasonic transmitter 21 and the ultrasonic receiver 22 can be pre-arranged at the edge of one side of the concrete structure 10 to be inspected. If there is no corresponding steel bar at this time, the ultrasonic receiver 22 cannot receive the reflected ultrasonic signal. The ultrasonic transmitter 21 and the ultrasonic receiver 22 are then moved a certain distance inward on the side of the concrete structure 10 until the ultrasonic receiver 22 receives the transmitted ultrasonic signal. Therefore, even in the absence of design drawings, the ultrasonic transmitter 21 and the ultrasonic receiver 22 can be arranged at the position corresponding to the steel bar to be inspected, thereby completing the stress detection of the steel bar.
[0042] The signal processing unit 23 is connected to the ultrasonic receiver 22 , and is used to calculate the energy entropy spectrum of the detection signal received by the ultrasonic receiver 22 to obtain a measured index.
[0043] The storage unit 24 is used to store the corresponding relationship between the identification index and the stress.
[0044] The stress calculation unit 25 is connected to the signal processing unit 23 and the storage unit 24. The stress calculation unit 25 is used to find the corresponding stress from the corresponding relationship between the identification index and the stress according to the measured index, as the stress of the steel bar, thereby completing the detection.
[0045] In a specific embodiment of the present invention, before performing ultrasonic testing on a concrete structure to be tested, the surface of the concrete structure to be tested is treated to ensure that the surface of the concrete structure is clean, flat, dry, and free of joints, construction joints, finishing layers, slurry, and grease. If necessary, a grinding wheel can be used to remove debris, grind uneven areas, and wipe off residual dust.
[0046] Furthermore, if Figure 3 As shown, when setting up the ultrasonic transmitter 21 and ultrasonic receiver 22, a support with an inclined surface is placed on the surface of the concrete structure 10 to be inspected. The transmission angle of the ultrasonic transmitter 21 and the reception angle of the ultrasonic receiver 22 are controlled according to the inclination angle of the selected support. Preferably, the support is a concrete block. In this way, the ultrasonic transmitter 21 can set an angle to transmit ultrasonic signals into the concrete structure 10 to be inspected, and the ultrasonic receiver 22 can receive the ultrasonic signals reflected by the steel bars 11. The ultrasonic receiver 22 can also record information such as the time required for the ultrasonic pulse to pass through the concrete, the waveform and amplitude of the received signal. The ultrasonic signal received by the ultrasonic receiver 22, along with the recorded information such as the time required for the ultrasonic pulse to pass through the concrete, the waveform and amplitude of the received signal, etc., are collectively used as the detection signal.
[0047] Furthermore, the detection system of the present invention further includes a signal amplifier, and the ultrasonic signal received by the ultrasonic receiver is amplified by the signal amplifier to facilitate subsequent processing of the ultrasonic signal.
[0048] In a specific embodiment of the present invention, the corresponding relationship between the identification index and the stress stored in the storage unit is obtained through experiments.
[0049] Specifically, multiple sets of test steel bars are provided, and a strain gauge is attached to each test steel bar;
[0050] Apply different prestresses to multiple groups of test steel bars and make corresponding concrete test components;
[0051] Use strain gauges to detect the actual stress in the corresponding test steel bars;
[0052] Arranging an ultrasonic transmitter and an ultrasonic receiver on the concrete test member to perform ultrasonic testing on the test steel bars in the concrete test member to obtain a test signal;
[0053] The energy entropy spectrum of the test signal is calculated. According to the set reference vector, the distance between the characteristic vector of the energy entropy spectrum and the set reference vector is calculated, and the calculated distance is used as the recognition index;
[0054] The obtained identification index is associated with the actual stress, thereby obtaining the corresponding relationship between the identification index and the stress.
[0055] Furthermore, the method for attaching strain gauges to the test steel bars is as follows: longitudinal grooves are cut on the steel bars with a groove depth of 3 mm to 5 mm, the strain gauges are attached to the grooves, the wires of the strain gauges are led out from the ends of the test steel bars, and then the grooves are sealed with epoxy resin and sprinkled with coarse sand to ensure good bonding between the test steel bars and the concrete.
[0056] Furthermore, the number of test steel bar groups and the corresponding prestress can be set according to the stress accuracy required for detection. The stress of cold-drawn prestressed steel bars is between 400MPa and 600MPa. The corresponding stress is selected within this range as the prestress applied to the test steel bars. For example, a stress can be selected every 5MPa, 10MPa, 20MPa, 50MPa, etc. for testing. The stress of ordinary steel bars is between 100MPa and 200MPa, that is, the stress of ordinary steel bars is less than the stress of prestressed steel bars. When the stress calculation unit 25 searches for the corresponding stress from the corresponding relationship between the identification index and the stress according to the measured index, if the measured index is less than the minimum identification index in the corresponding relationship between the identification index and the stress, the stress calculation unit 25 feedbacks that the steel bar stress is 100MPa to 200MPa, and the steel bar is ordinary steel bar. In this way, the detection system of the present invention can detect the stress of prestressed steel bars and can also identify ordinary steel bars.
[0057] Furthermore, when calculating the energy entropy spectrum of the test signal, the test signal is first processed, and the acoustic wave signal is processed using mathematical software such as fast Fourier transform (FFT) to convert the time domain signal into a frequency domain signal; then, based on the obtained spectrum signal, the guided wave energy entropy spectrum is calculated, and the guided wave energy entropy spectrum corresponding to a stress is used as a reference vector. For example, the guided wave energy entropy spectrum corresponding to the minimum stress can be selected as the reference vector.
[0058] When calculating the identification index, the distance between the characteristic vector of the waveguide energy entropy spectrum of each experimental signal and the reference vector is calculated, and this distance is the identification index.
[0059] With the identification index as the ordinate and the stress as the abscissa, a curve showing the change of the identification index with stress is drawn. Then, the curve showing the change of the identification index with stress is fitted to obtain a stress index line. This stress index line is the corresponding relationship between the identification index and stress.
[0060] Alternatively, in another embodiment, the correspondence between the identification index and the stress is tabulated to form a table of the correspondence between the identification index and the stress.
[0061] In a specific embodiment of the present invention, the signal processing unit 23 is further configured to calculate the distance between the characteristic vector of the energy entropy spectrum of the detection signal and the set reference vector based on the set reference vector, and record it as a measured index.
[0062] Specifically, the signal processing unit 23 processes the acoustic wave signal using mathematical software such as fast Fourier transform (FFT) to process the detection signal, and converts the time domain signal into a frequency domain signal; then, based on the obtained spectrum signal, the waveguide energy entropy spectrum is calculated, and the waveguide energy entropy spectrum corresponding to a stress is used as a reference vector. For example, the waveguide energy entropy spectrum corresponding to the minimum stress can be selected as the reference vector.
[0063] In a specific embodiment of the present invention, the signal processing unit is further configured to correct the propagation speed of the detection signal according to a calibrated sound speed-temperature system.
[0064] Specifically, the temperature coefficient of the speed of sound can be obtained through experimental calibration.
[0065] The relationship between the propagation velocity of ultrasound in concrete and temperature is typically linear or polynomial, specifically expressed as: V(T) = V0 [1 + α(T - T0)], where V(T) represents the propagation velocity of ultrasound in concrete, V0 represents the baseline sound velocity at reference temperature T0, α represents the sound velocity temperature coefficient, and T represents the current ambient temperature. Based on this expression, the sound velocity corresponding to temperature T0 and temperature T can be experimentally measured, and then the sound velocity temperature coefficient can be calculated. When processing the detection signal, the signal processing unit performs temperature correction on the propagation velocity of the ultrasound in the detection signal according to the above formula.
[0066] In one embodiment of the present invention, the distance between the ultrasonic transmitter and the ultrasonic receiver is 1.5 to 2 times the thickness of the steel bar cover on the concrete structure to be inspected. For example, if the steel bar cover is 30 mm thick, the sensor spacing can be set to 45 to 60 mm, avoiding the direct reflection path of the steel bar and capturing the guided wave signal propagating along the steel bar.
[0067] The present invention also provides a non-destructive detection method for prestressed steel bars based on ultrasound, which is described below.
[0068] like Figure 1 As shown, the detection method of the present invention comprises the following steps:
[0069] Executing step S11, providing an ultrasonic transmitter and an ultrasonic receiver, and arranging the ultrasonic transmitter and the ultrasonic receiver on the surface of the concrete structure to be inspected at intervals along the arrangement direction of the steel bars in the concrete structure to be inspected; then executing step S12;
[0070] Executing step S12, the ultrasonic transmitter transmits an ultrasonic signal at a set angle into the concrete structure to be inspected, and then the ultrasonic receiver receives the ultrasonic signal reflected by the steel bars in the concrete structure to be inspected to obtain a detection signal; then executing step S13;
[0071] Execute step S13 to calculate the energy entropy spectrum of the obtained detection signal to obtain the measured index; then execute step S14;
[0072] Execute step S14 to provide a corresponding relationship between the identification index and the stress; then execute step S15;
[0073] Execute step S15, and find the corresponding stress from the corresponding relationship between the identification index and the stress according to the measured index, and use it as the stress of the steel bar, thereby completing the detection.
[0074] Before conducting ultrasonic testing on the concrete structure to be tested, the surface of the concrete structure to be tested should be treated to ensure that the surface of the concrete structure is clean, flat, dry, and free of joints, construction joints, finishing layers, floating slurry and grease. If necessary, a grinding wheel can be used to remove debris, grind uneven areas, and wipe off residual dust.
[0075] In a specific embodiment of the present invention, a corresponding relationship between identification indicators and stress is provided:
[0076] Provide multiple sets of test steel bars, and attach strain gauges to each test steel bar;
[0077] Apply different prestresses to multiple groups of test steel bars and make corresponding concrete test components;
[0078] Use strain gauges to detect the actual stress in the corresponding test steel bars;
[0079] Arranging an ultrasonic transmitter and an ultrasonic receiver on the concrete test member to perform ultrasonic testing on the test steel bars in the concrete test member to obtain a test signal;
[0080] The energy entropy spectrum of the test signal is calculated. According to the set reference vector, the distance between the characteristic vector of the energy entropy spectrum and the set reference vector is calculated, and the calculated distance is used as the recognition index;
[0081] The obtained identification index is associated with the actual stress, thereby obtaining the corresponding relationship between the identification index and the stress.
[0082] In a specific embodiment of the present invention, when calculating the energy entropy spectrum of the detection signal, the distance between the eigenvector of the energy entropy spectrum of the detection signal and the set reference vector is calculated based on the set reference vector and recorded as the measured index.
[0083] In a specific embodiment of the present invention, the method further includes: obtaining a sound velocity temperature coefficient through experimental calibration;
[0084] The propagation velocity in the detection signal is corrected using the calibrated sound velocity temperature coefficient, and the energy entropy spectrum is calculated after correction.
[0085] In one embodiment of the present invention, the ultrasonic transmitter and receiver are arranged so that the spacing between them is 1.5 to 2 times the thickness of the steel bar cover on the concrete structure being inspected. For example, if the steel bar cover is 30 mm thick, the sensor spacing can be set to 45 to 60 mm, avoiding the direct reflection path of the steel bars and capturing the guided wave signals propagating along the steel bars.
[0086] The detection method and system of the present invention detect the stress of steel bars in concrete structures based on guided wave energy entropy spectrum. They can accurately identify the stress of prestressed steel bars and can also identify ordinary steel bars, with high detection accuracy and noise resistance.
[0087] The present invention has been described in detail above with reference to the embodiments of the accompanying drawings. A person skilled in the art can make various modifications to the present invention based on the above description. Therefore, certain details in the embodiments should not be construed as limiting the present invention. The scope of protection of the present invention shall be determined by the scope defined in the appended claims.
Claims
1. A non-destructive testing method for prestressed steel bars based on ultrasonic waves, characterized in that: The steps include: Providing an ultrasonic transmitter and an ultrasonic receiver, and arranging the ultrasonic transmitter and the ultrasonic receiver at intervals on the surface of the concrete structure to be inspected along the arrangement direction of the steel bars in the concrete structure to be inspected; The ultrasonic transmitter transmits an ultrasonic signal at a set angle into the concrete structure to be inspected, and the ultrasonic receiver receives the ultrasonic signal reflected by the steel bars in the concrete structure to be inspected to obtain a detection signal; Performing energy entropy spectrum calculation on the obtained detection signal to obtain the measured index; Provide the corresponding relationship between identification indicators and stress; According to the measured index, the corresponding stress is found from the corresponding relationship between the identification index and the stress, and is used as the stress of the steel bar, thereby completing the detection.
2. The ultrasonic nondestructive testing method for prestressed steel bars according to claim 1, wherein: Provide the corresponding relationship between identification indicators and stress: Provide multiple sets of test steel bars, and attach strain gauges to each test steel bar; Apply different prestresses to multiple groups of test steel bars and make corresponding concrete test components; Using the strain gauge to detect the actual stress in the corresponding test steel bar; Arranging an ultrasonic transmitter and an ultrasonic receiver on the concrete test member to perform ultrasonic detection on the test steel bars in the concrete test member to obtain a test signal; Calculating the energy entropy spectrum of the test signal, calculating the distance between the characteristic vector of the energy entropy spectrum and the set reference vector according to the set reference vector, and using the calculated distance as the recognition index; The obtained identification index is associated with the actual stress, thereby obtaining a corresponding relationship between the identification index and the stress.
3. The ultrasonic nondestructive testing method for prestressed steel bars according to claim 1, wherein: When calculating the energy entropy spectrum of the detection signal, the distance between the characteristic vector of the energy entropy spectrum of the detection signal and the set reference vector is calculated according to the set reference vector and recorded as the measured index.
4. The ultrasonic nondestructive testing method for prestressed steel bars according to claim 1, wherein: Also includes: The temperature coefficient of sound velocity is obtained through experimental calibration; The propagation velocity in the detection signal is corrected using the calibrated sound velocity temperature coefficient, and the energy entropy spectrum is calculated after the correction.
5. The ultrasonic nondestructive testing method for prestressed steel bars according to claim 1, wherein: When arranging the ultrasonic transmitter and the ultrasonic receiver, the interval between the ultrasonic transmitter and the ultrasonic receiver is arranged to be 1.5 to 2 times the thickness of the steel bar protective layer on the concrete structure to be detected.
6. A non-destructive testing system for prestressed steel bars based on ultrasonic waves, characterized in that: include: An ultrasonic transmitter is arranged on the surface of the concrete structure to be inspected, and is used to transmit ultrasonic signals into the concrete structure to be inspected; an ultrasonic receiver arranged on a surface of the concrete structure to be inspected, the ultrasonic receiver and the ultrasonic transmitter being arranged spaced apart along an arrangement direction of the steel bars in the concrete structure to be inspected, the ultrasonic receiver being configured to receive ultrasonic signals reflected by the steel bars in the concrete structure to be inspected to obtain a detection signal; a signal processing unit connected to the ultrasonic receiver and configured to calculate the energy entropy spectrum of the detection signal received by the ultrasonic receiver to obtain a measured index; A storage unit, used for storing the corresponding relationship between the identification index and the stress; A stress calculation unit is connected to the signal processing unit and the storage unit. The stress calculation unit is used to find the corresponding stress from the corresponding relationship between the identification index and the stress according to the measured index, as the stress of the steel bar.
7. The ultrasonic nondestructive testing system for prestressed steel bars according to claim 6, characterized in that: The corresponding relationship between the identification index stored in the storage unit and the stress is obtained through experiments.
8. The ultrasonic nondestructive testing system for prestressed steel bars according to claim 6, wherein: The signal processing unit is further configured to calculate the distance between the characteristic vector of the energy entropy spectrum of the detection signal and the set reference vector based on the set reference vector, and record the distance as a measured index.
9. The ultrasonic nondestructive testing system for prestressed steel bars according to claim 6, wherein: The signal processing unit is further configured to correct the propagation speed of the detection signal according to a calibrated sound speed temperature system.
10. The ultrasonic nondestructive testing system for prestressed steel bars according to claim 6, wherein: The distance between the ultrasonic transmitter and the ultrasonic receiver is 1.5 to 2 times the thickness of the steel bar protective layer on the concrete structure to be detected.