An apparatus and method for testing the strength of concrete.

Abstract

This invention relates to the field of concrete strength testing, specifically to a device and method for testing concrete strength. The device includes a pendulum module, a rebound angle detection module, an acoustic wave detection module, and a data processing module. The pendulum module includes a hammer rod and a hammer head, the hammer head being used to impact the concrete component being tested. The rebound angle detection module is used to collect the rebound angle change curve of the hammer rod. The acoustic wave detection module is used to collect the acoustic wave amplitude change curve of the concrete component being tested. The data processing module can compare and analyze the characteristic parameters of the rebound angle change curve and the acoustic wave amplitude change curve with the characteristic parameters in a standard atlas library of concrete strength grades, thereby determining the strength grade of the concrete component being tested. This invention enables multi-source information fusion judgment, effectively avoiding the limitations of a single parameter and reducing the systematic deviation between the estimated test value and the actual concrete strength.

Description

Technical Field

[0001] This invention relates to the field of concrete strength testing, and in particular to an apparatus and method for testing concrete strength. Background Technology

[0002] Among existing non-destructive testing technologies for concrete, the rebound hammer is one of the most commonly used testing devices. Based on the rebound method principle, it estimates the compressive strength of concrete by measuring the rebound distance of a heavy hammer after impacting the concrete surface.

[0003] However, the rebound method is a relatively simple testing method, and its test results are easily affected by various factors such as the surface condition of concrete (such as carbonation depth, moisture content, surface roughness, etc.) and internal structure (such as coarse aggregate type, age, etc.), which may lead to a large deviation between the estimated test value and the actual strength of concrete, resulting in insufficient test accuracy and reliability.

[0004] Therefore, there is an urgent need to propose a new concrete strength testing scheme to improve the accuracy and reliability of the test results. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem that existing technologies using rebound hammers to test concrete strength, due to their relatively singular testing method, may lead to a significant deviation between the estimated test value and the actual concrete strength. Therefore, this invention provides a device and method for testing concrete strength.

[0006] In a first aspect, the present invention provides an apparatus for testing the strength of concrete, comprising:

[0007] A pendulum module, comprising a hammer rod and a hammer head, wherein the hammer head is used to impact the concrete component being tested; A rebound angle detection module is used to collect the rebound angle change curve of the hammer rod after the hammer head is struck. The acoustic wave detection module is used to collect the acoustic wave amplitude change curve of the concrete component under test after the hammer is struck. The data processing module has a pre-stored standard spectrum library of concrete of all strength grades. The rebound angle detection module and the acoustic wave detection module are both electrically connected to the data processing module. The data processing module can compare and analyze the characteristic parameters of the rebound angle change curve and the acoustic wave amplitude change curve with the characteristic parameters in the standard spectrum library of concrete of all strength grades, thereby determining the strength grade of the concrete component under test.

[0008] This invention provides a device for testing the strength of concrete. The pendulum module includes a hammer rod that drives a hammer head to strike the concrete component under test. After the initial strike, the hammer head rebounds and strikes the component multiple times consecutively. A rebound angle detection module collects the real-time curve of the rebound angle of the hammer rod over time after each strike. A sonic wave detection module collects the real-time curve of the sonic wave amplitude of the concrete component under test over time after each strike. The rebound angle and sonic wave amplitude curves are transmitted to a data processing module via an electrical connection. The data processing module extracts feature parameters from both curves and compares these parameters with corresponding standard feature parameters in a full-strength-grade concrete standard atlas library to determine the strength grade of the concrete component under test.

[0009] This invention provides a device for detecting concrete strength. By collecting and extracting characteristic parameters from the rebound angle change curve and the acoustic amplitude change curve, and comparing them with standard characteristic parameters in a full-strength-grade concrete standard spectrum library, the strength grade of the tested concrete component is determined. Compared to traditional rebound hammers that rely solely on a single rebound value to estimate concrete strength, this method simultaneously acquires two physical parameters: the rebound angle response after hammering and the acoustic propagation characteristics of the tested component. This achieves multi-source information fusion judgment, effectively avoiding the limitations of a single parameter, reducing the systematic deviation between the estimated value and the actual concrete strength, and significantly improving the accuracy and reliability of concrete strength testing results.

[0010] The pendulum module can be driven to swing by a spring or by a motor.

[0011] Preferably, the pendulum module further includes a motor, with both ends of the hammer rod connected to the motor shaft and the hammer head respectively. The motor is used to drive the hammer rod to rotate, thereby causing the hammer head to swing around the shaft to strike.

[0012] In this solution, the hammer rod is directly driven to rotate by the motor. Compared with the spring-driven method, this solution can more accurately control the striking force of the hammer head.

[0013] Preferably, the device further includes a housing, in which the motor, the hammer rod, and the hammer head are all located. The motor is fixed to the bottom plate of the housing, and a through hole is provided on the bottom plate of the housing, through which the hammer head can pass.

[0014] In this design, the housing provides a stable mounting base for the motor and encapsulates the motor, hammer rod, and hammer head within it. This housing protects the motor, hammer rod, and hammer head from dust and impacts, preventing damage during transport or use. Simultaneously, the through-hole on the base plate provides a passage for the hammer head, allowing it to drive the motor and impact the concrete component under test. This ensures protection without compromising the hammering function.

[0015] Preferably, the upper surface of the housing is provided with a display, which is electrically connected to the data processing module, and the display is used to display the strength grade of the concrete component being tested.

[0016] In this solution, by setting a display on the box that is electrically connected to the data processing module, the strength grade of the tested concrete component can be displayed in real time in an intuitive digital form, so that the testing personnel can directly read the test results without the aid of external equipment, thereby improving the convenience of on-site testing and the efficiency of interpretation.

[0017] The acoustic wave detection module can obtain the acoustic wave amplitude variation curve of the tested concrete component through an acoustic wave probe or a laser vibration meter.

[0018] The acoustic wave probe operates based on the piezoelectric effect: when the piezoelectric ceramic sheet inside is mechanically excited by acoustic wave vibration, it generates an electric charge signal proportional to the vibration intensity. After amplification, this electric signal can reflect the amplitude of the acoustic wave and its change over time, thereby obtaining the amplitude attenuation curve of the acoustic wave propagating in the tested concrete component.

[0019] The laser vibration meter works based on the principle of laser Doppler interference: it emits a laser beam to the surface being measured. After the laser is reflected by the surface, it interferes with the internal reference beam. Since the surface vibrates with the sound wave and produces a small displacement, the frequency of the reflected light will shift due to the Doppler effect. By detecting this frequency shift, the vibration velocity and displacement of the surface can be accurately calculated, and thus the change curve of the sound wave amplitude over time can be obtained.

[0020] Preferably, the acoustic wave detection module includes an acoustic wave probe, which is installed on the bottom surface of the housing, and the sensing surface of the acoustic wave probe can contact the surface of the concrete component being tested.

[0021] Compared to laser vibration meters, the acoustic probe is based on the piezoelectric contact sensing principle, which does not require optical alignment and is unaffected by the roughness of the measured surface, dust, and lighting conditions. It has stronger environmental adaptability and signal stability in the complex working conditions of concrete site testing.

[0022] The rebound angle detection module can obtain the rebound angle change curve of the hammer rod through an angle sensor or encoder.

[0023] The angle sensor (such as a potentiometer-type angle sensor) is mounted on the rotating shaft of the hammer rod. It contains a resistive slide rail that rotates synchronously with the rotating shaft and a sliding contact that rotates with the rotating shaft. When the hammer rod rebounds, the rotating shaft drives the sliding contact to slide on the resistive slide rail, so that the resistance value (or voltage value) at the output of the sensor changes continuously with the change of the rotation angle. This converts the mechanical rotation angle of the hammer rod into an electrical signal in real time. After acquisition and processing, the rebound angle change curve of the hammer rod can be obtained.

[0024] The encoder is mounted on the rotating shaft of the hammer rod. Its code disk (or code disk grating) rotates synchronously with the rotating shaft. The code disk is engraved with equally spaced light-transmitting and light-blocking areas (or magnetic pole changing areas). When the hammer rod rebounds, the rotating shaft drives the code disk to rotate. The photoelectric detection element (or magnetic induction element) senses the alternating changes of light transmission / blocking (or magnetic poles) on the code disk and converts them into a series of pulse signals. By counting the number of pulses and analyzing the pulse frequency, the angular displacement of the rotating shaft at any moment can be accurately calculated, thereby obtaining the rebound angle change curve of the hammer rod.

[0025] Preferably, the rebound angle detection module includes an encoder, which is mounted on the rotating shaft of the hammer rod and is used to acquire the rebound angle change curve of the hammer rod.

[0026] Compared to angle sensors, the encoder outputs digital pulse signals, which have strong anti-electromagnetic interference capabilities and much higher resolution and measurement accuracy than potentiometer-type angle sensors. It can more accurately capture the small and continuous changes in angle during the rebound of the hammer rod, thereby obtaining a more accurate and smooth rebound angle change curve.

[0027] Preferably, the motor is a torque motor. In this design, the torque motor can output a constant torque to drive the hammer rod to rotate.

[0028] In a second aspect, the present invention provides a method for testing concrete strength, applied to an apparatus for testing concrete strength as described in the first aspect, comprising the following steps: S1: Use a hammer to strike the concrete component being tested; S2: Obtain the rebound angle change curve of the hammer head after hammering, and the acoustic amplitude change curve of the tested concrete component; S3: Extract the feature parameters of the rebound angle change curve and the acoustic amplitude change curve; calculate the similarity between the extracted feature parameters and the feature parameters of each spectrum in the full strength grade concrete standard spectrum library using the support vector machine algorithm, and take the strength grade corresponding to the standard spectrum with the highest similarity as the strength grade of the tested concrete component.

[0029] This invention provides a method for detecting concrete strength. By comparing and analyzing the characteristic parameters of the rebound angle change curve and the acoustic amplitude change curve with standard characteristic parameters in a standard atlas library of concrete strength grades, the strength grade of the tested concrete component is determined. Compared to traditional rebound hammers that rely solely on a single rebound value to estimate concrete strength, this method simultaneously acquires two physical parameters: the rebound angle response after hammering and the acoustic propagation characteristics of the tested component. This achieves multi-source information fusion judgment, effectively avoiding the limitations of a single parameter, reducing the systematic deviation between the estimated value and the actual concrete strength, and significantly improving the accuracy and reliability of concrete strength detection results.

[0030] Preferably, in step S3: The characteristic parameters of the rebound angle change curve include: the first rebound angle α1 and the attenuation rate k1, where k1=(α1-α2) / n, α2 represents the maximum rebound angle when the rebound angle is less than α1 / 10, and n represents the cumulative number of rebounds when the rebound angle is α2. The characteristic parameters of the acoustic wave amplitude variation curve include: the amplitude of the first hammer impact acoustic wave A1 and the amplitude attenuation rate k2, where k2=(A1-A2) / m, A2 represents the maximum hammer impact acoustic wave amplitude corresponding to when the hammer impact acoustic wave amplitude is less than A1 / 10, and m represents the cumulative number of hammer impacts corresponding to when the hammer impact acoustic wave amplitude is A2.

[0031] Preferably, step S3 further includes correcting the strength grade of the tested concrete component using the following formula: σ_corr=σ_raw×[1-0.008×(T-20)-0.012×(W-6)], Where σ_corr represents the corrected concrete strength value, σ_raw represents the strength grade value corresponding to the standard spectrum with the highest similarity, T represents the ambient temperature, and W represents the moisture content of the surface of the tested concrete component.

[0032] In this scheme, the modified formula can further reduce the influence of ambient temperature and the moisture content of the surface of the concrete component being tested on the measurement results, thereby further improving the accuracy of concrete strength test results.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention provides a device for detecting concrete strength. By collecting and extracting characteristic parameters from the rebound angle change curve and the acoustic amplitude change curve, and comparing them with standard characteristic parameters in a standard image library of concrete strength grades, the strength grade of the tested concrete component is determined. Compared with traditional rebound hammers that rely solely on a single rebound value to estimate concrete strength, this method simultaneously acquires two physical parameters: the rebound angle response after hammering and the acoustic propagation characteristics of the tested component. This achieves multi-source information fusion judgment, effectively avoiding the limitations of a single parameter, reducing the systematic deviation between the estimated value and the actual concrete strength, and significantly improving the accuracy and reliability of concrete strength detection results. 2. This invention provides a method for detecting concrete strength. By comparing and analyzing the characteristic parameters of the rebound angle change curve and the acoustic amplitude change curve with standard characteristic parameters in a standard image library of concrete strength grades, the strength grade of the tested concrete component is determined. Compared to traditional rebound hammers that rely solely on a single rebound value to estimate concrete strength, this method simultaneously acquires two physical parameters: the rebound angle response after hammering and the acoustic propagation characteristics of the tested component. This achieves multi-source information fusion judgment, effectively avoiding the limitations of a single parameter, reducing the systematic deviation between the estimated value and the actual concrete strength, and significantly improving the accuracy and reliability of concrete strength detection results. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of a device used to test the strength of concrete.

[0035] Figure 2 This is an oblique upward view of a device used to test the strength of concrete.

[0036] Figure 3 This is a front view of a device used to test the strength of concrete.

[0037] Figure 4 This is a left view of a device used to test the strength of concrete.

[0038] Figure 5 This is a top view of a device used to test the strength of concrete.

[0039] Figure 6 for Figure 3 A cross-sectional view along section line AA.

[0040] Figure 7 for Figure 5 A cross-sectional view along the BB section line.

[0041] Marked in the image: 1-Box body, 101 - Through hole, 2-Pendulum protective shell, 3-button, 4- Monitor, 5-Handle, 6-Hammerhead, 7-Hammer rod, 8-Motor, 9-Humidity probe, 10- Acoustic probe, 11-Data Processing Module 12-cell battery. Detailed Implementation

[0042] The present invention will now be described in further detail with reference to specific embodiments. However, this should not be construed as limiting the scope of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0043] Unless otherwise specified, the terms "upper," "lower," "left," "right," "center," "inner," and "outer," etc., used in the description of specific embodiments of the present invention to indicate orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationship in which the product / equipment / device is usually placed during use. These terms are merely for the purpose of facilitating the description of the present invention or simplifying the description in specific embodiments, and for enabling those skilled in the art to quickly understand the solution, and do not indicate or imply that a particular device / component / element must have a specific orientation, or be constructed and operated in a specific positional relationship. Therefore, they should not be construed as limitations on the present invention.

[0044] Furthermore, the use of terms such as "horizontal," "vertical," "suspended," "parallel," and "coaxial" does not imply that the corresponding device / component / element must be absolutely horizontal, vertical, suspended, parallel, or coaxial. Slight tilt or deviation is permissible, as long as it does not affect the normal function of the relevant component. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," not that the structure must be perfectly horizontal; a slight tilt is acceptable. "Coaxial" means that two components are arranged as coaxially as possible, allowing them to move coaxially or approximately coaxially when their relative positions change. Alternatively, it can be simplified to mean that the corresponding device / component / element, when arranged in "horizontal," "vertical," "suspended," "parallel," or "coaxial" directions, can have an error / deviation of ±10% relative to the corresponding direction, more preferably within ±8%, more preferably within ±6%, more preferably within ±5%, and more preferably within ±4%. For example, the deviation in the "coaxial" direction is controlled within 0.2-1mm, preferably within 0.2-0.5mm. As long as the corresponding device / component / element is within the error / deviation range, it can still achieve its function in the solution of the present invention.

[0045] Furthermore, the use of terms such as "first," "second," and "third" in terminology is merely for distinguishing descriptions of identical or similar components and should not be interpreted as emphasizing or implying the relative importance of a particular component.

[0046] Furthermore, in the description of the embodiments of the present invention, "several", "more than", and "a number of" represent at least two. The number can be any number, such as two, three, four, five, six, seven, eight, or nine, and can even exceed nine.

[0047] Furthermore, in the description of the technical solution of this invention, unless otherwise explicitly specified / limited / restricted, the terms "set up," "install," "connect," "link," "provided with," "laid out," and "arranged" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to connection methods commonly used in the art, such as welding, riveting, bolting, and threaded connections. Such connections can be mechanical, electrical, or communication connections; they can be direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components.

[0048] Example 1 like Figures 1 to 7 As shown, a device for detecting the strength of concrete includes a pendulum module, a rebound angle detection module, an acoustic detection module, and a data processing module 11.

[0049] The pendulum module includes a hammer rod 7 and a hammer head 6, the hammer head 6 being used to impact the concrete component being tested.

[0050] The rebound angle detection module is used to collect the rebound angle change curve of the hammer rod 7 after the hammer head 6 is struck.

[0051] The acoustic wave detection module is used to collect the acoustic wave amplitude change curve of the tested concrete component after the hammer head 6 is struck.

[0052] The data processing module 11 has a pre-stored standard spectrum library of concrete of all strength grades. The rebound angle detection module and the acoustic wave detection module are both electrically connected to the data processing module 11. The data processing module 11 can compare and analyze the characteristic parameters of the rebound angle change curve and the acoustic wave amplitude change curve with the characteristic parameters in the standard spectrum library of concrete of all strength grades, thereby determining the strength grade of the concrete component under test.

[0053] Specifically, the full strength grade concrete standard atlas library pre-stores standard atlases for 14 strength grades, including C15, C20, C25, C30, C35, C40, C45, C50, C55, C60, C65, C70, C75, and C80. Each grade contains 10 sets of parallel test data (to eliminate individual differences). The atlas dimensions are: x-axis for time and y-axis for rebound height or sonic amplitude.

[0054] During the acquisition of standard spectra and actual measurements, the hammer head 6's hammering starting position and initial kinetic energy were set to the same conditions.

[0055] Specifically, the weight of the entire device is kept below 1.5kg, making it easy to carry and operate on-site.

[0056] In an optional embodiment, the pendulum module may further include a motor 8, with the two ends of the hammer rod 7 connected to the rotating shaft of the motor 8 and the hammer head 6, respectively. The motor 8 is used to drive the hammer rod 7 to rotate, thereby causing the hammer head 6 to swing around the rotating shaft to strike.

[0057] Specifically, the hammer head 6 is used to impact the concrete component under test and generate a continuously decaying rebound after impact. The rebound angle detection module is coupled to the rotation shaft of the hammer rod 7 and is used to collect the rebound angle change curve of the hammer rod 7 in real time during the continuous decay rebound process.

[0058] In an optional embodiment, the device may also include a housing 1, in which the motor 8, the hammer rod 7, and the hammer head 6 are all located. The motor 8 is fixed to the bottom plate of the housing 1, and a through hole 101 is provided on the bottom plate of the housing 1, through which the hammer head 6 can pass.

[0059] Specifically, the top surface of the box 1 is also provided with a pendulum protective shell 2. Since the hammer head 6 will be higher than the top surface of the box 1 when the hammer rod 7 is lifted away from the bottom plate of the box 1, the pendulum protective shell 2 is used to protect the hammer rod 7 and the hammer head 6 after they are lifted; the shape of the pendulum protective shell 2 matches the swing trajectory of the hammer rod 7.

[0060] The swing plane of the hammer rod 7 is perpendicular to the bottom plate of the housing 1. The top surface of the housing 1 may also be equipped with a handle 5, which facilitates the operator in lifting the entire device and pressing it onto the surface of the concrete component being tested. The top surface of the housing 1 may also be equipped with a button 3, used to control the device's power on and off, and to control the pendulum module to initiate the hammering operation.

[0061] The data processing module 11 can also be installed inside the housing 1 and fixed to the bottom plate of the housing 1. A battery 12 can also be installed on the bottom plate inside the housing 1. The battery 12 supplies power to the pendulum module, the rebound angle detection module, the acoustic wave detection module, and the data processing module 11. Specifically, the battery 12 is a rechargeable lithium battery with a capacity of 2000mAh, a voltage of 3.7V, a battery life of ≥8 hours, supports fast charging (fully charged in 2 hours), and has a built-in low battery alarm function.

[0062] In an optional embodiment, the upper surface of the housing 1 may be provided with a display 4, which is electrically connected to the data processing module 11 and is used to display the strength grade of the concrete component being tested.

[0063] Specifically, display 4 is a 2.4-inch TFT color display with a resolution of 320×240, supports touch operation, and can display detection data in real time.

[0064] In an optional embodiment, the acoustic detection module may include an acoustic probe 10, which is mounted on the bottom surface of the housing 1, and the sensing surface of the acoustic probe 10 is capable of contacting the surface of the concrete component being tested.

[0065] Specifically, a humidity probe 9 may also be provided on the bottom surface of the box 1. The humidity probe 9 is used to detect the humidity of the surface of the concrete component being tested.

[0066] Specifically, the acoustic probe 10 is a piezoelectric ceramic probe with a frequency range of 20kHz-200kHz and a sensitivity of ≥-70dB. The sensing surface of the acoustic probe 10 is in contact with the surface of the concrete component under test, and is used to acquire the acoustic amplitude change curve of the concrete component under test in real time during the continuous attenuation and rebound process.

[0067] In an optional embodiment, the springback angle detection module may include an encoder, which is disposed on the rotating shaft of the hammer rod 7, and the encoder is used to acquire the springback angle change curve of the hammer rod 7.

[0068] In an optional embodiment, the motor 8 may be a torque motor.

[0069] Specifically, hammer head 6 is made of tungsten steel (hardness HRC≥60, with both wear resistance and corrosion resistance). Hammer head 6 has a diameter of 20mm, a height of 30mm, and a slightly convex bottom. Hammer shaft 7 is made of aluminum alloy (lightweight design), with a length of 150mm and a diameter of 18mm, and an internal lead screw guide groove (to prevent transmission misalignment).

[0070] The driving component in the pendulum module can also be a high-torque micro DC brushless motor and transmission mechanism. Through precise calibration of "torque-speed-transmission ratio", a fixed energy is released (set to 2.207J or 4.5J, 5.5J, consistent with the energy of the industry standard rebound hammer, to ensure data comparability). After the hammer head 6 collides with the surface of the concrete component being tested, the fixed torque is maintained through torque closed-loop control until the impact ends. At the same time, elastic feedback is used to achieve natural continuous attenuation of the hammer impact (attenuation times ≥ 8 times, to ensure the integrity of dynamic signal acquisition).

[0071] The specific model of the high-torque micro DC brushless motor is a coreless torque motor, weighing ≤50g. It features precise torque control (torque range 0.1-1N·m), fast response speed (start-up response time ≤10ms), high efficiency, and long lifespan. It can perfectly meet the dynamic requirements of "torque-kinetic energy conversion + fixed torque maintenance after impact", avoiding the wear and sparking problems of brushed motors.

[0072] Energy calibration scheme (torque-kinetic energy conversion) basic parameter calibration: By preset torque T (N·m) and speed parameters of the motor controller, combined with the mass M (kg) of the hammer head 6, the transmission ratio i of the transmission mechanism, and the radius r (m, i.e., lever arm) of the hammer rod 7, the kinetic energy is calculated by formula E=(T×i×s) / r (s is the impact stroke of the hammer head 6, set to 170mm). Through more than 100 sets of standard test block experiments, the output torque and speed parameters of the motor 8 corresponding to 2.207J energy or other required energy are calibrated to ensure that the impact energy error is ≤±2%.

[0073] The instantaneous power compensation mechanism adopts PWM (Pulse Width Modulation) speed regulation technology. In the initial stage of startup, it outputs a high duty cycle signal to provide a large instantaneous current to the high-torque micro brushless DC motor, so as to quickly reach the speed corresponding to the preset torque and avoid energy loss caused by startup lag.

[0074] The pendulum module also includes a torque feedback monitoring module and a main control unit. The torque feedback monitoring module is a miniature torque sensor (model: HBMT40B, range: 0-2N·m, accuracy: ±0.5%) installed between the high-torque miniature DC brushless motor and the transmission mechanism. It collects the torque data after the hammer head 6 comes into contact with the surface of the concrete component being tested in real time and transmits the signal to the main control unit in real time to realize closed-loop monitoring of torque.

[0075] Closed-loop control strategy for PID torque regulation: The main control unit adopts a PID (proportional-integral-derivative) control algorithm, comparing the actual torque value collected by the torque sensor with a preset fixed torque value, calculating the deviation, and dynamically adjusting the output torque of motor 8. Adaptive torque adjustment: When the actual torque is less than the preset value, the controller increases the output torque of motor 8; when the actual torque exceeds the preset value, the torque is reduced or even the speed is finely adjusted in the opposite direction to ensure that the torque remains stable within the set range after the impact until the impact ends.

[0076] An acceleration sensor can be installed on the hammer head 6. Specifically, the acceleration sensor is a miniature piezoelectric acceleration sensor with a range of ±50g, a frequency response of 0-1kHz, and a sensitivity of 100mV / g. It is attached to the center of the top of the hammer head 6 with special adhesive. The curve of the vibration acceleration signal of the hammer head 6 over time can be collected and used to verify the rebound angle change curve, further ensuring the accuracy and reliability of the data acquisition.

[0077] The data processing module 11 may include a data acquisition card, specifically a USB data acquisition card with a sampling rate ≥1kHz. The USB data acquisition card has a 12-bit resolution to ensure accurate signal acquisition. The USB data acquisition card is connected to the rebound angle detection module, the acoustic wave detection module, and the accelerometer, respectively.

[0078] The data processing module 11 may include an embedded chip, specifically an ARM Cortex-A9 processor (1GHz), which has a built-in machine learning algorithm (a graph matching model based on support vector machine SVM) and can complete data processing within 1 second.

[0079] The data processing module 11 has a built-in 8GB storage space (capable of storing 100,000 sets of detection data), supports USB 2.0 interface and Bluetooth 5.0, and can export data to a computer (format: CSV / Excel) for easy subsequent analysis.

[0080] The construction of a standard atlas library of concrete of all strength grades can be carried out in the following manner: 1. Preparation of Standard Specimens. In accordance with the "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" (GB / T 50081-2019), standard cubic specimens (150mm×150mm×150mm) for 14 strength grades—C15, C20, C25, C30, C35, C40, C45, C50, C55, C60, C65, C70, C75, and C80—were prepared, with 20 sets of specimens for each grade. The mix design covered the range of conventional engineering projects: water-cement ratio 0.35-0.70, P·O 42.5 ordinary Portland cement, 5-25mm continuously graded crushed stone as coarse aggregate, medium sand as fine aggregate, and slump controlled at 30-50mm. The specimens were cured in a standard curing room (temperature 20±2℃, relative humidity ≥95%) for 28 days.

[0081] 2. Data Acquisition. The cured specimens were removed from the standard curing room and placed in a laboratory environment with a temperature of 20±2℃ and a relative humidity of 60±5% for 24 hours. Using the same impact parameters (hammer head mass 6, impact stroke, released kinetic energy 2.207J) and acquisition parameters (sampling rate ≥1kHz) as the device of this invention, continuous attenuation hammer impact tests were performed on each specimen, and the rebound angle change curve and the sound wave amplitude change curve were acquired simultaneously. Three valid data points were collected for each specimen.

[0082] 3. Data preprocessing. The acquired raw signals are filtered and denoised (using an 8th-order Butterworth bandpass filter with a passband of 20Hz-500Hz), outlier data (such as hammer impact offset, sensor detachment, etc.) are removed, and valid data segments with continuous attenuation (attenuation times ≥ 8 times) are retained.

[0083] 4. Feature Parameter Extraction. For each curve, extract the angle attenuation feature parameters and amplitude attenuation feature parameters. The angle attenuation feature parameters include: the first rebound angle α1 (unit: degrees), and the angle attenuation rate k1 = (α1 - α2) / n; the amplitude attenuation feature parameters include: the first impact sound wave amplitude A1 (unit: mV), and the amplitude attenuation rate k2 = (A1 - A2) / m. Where α2 is defined as the last recognizable peak angle when the rebound angle attenuates to below α1 / 10, A2 is defined as the last recognizable peak amplitude when the sound wave amplitude attenuates to below A1 / 10, and n and m are the corresponding cumulative attenuation counts.

[0084] 5. Feature Vector Construction and Atlas Storage. For all valid specimen data at each intensity level, calculate the statistical mean and standard deviation of the feature parameters, construct a standard four-dimensional feature vector [α1_mean, k1_mean, A1_mean, k2_mean] for that intensity level, and record the statistical distribution range of each parameter. Store the standard feature vectors of the 14 intensity levels in the atlas library in order of intensity level, forming a standard atlas database with intensity level index.

[0085] 6. Spectrum Verification. Leave-one-out cross-validation is used to verify the matching accuracy of the spectrum library: one specimen is selected as the test sample each time, and the remaining specimens are used to construct a temporary spectrum library. A machine learning algorithm is then used to determine the matching accuracy. Actual testing shows that the spectrum library constructed in this embodiment achieves a cross-validation matching accuracy of over 96.5% across 14 intensity levels, meeting engineering testing requirements.

[0086] The data structure of the spectral library is as follows: Intensity levels (C15-C80) serve as the primary index. Each level stores a standard four-dimensional feature vector, the statistical distribution range of feature parameters, and the feature boundary discrimination function between levels. The spectral library supports incremental updates and adaptive optimization using field calibration data.

[0087] Example 2 A method for testing concrete strength, applied to the apparatus for testing concrete strength described in Example 1, includes the following steps: S1: Use hammer head 6 to hammer the concrete component being tested.

[0088] S2: Obtain the rebound angle change curve of the hammer head 6 after hammering, and the acoustic amplitude change curve of the tested concrete component.

[0089] Specifically, before hammering, the concrete component to be tested undergoes surface treatment and test point marking. Surface treatment involves using 120-grit sandpaper to polish the concrete surface to remove laitance, impurities, and weathered layers, preventing unevenness from affecting hammering contact. Test point marking involves using a marker to mark test points in the testing area, with a spacing of ≥50mm between adjacent test points, avoiding areas ≥20mm from concrete edges, rebar locations (which can be located using a rebar detector), and areas with defects such as cracks, honeycomb, and pitting. At least three test points are arranged in each testing area (average value).

[0090] Then, the device is started, positioned and stabilized, impact triggered, and signal stored. The device is started by pressing and holding the power button for three seconds to turn it on. The device automatically completes sensor self-test (displaying "Self-test passed") and enters the detection mode. Positioning and stabilization are performed by holding the handle 5 of the device and pressing it firmly, aligning the through hole 101 on the bottom plate of the housing 1 with the detection area. The humidity probe 9 simultaneously collects the humidity of the concrete surface as part of the correction value. Impact triggering is performed by pressing the start button. The motor 8 outputs torque according to the pre-calibrated parameters, driving the hammer head 6 to accelerate and impact the surface of the concrete component being tested along the stroke direction via the hammer rod 7, releasing 2.207J of energy. After the impact, the motor 8 maintains a fixed torque through torque closed-loop control, simultaneously forming a continuous attenuation hammer impact. The rebound angle detection module and the acoustic wave detection module simultaneously collect dynamic signals. Signal storage is performed by the device automatically storing the original signal data of this test, named in the format "date-time-measurement point number", such as "20251109-1430-01".

[0091] S3: Extract the feature parameters of the rebound angle change curve and the acoustic amplitude change curve; calculate the similarity between the extracted feature parameters and the feature parameters of each spectrum in the full strength grade concrete standard spectrum library using the support vector machine algorithm, and take the strength grade corresponding to the standard spectrum with the highest similarity as the strength grade of the tested concrete component.

[0092] Specifically, signal cleaning is performed before feature parameter extraction. Signal cleaning involves the algorithm automatically removing abnormal data (such as sudden changes in rebound height caused by hammer impact offset, or signals with frequency fluctuations exceeding ±10% caused by sensor interference), while retaining valid data segments with continuous attenuation.

[0093] This embodiment uses the support vector machine algorithm for graph matching. Those skilled in the art can also use other machine learning algorithms such as neural networks, random forests, or gradient boosting trees to achieve the same function as needed. In an optional implementation, in step S3: The characteristic parameters of the rebound angle change curve may include: the first rebound angle α1 and the attenuation rate k1, where k1=(α1-α2) / n, α2 represents the maximum rebound angle when the rebound angle is less than α1 / 10, and n represents the cumulative number of rebounds when the rebound angle is α2. The characteristic parameters of the acoustic wave amplitude variation curve may include: the amplitude of the first hammer impact acoustic wave A1 and the amplitude attenuation rate k2, where k2=(A1-A2) / m, A2 represents the maximum hammer impact acoustic wave amplitude corresponding to when the hammer impact acoustic wave amplitude is less than A1 / 10, and m represents the cumulative number of hammer impacts corresponding to when the hammer impact acoustic wave amplitude is A2.

[0094] In an optional implementation, step S3 may further include correcting the strength grade of the tested concrete component using the following formula: σ_corr=σ_raw×[1-0.008×(T-20)-0.012×(W-6)], Where σ_corr represents the corrected concrete strength value, σ_raw represents the strength grade value corresponding to the standard spectrum with the highest similarity, T represents the ambient temperature, and W represents the moisture content of the surface of the tested concrete component.

[0095] In the above correction formula, the coefficient 0.008 is the temperature correction coefficient, and the coefficient 0.012 is the moisture content correction coefficient.

[0096] Specifically, the system also includes a result output step, which comprises real-time display, data export, and anomaly alarm. The real-time display shows the test results on the screen within 10 seconds, including: intensity value (unit: MPa), acoustic amplitude change curve, rebound angle change curve, test point number, and test time. The data export allows the test data to be exported to a computer via USB or Bluetooth, generating a test report. The report includes test point location, environmental parameters, intensity results, and spectrum comparison charts. The anomaly alarm indicates that if the test result exceeds the C15-C80 range, or the similarity is <90%, the device displays "Detection abnormal, please retest," and suggests possible causes (such as improper surface treatment or hammer offset).

[0097] The above step S3 can also be replaced by: performing adaptive environmental correction on the determined strength grade based on the ambient temperature during the test and the moisture content of the surface of the concrete component being tested. The adaptive environmental correction is implemented based on a machine learning model trained on training samples containing different temperature and humidity conditions in the atlas library.

[0098] Specifically, in constructing a standard atlas library for concrete of all strength grades, in addition to data under standard temperature and humidity conditions (temperature: 20℃, humidity: 60%), feature parameter data under different temperature gradients (5℃, 10℃, 15℃, 25℃, 30℃, 35℃) and different moisture content gradients (3%, 6%, 9%, 12%, 15%) are also collected to form an extended atlas library covering multiple environmental conditions. The machine learning algorithm in data processing module 11 learns both the feature parameter-strength grade relationship and the environmental condition-bias correction relationship during the training phase. This allows it to automatically perform environmental adaptive corrections on the initial matching results based on real-time ambient temperature and moisture content data during the detection phase, without the need for explicit correction formulas.

[0099] The advantages of this adaptive correction strategy are: 1. It avoids the problem of lack of basis for empirical coefficients; 2. The correction effect is continuously optimized as training data accumulates; 3. It can be extended to more environmental conditions through incremental learning.

[0100] The device for testing concrete strength provided by this invention also has the following beneficial effects and advantages: 1. Significantly improved efficiency: Continuous testing can be completed with a single trigger, and the operation time for a single test point is ≤10 seconds, which is more than 50% more efficient than the ultrasonic rebound method, making it suitable for batch testing on site.

[0101] 2. Higher detection accuracy: Multi-source information fusion judgment, combined with machine learning map matching algorithm, avoids the limitations of single parameters, the detection error is ±5%, which is more than 30% more accurate than the existing technology, and can simultaneously locate internal defects (depth error is ±10mm).

[0102] 3. Extremely low operating threshold: No professional training is required; ordinary workers can operate the equipment, which automatically completes data processing and result output, solving the pain point of existing technologies that "rely on the experience of operators".

[0103] 4. Extremely versatile: It is compatible with concrete of all strength grades from C15 to C80, and is not significantly affected by aggregate type, ambient temperature and humidity (0-40℃), or surface flatness (≤0.5mm / m). It can be used for testing in multiple scenarios such as building floor slabs, beams and columns, bridges, and tunnels.

[0104] 5. Data traceability: Built-in large-capacity storage supports data export and report generation, meeting the file management needs of engineering testing and avoiding errors from manual recording.

[0105] 6. Lightweight and portable: The overall weight is ≤1.5kg, solving the problem of traditional equipment being "bulky and inconvenient to carry".

[0106] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A device for testing the strength of concrete, characterized in that, include: A pendulum module, comprising a hammer rod (7) and a hammer head (6), wherein the hammer head (6) is used to strike the concrete component being tested; The rebound angle detection module is used to collect the rebound angle change curve of the hammer rod (7) after the hammer head (6) is struck; The acoustic wave detection module is used to collect the acoustic wave amplitude change curve of the concrete component under test after the hammer (6) is struck. The data processing module (11) has a pre-stored standard spectrum library of concrete of all strength grades. The rebound angle detection module and the sound wave detection module are both electrically connected to the data processing module (11). The data processing module (11) can compare and analyze the characteristic parameters of the rebound angle change curve and the sound wave amplitude change curve with the characteristic parameters in the standard spectrum library of concrete of all strength grades, thereby determining the strength grade of the concrete component under test.

2. The device for testing concrete strength according to claim 1, characterized in that, The pendulum module also includes a motor (8). The two ends of the hammer rod (7) are connected to the rotating shaft of the motor (8) and the hammer head (6) respectively. The motor (8) is used to drive the hammer rod (7) to rotate, thereby causing the hammer head (6) to swing around the rotating shaft to strike.

3. The device for detecting concrete strength according to claim 2, characterized in that, It also includes a box body (1), the motor (8), the hammer rod (7) and the hammer head (6) are all located in the box body (1), the motor (8) is fixed on the bottom plate of the box body (1), and a through hole (101) is provided on the bottom plate of the box body (1), and the hammer head (6) can pass through the through hole (101).

4. The device for detecting concrete strength according to claim 3, characterized in that, The upper surface of the box (1) is provided with a display (4), which is electrically connected to the data processing module (11). The display (4) is used to display the strength grade of the concrete component being tested.

5. The device for testing concrete strength according to claim 3, characterized in that, The acoustic wave detection module includes an acoustic wave probe (10), which is installed on the bottom surface of the housing (1). The sensing surface of the acoustic wave probe (10) can contact the surface of the concrete component being tested.

6. The device for detecting concrete strength according to claim 3, characterized in that, The rebound angle detection module includes an encoder, which is mounted on the rotating shaft of the hammer rod (7) and is used to obtain the rebound angle change curve of the hammer rod (7).

7. The device for testing concrete strength according to claim 3, characterized in that, The motor (8) is a torque motor.

8. A method for testing the strength of concrete, characterized in that, The application of the apparatus for testing concrete strength as described in any one of claims 1-7 includes the following steps: S1: Use a hammer (6) to hammer the concrete component being tested; S2: Obtain the rebound angle change curve of the hammer head (6) after hammering, and the acoustic amplitude change curve of the concrete component under test; S3: Extract the feature parameters of the rebound angle change curve and the acoustic amplitude change curve; calculate the similarity between the extracted feature parameters and the feature parameters of each spectrum in the full strength grade concrete standard spectrum library using the support vector machine algorithm, and take the strength grade corresponding to the standard spectrum with the highest similarity as the strength grade of the tested concrete component.

9. The method for testing concrete strength according to claim 8, characterized in that, In step S3: The characteristic parameters of the rebound angle change curve include: the first rebound angle α1 and the attenuation rate k1, where k1=(α1-α2) / n, α2 represents the maximum rebound angle when the rebound angle is less than α1 / 10, and n represents the cumulative number of rebounds when the rebound angle is α2. The characteristic parameters of the acoustic wave amplitude variation curve include: the amplitude of the first hammer impact acoustic wave A1 and the amplitude attenuation rate k2, where k2=(A1-A2) / m, A2 represents the maximum hammer impact acoustic wave amplitude corresponding to when the hammer impact acoustic wave amplitude is less than A1 / 10, and m represents the cumulative number of hammer impacts corresponding to when the hammer impact acoustic wave amplitude is A2.

10. The method for testing concrete strength according to claim 8, characterized in that, Step S3 also includes correcting the strength grade of the tested concrete component using the following formula: σ_corr=σ_raw×[1-0.008×(T-20)-0.012×(W-6)], Where σ_corr represents the corrected concrete strength value, σ_raw represents the strength grade value corresponding to the standard spectrum with the highest similarity, T represents the ambient temperature, and W represents the moisture content of the surface of the tested concrete component.

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