Concrete mechanical property testing equipment and use method thereof

Abstract

The invention relates to concrete mechanical property testing equipment, which comprises a temperature control cavity, a mechanical loading system, a test piece fixing and monitoring device, a multi-source monitoring device and a data acquisition and intelligent control module, the mechanical loading system comprises an electro-hydraulic servo driving device and a heat insulation loading chain, the heat insulation loading chain is composed of a vacuum multi-cavity heat insulation rod, an end face isothermal ring and a compensation type force measuring ring, and the test piece fixing and monitoring device comprises a base, a longitudinal sliding rail, a transverse sliding rail, a movable pressing plate, a lead screw adjusting mechanism, a flexible liner, an air bag pressure equalizing module and a locking mechanism. The multi-source monitoring device comprises a distributed optical fiber, an acoustic emission sensor and a displacement meter, and the data acquisition and intelligent control module is used for realizing real-time linkage of temperature control, loading and monitoring signals. The method has the advantages of high detection precision, wide application range, high simulation authenticity, rich monitoring information and remarkable application value.

Description

Technical Field

[0001] This invention belongs to the field of concrete material performance testing technology, specifically relating to a concrete mechanical performance testing device and its usage method. Background Technology

[0002] Since the advent of silicate cement concrete, numerous studies have demonstrated the significant impact of ambient temperature on the mechanical properties of concrete. Ambient temperature can be categorized into three main types: high temperature, low temperature, and temperature cycling. In high-temperature environments, as temperature increases, the evaporation of moisture within the concrete accelerates, while humidity decreases significantly. At this point, the hydration products of the cementitious materials decompose, leading to a decrease in concrete density and affecting its mechanical properties. Furthermore, under high temperatures, the interface between mortar and coarse aggregate generates thermal stress due to differences in thermal expansion, thus weakening the overall mechanical properties of the concrete. In low-temperature and sub-zero conditions, pore water in concrete gradually freezes. Unfrozen water infiltrates adjacent pores, generating frost heave pressure, which promotes the formation and connection of pore cracks. However, the impact of this process on the mechanical properties of concrete is uncertain; in some cases, it may even lead to an initial increase in strength followed by deterioration, further affecting the overall mechanical properties of the concrete. During temperature cycling, especially under freeze-thaw cycles, the pore structure of concrete continues to deteriorate, and its thermal expansion coefficient and mechanical properties also change accordingly. Although existing experimental and simulation studies have revealed some patterns, most of them focus on concrete during its service life, and there is still insufficient research on the evolution of mechanical properties under large temperature difference conditions in early age.

[0003] Although many devices and methods exist to assist in testing the mechanical properties of concrete under temperature difference conditions, existing experimental testing methods and devices still have many problems. First, most testing machines can only be used under constant temperature or single temperature control conditions, making it difficult to truly simulate the complex temperature difference environment in engineering. Temperature control and loading systems are mostly independent structures, which cannot achieve synchronous coupling of force and temperature difference. Second, most specimen clamps are fixed rigid structures, which are difficult to adapt to thermal expansion and contraction under temperature difference conditions, and are prone to uneven stress or even slippage. Finally, the testing methods are often limited to macroscopic strength or displacement indicators, lacking the acquisition of multi-dimensional parameters such as crack propagation and local damage, making it difficult for the test results to fully reflect the performance of concrete in actual environment.

[0004] To address these issues, we propose a concrete mechanical property testing device and its usage method, which solves the problems existing in current applications, such as the disconnect between temperature control and loading, the lack of simplistic temperature difference simulation, unstable specimen fixation, and limited testing methods. Summary of the Invention

[0005] In view of this, the present invention proposes a concrete mechanical property testing device and its usage method, which is applied to the field of concrete material performance testing technology, and solves the existing technical problems of temperature control and loading separation, single temperature difference simulation, unstable specimen fixation, and limited testing methods.

[0006] To achieve the above-mentioned technical objectives, the specific technical solution adopted by the present invention is as follows: A concrete mechanical performance testing device includes a temperature-controlled chamber, a mechanical loading system, a specimen fixing and monitoring device, a multi-source monitoring device, and a data acquisition and intelligent control module. The temperature-controlled chamber is used to create high-temperature, low-temperature, and positive / negative temperature difference cyclic environments, and generates linear gradients, nonlinear waveforms, and periodic cyclic temperature difference fields through the synergistic effect of hot and cold fluids and zoned electrothermal films. The mechanical loading system includes an electro-hydraulic servo drive device and an adiabatic loading chain. The adiabatic loading chain consists of a vacuum multi-cavity insulated rod, an end-face isothermal ring, and a compensated force-measuring ring, capable of applying compressive, tensile, or bending loads under temperature difference conditions while avoiding heat conduction interference and force drift. The specimen fixing and monitoring device includes… The system comprises a base, longitudinal and transverse slide rails, a movable pressure plate, a lead screw adjustment mechanism, a flexible pad, an airbag pressure equalization module, and a locking mechanism. The longitudinal and transverse slide rails are orthogonally arranged to achieve bidirectional adjustment of the pressure plate, the lead screw is used for micron-level adjustment, the flexible pad buffers thermal expansion and contraction, the airbag pressure equalization module compensates for uneven force distribution, and the locking mechanism quickly fixes the system after adjustment. The multi-source monitoring device includes distributed optical fibers, acoustic emission sensors, and displacement gauges to acquire the overall strain distribution, crack initiation and propagation locations, and overall deformation. The data acquisition and intelligent control module is used to achieve real-time linkage between temperature control, loading, and monitoring signals, and establishes a temperature difference-mechanical performance coupling model through predictive control and data fusion algorithms.

[0007] Furthermore, the base is fixedly connected to the center of the temperature control chamber bottom plate. Its upper surface is provided with longitudinal and transverse slide rails, which are orthogonally arranged to form a rectangular guide structure. The movable pressure plate is slidably connected to the base along the longitudinal and transverse slide rails. Rollers or sliders are provided on both sides of the movable pressure plate to reduce friction. The position is finely adjusted by a screw adjustment mechanism. One end of the adjusting screw in the screw adjustment mechanism is fixed to the side wall of the base, and the other end is threaded to the pressure plate. The flexible pad is fixedly attached to the inner side of the pressure plate, corresponding to the contact end face of the concrete specimen. The flexible pad is made of elastic material resistant to high and low temperatures. The airbag pressure equalization module is embedded between the pressure plate and the flexible pad. The airbag pressure equalization module is connected to an external air source through an air pipe to form a uniformly distributed contact pressure during the pressing process of the pressure plate. The locking mechanism is arranged at the end of the longitudinal and transverse slide rails. The locking mechanism adopts one of eccentric lock or quick-release buckle to lock the position of the pressure plate after it is adjusted to the correct position.

[0008] Furthermore, the upper layer of the double-layer fluid microchannel in the temperature control cavity is infused with high-temperature fluid, while the lower layer is infused with low-temperature fluid. The flow rate and temperature of the two fluid layers can be independently controlled, thereby forming a linear temperature gradient in the longitudinal or transverse direction of the specimen within the range of −40 ℃ to +200 ℃, with a temperature control accuracy of not less than ±0.2 ℃.

[0009] Furthermore, the partitioned electric heating film is integrated with the inner wall of the cavity, with a heating power range of 0 to 200 W. Each partition can be independently controlled to generate dynamic temperature difference waveforms such as step waves, triangular waves, sine waves, or quasi-random spectra, and can construct complex spatial temperature fields through multi-partition linkage.

[0010] Furthermore, the vacuum multi-cavity heat insulation rod of the thermally insulating loading chain can block heat conduction, so that the temperature difference between the loading end and the external temperature control cavity is less than 0.5 ℃. The isothermal ring on the end face is connected to the constant temperature bath to keep the temperature of the loading end stable. The compensating force measuring ring adopts a double-bridge differential strain gauge arrangement, which can correct the force value deviation under temperature drift, with an error not exceeding ±0.5%.

[0011] A method of using the above-mentioned concrete mechanical property testing equipment includes the following steps: S1. Specimen layout and sensor installation: Place the concrete specimen in the adjustable clamp, adjust the longitudinal and transverse slide rails and the pressure plate to make the specimen be subjected to uniform force, and install distributed optical fiber, acoustic emission sensor and displacement meter inside or on the surface of the specimen. S2. Equipment calibration: Calibrate the temperature control cavity, loading system and sensors at room temperature, establish temperature drift compensation coefficient, and calibrate the clamping force of the fixture. S3. Environment setup: Set the target temperature difference mode, achieve temperature control through a combination of hot and cold fluids and zoned electric heating films, and maintain the temperature difference accuracy of ±0.2 ℃ using a closed-loop control algorithm. S4. Mechanical loading: Compression, tension or three-point bending loads are applied through an electro-hydraulic servo loading device, and the loading rate is synchronized with the temperature difference change. S5. Data acquisition and monitoring: Real-time recording of temperature, stress, strain, crack propagation and overall displacement information; S6. Dynamic adjustment and online replanning: When the strain or temperature difference of the specimen is detected to exceed the limit, the loading curve or temperature difference curve is automatically adjusted to ensure test safety and data continuity. S7. Output Results: Outputs the compressive strength, elastic modulus, crack propagation rate, and damage index of concrete under different temperature differences, and generates corresponding charts and visualizations.

[0012] Furthermore, in the environment construction of step S3, the temperature difference mode includes three types: high temperature cycling, low temperature freeze-thaw, and alternating positive and negative temperatures. The upper limit of the temperature for high temperature cycling can reach 200℃, the lower limit of the temperature for low temperature freeze-thaw can reach -40℃, and the alternating positive and negative temperature cycle can be switched within the range of -20℃ to +60℃. The number of temperature difference cycles can be set from 1 to 1000 times, the heating and cooling rate can be continuously adjusted within the range of 0.1℃ to 5℃ / min, the temperature fluctuation period can be set from 1 to 60min, and step wave, sine wave, triangular wave or random wave can be selected according to the preset waveform to realize the simulation of the actual engineering environment.

[0013] Furthermore, in the data acquisition and monitoring of step S5, the spatial resolution of the distributed fiber optic sensor is no higher than 10 mm, used to obtain the longitudinal and circumferential strain distribution of the specimen; the crack location accuracy of the acoustic emission sensor is better than 5 cm, and it can identify the crack initiation time and propagation rate; the measurement accuracy of the displacement gauge is ±0.01 mm, and the sampling frequency is no less than 100 Hz; all monitoring signals are fused and processed by the central data acquisition module, and corrected by Kalman filtering and adaptive noise suppression methods to ensure the accuracy and continuity of the monitoring data.

[0014] Furthermore, in the dynamic adjustment and online replanning of step S6, the system predicts the thermal stress distribution and crack propagation trend inside the test specimen in real time based on the model predictive control algorithm. When the strain value monitored by the distributed optical fiber exceeds 300με, or when the acoustic emission sensor detects a high-energy event, the system automatically reduces the loading rate by 50% and reduces the rate of temperature change to 0.5℃ / min. At the same time, it adjusts the pressure of the airbag equalization module by ±20kPa to maintain uniform stress on the specimen. When the temperature sensor array detects that the temperature distribution deviation exceeds 0.5℃, the partitioned electrothermal film automatically compensates for heating or cooling to achieve rapid correction.

[0015] Furthermore, the output of step S7 includes generating a temperature difference-mechanical property coupling curve, a stress-strain curve, and a three-dimensional reconstruction map of crack propagation, and calculating the compressive strength, elastic modulus, crack propagation rate, and damage index of concrete under different temperature difference conditions; furthermore, based on multi-source data fusion and Kalman filtering, the temperature field and strain field are inverted to obtain the equivalent thermal expansion coefficient α(T,∇T) and the equivalent modulus E*(T,ΔT), and a temperature difference-damage prediction model is established; the model can output the evolution curve of damage index with the number of cycles, and generate a comprehensive visualization report including temperature field distribution, crack evolution process, and mechanical property parameters.

[0016] By adopting the above technical solution, the present invention can also bring the following beneficial effects: 1. This invention discloses a concrete mechanical property testing device and its usage method. By employing adjustable clamps, it is easier to clamp, fix, and adjust the position of concrete specimens during the concrete mechanical property testing process. Through the combination of "longitudinal and transverse slide rails + screw adjustment + flexible pads + micro airbag pressure equalization module", it can not only quickly adapt to concrete specimens of different sizes, but also achieve automatic force equalization during clamping. The airbag module provides real-time compensation during the testing process, and the internal pressure is precisely adjusted by the control unit, effectively solving the influence of specimen expansion or contraction caused by temperature difference on the clamping force, thereby ensuring the long-term stability of specimen fixation. It has the advantages of high testing precision, strong clamping stability, and wide applicability.

[0017] This invention discloses a concrete mechanical performance testing device and its usage method. By combining temperature control and loading, the temperature control chamber can form multiple temperature difference modes within the range of −40 to +200 ℃. Combined with an electro-hydraulic servo loading system, it can simultaneously realize multiple loading conditions such as compression, tension, and bending. At the same time, the loading and temperature difference changes are linked by a central control module. When the temperature changes rapidly, the loading rate is automatically reduced, and a constant load is maintained during the constant temperature stage. This can realistically reflect the complexity of the environment, making the test results highly consistent with actual engineering conditions. It overcomes the problem of the disconnect between temperature control and mechanics, and has the advantages of multiple temperature control modes, unified processing through a central control module, and improved simulation realism.

[0018] This invention discloses a concrete mechanical performance testing device and its usage method. It introduces three types of sensing methods: distributed optical fiber, acoustic emission, and displacement gauge. Through an intelligent control module, it achieves multi-source fusion and combines Kalman filtering and model predictive control algorithms to perform real-time correction and prediction of the test data. It can not only output macroscopic indicators such as strength and modulus, but also obtain crack initiation location, propagation rate, and damage index. It generates a temperature difference-mechanical coupling model and a three-dimensional crack evolution diagram, which improves the detection from "single parameter" to "multi-scale holographic monitoring". It has the advantages of using multi-source data fusion analysis, real-time correction of test data, and obtaining multi-scale holographic monitoring data results. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This invention provides a schematic diagram of a module for testing the mechanical properties of concrete. Figure 2A schematic diagram of the specimen fixing and monitoring device in an embodiment of the present invention; Figure 3 The present invention provides a flowchart of a method for using a concrete mechanical property testing device; Figure descriptions: 1. Base; 2. Cavity bottom plate; 3. Pressure plate; 4. Screw adjustment mechanism; 5. Flexible pad; 6. Airbag pressure equalization module; 7. Locking mechanism; 8. Longitudinal slide rail; 9. Transverse slide rail; 10. Concrete specimen; 11. Air pipe. Detailed Implementation

[0021] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0022] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0023] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this invention, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using other structures and / or functionalities besides one or more of the aspects set forth herein.

[0024] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. The drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0025] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.

[0026] In one embodiment of the present invention, such as Figure 1 As shown, a concrete mechanical performance testing device includes a temperature-controlled chamber, a mechanical loading system, a specimen fixation and monitoring device, a multi-source monitoring device, and a data acquisition and intelligent control module. The temperature-controlled chamber is located in the central area of ​​the main body of the device, used to create a high-temperature, low-temperature, and positive / negative temperature difference cyclic environment. Its interior is equipped with a double-layer fluid microchannel; the upper layer receives a high-temperature fluid, and the lower layer receives a low-temperature fluid. The flow rate and temperature of the two fluid layers can be independently controlled, thereby forming a linear temperature gradient within the range of −40 ℃ to +200 ℃ in the longitudinal or transverse direction of the specimen, with a temperature control accuracy maintained at ±0.2 ℃. Furthermore, the inner wall of the chamber integrates a zoned electrothermal film, with a single zone heating power range of 0–200W. Each zone can be independently controlled to generate dynamic temperature difference waveforms such as step waves, triangular waves, sine waves, or quasi-random spectra, and complex spatial temperature fields can be constructed through multi-zone linkage. The mechanical loading system is arranged below the temperature-controlled chamber and includes an electro-hydraulic servo drive device and an adiabatic loading chain.

[0027] The adiabatic loading chain consists of a vacuum multi-cavity insulating rod, an end-face isothermal ring, and a compensating force-measuring ring. The vacuum multi-cavity insulating rod can block heat conduction, keeping the temperature difference between the loading end and the external cavity within 0.5 ℃. The end-face isothermal ring maintains temperature stability through a constant temperature bath, avoiding temperature drift at the loading end. The compensating force-measuring ring uses a double-bridge differential strain gauge arrangement, which can effectively correct the force deviation caused by temperature fluctuations, with a force measurement error not exceeding ±0.5%.

[0028] like Figure 2 As shown, the specimen fixing and monitoring device is installed at the center of the bottom plate inside the temperature control chamber. It includes a base, longitudinal and transverse slide rails, a movable pressure plate, a screw adjustment mechanism, a flexible pad, an airbag pressure equalization module, and a locking mechanism. The base is fixedly connected to the bottom plate of the chamber, and its upper surface is equipped with longitudinal and transverse slide rails, which orthogonally form a rectangular guide structure. The movable pressure plate slides along the longitudinal and transverse slide rails to the base. Rollers or sliders are provided on both sides of the pressure plate to reduce frictional resistance. The pressure plate is finely adjusted in position via a screw adjustment mechanism; one end of the screw is fixed to the side wall of the base, and the other end is threaded to the pressure plate. A flexible pad, made of high and low temperature resistant elastic material, is fixedly installed inside the pressure plate and fits tightly against the end face of the concrete specimen. The airbag pressure equalization module is embedded between the pressure plate and the flexible pad and is connected to an external air source through an air pipe, automatically forming uniform contact pressure during specimen clamping. The ends of the longitudinal and transverse slide rails are equipped with locking mechanisms, which adopt eccentric locking or quick-release buckle structures to reliably lock them after the pressure plate is adjusted to the correct position.

[0029] The multi-source monitoring device includes distributed optical fibers, acoustic emission sensors, and displacement gauges. The optical fibers can be laid inside or on the surface of the specimen to form a full-field strain monitoring network with a spatial resolution of no more than 10 mm. The acoustic emission sensors are attached to the outer wall of the specimen to capture crack initiation and propagation signals, with a positioning accuracy better than 5 cm. The displacement gauges are arranged at the upper and lower ends of the specimen to record the overall axial displacement with a measurement accuracy of ±0.01 mm.

[0030] The data acquisition and intelligent control module is electrically connected to each subsystem to realize real-time linkage of temperature control, loading and monitoring signals. It uses Kalman filtering and predictive control algorithms to fuse and correct multi-source data and automatically establish a temperature difference-mechanical performance coupling model.

[0031] like Figure 3 As shown, a method for using a concrete mechanical property testing device includes the following steps: S1. Specimen layout and sensor installation; The concrete specimen is placed in an adjustable clamp, and its position is adjusted via longitudinal and transverse slide rails and pressure plates to ensure uniform force distribution during clamping. Micrometer-level fine-tuning is achieved through a screw mechanism. Once the pressure plates are clamped, an airbag pressure equalization module provides stable and uniform clamping pressure. To enable multi-scale monitoring, distributed optical fibers are pre-embedded inside the specimen, acoustic emission sensors are attached to the surface, and displacement gauges are installed at the top and bottom of the specimen.

[0032] S2, Equipment Calibration; The temperature control system is operated at room temperature to calibrate the temperature control accuracy of the temperature control cavity; the force measuring ring is calibrated by gradual loading and a temperature drift compensation coefficient is established; at the same time, the clamping force of the fixture is detected and calibrated to ensure that it remains stable and reliable under different temperature conditions.

[0033] S3, Environment Setup; A target temperature difference mode is set, including high-temperature cycling, low-temperature freeze-thaw cycles, and alternating positive and negative temperatures. The upper limit of the high-temperature cycle temperature can reach 200 ℃, the lower limit of the low-temperature freeze-thaw cycle temperature can reach -40 ℃, and the alternating positive and negative temperature cycle can switch within the range of -20 to +60 ℃. The number of temperature difference cycles is set to 1 to 1000 times, the heating and cooling rate is 0.1 to 5 ℃ / min, the fluctuation period is 1 to 60 min, and step wave, sine wave, triangular wave, or random wave can be selected to simulate actual working conditions. The hot and cold fluids and the zoned electrothermal film are controlled collaboratively, and the closed-loop algorithm ensures the stability of the temperature field and the temperature difference control accuracy within ±0.2 ℃.

[0034] S4, Mechanical loading; Compression, tension, or three-point bending loads are applied by an electro-hydraulic servo loading device, and the loading rate is synchronized with the temperature difference change, thereby avoiding the sudden failure of the specimen caused by the superposition of thermal stress and external loading force.

[0035] S5. Data Acquisition and Monitoring; Data on temperature, stress, strain, crack propagation, and overall displacement are acquired in real time at a frequency of at least 100 Hz. The strain resolution of the distributed optical fiber is no higher than 10 mm, the crack localization accuracy of the acoustic emission sensor is better than 5 cm, and the displacement gauge accuracy reaches ±0.01 mm. All monitoring signals are fused and processed by the central acquisition module and corrected through Kalman filtering and adaptive noise suppression to ensure the authenticity and continuity of the monitoring data.

[0036] S6, Dynamic Adjustment and Online Replanning; The system uses a model predictive control algorithm to predict the thermal stress distribution and crack propagation trend inside the test specimen in real time. When the distributed fiber strain value exceeds 300 με, or when the acoustic emission sensor detects a high-energy event, the system automatically reduces the loading rate by 50% and adjusts the temperature difference change rate to 0.5 ℃ / min. Simultaneously, it adjusts the pressure of the airbag equalization module to ±20 kPa to ensure uniform stress on the specimen. When the temperature sensor detects a temperature difference distribution deviation exceeding 0.5 ℃, the zoned heating film immediately initiates compensation adjustment to quickly restore the target temperature control.

[0037] S7. Output the results; After the test is completed, the system automatically outputs the test results, including the temperature difference-mechanical property coupling curve, stress-strain curve, and three-dimensional reconstruction map of crack propagation; it calculates the compressive strength, elastic modulus, crack propagation rate, and damage index of the concrete; further, it performs inversion calculations through Kalman filtering and multi-source data fusion to obtain the equivalent thermal expansion coefficient α(T,∇T) and equivalent modulus E*(T,ΔT). Based on the above data, the system establishes a temperature difference-damage prediction model, outputs the evolution curve of damage index with the number of cycles, and generates a comprehensive visualization report including temperature field distribution, crack evolution process, and mechanical property parameters.

[0038] In summary, this invention organically integrates temperature difference environment simulation, mechanical loading, specimen fixation, and multi-source monitoring, enabling realistic testing of concrete under various working conditions, including compression, tension, and bending, within a range of -40 to +200 ℃. It solves the problems of disconnected temperature control and loading, limited temperature difference simulation, unstable specimen fixation, and limited testing methods in existing technologies. Through an adjustable clamp design consisting of "longitudinal and transverse slide rails + screw adjustment + flexible padding + airbag pressure equalization module," it not only adapts to specimens of different specifications but also maintains uniform clamping force during temperature changes, ensuring testing stability and precision. Furthermore, by combining multi-source monitoring with distributed optical fibers, acoustic emission sensors, and displacement gauges, along with a fusion algorithm of Kalman filtering and model predictive control, it can output strength, modulus, crack initiation and propagation, and damage index, achieving multi-scale holographic detection from macroscopic mechanical indicators to microscopic damage evolution. This invention has the advantages of high detection accuracy, wide applicability, strong simulation realism, rich monitoring information, and significant application value.

[0039] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A concrete mechanical property testing device, characterized in that: The system includes a temperature-controlled cavity, a mechanical loading system, a specimen fixing and monitoring device, a multi-source monitoring device, and a data acquisition and intelligent control module. The temperature-controlled cavity is used to create high-temperature, low-temperature, and positive / negative temperature difference cyclic environments, and generates linear gradients, nonlinear waveforms, and periodic cyclic temperature difference fields through the synergistic effect of hot and cold fluids and zoned electrothermal films. The mechanical loading system includes an electro-hydraulic servo drive device and an adiabatic loading chain. The adiabatic loading chain consists of a vacuum multi-cavity insulated rod, an isothermal ring at the end face, and a compensated force-measuring ring, capable of applying compressive, tensile, or bending loads under temperature difference conditions while avoiding heat conduction interference and force drift. The specimen fixing and monitoring device includes a base, longitudinal and transverse slide rails, and... The system includes a movable pressure plate, a lead screw adjustment mechanism, a flexible pad, an airbag pressure equalization module, and a locking mechanism. The orthogonally arranged longitudinal and transverse slide rails enable bidirectional adjustment of the pressure plate, the lead screw allows for micron-level adjustment, the flexible pad buffers thermal expansion and contraction, the airbag pressure equalization module compensates for uneven force distribution, and the locking mechanism quickly fixes the system after adjustment. The multi-source monitoring device includes distributed optical fibers, acoustic emission sensors, and displacement gauges to acquire the overall strain distribution, crack initiation and propagation locations, and overall deformation. The data acquisition and intelligent control module enables real-time linkage between temperature control, loading, and monitoring signals, and establishes a temperature difference-mechanical performance coupling model through predictive control and data fusion algorithms.

2. The concrete mechanical property testing equipment according to claim 1, characterized in that: The base is fixedly connected to the center of the bottom plate of the internal cavity of the temperature control chamber. The upper surface of the base is provided with longitudinal and transverse slide rails, which are orthogonally arranged to form a rectangular guide structure. The movable pressure plate is slidably connected to the base along the longitudinal and transverse slide rails. Rollers or sliders are provided on both sides of the movable pressure plate to reduce friction, and the position is finely adjusted by a screw adjustment mechanism. One end of the adjusting screw in the screw adjustment mechanism is fixed to the side wall of the base, and the other end is threaded to the pressure plate. The flexible pad is fixedly attached to the inner side of the pressure plate, corresponding to the contact end of the concrete specimen. The flexible pad is made of elastic material resistant to high and low temperatures. The airbag pressure equalization module is embedded between the pressure plate and the flexible pad. The airbag pressure equalization module is connected to an external air source through an air pipe to form a uniformly distributed contact pressure during the pressing process of the pressure plate. The locking mechanism is arranged at the end of the longitudinal and transverse slide rails. The locking mechanism adopts one of eccentric lock or quick-release buckle to lock the position of the pressure plate after it is adjusted to the correct position.

3. The concrete mechanical property testing equipment according to claim 2, characterized in that: The temperature control cavity has a double-layered fluid microchannel with a high-temperature fluid flowing into the upper layer and a low-temperature fluid flowing into the lower layer. The flow rate and temperature of the two fluid layers can be independently adjusted, thereby forming a linear temperature gradient in the longitudinal or transverse direction of the specimen within the range of −40 ℃ to +200 ℃, with a temperature control accuracy of not less than ±0.2 ℃.

4. The concrete mechanical property testing equipment according to claim 3, characterized in that: The partitioned electrothermal film is integrated with the inner wall of the cavity, and the heating power ranges from 0 to 200 W. Each partition can be independently controlled to generate dynamic temperature difference waveforms such as step waves, triangular waves, sine waves, or quasi-random spectra. It can also construct complex spatial temperature fields through multi-partition linkage.

5. The concrete mechanical property testing equipment according to claim 4, characterized in that: The vacuum multi-cavity heat insulation rod of the thermally insulating loading chain can block heat conduction, so that the temperature difference between the loading end and the external temperature control cavity is less than 0.5 ℃. The isothermal ring on the end face is connected to the constant temperature bath to keep the temperature of the loading end stable. The compensation force measuring ring adopts a double-bridge differential strain gauge arrangement, which can correct the force value deviation under temperature drift, with an error not exceeding ±0.5%.

6. A method of using the concrete mechanical property testing equipment according to claim 1, characterized in that, The steps include the following: S1. Specimen layout and sensor installation: Place the concrete specimen in the adjustable clamp, adjust the longitudinal and transverse slide rails and the pressure plate to make the specimen be subjected to uniform force, and install distributed optical fiber, acoustic emission sensor and displacement meter inside or on the surface of the specimen. S2. Equipment calibration: Calibrate the temperature control cavity, loading system and sensors at room temperature, establish temperature drift compensation coefficient, and calibrate the clamping force of the fixture. S3. Environment setup: Set the target temperature difference mode, achieve temperature control through a combination of hot and cold fluids and zoned electric heating film, and maintain the temperature difference accuracy of ±0.2 ℃ using a closed-loop control algorithm; S4. Mechanical loading: Compression, tension or three-point bending loads are applied through an electro-hydraulic servo loading device, and the loading rate is synchronized with the temperature difference change. S5. Data acquisition and monitoring: Real-time recording of temperature, stress, strain, crack propagation and overall displacement information; S6. Dynamic adjustment and online replanning: When the strain or temperature difference of the specimen is detected to exceed the limit, the loading curve or temperature difference curve is automatically adjusted to ensure test safety and data continuity. S7. Output Results: Outputs the compressive strength, elastic modulus, crack propagation rate, and damage index of concrete under different temperature differences, and generates corresponding charts and visualizations.

7. The method of using the concrete mechanical property testing equipment according to claim 6, characterized in that: In the environment construction of step S3, the temperature difference mode includes three types: high temperature cycle, low temperature freeze-thaw, and alternating positive and negative temperatures. The upper limit of the temperature for high temperature cycle can reach 200℃, the lower limit of the temperature for low temperature freeze-thaw can reach -40℃, and the alternating positive and negative temperature cycle can be switched within the range of -20℃ to +60℃. The number of temperature difference cycles can be set from 1 to 1000 times, the heating and cooling rate can be continuously adjusted within the range of 0.1℃ to 5℃ / min, the temperature fluctuation period can be set from 1 to 60min, and a step wave, sine wave, triangular wave, or random wave can be selected according to the preset waveform to realize the simulation of the actual engineering environment.

8. The method of using the concrete mechanical property testing equipment according to claim 7, characterized in that: In the data acquisition and monitoring of step S5, the spatial resolution of the distributed fiber optic sensor is no higher than 10 mm, used to obtain the longitudinal and circumferential strain distribution of the specimen; the crack location accuracy of the acoustic emission sensor is better than 5 cm, and it can identify the crack initiation time and propagation rate; the displacement gauge has a measurement accuracy of ±0.01 mm and a sampling frequency of no less than 100 Hz; all monitoring signals are fused and processed by the central data acquisition module, and corrected by Kalman filtering and adaptive noise suppression methods to ensure the accuracy and continuity of the monitoring data.

9. The method of using the concrete mechanical property testing equipment according to claim 8, characterized in that: In the dynamic adjustment and online replanning of step S6, the system predicts the thermal stress distribution and crack propagation trend inside the test specimen in real time based on the model predictive control algorithm. When the strain value monitored by the distributed optical fiber exceeds 300με, or when the acoustic emission sensor detects a high-energy event, the system automatically reduces the loading rate by 50% and reduces the temperature difference change rate to 0.5℃ / min. At the same time, it adjusts the pressure of the airbag equalization module by ±20kPa to keep the specimen under uniform stress. When the temperature sensor array detects that the temperature difference distribution deviation exceeds 0.5℃, the partitioned electrothermal film automatically compensates for heating or cooling to achieve rapid correction.

10. The method of using the concrete mechanical property testing equipment according to claim 9, characterized in that: The output of step S7 includes generating a temperature difference-mechanical property coupling curve, a stress-strain curve, and a three-dimensional reconstruction map of crack propagation. It calculates the compressive strength, elastic modulus, crack propagation rate, and damage index of concrete under different temperature difference conditions. Furthermore, based on multi-source data fusion and Kalman filtering, the temperature field and strain field are inverted to obtain the equivalent thermal expansion coefficient α(T,∇T) and the equivalent modulus E*(T,ΔT), and a temperature difference-damage prediction model is established. The model can output the evolution curve of the damage index with the number of cycles and generate a comprehensive visualization report containing the temperature field distribution, crack evolution process, and mechanical property parameters.

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