A Brazilian splitting test device and method based on multiple heating modes

Abstract

The present invention discloses a Brazilian splitting test device and method based on multiple heating modes, belonging to the technical field of splitting tests; it includes a base, a Brazilian splitting fixture, a kettle body, a heating system, a heat carrier fluid injection hole, an axial pressure head, a temperature and pressure monitoring and heat carrier fluid outlet, a magnetic particle imaging system, and a high-temperature warning system; the temperature and pressure monitoring and heat carrier fluid outlet is used to connect an external real-time observation system for temperature and pressure monitoring, and at the same time serves as the outlet of the heat carrier fluid; the magnetic particle imaging system is used to observe the distribution state of nano-magnetic induction particles inside the kettle body; the present invention can conduct real-time high-temperature Brazilian splitting tests under multiple heating modes such as convective heating, conductive heating, and supercritical fluid heating, and can monitor the generation and expansion process of cracks inside the sample in real time, and is applicable to testing the strength and crack propagation of rocks under thermal stress conditions that may be encountered in actual engineering.

Description

Technical Field

[0001] The present invention belongs to the technical field of splitting experiments, and relates to a Brazilian splitting experiment device and method based on multiple heating modes. Background Art

[0002] In the fields of civil engineering and mineral resource development, especially under extreme temperature and pressure conditions, the tensile strength test of rock or soil materials has important practical application requirements. Taking the long-term stability assessment of underground nuclear waste repositories as an example, it is necessary to comprehensively master the mechanical parameters such as the tensile strength of the surrounding rock of the repository under extreme temperature and pressure conditions such as high temperature and supercritical water; during the development of enhanced geothermal systems, the construction of underground heat reservoirs also requires accurate determination of the tensile strength and other mechanical properties of high-temperature rock formations. Therefore, conducting systematic research on the tensile properties and cracking mechanisms of rock or soil materials under high-temperature and high-pressure environments has significant theoretical significance and practical application value.

[0003] Tensile strength is a key parameter affecting the initiation pressure in the fracturing process and is often tested through Brazilian splitting experiments. Due to its simple operation and relatively high test accuracy, the Brazilian splitting experiment has become a common method for measuring the tensile strength of rocks or soils. However, existing experimental equipment generally has the following limitations: First, it is unable to conduct real-time high-temperature Brazilian splitting experiments under multiple heating methods. Most existing equipment can only adopt a single heating method, making it difficult to meet the requirements of multi-condition experiments and real-time monitoring under high-temperature and high-pressure environments; second, under high-temperature and high-pressure conditions, the crack propagation morphology in Brazilian splitting experiments is difficult to monitor in real time. Traditional experimental equipment cannot accurately capture the dynamic development process of cracks, resulting in the lack of comprehensiveness and real-time nature of experimental results. Therefore, in order to comprehensively study the tensile strength and cracking mechanisms of rock or soil materials under different heating methods and temperature conditions, there is an urgent need to develop a new type of experimental device.

[0004] In the currently published patents, the patent with publication number CN115308043A has proposed a fluid-rock splitting grouting temperature change reaction experimental system; the patent with publication number CN109444020A has proposed an observation device and observation method for the microscopic characteristics of rock mass fractures based on 3D printing technology.

[0005] However, the above patents have not been able to solve the Brazilian splitting experiment test under multiple heating methods (convection, conduction, supercritical fluid) and real-time axial load application conditions, and cannot monitor the crack propagation morphology in Brazilian splitting experiments under high-temperature and high-pressure environments in real time. Summary of the Invention

[0006] The present invention overcomes the deficiencies of the prior art and proposes a Brazilian splitting experiment device and method based on multiple heating modes. The present invention is realized through the following technical solutions:

[0007] A Brazilian splitting test device based on multiple heating modes, comprising a base, a Brazilian splitting fixture for placing a specimen, a kettle body for placing the Brazilian splitting fixture, a heating system for heating the specimen, a heat-carrying fluid injection hole, an axial pressure head for applying an axial load to the specimen, a temperature and pressure monitoring and heat-carrying fluid outlet, a magnetic particle imaging system, and a high-temperature warning system; the temperature and pressure monitoring and heat-carrying fluid outlet is used to connect to an external real-time observation system for temperature and pressure monitoring and at the same time serves as the outlet of the heat-carrying fluid; the magnetic particle imaging system is used to observe the distribution state of nano magnetic induction particles inside the kettle body;

[0008] The Brazilian splitting fixture includes an upper Brazilian splitting fixture, a lower Brazilian splitting fixture, and Brazilian splitting fixture limit rods; two Brazilian splitting fixture limit rods are symmetrically connected to the lower Brazilian splitting fixture, two corresponding through holes are symmetrically opened on the upper Brazilian splitting fixture, and the tops of the two Brazilian splitting fixture limit rods pass through the through holes and are detachably connected to the upper Brazilian splitting fixture; the specimen is located between the upper Brazilian splitting fixture and the lower Brazilian splitting fixture;

[0009] The heating system includes an annular constant-temperature heat-insulating box and heating wires arranged inside the annular constant-temperature heat-insulating box;

[0010] The Brazilian splitting fixture is placed on the base and located inside the kettle body, the base is hermetically connected to the bottom of the kettle body, and the outside of the kettle body is wrapped with an annular constant-temperature heat-insulating box for heating the specimen; a temperature and pressure monitoring and heat-carrying fluid outlet is opened on the side of the annular constant-temperature heat-insulating box, the temperature and pressure monitoring and heat-carrying fluid outlet passes through the kettle body and is communicated with the inside of the kettle body; the axial pressure head passes through the top of the kettle body and contacts the upper surface of the upper Brazilian splitting fixture, and the axial pressure head is hermetically and slidably connected to the kettle body; a heat-carrying fluid injection hole is provided on the base, one end of the heat-carrying fluid injection hole is communicated with the outside, and the other end is communicated with the inside of the kettle body; the heat-carrying fluid injection hole is used to inject a heat-carrying fluid mixed with nano magnetic induction particles into the kettle body;

[0011] The magnetic particle imaging system includes a radio frequency coil arranged on the inner wall of the kettle body and a magnetic particle imaging device for observing the distribution state of nano magnetic induction particles inside the specimen; a radio frequency coil outlet is opened on the side wall of the kettle body; one end of the radio frequency coil outlet is communicated with the inside of the kettle body, and the other end passes through the annular constant-temperature heat-insulating box and is communicated with the outside; the end of the radio frequency coil extends out to the outside through the radio frequency coil outlet and is connected to the magnetic particle imaging device;

[0012] The high-temperature warning system includes an integrated infrared temperature sensor array data acquisition processor for high-temperature alarm, an infrared temperature sensor, and an alarm device; a plurality of infrared temperature sensors are arranged at different positions on the periphery of the annular constant-temperature heat-insulating box, and the infrared temperature sensors are respectively connected to the integrated infrared temperature sensor array data acquisition processor and the alarm device.

[0013] Further, a limiting groove is provided on the upper surface of the base, and the Brazilian splitting lower fixture at the bottom of the Brazilian splitting fixture is located within the limiting groove.

[0014] Further, an upper flange is provided at the upper part of the kettle body. The upper flange is provided with a stepped through hole, and the axial pressure head passes through the stepped through hole. Axial pressure head sealing packing is placed on both sides of the stepped through hole; an upper flange is arranged above the upper flange. Upper flange bolt holes are provided on the upper surface of the upper flange, and the upper flange is connected to the upper flange through the upper flange bolt holes and upper flange bolts.

[0015] Further, a lower flange is provided at the lower part of the kettle body; the lower flange is provided with a protrusion, a gap sealing ring is arranged between the base and the kettle body, and the protrusion presses on the gap sealing ring; the lower surface of the lower flange presses on the base, and the base is connected to the lower flange through the lower flange bolt holes and lower flange bolts provided on the lower flange.

[0016] Further, a water-cooling circulation through hole is provided at the bottom of the base.

[0017] A Brazilian splitting experiment method based on multiple heating modes, using the described Brazilian splitting experiment device based on multiple heating modes, includes the following steps:

[0018] Step 1: Place the specimen on the Brazilian splitting lower fixture, then assemble the Brazilian splitting fixture limiting rod with the Brazilian splitting lower fixture, and install the Brazilian splitting upper fixture along the Brazilian splitting fixture limiting rod so that the lower surface of the Brazilian splitting upper fixture is in contact with the specimen; then place the Brazilian splitting fixture together with the specimen into the kettle body to complete the assembly of the Brazilian splitting experiment device.

[0019] Step 2: Heat the specimen and keep it at a constant temperature after reaching the required experimental temperature.

[0020] The heating method adopts any one of the following three heating methods according to the experimental requirements:

[0021] The first is the convective heating method: When adopting the convective heating method, a heating fluid is injected into the kettle body through the heat-carrying fluid injection hole, and the heating fluid is discharged through the temperature and pressure monitoring and heat-carrying fluid outlet for convective heating; nano magnetic induction particles are mixed in the heating fluid.

[0022] The second is the conductive heating method: When adopting the conductive heating method, close the temperature and pressure monitoring and heat-carrying fluid outlet, first inject a protective gas into the kettle body through the heat-carrying fluid injection hole, plug the heat-carrying fluid injection hole and the RF coil outlet with a plug after the protective gas is injected, and then turn on the annular constant temperature heat insulation box for heating; nano magnetic induction particles are mixed in the protective gas.

[0023] The third is the supercritical fluid heating method: When using supercritical fluid heating, at this time, a back pressure valve is connected to the temperature and pressure monitoring and the heat-carrying fluid outlet. After setting the back pressure of the back pressure valve, supercritical fluid is injected into the kettle body through the heat-carrying fluid injection hole to heat the specimen; nano magnetic induction particles are mixed in the supercritical fluid;

[0024] Step 3: After heating to the required experimental temperature, apply an axial load to the specimen through the axial pressure head, and observe the temperature of the specimen in the kettle through the real-time observation system connected to the temperature and pressure monitoring and the heat-carrying fluid outlet. Observe the distribution of nano magnetic induction particles inside the specimen through the magnetic particle imaging device; When a connected nano magnetic induction particle distribution channel is observed inside the specimen, that is, the specimen generates cracks and cracks, stop loading.

[0025] The beneficial effects of the present invention compared with the prior art are as follows:

[0026] 1. The experimental device proposed by the present invention can perform real-time high-temperature Brazilian splitting experiments under various heating modes such as convective heating, conductive heating, and supercritical fluid heating. This device integrates an infrared temperature sensor array and uses the infrared radiation principle for temperature measurement. When the temperature of an object is higher than absolute zero, it will radiate infrared rays. The infrared temperature sensor detects these radiations and calculates the surface temperature of the object based on characteristics such as wavelength and intensity. Compared with traditional contact temperature sensors, infrared temperature sensors have the advantages of non-contact and fast response, and are particularly suitable for detecting the surface temperature of high-temperature, moving, or difficult-to-contact objects. Therefore, the Brazilian splitting experimental device of the present invention can achieve real-time high-temperature testing under various heating modes and has efficient and accurate temperature monitoring functions, with broad application prospects.

[0027] 2. The present invention can conduct experiments under various heating methods (such as convective heating, conductive heating, and supercritical fluid heating) through the heat-carrying fluid injection hole or the annular constant-temperature heat insulation box. This design allows real-time testing of samples under various heating environments; apply an axial load through the pressurization system and study the tensile strength of the sample at high temperature through various heating methods. The experimental content focuses on the testing of mechanical properties; mainly used for Brazilian splitting experiments to test the tensile strength of samples under different heating methods, especially to study the mechanical behavior of samples under high-temperature conditions through convective heating, conductive heating, or real-time supercritical fluid heating; applicable to the geotechnical engineering field, especially the study of the tensile strength of materials at high temperature.

[0028] 3. The present invention can, through the distribution state of nano magnetic induction particles, monitor in real time the generation and expansion process of cracks inside the sample, thereby providing more comprehensive and accurate data support for the study of the mechanical behavior and cracking mechanism of rock or soil materials. By using this device, researchers can more comprehensively understand the tensile strength and cracking mechanism of rock or soil materials under extreme temperature and pressure conditions, providing strong technical support for engineering applications in related fields.

[0029] 4. Compared with the prior art, the present invention integrates a magnetic particle imaging system to observe the distribution of magnetic induction particles in the sample and has a high-temperature warning system; compared with PIV particles, nano magnetic induction particles have significant advantages in characterizing the crack propagation and evolution inside rocks. First, nano magnetic induction particles have a smaller particle size, can penetrate deep into the rock interior and provide high-resolution microscopic imaging, accurately tracking the crack propagation process at the microscopic scale. Second, nano magnetic induction particles can be imaged non-invasively through a magnetic field, without damaging the rock structure, and can stably monitor crack development for a long time under extreme conditions. PIV particles are mainly suitable for the measurement of surface motion and have a relatively large particle size, which limits their ability to observe microcracks or microscopic deformations inside rocks. Nuclear magnetic resonance imaging is more suitable for observing microscopic physical structures, while X-ray imaging can only clearly show the macroscopic cracks in the rock mass; this device has multiple heating methods and a complex heating system (such as a circular constant-temperature heat insulation box) and heat-carrying fluid injection holes for fluid heating; compared with PIV particles, the main advantage of nano magnetic induction particles in crack propagation and evolution is that they can penetrate deep into the rock interior for real-time, non-invasive high-resolution imaging, providing more detailed and comprehensive crack monitoring, especially in extreme environments such as high temperature and high pressure. PIV particles rely more on surface observation and image processing, although they perform well in surface crack monitoring, but are limited in capturing the dynamic evolution and microscopic characteristics of deep cracks. The present invention is applicable to testing the strength and crack propagation of rocks under thermal stress conditions that may be encountered in actual engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a 3D overall structure diagram of the Brazilian splitting test device based on multiple heating modes provided by the present invention.

[0031] Figure 2 It is a schematic diagram of the position of the radio frequency coil described in the present invention.

[0032] Figure 3 It is a schematic diagram of the structure of the Brazilian splitting fixture described in the present invention.

[0033] Figure 4 It is a schematic diagram of the connection structure between the limiting rod of the Brazilian splitting fixture and the lower Brazilian splitting fixture described in the present invention.

[0034] Figure 5Schematic diagram of the structure of the upper fixture for Brazilian splitting in the present invention.

[0035] In the figure: 1 - axial pressure head; 2 - upper flange; 3 - packing for axial pressure head seal; 4 - annular constant temperature heat insulation box; 5 - temperature and pressure monitoring and heat - carrying fluid outlet; 6 - upper fixture for Brazilian splitting; 7 - limiting rod for Brazilian splitting fixture; 8 - bolt holes for lower flange; 9 - lower fixture for Brazilian splitting; 10 - water - cooling circulation passage hole; 11 - heat - carrying fluid injection hole; 12 - gap sealing ring; 13 - base; 14 - lower flange plate; 15 - specimen; 16 - autoclave body; 17 - upper flange plate; 18 - bolt holes for upper flange; 19 - limiting groove; 20 - RF coil; 21 - infrared temperature sensor; 22 - RF coil outlet. Detailed implementation manners

[0036] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the present invention will be further described in detail in combination with embodiments and drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. The technical solutions of the present invention will be described in detail below in combination with embodiments and drawings, but the protection scope is not limited hereby.

[0037] Refer to Figures 1 to 5 , this embodiment proposes a Brazilian splitting experimental device and its usage method for realizing convective heating, conductive heating or real - time heating with supercritical fluid. The experimental device includes a Brazilian splitting fixture for placing the specimen 15, an autoclave body 16 for placing the Brazilian splitting fixture, a heating system for heating the specimen 15, a heat - carrying fluid injection hole 11, an axial pressure head 1 for applying axial load to the specimen 15, a temperature and pressure monitoring and heat - carrying fluid outlet 5, a magnetic particle imaging system and a high - temperature warning system; among them, the temperature and pressure monitoring and heat - carrying fluid outlet 5 is used to connect an external real - time observation system for temperature and pressure monitoring and can also be used as the outlet of the heat - carrying fluid; the magnetic particle imaging system is used to observe the distribution state of nano - magnetic - sensitive particles inside the autoclave body 16.

[0038] See Figures 3 to 5, the Brazilian splitting fixture for placing the test piece 15 is composed of a Brazilian splitting upper fixture 6, a Brazilian splitting lower fixture 9, and Brazilian splitting fixture limit rods 7; two Brazilian splitting fixture limit rods 7 are symmetrically connected to the Brazilian splitting lower fixture 9, and two corresponding through holes are symmetrically opened on the Brazilian splitting upper fixture 6. The tops of the two Brazilian splitting fixture limit rods 7 pass through the through holes and are threadedly connected to the Brazilian splitting upper fixture 6. This threaded connection structure allows the Brazilian splitting upper fixture 6 to be adjusted up and down along the Brazilian splitting fixture limit rods 7. The Brazilian splitting upper fixture 6 and the Brazilian splitting lower fixture 9 cooperate with each other to form a clamping structure; the above-mentioned Brazilian splitting fixture limit rods 7 are used to limit the movement range of the Brazilian splitting fixture to ensure that the test piece 15 is stably fixed during the experiment. Moreover, the distance between the Brazilian splitting upper fixture 6 and the Brazilian splitting lower fixture 9 can be adjusted according to the diameter of the test piece 15, so it has a wider applicability. The Brazilian splitting fixture limit rods 7 are made of high-strength wear-resistant materials, with high durability and corrosion resistance, effectively extending the service life of the Brazilian splitting fixture; the Brazilian splitting upper fixture 6 and the Brazilian splitting lower fixture 9 are both made of alloy materials with good compressive properties, capable of withstanding large compressive forces, and are suitable for high-strength Brazilian splitting experiments.

[0039] A connection locking mechanism can also be adopted at the connection parts between the Brazilian splitting fixture limit rods 7, the Brazilian splitting upper fixture 6, and the Brazilian splitting lower fixture 9 to ensure that the whole Brazilian splitting fixture does not loosen during the experiment and can be disassembled and replaced quickly and conveniently. The contact surfaces between the Brazilian splitting upper fixture 6 and the Brazilian splitting lower fixture 9 and the test piece 15 are all specially treated with anti-sliding and anti-wear coatings to improve the stability and reusability of the Brazilian splitting fixture.

[0040] The Brazilian splitting fixture is placed inside the kettle body 16, and the kettle body 16 is externally wrapped with an annular constant temperature heat insulation box 4 for heating the test piece 15.

[0041] Specifically, an upper flange 17 is provided at the upper part of the kettle body 16, and a lower flange 14 is provided at the lower part; a stepped through hole is opened on the upper flange 17, and the axial pressure head 1 passes through the stepped through hole. Axial pressure head sealing packing 3 is placed on both sides of the stepped through hole; an upper flange 2 is arranged above the upper flange 17, and upper flange bolt holes 18 are provided on the upper surface of the upper flange 2. The upper flange 2 is connected to the upper flange 17 through the upper flange bolt holes 18 and upper flange bolts; the lower flange 14 is provided with a protrusion, and a gap sealing ring 12 is arranged between the base 13 and the kettle body 16, and the protrusion presses on the gap sealing ring 12; the lower surface of the lower flange 14 presses on the base 13, and the base 13 is connected to the lower flange 14 through the lower flange bolt holes 8 and lower flange bolts provided on the lower flange 14.

[0042] The design of the upper flange 17 and the lower flange 14 not only improves the stability of the equipment, but also facilitates the fixation and sealing of the specimen 15, ensuring the enclosure of the experimental environment and the firm fixation of the specimen 15. The opening of the stepped through-hole enables the accurate placement of the axial pressure head sealing packing 3 and the axial pressure head 1 during the experiment, ensuring good sealing contact between the axial pressure head 1 and the kettle body 16 and avoiding possible leakage problems. This design guarantees the temperature and pressure stability and operational safety during the experiment. A through-hole is opened at the top of the kettle body 16 for the axial pressure head 1 to extend inward, and at the same time, it can ensure that the axial pressure head 1 enters and makes parallel contact with the Brazilian splitting upper fixture 6, avoiding the possibility of adverse effects on the experimental results caused by eccentric forces, etc. during the experiment. The raised part of the lower flange 14 not only strengthens the sealing effect between the base 13 and the kettle body 16, but also further improves the sealing performance by compressing the gap sealing ring 12 between the base 13 and the kettle body 16, effectively preventing pressure leakage during the experiment and ensuring the accuracy of experimental data and the reliability of the device.

[0043] At the same time, a passage is opened on the base 13 as the heat-carrying fluid injection hole 11. One end of the heat-carrying fluid injection hole 11 is connected to the outside, and the other end is connected to the inside of the kettle body 16; the function of the heat-carrying fluid injection hole 11 is to serve as an injection pipe for the heat-carrying fluid (which can be supercritical water, superheated steam, etc.), and it is connected to the external medium injection system during the experiment; a circular through-hole is opened at the bottom of the base 13 as the water-cooling circulation through-hole 10 for water-cooling circulation.

[0044] The base 13 realizes the combination of heat-carrying medium injection and water-cooling circulation. Heat-carrying media such as supercritical water, CO2 or superheated steam can be connected to the external temperature control system through the heat-carrying fluid injection hole 11 on the base 13. By adjusting the flow rate and temperature of the heat-carrying fluid, it further ensures that the specimen 15 always maintains a stable temperature environment during the application of the axial load. At the same time, the circular through-hole conducts water-cooling circulation, effectively maintaining the temperature stability during the experiment, avoiding experimental errors caused by overheating, and improving the accuracy and reliability of the experiment.

[0045] A limiting groove 19 is provided on the upper surface of the base 13. The limiting groove 19 can effectively fix the Brazilian splitting fixture on the base, prevent the Brazilian splitting fixture from shifting or loosening during the experiment, and ensure the stability of the equipment during the experiment. This design ensures the accurate position of the specimen 15 in the Brazilian splitting fixture, thereby improving the repeatability and reliability of the experimental results.

[0046] The heating system consists of a circular constant-temperature heat-insulating box 4 wrapped around the periphery of the kettle body 16 and high-temperature electric heating wires inside it. A through-hole is opened on the side of the circular constant-temperature heat-insulating box 4 as the temperature and pressure monitoring and heat-carrying fluid outlet 5, and the temperature and pressure monitoring and heat-carrying fluid outlet 5 passes through the kettle body 16 and is always connected to the inside of the kettle body 16; during the experiment, the temperature and pressure monitoring and heat-carrying fluid outlet 5 is used to be connected to an external real-time detection system to observe the temperature of the test piece 15 in the kettle body 16 in real time; when supercritical fluid heating is adopted, a back-pressure valve can be added at the temperature and pressure monitoring and heat-carrying fluid outlet 5. The heating range of the heating system is 25~550°C.

[0047] The circular constant-temperature heat-insulating box 4 ensures uniform heat distribution and no heat loss during the heating process through the circular structure wrapped around the outside of the kettle body 16; this design greatly improves the heating efficiency, avoids experimental errors caused by uneven heat, and reduces the influence of external environmental temperature changes on the experimental results, thus improving the accuracy and repeatability of the experiment.

[0048] Temperature and pressure monitoring can observe the temperature and pressure in the experiment in real time to ensure a stable heating environment during the experiment; the temperature and pressure monitoring and heat-carrying fluid outlet 5 is connected to an external medium collection system, which can smoothly discharge the heat-carrying fluid; when adopting the convective heating method or the supercritical fluid heating method, it ensures the hydrodynamic stability of the heating process.

[0049] When the supercritical fluid heating method is adopted for the temperature and pressure monitoring and heat-carrying fluid outlet 5, a back-pressure valve needs to be connected to control the discharge pressure of the fluid, so as to ensure the pressure stability during the supercritical fluid heating process and avoid affecting the accuracy of the experiment due to pressure fluctuations. This structure ensures the fluid stability during the heating process, improves the heating efficiency and ensures the rigor of the experimental conditions.

[0050] The inner and outer walls of the circular constant-temperature heat-insulating box 4 adopt high-efficiency heat-insulating materials, which significantly reduce heat loss, improve the utilization efficiency of thermal energy, and further improve the energy efficiency ratio of the heating system. This design not only saves energy, but also ensures a stable temperature control effect during the heating process, and further improves the energy-saving performance and environmental friendliness of the experimental equipment.

[0051] An existing intelligent temperature control system can be used to accurately control the heating power of the heating wire and adjust the heating temperature in real time to ensure that the test piece 15 maintains a constant temperature during the experiment.

[0052] The magnetic particle imaging system includes an RF coil 20 arranged on the inner wall of the kettle body 16 and a magnetic particle imaging device for observing the distribution state of nano-magnetic-sensing particles inside the test piece 15. The magnetic particle imaging device is an existing device, and the specific model adopted in this embodiment is HiperSense High-Resolution MPI System; an RF coil outlet 22 is provided on the side wall of the kettle body 16; one end of the RF coil outlet 22 communicates with the inside of the kettle body 16, and the other end passes through the annular constant-temperature heat insulation box 4 and communicates with the outside; the end of the RF coil 20 extends to the outside through the RF coil outlet 22 and is connected to the magnetic particle imaging device; the magnetic particle imaging device is used to observe the distribution state of nano-magnetic-sensing particles inside the test piece 15. When arranging the RF coil 20, it is necessary to ensure that its height is not lower than the height of the test piece 15 to prevent adverse effects on imaging.

[0053] During the experiment, the heat-carrying fluid is mixed with nano-magnetic-sensing particles, and the nano-magnetic-sensing particles can be any one of ferrite nano-particles, alloy magnetic nano-particles, cobalt-based magnetic nano-particles, rare-earth metal magnetic nano-particles, etc. Under high-temperature and high-pressure environments, the nano-magnetic-sensing particles can provide stable crack evolution information through the magnetic particle imaging device, and can accurately track the evolution of cracks at a micro scale without damaging the rock structure, especially the formation and expansion of crack tips and micro-cracks. Especially in extreme environments such as high temperature and high pressure, the nano-magnetic-sensing particles can provide long-term stable observations; at the same time, the evolution process of cracks can be dynamically captured by ultrafast laser imaging technology, and the acoustic imaging and electromagnetic imaging functions in the magnetic particle imaging device are used to detect the crack evolution inside the test piece 15, and the acoustic wave propagation changes during crack propagation are detected by acoustic imaging, and comprehensive analysis is carried out in combination with electromagnetic imaging.

[0054] The high-temperature warning system includes an integrated infrared temperature sensor array data acquisition processor, an infrared temperature sensor 21 and an alarm device for high-temperature alarm. The high-temperature warning system is an existing device system, and the model of the integrated infrared temperature sensor array data acquisition processor is Melexis MLX90640.

[0055] A plurality of infrared temperature sensors 21 are arranged at different positions on the periphery of the annular constant-temperature heat insulation box 4 to ensure comprehensive temperature monitoring of the key areas of the equipment. The infrared temperature sensors 21 at different positions can monitor the temperature changes simultaneously, thereby improving the monitoring accuracy of the system and avoiding false alarms due to local temperature anomalies. The infrared temperature sensor 21 can respond to temperature changes in real time, especially in an experimental environment with large temperature fluctuations, it can quickly detect small temperature deviations to ensure timely warning and prevent equipment damage or rupture of the test piece 15 caused by excessive temperature.

[0056] The integrated infrared temperature sensor array data acquisition processor receives the data of the infrared temperature sensor 21 in real time and analyzes it through an efficient data processing algorithm. When the temperature exceeds the set threshold, the system can immediately judge and trigger an alarm signal. This design greatly improves the response speed of the system, enabling the operator to take measures at the first moment of temperature abnormality to ensure the safety of the equipment during the experiment.

[0057] The alarm device has an audible and visual alarm function and can remind the operator through audible and visual signals when the temperature exceeds the limit. Through hierarchical alarm, the system can trigger alarms of different intensities according to the severity of the temperature abnormality, thus helping the operator quickly judge the severity of the abnormal situation and take emergency measures in a timely manner to prevent accidents.

[0058] The upper end of the axial pressure head 1 applying axial load to the specimen 15 is connected to the servo press. The servo press pressurizes the axial pressure head 1 to apply axial load to the specimen 15 for splitting experiment. The lower end of the axial pressure head 1 is in direct contact with the Brazilian splitting upper fixture 6, and the two are detachable.

[0059] The direct contact between the axial pressure head 1 and the Brazilian splitting upper fixture 6 eliminates the possible pressure loss problem in the existing device. This direct contact method can ensure that the applied axial load is accurately transmitted to the specimen 15, avoiding experimental errors caused by uneven or poor contact of the contact interface, thereby improving the reliability and stability of the experimental data. The bottom surface of the axial pressure head 1 and the upper surface of the Brazilian splitting upper fixture 6 both adopt a precision-machined plane design to ensure high-precision, uniform and close contact of the contact surface.

[0060] The present invention is used to implement the Brazilian splitting experiment under convective heating, conductive heating or supercritical fluid real-time heating, and is convenient for exploring the tensile strength of different rock and soil at different temperatures. The pressure loading system can apply an axial load of 300 MPa, and its heating system can heat in the range of 25 - 550 °C.

[0061] The specific usage method of this experimental device includes the following steps:

[0062] Step 1: Cut the specimen 15 according to the experimental requirements to meet the experimental requirements, and the size of the specimen 15 meets the requirements of the Brazilian splitting experiment.

[0063] Step 2: Place the Brazilian splitting lower fixture 9 in the limit groove 19 on the base 13 and clamp it tightly. Place the specimen 15 on the Brazilian splitting lower fixture 9, then assemble the Brazilian splitting fixture limit rod 7 with the Brazilian splitting lower fixture 9, and install the Brazilian splitting upper fixture 6 along the Brazilian splitting fixture limit rod 7 so that the lower surface of the Brazilian splitting upper fixture 6 is in contact with the specimen 15.

[0064] Step 3: Place the gap sealing ring 12 in the groove opened on the base 13, then place the kettle body 16 above the base 13, and use the extended part at the lower part of the lower flange 14 to combine with the groove on the base 13 to compress the gap sealing ring 12, and then tighten the lower bolts between the lower flange 14 and the base 13.

[0065] Step 4: Arrange the RF coil 20 on the inner wall of the kettle body 16, ensure that the height of the RF coil 20 is not lower than the height of the specimen 15 to comprehensively observe the distribution of nano magnetic induction particles inside the specimen 15, and the other end extends outwards from the RF coil outlet 22 and is connected to the magnetic particle imaging device.

[0066] Step 5: After installing the kettle body 16 and the base 13, place the shaft pressure head packing 3 in the groove opened on the upper part of the kettle body 16, and use the extended part of the upper flange 2 to compress the shaft pressure head packing 3, and then tighten the upper flange bolts between the upper flange 17 and the upper flange 2.

[0067] Step 6: Insert the shaft pressure head 1 into the through hole opened above the kettle body 16, ensure that the lower end of the shaft pressure head 1 is in full contact and parallel with the Brazilian split upper fixture 6, and the upper end of the shaft pressure head 1 is connected to the external servo press.

[0068] Step 7: Wrap the annular constant temperature heat insulation box 4 around the periphery of the kettle body 16.

[0069] Step 8: Arrange the sensing ends of no less than 5 infrared temperature sensors 21 on the periphery of the annular constant temperature heat insulation box 4, and try to ensure that their spacing is equal during the arrangement process. After the arrangement is completed, connect the infrared temperature sensors 21 to the integrated infrared temperature sensor array data acquisition processor and the alarm device respectively.

[0070] Step 9: Heat the specimen 15, and keep it at a constant temperature after reaching the required experimental temperature.

[0071] The heating method can adopt any one of the following three heating methods according to the experimental requirements:

[0072] The first is the convective heating method: When adopting the convective heating method, inject the heating fluid into the kettle body 16 from the heat-carrying fluid injection hole 11, and discharge the heating fluid from the temperature and pressure monitoring and heat-carrying fluid outlet 5 for convective heating; nano magnetic induction particles are mixed in the heating fluid;

[0073] The second is the conductive heating method: When adopting the conductive heating method, close the temperature and pressure monitoring and heat-carrying fluid outlet 5; first inject the protective gas (such as nitrogen, etc.) into the kettle body 16 from the heat-carrying fluid injection hole 11, and use a plug to block the heat-carrying fluid injection hole 11 and the RF coil outlet 22 after the protective gas is injected, and then turn on the annular constant temperature heat insulation box 4 for heating; nano magnetic induction particles are mixed in the protective gas;

[0074] The third is the supercritical fluid heating method: When using supercritical fluid heating, at this time, a back pressure valve is connected to the temperature and pressure monitoring and heat-carrying fluid outlet 5. After setting the back pressure of the back pressure valve, supercritical fluid is injected into the inside of the autoclave body 16 through the heat-carrying fluid injection hole 11 to heat the specimen 15. Nano-magnetic induction particles are mixed in the supercritical fluid. Commonly used supercritical fluids mainly include supercritical water and supercritical carbon dioxide. The critical conditions of supercritical water are 347 °C and 22.1 Mpa; the critical conditions of supercritical carbon dioxide are 31 °C and 7.3 MPa; when using supercritical water to heat the sample, the pressure setting range of the back pressure valve is ≥22.1 MPa, and when using supercritical carbon dioxide to heat the sample, the pressure setting range of the back pressure valve is ≥7.3 MPa. The specific pressure value is determined according to the specific experimental conditions and the type of fluid used.

[0075] Step 10: After heating to the experimental required temperature, apply an axial load to the specimen 15 through the axial pressure head 1, and observe the temperature of the specimen 15 in the autoclave body 16 in real time through the temperature and pressure monitoring and heat-carrying fluid outlet 5. Observe the distribution of nano-magnetic induction particles inside the specimen 15 through the magnetic particle imaging device and use the ultrafast laser imaging technology to dynamically capture the evolution process of cracks. At the same time, record the experimental data such as the deformation and failure of the specimen 15 through the external pressure and displacement sensors of the axial pressure head 1. When observing that there is a connected nano-magnetic induction particle distribution channel inside the specimen 15, it means that the specimen 15 generates cracks and cracks, and finally stop loading.

[0076] Note: If the convective heating method is used, it is also necessary to collect the heating fluid discharged from the temperature and pressure monitoring and heat-carrying fluid outlet 5 to prevent environmental pollution and waste of resources, and it is convenient for subsequent experiments.

[0077] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific embodiments of the present invention are limited to this. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the premise of the present invention, several simple deductions or substitutions can be made, which should all be regarded as belonging to the patent protection scope determined by the claims submitted by the present invention.

Claims

1. A Brazilian splitting test device based on multiple heating modes, characterized in that: It comprises a base (13), a Brazilian splitting fixture for placing a test piece (15), a kettle body (16) for placing the Brazilian splitting fixture, a heating system for heating the test piece (15), a heat transfer fluid injection hole (11), an axial pressure head (1) for applying an axial load to the test piece (15), a temperature and pressure monitoring and heat transfer fluid outlet (5), a magnetic particle imaging system and a high temperature early warning system; the temperature and pressure monitoring and heat transfer fluid outlet (5) is used to connect to an external real-time observation system for temperature and pressure monitoring, and also serves as an outlet for the heat transfer fluid; the magnetic particle imaging system is used to observe the distribution state of nano-magnetic particles inside the kettle body (16); The Brazilian splitting fixture comprises a Brazilian splitting upper fixture (6), a Brazilian splitting lower fixture (9) and a Brazilian splitting fixture limiting rod (7); two Brazilian splitting fixture limiting rods (7) are symmetrically connected to the Brazilian splitting lower fixture (9); two corresponding through holes are symmetrically opened on the Brazilian splitting upper fixture (6); the tops of the two Brazilian splitting fixture limiting rods (7) pass through the through holes and are detachably connected to the Brazilian splitting upper fixture (6); the test piece (15) is located between the Brazilian splitting upper fixture (6) and the Brazilian splitting lower fixture (9); The heating system comprises an annular constant temperature insulation box (4) and an electric heating wire arranged inside the annular constant temperature insulation box (4); The Brazilian splitting fixture is placed on a base (13) and is located inside a kettle body (16); the base (13) is sealed and connected to the bottom of the kettle body (16); the kettle body (16) is wrapped with an annular constant temperature insulation box (4) for heating the test piece (15); a temperature and pressure monitoring and heat transfer fluid outlet (5) is provided on the side of the annular constant temperature insulation box (4); the temperature and pressure monitoring and heat transfer fluid outlet (5) passes through the kettle body (16) and is connected to the inside of the kettle body (16); the axial pressure head (1) passes through the top of the kettle body (16) and contacts the upper surface of the Brazilian splitting upper fixture (6), and the axial pressure head (1) is sealed and slidably connected to the kettle body (16); a heat transfer fluid injection hole (11) is provided on the base (13); one end of the heat transfer fluid injection hole (11) is connected to the outside, and the other end is connected to the inside of the kettle body (16); the heat transfer fluid mixed with nano-magnetic particles is injected into the kettle body (16) through the heat transfer fluid injection hole (11); The magnetic particle imaging system comprises a radio frequency coil (20) arranged on the inner wall of a kettle body (16) and a magnetic particle imaging device for observing the distribution state of nano-magnetic particles inside a test piece (15); a radio frequency coil outlet (22) is provided on the side wall of the kettle body (16); one end of the radio frequency coil outlet (22) is connected to the inside of the kettle body (16), and the other end passes through an annular constant temperature insulation box (4) and is connected to the outside; the end of the radio frequency coil (20) extends to the outside through the radio frequency coil outlet (22) and is connected to the magnetic particle imaging device; The high temperature early warning system comprises an integrated infrared temperature sensor array data acquisition processor for high temperature alarm, an infrared temperature sensor (21) and an alarm device; a plurality of infrared temperature sensors (21) are arranged at different positions on the periphery of the annular constant temperature insulation box (4), and the infrared temperature sensors (21) are respectively connected to the integrated infrared temperature sensor array data acquisition processor and the alarm device.

2. The Brazilian splitting test device based on multiple heating modes according to claim 1 is characterized in that: A limiting groove (19) is provided on the upper surface of the base (13), and a Brazilian splitting lower clamp (9) at the bottom of the Brazilian splitting clamp is located in the limiting groove (19).

3. The Brazilian splitting test device based on multiple heating modes according to claim 1 is characterized in that: An upper flange (17) is provided on the upper part of the kettle body (16). The upper flange (17) has a stepped through hole. The shaft pressure head (1) passes through the stepped through hole. Shaft pressure head sealing packings (3) are placed on both sides of the stepped through hole. An upper flange (2) is provided above the upper flange (17). An upper flange bolt hole (18) is provided on the upper surface of the upper flange (2). The upper flange (2) is connected to the upper flange (17) through the upper flange bolt hole (18) and the upper flange bolts.

4. The Brazilian splitting test device based on multiple heating modes according to claim 1 is characterized in that: A lower flange (14) is provided at the lower part of the kettle body (16); the lower flange (14) is provided with a protrusion, a gap sealing ring (12) is provided between the base (13) and the kettle body (16), and the protrusion is pressed on the gap sealing ring (12); the lower surface of the lower flange (14) is pressed on the base (13), and the base (13) and the lower flange (14) are connected through lower flange bolt holes (8) and lower flange bolts provided on the lower flange (14).

5. The Brazilian splitting test device based on multiple heating modes according to claim 1 is characterized in that: A water cooling circulation hole (10) is provided at the bottom of the base (13).

6. A Brazilian splitting test method based on multiple heating modes, characterized in that: A Brazilian splitting test device based on multiple heating modes as described in any one of claims 1 to 5 is used, comprising the following steps: Step 1, placing the test piece (15) on the Brazilian splitting lower fixture (9), then assembling the Brazilian splitting fixture limit rod (7) and the Brazilian splitting lower fixture (9), installing the Brazilian splitting upper fixture (6) along the Brazilian splitting fixture limit rod (7), so that the lower surface of the Brazilian splitting upper fixture (6) is in contact with the test piece (15); then placing the Brazilian splitting fixture together with the test piece (15) in the kettle body (16), and the Brazilian splitting experimental device is assembled; Step 2, heating the test piece (15) and maintaining the constant temperature after reaching the temperature required for the experiment; Heating method: According to the experimental requirements, any of the following three heating methods is used: The first is a convection heating method: when the convection heating method is adopted, a heating fluid is injected into the kettle body (16) through the heat carrier fluid injection hole (11), and the heating fluid is discharged through the temperature and pressure monitoring and heat carrier fluid outlet (5) to perform convection heating; the heating fluid is mixed with nano-magnetic particles; The second method is a conduction heating method. When the conduction heating method is used, the temperature and pressure monitoring and the heat carrier fluid outlet (5) are closed, and a protective gas is first injected into the interior of the kettle body (16) through the heat carrier fluid injection hole (11). After the protective gas is injected, the heat carrier fluid injection hole (11) and the radio frequency coil outlet (22) are blocked with a plug, and then the annular constant temperature insulation box (4) is opened for heating; the protective gas is mixed with nano magnetic particles; The third method is supercritical fluid heating: When supercritical fluid heating is used, a back pressure valve is connected between the temperature and pressure monitoring and the heat carrier fluid outlet (5), and after the back pressure of the back pressure valve is set, supercritical fluid is injected into the kettle body (16) through the heat carrier fluid injection hole (11) to heat the test piece (15); the supercritical fluid is mixed with nano-magnetic particles; Step 3: After heating to the temperature required for the experiment, an axial load is applied to the test piece (15) through the axial pressure head (1), and the temperature of the test piece (15) in the kettle body (16) is observed through a real-time observation system connected to the outlet (5) of the heat-carrying fluid through temperature and pressure monitoring, and the distribution of nano-magnetic particles in the test piece (15) is observed through a magnetic particle imaging device; when a connected nano-magnetic particle distribution channel is observed in the test piece (15), that is, the test piece (15) has cracks and cracks, the loading is stopped.

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