Brazilian splitting experiment device and method based on multiple heating modes

Abstract

The invention discloses a Brazilian splitting experiment device and method based on multiple heating modes, and belongs to the technical field of splitting experiments. Comprising a base, a Brazilian splitting clamp, a kettle body, a heating system, a heat transfer fluid injection hole, an axial pressure head, a temperature and pressure monitoring and heat transfer fluid outlet, a magnetic particle imaging system and a high-temperature early warning system, the temperature and pressure monitoring and heat-carrying fluid outlet is used for being connected with an external real-time observation system to conduct temperature and pressure monitoring and serves as an outlet of heat-carrying fluid at the same time. The magnetic particle imaging system is used for observing the distribution state of nano magnetic induction particles in the kettle body; the real-time high-temperature Brazilian splitting experiment can be carried out in multiple heating modes such as convection heating, conduction heating and supercritical fluid heating, the generation and expansion process of cracks in a sample can be monitored in real time, and the device is suitable for testing the strength and crack expansion of rocks under the thermal stress condition possibly encountered in actual engineering.

Description

Technical Field

[0001] The 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 needs. Taking the long-term stability assessment of underground nuclear waste storage as an example, it is necessary to fully understand the mechanical parameters such as the tensile strength of the surrounding rock of the storage under extreme temperature and pressure conditions such as high temperature and supercritical water; and in the process of dry hot rock development, the construction of underground heat storage also requires accurate measurement of the tensile strength and other mechanical properties of high-temperature rock formations. Therefore, it is of great theoretical significance and practical application value to carry out systematic research on the tensile properties and cracking mechanism of rock or soil materials under high temperature and high pressure environments.

[0003] Tensile strength is a key parameter that affects the fracture initiation pressure of the fracturing process and is often tested through the Brazilian splitting test. The Brazilian splitting test has become a common method for measuring the tensile strength of rocks or soils because of its simple operation and high test accuracy. However, the existing experimental equipment generally has the following limitations: First, it is impossible to conduct real-time high-temperature Brazilian splitting experiments under multiple heating methods. Most of the existing equipment can only use a single heating method, which is difficult to meet the needs 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 extension morphology in the Brazilian splitting experiment is difficult to monitor in real time, and traditional experimental equipment cannot accurately capture the dynamic development process of the cracks, resulting in a lack of comprehensiveness and real-time performance of the experimental results. Therefore, in order to comprehensively study the tensile strength and cracking mechanism of rock or soil materials under different heating methods and temperature conditions, it is urgent to develop a new experimental device.

[0004] Among the patents that have been published so far, 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 a rock fracture seepage micro-characteristics observation equipment and observation method based on 3D printing technology.

[0005] However, the above patents fail to solve the Brazilian splitting test under various heating methods (convection, conduction, supercritical fluid) and real-time axial load application conditions, and cannot monitor the crack expansion morphology of the Brazilian splitting test under high temperature and high pressure environment in real time. Summary of the invention

[0006] The present invention overcomes the shortcomings of the prior art and proposes a Brazilian splitting test device and method based on multiple heating modes. The present invention is achieved through the following technical solutions: A Brazilian splitting experimental device based on multiple heating modes comprises a base, a Brazilian splitting fixture for placing a test piece, a kettle body for placing the Brazilian splitting fixture, a heating system for heating the test piece, a heat-carrying fluid injection hole, an axial pressure head for applying an axial load to the test piece, a temperature and pressure monitoring and heat-carrying fluid outlet, a magnetic particle imaging system and a high-temperature early warning system; the temperature and pressure monitoring and heat-carrying fluid outlet are used to connect to an external real-time observation system for temperature and pressure monitoring, and also serve as an outlet for the heat-carrying fluid; the magnetic particle imaging system is used to observe the distribution state of nano-magnetic particles inside the kettle body; The Brazilian splitting fixture comprises a Brazilian splitting upper fixture, a Brazilian splitting lower fixture and a Brazilian splitting fixture limiting rod; two Brazilian splitting fixture limiting rods are symmetrically connected to the Brazilian splitting lower fixture, and two corresponding through holes are symmetrically opened on the Brazilian splitting upper fixture, and the tops of the two Brazilian splitting fixture limiting rods pass through the through holes and are detachably connected to the Brazilian splitting upper fixture; the test piece is located between the Brazilian splitting upper fixture and the Brazilian splitting lower fixture; The heating system comprises an annular constant temperature insulation box and an electric heating wire arranged inside the annular constant temperature insulation box; The Brazilian splitting fixture is placed on the base and located inside the kettle body. The base is sealed and connected to the bottom of the kettle body. The outside of the kettle body is wrapped with an annular constant temperature insulation box for heating the test piece; the side of the annular constant temperature insulation box is provided with a temperature and pressure monitoring and heat-carrying fluid outlet, which passes through the kettle body and is connected to 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 Brazilian splitting upper fixture, and the axial pressure head is sealed and slidably connected to the kettle body; a heat-carrying fluid injection hole is provided on the base, one end of which is connected to the outside, and the other end is connected to the inside of the kettle body; the heat-carrying fluid injection hole is used to inject a heat-carrying fluid mixed with nano-magnetic particles into the inside of the kettle body; 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 particles inside the test piece; a radio frequency coil outlet is opened on the side wall of the kettle body; one end of the radio frequency coil outlet is connected to the inside of the kettle body, and the other end passes through the annular constant temperature insulation box and is connected to the outside; the end of the radio frequency coil extends to the outside through the radio frequency coil outlet and is connected to the magnetic particle imaging device; The high temperature warning system includes an integrated infrared temperature sensor array data acquisition processor, an infrared temperature sensor and an alarm device for high temperature alarm; multiple infrared temperature sensors are arranged at different positions around the annular constant temperature insulation box, and the infrared temperature sensors are respectively connected to the integrated infrared temperature sensor array data acquisition processor and the alarm device.

[0007] Furthermore, a limiting groove is provided on the upper surface of the base, and the Brazilian splitting lower clamp at the bottom of the Brazilian splitting clamp is located in the limiting groove.

[0008] Furthermore, an upper flange is provided on the upper part of the kettle body, and a step-shaped through hole is opened on the upper flange. The axial pressure head passes through the step-shaped through hole, and axial pressure head sealing packings are placed on both sides of the step-shaped through hole; an upper flange is provided above the upper flange, and an upper flange bolt hole is provided on the upper surface of the upper flange. The upper flange is connected to the upper flange through the upper flange bolt hole and the upper flange bolts.

[0009] Furthermore, a lower flange is provided at the lower part of the kettle body; a protrusion is provided on the lower flange, and a gap sealing ring is provided between the base and the kettle body, and the protrusion is pressed on the gap sealing ring; the lower surface of the lower flange is pressed 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.

[0010] Furthermore, a water cooling circulation hole is opened at the bottom of the base.

[0011] A Brazilian splitting test method based on multiple heating modes, using the Brazilian splitting test device based on multiple heating modes, comprises the following steps: Step 1: Place the specimen on the Brazilian splitting lower fixture, then assemble the Brazilian splitting fixture limit rod with the Brazilian splitting lower fixture, install the Brazilian splitting upper fixture along the Brazilian splitting fixture limit rod, so that the lower surface of the Brazilian splitting upper fixture contacts the specimen; then place the Brazilian splitting fixture together with the specimen in the kettle, and assemble the Brazilian splitting experimental device; Step 2: Heat the test piece through the heating system and keep the temperature constant 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 convection heating: when the convection heating method is adopted, the heating fluid is injected into the kettle body through the heat carrier fluid injection hole, and the heating fluid is discharged through the temperature and pressure monitoring and the heat carrier fluid outlet for convection heating; the heating fluid is mixed with nano magnetic induction particles; The second is the conduction heating method: when the conduction heating method is adopted, the temperature and pressure monitoring and the outlet of the heat carrier fluid are closed, and the protective gas is first injected into the interior of the kettle through the heat carrier fluid injection hole. After the protective gas is injected, the heat carrier fluid injection hole and the outlet of the radio frequency coil are blocked with a plug, and then the annular constant temperature insulation box 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 outlet of the heat-carrying fluid. After the back pressure of the back pressure valve is set, supercritical fluid is injected into the kettle through the heat-carrying fluid injection hole to heat the specimen; the supercritical fluid is mixed with nano-magnetic particles; Step 3. After heating to the required temperature for the experiment, apply an axial load to the specimen through the axial pressure head, and observe the temperature of the specimen in the kettle through a real-time observation system connected to the outlet of the heat-carrying fluid through temperature and pressure monitoring, and observe the distribution of nano-magnetic particles inside the test piece through a magnetic particle imaging device; when a connected nano-magnetic particle distribution channel is observed inside the specimen, it means that the specimen has cracks and cracks, and loading is stopped.

[0012] The beneficial effects of the present invention compared with the prior art are as follows: 1. The experimental device proposed in the present invention can perform real-time high-temperature Brazilian splitting experiments under various heating modes such as convection heating, conduction heating and supercritical fluid heating. The device integrates an infrared temperature sensor array and uses the principle of infrared radiation to measure temperature. 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 rapid response, and are particularly suitable for surface temperature detection of high-temperature, moving or difficult-to-touch objects. Therefore, the Brazilian splitting experimental device of the present invention can realize real-time high-temperature testing under various heating modes, and has efficient and accurate temperature monitoring functions, and has broad application prospects.

[0013] 2. The present invention can conduct experiments under various heating methods (such as convection heating, conduction heating and supercritical fluid heating) through the heat-carrying fluid injection hole or the annular constant temperature insulation box. This design allows real-time testing of samples under various heating environments; an axial load is applied through a pressurized system, and the tensile strength of the sample at high temperature is studied through various heating methods. The experimental content focuses on the testing of mechanical properties; it is mainly used in Brazilian splitting experiments to test the tensile strength of samples under different heating methods, especially through convection heating, conduction heating or supercritical fluid real-time heating to study the mechanical behavior of samples under high temperature conditions; it is suitable for the field of geotechnical engineering, especially the study of the tensile strength of materials at high temperatures.

[0014] 3. The present invention can monitor the generation and expansion process of cracks inside the sample in real time through the distribution state of nanomagnetic particles, thereby providing more comprehensive and accurate data support for the study of the mechanical behavior and cracking mechanism of rock or soil materials. Through the use of this device, researchers can more comprehensively grasp the tensile strength and cracking mechanism of rock or soil materials under extreme temperature and pressure conditions, and provide strong technical support for engineering applications in related fields.

[0015] 4. Compared with the prior art, the present invention integrates a magnetic particle imaging system for observing the distribution of magnetic particles of the sample, and has a high-temperature early warning system; compared with PIV particles, nano-magnetic particles have significant advantages in characterizing the evolution of crack expansion inside rocks. First, nano-magnetic particles have a smaller particle size, can penetrate deep into the rock and provide high-resolution microscopic imaging, accurately tracking the expansion process of cracks on a microscopic scale. Secondly, nano-magnetic particles can be imaged non-invasively through a magnetic field without destroying the rock structure, and can stably monitor crack development for a long time under extreme conditions. PIV particles are mainly suitable for measuring surface movement, and have a larger 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 of the rock mass; this device has multiple heating methods and is equipped with a complex heating system (such as a ring-shaped constant temperature insulation box) and a heat carrier fluid injection hole for fluid heating; compared with PIV particles, the main advantage of nanomagnetic particles in crack extension and evolution is that they can penetrate deep into the rock for real-time, non-invasive high-resolution imaging, and can provide 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, they are limited in the dynamic evolution of deep cracks and the capture of microscopic features. The present invention is suitable for testing the strength and crack extension of rocks under thermal stress conditions that may be encountered in actual engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The 3D overall structure diagram of the Brazilian splitting experimental device based on multiple heating modes provided by the present invention.

[0017] Figure 2 The figure is a schematic diagram of the position of the radio frequency coil according to the present invention.

[0018] Figure 3 It is a schematic structural diagram of the Brazilian splitting fixture of the present invention.

[0019] Figure 4 It is a schematic diagram of the connection structure of the limiting rod of the Brazilian splitting clamp and the Brazilian splitting lower clamp of the present invention.

[0020] Figure 5 It is a schematic structural diagram of the Brazilian splitting upper clamp of the present invention.

[0021] In the figure: 1-axial pressure head; 2-upper flange; 3-axial pressure head sealing packing; 4-annular constant temperature insulation box; 5-temperature and pressure monitoring and heat transfer fluid outlet; 6-Brazilian splitting upper fixture; 7-Brazilian splitting fixture limit rod; 8-lower flange bolt hole; 9-Brazilian splitting lower fixture; 10-water cooling circulation flow hole; 11-heat transfer fluid injection hole; 12-gap sealing ring; 13-base; 14-lower flange; 15-test piece; 16-kettle body; 17-upper flange; 18-upper flange bolt hole; 19-limiting groove; 20-RF coil; 21-infrared temperature sensor; 22-RF coil outlet. DETAILED DESCRIPTION

[0022] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention is further described in detail in conjunction with the embodiments and the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. The technical solutions of the present invention are described in detail below in conjunction with the embodiments and the accompanying drawings, but the scope of protection is not limited thereto.

[0023] refer to Figures 1 to 5 This embodiment proposes a Brazilian splitting experimental device and a method of using the Brazilian splitting experimental device under convection heating, conduction heating or supercritical fluid real-time heating. The experimental device includes 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-carrying 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-carrying fluid outlet 5, a magnetic particle imaging system and a high temperature early warning system; wherein the temperature and pressure monitoring and heat-carrying fluid outlet 5 is used to connect to an external real-time observation system for temperature and pressure monitoring, and can also be used as an outlet for the heat-carrying fluid; the magnetic particle imaging system is used to observe the distribution state of nano-magnetic particles inside the kettle body 16.

[0024] See also Figures 3 to 5The Brazilian splitting fixture for placing the specimen 15 is composed of 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, and 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 connected to the Brazilian splitting upper fixture 6 by threads. This threaded connection structure can make the Brazilian splitting upper fixture 6 adjust up and down along the Brazilian splitting fixture limiting rod 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 limiting rod 7 is used to limit the range of motion of the Brazilian splitting fixture to ensure that the specimen 15 is stably fixed during the experiment. And the space between the Brazilian splitting upper fixture 6 and the Brazilian splitting lower fixture 9 can be adjusted according to the diameter of the specimen 15, so it has a wider applicability. The Brazilian splitting clamp limit rod 7 is made of high-strength wear-resistant material, has high durability and corrosion resistance, and effectively extends the service life of the Brazilian splitting clamp; the Brazilian splitting upper clamp 6 and the Brazilian splitting lower clamp 9 are both made of alloy materials with good compressive resistance, can withstand large compression force, and are suitable for high-strength Brazilian splitting experiments.

[0025] The connection parts between the limit rod 7 of the Brazilian splitting fixture and the upper Brazilian splitting fixture 6 and the lower Brazilian splitting fixture 9 can also adopt a connection locking mechanism to ensure that the Brazilian splitting fixture as a whole does not loosen during the experiment and can be quickly and conveniently disassembled and replaced. The contact surfaces of the upper Brazilian splitting fixture 6 and the lower Brazilian splitting fixture 9 with the test piece 15 are specially treated with anti-slip and anti-wear coatings to improve the stability and reusability of the Brazilian splitting fixture.

[0026] The Brazilian splitting fixture is placed inside the kettle body 16 , and the outside of the kettle body 16 is wrapped with an annular constant temperature insulation box 4 for heating the test piece 15 .

[0027] Specifically, an upper flange 17 is provided on the upper part of the kettle body 16, and a lower flange 14 is provided on the lower part; the upper flange 17 is provided with a stepped through hole, the shaft pressure head 1 passes through the stepped through hole, and 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, and an upper flange bolt hole 18 is provided on the upper surface of the upper flange 2, and the upper flange 2 is connected to the upper flange 17 through the upper flange bolt hole 18 and the upper flange bolt; the lower flange 14 is provided with a protrusion, and 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 is connected to the lower flange 14 through the lower flange bolt hole 8 and the lower flange bolts provided on the lower flange 14.

[0028] 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 test piece 15, ensuring the closedness of the experimental environment and the firm fixation of the test piece 15. The opening of the stepped through hole allows the shaft pressure head sealing packing 3 and the shaft pressure head 1 to be accurately placed during the experiment, ensuring good sealing contact between the shaft pressure head 1 and the kettle body 16, avoiding possible leakage problems, and this design ensures the temperature and pressure stability and operational safety during the experiment. A through hole is provided on the top of the kettle body 16 for the shaft pressure head 1 to extend inward, and at the same time it can ensure that the shaft pressure head 1 enters and is in parallel contact with the Brazilian splitting upper fixture 6, avoiding the possibility of adverse effects on the experimental results caused by eccentric force 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 compacting 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 the experimental data and the reliability of the device.

[0029] At the same time, a passage is opened on the base 13 as a 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 heat-carrying fluid injection hole 11 serves as an injection pipe for the heat-carrying fluid (which can be supercritical water, superheated water vapor, etc.), and is connected to the external medium injection system during the experiment; an annular through hole is opened at the bottom of the base 13 as a water-cooling circulation flow hole 10 for circulating water cooling.

[0030] The base 13 combines the injection of heat medium with circulating water cooling. The heat medium, such as supercritical water, CO2 or superheated water vapor, can be connected to the external temperature control system through the heat medium injection hole 11 on the base 13. By adjusting the flow rate and temperature of the heat medium, it is further ensured that the specimen 15 always maintains a stable temperature environment during the application of the axial load. At the same time, the annular through hole performs water cooling circulation, which effectively maintains the temperature stability during the experiment, avoids the experimental error caused by overheating, and improves the accuracy and reliability of the experiment.

[0031] A limiting groove 19 is provided on the upper surface of the base 13, which can effectively fix the Brazilian splitting fixture on the base to prevent the Brazilian splitting fixture from being displaced or loosened during the experiment, thereby ensuring 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.

[0032] The heating system is composed of an annular constant temperature insulation box 4 wrapped around the outside of the kettle body 16 and a high temperature electric heating wire inside. The annular constant temperature insulation box 4 has a through hole on the side as a temperature and pressure monitoring and heat transfer fluid outlet 5. The temperature and pressure monitoring and heat transfer fluid outlet 5 pass through the kettle body 16 and are always connected to the inside of the kettle body 16. During the experiment, the temperature and pressure monitoring and heat transfer fluid outlet 5 are used to connect with 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 transfer fluid outlet 5. The heating system can heat in the range of 25~550℃.

[0033] The annular constant temperature insulation box 4 ensures uniform heat distribution and heat preservation during the heating process through the annular structure wrapped around the outside of the kettle body 16; this design greatly improves the heating efficiency and avoids experimental errors caused by uneven heat, while reducing the impact of changes in external ambient temperature on the experimental results, thereby improving the accuracy and repeatability of the experiment.

[0034] The 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; and the temperature and pressure monitoring is connected to the heat carrier fluid outlet 5 and the external medium collection system, which can smoothly discharge the heat carrier fluid; when using convection heating or supercritical fluid heating, the fluid dynamics stability of the heating process is guaranteed.

[0035] When using supercritical fluid heating, the temperature and pressure monitoring and heat-carrying fluid outlet 5 need to be connected to a back pressure valve to control the discharge pressure of the fluid, thereby ensuring the pressure stability during the supercritical fluid heating process and avoiding the accuracy of the experiment affected by pressure fluctuations. This structure ensures the stability of the fluid during the heating process, improves the heating efficiency and ensures the rigor of the experimental conditions.

[0036] The inner and outer walls of the annular constant temperature insulation box 4 are made of high-efficiency insulation materials, which significantly reduces heat loss, improves the utilization efficiency of heat energy, and further improves 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, further improving the energy saving and environmental friendliness of the experimental equipment.

[0037] The 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.

[0038] The magnetic particle imaging system includes a radio frequency 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 particles inside the specimen 15. The magnetic particle imaging device is an existing device, and the specific model used in this embodiment is HiperSense High-Resolution MPI System; a radio frequency coil outlet 22 is opened 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 the 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 magnetic particle imaging device is used to observe the distribution state of nano-magnetic particles inside the specimen 15. When arranging the radio frequency coil 20, it is necessary to ensure that its height is not lower than the height of the specimen 15 to prevent adverse effects on imaging.

[0039] During the experiment, nano-magnetic particles are mixed in the heat-carrying fluid, and the nano-magnetic particles can be selected from any 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 environment, the nano-magnetic particles can provide stable crack evolution information through the magnetic particle imaging device, and can accurately track the evolution of cracks on a micro scale without destroying the rock structure, especially the formation and expansion of crack tips and microcracks. Especially under extreme environments such as high temperature and high pressure, the nano-magnetic particles can provide long-term and stable observation; at the same time, the evolution of cracks can be dynamically captured through 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 imaging is used to detect the changes in acoustic wave propagation during crack expansion, and combined with electromagnetic imaging for comprehensive analysis.

[0040] The high temperature warning system includes an integrated infrared temperature sensor array data acquisition processor for high temperature alarm, an infrared temperature sensor 21 and an alarm device. The high temperature warning system is an existing device system, wherein the integrated infrared temperature sensor array data acquisition processor model is Melexis MLX90640.

[0041] Multiple infrared temperature sensors 21 are arranged at different positions on the periphery of the annular constant temperature insulation box 4 to ensure comprehensive temperature monitoring of key areas of the equipment. Infrared temperature sensors 21 at different positions can monitor temperature changes simultaneously, thereby improving the monitoring accuracy of the system and avoiding underreporting 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, and can quickly detect small temperature deviations to ensure timely warnings to prevent damage to the equipment or rupture of the test piece 15 caused by excessive temperature.

[0042] The integrated infrared temperature sensor array data acquisition processor receives the infrared temperature sensor 21 data in real time and analyzes it through an efficient data processing algorithm. When the temperature exceeds the set threshold, the system can immediately determine and trigger an alarm signal. This design greatly improves the response speed of the system, allowing operators to take measures as soon as temperature anomalies occur to ensure the safety of equipment during the experiment.

[0043] The alarm device has an audible and visual alarm function, which can remind the operator through audible and visual signals when the temperature exceeds the limit. Through graded alarm, the system can trigger alarms of different intensities according to the severity of the temperature anomaly, thereby helping the operator to quickly judge the severity of the abnormal situation and take emergency measures in time to prevent accidents.

[0044] The upper end of the axial pressure head 1 that applies an axial load to the specimen 15 is connected to a servo press. The servo press is used to pressurize the axial pressure head 1 and then apply an axial load to the specimen 15 to perform a 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 can be separated.

[0045] The direct contact between the axial pressure head 1 and the Brazilian split upper fixture 6 eliminates the pressure loss problem that may occur in the existing device. This direct contact method can ensure that the applied axial load is accurately transmitted to the test piece 15, avoiding experimental errors caused by uneven contact interface or poor contact, thereby improving the reliability and stability of experimental data. The bottom surface of the axial pressure head 1 and the upper surface of the Brazilian split upper fixture 6 are both precision-machined plane designs to ensure high-precision, uniform and close contact between the contact surfaces.

[0046] The present invention is used to realize Brazilian splitting experiment under convection heating, conduction heating or supercritical fluid real-time heating, and is convenient for exploring the tensile strength of different rocks and soils at different temperatures. The pressure loading system can apply an axial load of 300MPa, and the heating system can heat in the range of 25-550°C.

[0047] The specific method of using this experimental device includes the following steps: Step 1: According to the experimental requirements, the specimen 15 is cut to meet the experimental requirements. The size of the specimen 15 meets the requirements of the Brazilian splitting experiment.

[0048] Step 2: Place the Brazilian splitting lower fixture 9 in the limiting groove 19 on the base 13 and clamp it, place the specimen 15 on the Brazilian splitting lower fixture 9, then assemble the Brazilian splitting fixture limiting rod 7 with the Brazilian splitting lower fixture 9, and install the Brazilian splitting upper fixture 6 along the Brazilian splitting fixture limiting rod 7 so that the lower surface of the Brazilian splitting upper fixture 6 contacts the specimen 15.

[0049] Step 3, place the gap sealing ring 12 in the groove opened on the base 13, then place the kettle body 16 on the base 13, and use the protruding 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.

[0050] 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 test piece 15 to fully observe the distribution of the nano magnetic particles inside the test piece 15, and the other end extends outward from the RF coil outlet 22 and is connected to the magnetic particle imaging device.

[0051] Step 5: After the kettle body 16 and the base 13 are installed, the shaft pressure head sealing packing 3 is placed in the groove opened on the upper part of the kettle body 16, and the shaft pressure head sealing packing 3 is pressed with the protruding part of the upper flange 2, and then the upper flange bolts between the upper flange plate 17 and the upper flange 2 are tightened.

[0052] Step 6: Insert the axial pressing head 1 inward from the through hole opened above the kettle body 16, ensure that the lower end of the axial pressing head 1 is fully in contact with and parallel to the Brazilian splitting upper clamp 6, and the upper end of the axial pressing head 1 is connected to the external servo press.

[0053] Step 7: Wrap the annular constant temperature insulation box 4 around the kettle body 16.

[0054] Step 8, arrange the sensing ends of no less than 5 infrared temperature sensors 21 on the periphery of the annular constant temperature insulation box 4, and ensure that the spacing between them is equal as much as possible 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.

[0055] Step 9: Heat the test piece 15 and keep the temperature constant after reaching the temperature required for the experiment.

[0056] Heating method: Any of the following three heating methods can be used according to the experimental requirements: The first is a convection heating method: when the convection heating method is adopted, the 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 for convection heating; the heating fluid is mixed with nano magnetic induction particles; The second method is conduction heating: when the conduction heating method is used, the temperature and pressure monitoring and the heat carrier fluid outlet 5 are closed; first, a protective gas (such as nitrogen, etc.) is injected into the kettle body 16 through the heat carrier fluid injection hole 11, and after the protective gas is injected, the heat carrier fluid injection hole 11 and the RF 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. After the back pressure of the back pressure valve is set, supercritical fluid is injected into the kettle 16 through the heat carrier fluid injection hole 11 to heat the test piece 15. Nanomagnetic particles are mixed in the supercritical fluid. Commonly used supercritical fluids are mainly supercritical water and supercritical carbon dioxide. The critical conditions of supercritical water are 347°C and 22.1Mpa; the critical conditions of supercritical carbon dioxide are 31°C and 7.3MPa; when supercritical water is used to heat the sample, the pressure setting range of the back pressure valve is ≥22.1MPa, and when supercritical carbon dioxide is used to heat the sample, the pressure setting range of the back pressure valve is ≥7.3MPa. The specific pressure value is determined according to the specific experimental conditions and the type of fluid used.

[0057] Step 10, after heating to the temperature required for the experiment, apply an axial load to the test piece 15 through the axial pressure head 1, and observe the temperature of the test piece 15 in the kettle body 16 in real time through the temperature and pressure monitoring and the heat-carrying fluid outlet 5, observe the distribution of nano-magnetic particles inside the test piece 15 through the magnetic particle imaging device, and use ultrafast laser imaging technology to dynamically capture the evolution of the crack, and at the same time, record the deformation and damage of the test piece 15 and other experimental data through the external pressure and displacement sensor of the axial pressure head 1. When it is observed that there is a connected nano-magnetic particle distribution channel inside the test piece 15, it means that the test piece 15 has cracks and cracks, and finally stop loading.

[0058] Note: If convection heating is used, it is also necessary to collect the temperature and pressure monitoring and the heating fluid discharged from the heat carrier fluid outlet 5 to prevent environmental pollution and waste of resources, and to facilitate subsequent experimental use.

[0059] The above content is a further detailed description of the present invention in combination with a specific preferred embodiment. It cannot be determined that the specific embodiments of the present invention are limited to this. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the present invention, which should be regarded as belonging to the present invention and the scope of patent protection determined by the submitted claims.

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) by a heating system, and maintaining a 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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