A quasi-triaxial in-situ nanoindentation testing device and method

Abstract

This invention proposes a pseudo-triaxial in-situ nanoindentation testing device and method, belonging to the field of underground rock detection technology. To address the problem of effective confining pressure failure caused by gas infiltration into pores due to direct encapsulation by high-pressure gas in existing high-temperature and high-pressure in-situ nanoindentation tests, the pseudo-triaxial in-situ nanoindentation testing device includes a high-pressure resistant vessel (1), an axial pressure loading component (2), a nanoindentation loading component (3), an encapsulation layer (4), and a high-pressure fluid loading system (5). The axial pressure loading component is a hollow structure, and the axial pressure loading component and the nanoindentation loading component are coaxially arranged, thereby solving the spatial interference problem between macroscopic loading and microscopic detection. This invention achieves, for the first time, in-situ micromechanical characterization under the coupling of three fields: temperature, fluid confining pressure, and axial stress.

Description

Technical Field

[0001] This invention relates to the field of underground rock detection technology, specifically a pseudo-triaxial in-situ nanoindentation testing device and method. Background Technology

[0002] With the continuous development of deep earth science, nuclear energy engineering, and aerospace, materials are often subjected to complex service environments involving multi-field coupling, such as high temperature, high confining pressure, and axial stress (i.e., pseudo-triaxial). Nanoindentation technology, as an important means of characterizing the microscopic mechanical properties of materials, has been widely used in the testing of various advanced materials and soil media.

[0003] However, existing high-temperature, high-pressure in-situ nanoindentation instruments typically employ a "fully gas-enclosed" method of directly pressurizing exposed samples to apply environmental pressure. According to the classical effective stress principle in rock mechanics, the effective stress borne by the porous media skeleton (… ) equals the total external confining pressure ( ) and pore fluid pressure ( The difference is... When high-pressure gas is used to directly encapsulate and pressurize rocks and solid materials with pores or microcracks, the high-pressure gas will rapidly penetrate into the interconnected pores inside the material, leading to an increase in pore fluid pressure within the material. ) rises sharply and is related to the total confining pressure exerted externally ( The material tends to reach equilibrium. This directly leads to an effective confining pressure acting on the material skeleton ( The value approaches zero, making the test results completely unable to reflect the true mechanical response of the rock skeleton in deep strata under three-dimensional compression.

[0004] On the other hand, traditional pseudo-triaxial mechanical testing equipment generally uses a solid loading plate because it needs to apply independent axial stress to the sample. This completely closes the sample end face in physical space, which makes it impossible for micro-test probes (such as the indenter of a nanoindenter) to obtain a physical path to enter the sample surface for in-situ detection.

[0005] Therefore, existing testing technologies are trapped in a technical bottleneck: "applying pseudo-triaxial macroscopic stress makes it impossible to perform microscopic detection, and performing microscopic detection makes it impossible to establish a real multi-field coupling boundary." Existing nanoindenters cannot establish a real "skeleton stress" while maintaining microscopic resolution. Summary of the Invention

[0006] To address the problem of effective confining pressure failure caused by gas infiltration into pores due to direct encapsulation of high-pressure gas in existing high-temperature and high-pressure in-situ nanoindentation tests, this invention provides a pseudo-triaxial in-situ nanoindentation testing device and method. By introducing "flexible metal film sealing technology" to achieve solid-gas isolation and establish the effective stress of the real skeleton, and combining it with "hollow coaxial mechanical transmission path" to solve the spatial interference between loading and detection, this invention enables accurate characterization of the in-situ micromechanical properties of materials under multi-field coupling environment.

[0007] The technical solution adopted by the embodiments of the present invention to solve its technical problem is as follows: A pseudo-triaxial in-situ nanoindentation testing device includes: The pressure-resistant vessel body contains a sealed test cavity inside, where the test sample can be placed. An axial pressure loading component is fitted onto a high-pressure vessel. The axial pressure loading component can apply axial pressure to the test sample and contains an axial mounting channel. The nanoindentation loading component is fitted into the axial mounting channel of the axial compression loading component. The inner end of the nanoindentation loading component is provided with a nanoindenter, which can press the sample to be tested. The encapsulation layer is located inside the sealed test cavity and can be fitted onto the outer side circumferential surface of the test sample. The high-pressure fluid loading system is connected to the high-pressure vessel body. The high-pressure fluid loading system can inject high-pressure fluid into the sealed test cavity and apply confining pressure to the test sample through the wrapping layer.

[0008] A pseudo-triaxial in-situ nanoindentation testing method, wherein the pseudo-triaxial in-situ nanoindentation testing method employs the aforementioned pseudo-triaxial in-situ nanoindentation testing device, and the pseudo-triaxial in-situ nanoindentation testing method comprises the following steps in sequence: Step 1: Sample encapsulation and establishment of effective confining pressure boundary: The test sample is processed into a columnar shape, and a sealing material sheet is matched and wrapped around the side circumference of the test sample to form a wrapping layer. The test sample containing the wrapping layer is placed on the stage in the sealed test cavity. Step 2, Macro and Micro loading component assembly: The annular indenter of the axial compression loading component is installed in the sealed test cavity, and the annular indenter is connected to the test sample from top to bottom. The nano-indentation loading component is installed in the axial installation channel of the axial compression loading component. Step 3: Construct a multi-field coupling environment: The top cover and the vessel body are sealed and connected, and the temperature inside the sealed test cavity is increased. At the same time, high-pressure gas is injected into the sealed test cavity. The pressure of the high-pressure gas is transmitted to the side circumference of the test sample through the wrapping layer to form an effective confining pressure. The wrapping layer prevents the gas from entering the internal pores of the test sample. Step 4: Apply axial stress: The axial compression loading component moves downward, and the axial compression loading component and the stage clamp and fix the test sample. The annular indenter applies axial stress to the test sample, so that the test sample is in a pseudo-triaxial stress equilibrium state. Step 5: In-situ microscopic testing: After the temperature and stress field stabilize, the nanoindentation loading component moves downward and the nanoindenter presses into the upper surface of the test sample which is constrained by multiple fields, and the load-displacement curve of the nanoindentation loading component is obtained.

[0009] The beneficial effects of the embodiments of the present invention are: 1. Realistic stratigraphic simulation: By introducing a ductile encapsulation layer, the penetration of high-pressure fluid into the sample pores was successfully blocked. Based on the effective stress principle, this device and method purely convert fluid pressure into mechanical confining pressure that laterally compresses the material skeleton, solving the theoretical problem that gaseous media cannot be used for pseudo-triaxial testing of rocks, and realistically simulating the stress environment of the skeleton in deep strata.

[0010] 2. Solving the problem of space interference: The design employs a coaxial nesting of a hollow axial compression loading component and a nano-indentation loading component, where macroscopic loading is applied to the edge of the sample and a microscopic probe passes through the center, cleverly solving the spatial interference problem between macroscopic axial loading and microscopic indentation detection.

[0011] 3. Thermal-mechanical-fluid decoupling and elimination of thermal drift: By utilizing a hollow channel to create an isothermal environment for thermal radiation and gas convection, the nanoindenter reaches thermal equilibrium before contact, greatly eliminating thermal drift caused by multi-field coupled temperature differences and ensuring the accuracy of nanoscale testing.

[0012] 4. For the first time, in-situ micromechanical testing under the coupling of three fields of temperature, fluid confining pressure and axial stress was achieved, filling a gap in the industry. Attached Figure Description

[0013] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0014] Figure 1 This is a schematic diagram of the working state of the pseudo-triaxial in-situ nanoindentation testing device described in this invention.

[0015] Figure 2 This is a schematic diagram of an axially compressed loading component.

[0016] Figure 3 This is a schematic diagram of the nanoindentation loading component.

[0017] Figure 4 This is a schematic diagram of the sample to be tested.

[0018] The annotations in the attached figures are explained as follows: 1. High-pressure vessel body; 2. Axial pressure loading component; 3. Nano-indentation loading component; 4. Coating layer; 5. High-pressure fluid loading system; 6. Insulation layer; 7. First pressurization drive mechanism; 8. Second pressurization drive mechanism; 9. Stage; 10. Test sample; 101. Sealing test cavity; 102. Top cover; 103. Vessel body; 104. Injection port; 201. Axial mounting channel; 202. Loading rod; 203. Annular pressure head; 204. Second heating component; 301. Nano-indenter; 302. Nano-indentation loading rod; 601. First heating element; 901. Sample mounting slot; 1001, Side peripheral surface; 1002, Top end surface. Detailed Implementation

[0019] For ease of understanding and description, the following description of the present invention uses absolute positional relationships. Unless otherwise specified, the directional term "above" indicates... Figure 1 The direction above, the directional word "down" indicates Figure 1 The lower side of the middle, "left" indicates Figure 1 The left side of the direction, the directional word "right" indicates Figure 1 The orientation is to the right. This invention is described from the perspective of the reader or user, but the aforementioned directional terms should not be understood or interpreted as limiting the scope of protection of this invention. Regarding the material, weight, size, angle, and parameters of the components, those skilled in the art can determine or replace them according to actual needs or a limited number of experiments.

[0020] In this embodiment, as Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown, the pseudo-triaxial in-situ nanoindentation testing device includes: The high-pressure resistant vessel 1 contains a sealed test cavity 101 inside, and the test sample 10 can be placed inside the sealed test cavity 101. Axial pressure loading component 2 is partially sleeved on the high-pressure vessel body 1. Axial pressure loading component 2 can apply axial pressure to the test sample 10. Axial pressure loading component 2 contains an axial installation channel 201. The nanoindentation loading component 3 is sleeved in the axial mounting channel 201 of the axial compression loading component 2. The inner end of the nanoindentation loading component 3 is provided with a nanoindenter 301, which can press the surface of the test sample 10. The wrapping layer 4 (also known as the metal wrapping layer) is located inside the sealed test cavity 101 and can be fitted onto the side circumferential surface 1001 of the test sample 10. The high-pressure fluid loading system 5 is connected to the high-pressure vessel body 1. The high-pressure fluid loading system 5 can inject high-pressure fluid into the sealed test cavity 101 and apply confining pressure to the test sample 10 through the wrapping layer 4.

[0021] In this invention, the axial compression loading component 2 is a hollow structure, and the axial compression loading component 2 and the nanoindentation loading component 3 are coaxially arranged, which solves the problem of spatial interference between macroscopic loading and microscopic detection, and realizes for the first time in-situ micromechanical characterization under the coupling of three fields of temperature, fluid confining pressure and axial stress.

[0022] like Figure 1 As shown, the high-pressure resistant vessel 1 is an upright cylindrical structure. The high-pressure resistant vessel 1 includes an upper cover 102 and a vessel body 103 connected vertically. The vessel body 103 includes a side wall and a bottom wall connected vertically. The upper cover 102 and the side wall of the vessel body 103 are detachably and sealed. An injection port 104 is provided on the side wall of the vessel body 103. The outlet end of the high-pressure fluid loading system 5 is connected to the injection port 104 through a high-pressure pipeline.

[0023] The sealing test cavity 101 is located inside the vessel body 103, and the side walls of the vessel body 103 are fitted outside the sealing test cavity 101. The axis of the high-pressure vessel body 1, the axis of the axial pressure loading component 2, the axis of the nano-indentation loading component 3, and the axis of the wrapping layer 4 coincide. The axis of the high-pressure vessel body 1 extends in the vertical direction, and in the vertical direction, the injection port 104 is located between the lower end of the axial pressure loading component 2 and the bottom wall of the vessel body 103.

[0024] like Figure 1 As shown, the inner surface of the vessel body 103 is provided with a heat insulation layer 6, which can be made of heat insulation material. The inner surface of the heat insulation layer 6 is provided with a first heating element 601, which can heat the sealed test cavity 101 to the required temperature, thereby realistically simulating the formation environment temperature.

[0025] An axial mounting channel 201 (along the axis of the axial pressure loading component 2) axially passes through the axial pressure loading component 2. The axial pressure loading component 2 includes a loading rod 202 and an annular pressure head 203 that are fixedly connected (e.g., welded) vertically. The loading rod 202 is a tubular structure, and the annular pressure head 203 is an annular structure. The annular pressure head 203 is located inside the sealing test cavity 101, and the loading rod 202 passes through the upper cover 102. A set gap may exist between the annular pressure head 203 and the heat insulation layer 6.

[0026] The outer diameter of the annular pressure head 203 is larger than the outer diameter of the loading rod 202 and the outer diameter of the wrapping layer 4. The loading rod 202 is connected to the first pressure driving mechanism 7, which can drive the axial pressure loading component 2 to move up and down. The first pressure driving mechanism 7 is located outside the high-pressure resistant vessel body 1. The first pressure driving mechanism 7 can be a hydraulic cylinder. The loading rod 202 is movably and sealedly connected to the upper cover 102.

[0027] like Figure 1 , Figure 2 , Figure 3 As shown, a second heating element 204 may be provided inside the lower end of the loading rod 202 or inside the annular pressure head 203. The second heating element 204 can heat the lower part of the axial mounting channel 201 to make the temperature of the lower part of the axial mounting channel 201 the same as the temperature inside the sealed test cavity 101.

[0028] The nanoindentation loading component 3 also includes a nanoindentation loading rod 302, which is vertically connected and fixed to the nanoindenter 301. The outer diameter of the nanoindentation loading rod 302 is equal to the diameter of the axial mounting channel 201, which can be 2.5 ± 0.1 cm. The diameter of the axial mounting channel 201 is larger than the diameter of the nanoindenter 301. The nanoindentation loading rod 302 is movably and sealingly connected to the axial mounting channel 201. The axial mounting channel 201 serves as a channel for thermal radiation and gas convection, enabling the nanoindenter 301 to reach a thermal equilibrium isothermal environment with the sample surface before contacting the sample.

[0029] The upper end of the nanoindentation loading rod 302 is externally connected to a second pressure driving mechanism 8, which can drive the nanoindentation loading component 3 to move up and down. The second pressure driving mechanism 8 can be a hydraulic cylinder.

[0030] like Figure 1 , Figure 4 As shown, the encapsulation layer 4 can seal and encapsulate the entire circumferential surface 1001 of the test sample 10. The material of the encapsulation layer 4 can be a solid metal or a solid alloy, such as copper, gold, steel, or copper, preferably steel or copper. The encapsulation layer 4 is used to isolate the high-pressure gas from the test sample 10, ensuring that the confining pressure of the fluid is effectively converted into lateral compressive stress acting on the sample skeleton.

[0031] The wrapping layer 4 has good high-temperature resistance and ductility, thus it can effectively conduct pressure to form an effective confining pressure. The thickness of the wrapping layer 4 can be 4mm to 6mm. The upper end of the wrapping layer 4 is not higher than the upper surface of the test sample 10, and the lower end of the wrapping layer 4 is not lower than the lower surface of the test sample 10. Preferably, the upper end of the wrapping layer 4 is flush with the upper surface of the test sample 10, and the lower end of the wrapping layer 4 is flush with the lower surface of the test sample 10.

[0032] The pseudo-triaxial in-situ nanoindentation testing device also includes a stage 9, which is located at the lower end of the sealed test cavity 101. A sample mounting groove 901 is provided in the upper end surface of the stage 9. The axial compression loading component 2, the test sample 10 and the stage 9 can be arranged sequentially from top to bottom. The axial compression loading component 2 and the stage 9 can clamp and fix the test sample 10 from top to bottom.

[0033] like Figure 1 As shown, the stage 9 has a T-shaped cross-section. The axis of the stage 9 coincides with the axis of the high-pressure vessel 1. The lower end of the stage 9 is connected to the bottom wall of the vessel 103. The bottom wall of the vessel 103 can support the stage 9. The outer diameter of the stage 9 is larger than the diameter of the test sample 10. The lower end of the test sample 10 and the lower end of the wrapping layer 4 can be matched and inserted into the sample mounting groove 901 of the stage 9.

[0034] The following describes a pseudo-triaxial in-situ nanoindentation testing method. This method utilizes the aforementioned pseudo-triaxial in-situ nanoindentation testing device and includes the following steps: Step 1: Sample encapsulation and establishment of effective confining pressure boundary: A core sample of shale (or coal) rock from a deep stratum is drilled and processed into a columnar shape, i.e., the test sample 10 is processed into a columnar shape (such as a cylinder). The diameter of the test sample 10 can be 2.5 mm. A sealing material sheet is matched and covered on the side circumferential surface 1001 of the test sample 10. The material of the sealing material sheet can be metal or alloy (such as annealed copper or steel). The two circumferential ends of the sealing material sheet are heat-shrinked or welded to form a cylindrical wrapping layer 4. The test sample 10 containing the wrapping layer 4 is placed on the stage 9 in the sealed test cavity 101.

[0035] Because the pores of shale / coal are interconnected, this encapsulating layer 4 can undergo slight plastic deformation under subsequent pressurization, closely conforming to the microscopic undulations of the rock surface and completely blocking the intrusion of external high-pressure fluid media into the natural micro-crack network inside the rock. The central region of the upper surface of the test sample 10 exposes the target mineral phase (such as kerogen organic matter or specific clay mineral particles) to be detected.

[0036] Step 2, Macro and Micro loading component assembly: The annular indenter 203 of the axial compression loading component 2 is installed in the sealed test cavity 101. The annular indenter 203 is connected vertically to the test sample 10. The nano-indentation loading component 3 is suspended and installed in the axial installation channel 201 of the axial compression loading component 2.

[0037] At this point, the axes of the high-pressure vessel body 1, the axial pressure loading component 2, the nanoindentation loading component 3, the coating layer 4, the test sample 10, and the stage 9 are aligned. The nanoindentation loading component 3 and the test sample 10 are positioned vertically at intervals.

[0038] Step 3: Construct a multi-field coupling environment: The top cover 102 and the vessel body 103 are sealed and cemented together. The first heating component 601 heats the sealed test cavity 101. At the same time, the high-pressure fluid loading system 5 fills the sealed test cavity 101 with high-pressure gas (for example, simulating the formation confining pressure at a depth of 3000 meters, filling with high-pressure gas of about 30MPa). The pressure of the high-pressure gas is transmitted to the side circumferential surface 1001 of the test sample 10 through the wrapping layer 4 to form an effective confining pressure. The encapsulation layer 4 blocks gas from entering the internal pores of the test sample 10.

[0039] Based on the principle of effective stress, the gas pressure is purely converted into effective mechanical confining pressure that laterally squeezes the shale skeleton, realistically reconstructing the confining pressure state of the deep-earth environment. The first heating component 601 is activated to raise the ambient temperature to the target formation temperature. Furthermore, in step 3, the confining pressure is precisely controlled by adjusting the pressure value of the high-pressure gas source in the high-pressure fluid loading system 5. Through the physical barrier of the metal encapsulation layer 4, the effective confining pressure acting on the test sample 10 is equal to the external gas pressure, eliminating the offsetting effect of pore fluid pressure on the skeleton stress.

[0040] Step 4: Apply axial stress: The first pressurizing drive mechanism 7 drives the axial pressure loading component 2 to move downward. The axial pressure loading component 2 and the stage 9 clamp and fix the test sample 10. Axial stress is applied to the test sample 10 through the annular indenter 203 (and the stage 9). This puts the test sample 10 into a pseudo-triaxial stress equilibrium state. ).

[0041] Step 5: In-situ microscopic testing: After the temperature and stress field stabilize, the second pressure driving mechanism 8 drives the nanoindentation loading component 3 to move downward, and the nanoindenter 301 presses into the center of the exposed upper surface 1002 of the test sample 10 which is subject to multi-field constraints, and obtains the load-displacement curve of the nanoindentation loading component 3.

[0042] This allows us to obtain the true elastic modulus, hardness, and creep characteristics of different micro-components within the rock under real multi-field coupled stress conditions deep underground. Because the central region is subjected to the combined effects of gas pressure (pore pressure) and skeletal stress transmitted from the edges, the in-situ mechanical properties under the solid-fluid coupled boundary can be measured.

[0043] Shale and coal are typical porous / fractured media, with numerous nanoscale pores and microfractures (such as cleavage in coal). In traditional testing, directly applying high-pressure gas causes the gas to rapidly infiltrate the rock along the fracture network, leading to the instantaneous failure of the effective confining pressure. This invention can solve the problem in existing high-temperature, high-pressure in-situ nanoindentation tests where high-pressure gas directly envelops the rock, causing gas infiltration into the pores and resulting in the failure of the effective confining pressure; and the technical challenge of traditional pseudo-triaxial macroscopic loading solid pressure plates completely sealing the sample end face in physical space, preventing microscopic testing probes from entering and causing spatial interference, thus hindering in-situ microscopic detection.

[0044] The above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, substitutions of equivalent components, or equivalent changes and modifications made within the scope of protection of the present invention, should still fall within the scope of the present invention. Furthermore, the technical features, technical solutions, and embodiments of the present invention can be freely combined and used.

Claims

1. A pseudo-triaxial in-situ nanoindentation testing device, characterized in that, The pseudo-triaxial in-situ nanoindentation testing device includes: The high-pressure resistant vessel body (1) contains a sealed test cavity (101) inside, and the test sample (10) can be placed in the sealed test cavity (101); Axial pressure loading component (2) is fitted onto the high-pressure vessel body (1). The axial pressure loading component (2) can apply axial pressure to the test sample (10). The axial pressure loading component (2) contains an axial mounting channel (201). The nanoindentation loading component (3) is fitted into the axial mounting channel (201) of the axial compression loading component (2). The inner end of the nanoindentation loading component (3) is provided with a nanoindenter (301), which can press the sample to be tested (10). The wrapping layer (4) is located inside the sealed test cavity (101), and the wrapping layer (4) can be fitted onto the side circumferential surface (1001) of the test sample (10); The high-pressure fluid loading system (5) is connected to the high-pressure vessel body (1). The high-pressure fluid loading system (5) can inject high-pressure fluid into the sealed test cavity (101) and apply confining pressure to the test sample (10) through the wrapping layer (4).

2. The pseudo-triaxial in-situ nanoindentation testing device according to claim 1, characterized in that, The high-pressure resistant vessel body (1) is an upright cylindrical structure. The high-pressure resistant vessel body (1) contains an upper cover (102) and a vessel body (103) connected vertically. The sealed test cavity (101) is located inside the vessel body (103). The axis of the high-pressure resistant vessel body (1), the axis of the axial pressure loading component (2), the axis of the nano-indentation loading component (3), and the axis of the wrapping layer (4) coincide.

3. The pseudo-triaxial in-situ nanoindentation testing device according to claim 2, characterized in that, The inner surface of the vessel body (103) is provided with a heat insulation layer (6), and the inner surface of the heat insulation layer (6) is provided with a first heating element (601). The first heating element (601) can heat the sealed test cavity (101).

4. The pseudo-triaxial in-situ nanoindentation testing device according to claim 2, characterized in that, The axial installation channel (201) axially passes through the axial pressure loading component (2), which contains a loading rod (202) and an annular pressure head (203) connected vertically. The annular pressure head (203) is located in the sealing test cavity (101), and the loading rod (202) passes through the upper cover (102).

5. The pseudo-triaxial in-situ nanoindentation testing device according to claim 4, characterized in that, The outer diameter of the annular pressure head (203) is larger than the outer diameter of the loading rod (202) and the outer diameter of the wrapping layer (4). The loading rod (202) is connected to the first pressure driving mechanism (7). The first pressure driving mechanism (7) can drive the axial pressure loading component (2) to move up and down. The first pressure driving mechanism (7) is located outside the high pressure vessel body (1). The loading rod (202) is sealed to the upper cover (102). A second heating component (204) is provided in the lower end of the loading rod (202) or in the annular pressure head (203).

6. The pseudo-triaxial in-situ nanoindentation testing device according to claim 2, characterized in that, The nanoindentation loading component (3) also includes a nanoindentation loading rod (302), which is connected and fixed to the nanoindenter (301) at the top and bottom. The outer diameter of the nanoindentation loading rod (302) is equal to the diameter of the axial installation channel (201).

7. The pseudo-triaxial in-situ nanoindentation testing device according to claim 6, characterized in that, The upper end of the nanoindentation loading rod (302) is externally connected to a second pressure driving mechanism (8), which can drive the nanoindentation loading component (3) to move up and down.

8. The pseudo-triaxial in-situ nanoindentation testing device according to claim 1, characterized in that, The wrapping layer (4) can seal and wrap the entire side circumference (1001) of the test sample (10). The material of the wrapping layer (4) is solid metal or solid alloy. The thickness of the wrapping layer (4) is 4mm to 6mm. The upper end of the wrapping layer (4) is flush with the upper end of the test sample (10), and the lower end of the wrapping layer (4) is flush with the lower end of the test sample (10).

9. The pseudo-triaxial in-situ nanoindentation testing device according to claim 2, characterized in that, The pseudo-triaxial in-situ nanoindentation testing device also includes a stage (9), which is located at the lower end of the sealed test cavity (101). A sample mounting groove (901) is provided in the upper surface of the stage (9). The axial compression loading component (2), the test sample (10), and the stage (9) can be arranged sequentially from top to bottom. The axial compression loading component (2) and the stage (9) can clamp and fix the test sample (10).

10. A pseudo-triaxial in-situ nanoindentation testing method, characterized in that, The pseudo-triaxial in-situ nanoindentation testing method employs the pseudo-triaxial in-situ nanoindentation testing device as described in claim 9, and the pseudo-triaxial in-situ nanoindentation testing method includes the following steps in sequence: Step 1: Sample encapsulation and establishment of effective confining pressure boundary: The test sample (10) is processed into a column shape, and a sealing material sheet is matchedly wrapped on the side circumferential surface (1001) of the test sample (10) to form a wrapping layer (4). The test sample (10) containing the wrapping layer (4) is placed on the stage (9) in the sealed test cavity (101). Step 2, Macro and Micro loading component assembly: The annular indenter (203) of the axial compression loading component (2) is installed in the sealed test cavity (101), and the annular indenter (203) is connected to the test sample (10) from top to bottom. The nano-indentation loading component (3) is installed in the axial installation channel (201) of the axial compression loading component (2). Step 3: Construct a multi-field coupling environment: The top cover (102) and the vessel body (103) are sealed and cemented together, and the temperature inside the sealed test cavity (101) is heated. At the same time, high-pressure gas is injected into the sealed test cavity (101). The pressure of the high-pressure gas is transmitted to the side circumferential surface (1001) of the test sample (10) through the wrapping layer (4) to form an effective confining pressure. The wrapping layer (4) blocks the gas from entering the internal pores of the test sample (10). Step 4: Apply axial stress: The axial compression loading component (2) moves downward, and the axial compression loading component (2) and the stage (9) clamp and fix the test sample (10). The annular indenter (203) applies axial stress to the test sample (10) so that the test sample (10) is in a pseudo-triaxial stress equilibrium state. Step 5: In-situ microscopic testing: After the temperature and stress field stabilize, the nanoindentation loading component (3) moves downward and the nanoindenter (301) presses into the upper end face (1002) of the test sample (10) which is subject to multi-field constraints, and obtains the load-displacement curve of the nanoindentation loading component (3).

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