A triaxial Hopkinson radial displacement measuring device for granular materials

Abstract

This invention discloses a measuring device for radial deformation of granular materials in a triaxial Hopkinson test. The device includes a fixed base and a displacement sensor and a displacement transmission device mounted thereon. The displacement sensor is fixedly connected to the displacement transmission device through a through-hole in the fixed base. The displacement transmission device includes a piston shaft, a sliding sleeve, and a positioning sleeve. The sliding sleeve includes an upper cavity, a lower cavity, and several holes located at the transition between the upper and lower cavities. This invention achieves pressure balance between the displacement transmission device and the confining pressure chamber by pre-drilling holes in the middle of the sliding sleeve, avoiding the situation where the piston shaft slides outward due to pressure rise rather than specimen deformation during confining pressure loading. Furthermore, the invention solves the sealing problem caused by sliding during piston shaft displacement transmission by installing a Gladley ring in the inner groove of the piston shaft. The radial deformation of the specimen after being compressed is transmitted to the displacement sensor through the displacement transmission device, realizing the measurement of radial deformation of the granular material specimen in a three-dimensional impact test, providing technical support for promoting impact testing of granular materials.

Description

Technical Field

[0001] This invention relates to displacement measuring devices, and more particularly to a triaxial Hopkinson radial displacement measuring device for granular materials. Background Technology

[0002] The Split Hopkinson-Kolsky Pressure Bar (SHPB) apparatus is one of the main methods for studying the mechanical response of materials under medium to high strain rates, and can achieve 10 2 -10 4 / s strain rate loading test. The active confining pressure (SHPB) test technique references the concept of a triaxial hydraulic (quasi-static) loading system. It uses a limiter to fix the incident rod, adds an axial pressure chamber at the end of the transmission rod, and adds a confining pressure chamber around the specimen. Initial pressure is applied to the specimen through the axial pressure chamber and the confining pressure chamber before the impact test. The two existing active confining pressure (SHPB) test methods are only suitable for block materials such as concrete and rock. For granular materials such as sand and glass spheres, their mechanical properties are highly stress state dependent. Taking soil as an example, natural soil itself is under a certain stress state, and the stress state directly determines the soil's dilatation and contraction properties. Under high stress states, particle breakage can affect the soil skeleton characteristics.

[0003] However, there are still barriers to triaxial SHPB testing of granular materials: First, constant confining pressure cannot be achieved, mainly because the pressure changes rapidly during the application of impact loads, and there is no pressure system that can be adjusted so sensitively and quickly; second, there is no internationally recognized method for testing radial stress and radial deformation in the existing triaxial SHPB testing system; and third, the drainage and venting boundaries of the specimen cannot be controlled.

[0004] Patent CN2022102048048 discloses a triaxial Hopkinson confining pressure loading device for granular materials. Through a built-in sealing sleeve, the device compresses and contracts under pressure, clamping the pressure rod to form a seal, thus achieving three-dimensional impact loading of the granular material. The development of this triaxial Hopkinson confining pressure loading device for granular materials solves the problem of confining pressure systems. However, without measuring radial deformation, it is impossible to obtain the shear deformation and volumetric deformation of the sample. Therefore, mastering the radial displacement measurement technology for active confining pressure (SHPB) impact tests of granular materials is crucial. Summary of the Invention

[0005] Purpose of the invention: The present invention aims to provide a triaxial Hopkinson radial displacement measuring device that can realize radial deformation measurement of granular materials under three-dimensional impact loading.

[0006] Technical Solution: The triaxial Hopkinson radial displacement measuring device for granular materials of the present invention includes a fixed base and a displacement sensor and a displacement transmission device mounted thereon. The displacement sensor passes through a through hole in the fixed base and is fixedly connected to the displacement transmission device. The displacement transmission device includes a piston shaft, a friction plate, and a sliding sleeve and a positioning sleeve sequentially fitted onto the piston shaft from top to bottom. The piston shaft includes a first section, a second section, and a third section with successively decreasing outer diameters. The first section has a first inner groove at the top and a first sealing edge and a second sealing edge extending vertically and radially from the bottom. A second inner groove is provided between the two sealing edges. A third inner groove is provided at the bottom of the second section. A Glyd ring for sealing is placed in each of the three inner grooves. The first and second sections have internal threads. The passageway is used to adjust the height of the displacement sensor. The third section has a threaded cavity for mounting a friction plate, with the contact plate of the friction plate close to the sample. The sliding sleeve includes an upper cavity, a lower cavity, an end interface, and several holes located at the transition between the upper and lower cavities, with progressively increasing inner diameters. The inner diameter of the upper cavity is the same as the outer diameter of the first section, and the inner diameter of the lower cavity is the same as the outer diameter of the first sealing edge. The end interface has internal threads that connect to the top external threads of the positioning sleeve. During the impact of the initial SHPB triaxial test, the sample undergoes radial deformation, which is transmitted to the displacement sensor through the displacement transmission device to measure the sample's radial direction. The piston shaft of the displacement transmission device slides in the third section within the positioning sleeve, the second section slides within both the positioning sleeve and the sliding sleeve, and the first section slides within the sliding sleeve. Because the sliding sleeve has pre-drilled holes, water or oil can enter the sliding sleeve within the displacement transmission device through these holes during confining pressure loading, ensuring that the pressure inside the displacement transmission device is the same as that inside the confining pressure cavity. Therefore, the piston shaft will not move outward due to the increased pressure during confining pressure loading.

[0007] Furthermore, the fixed base includes a flange, a displacement sensor support mounted on the flange, and a drain valve. A drain hole is also provided below the drain valve. The displacement sensor mounting hole on the flange includes a first through hole and a sliding sleeve interface, the sliding sleeve interface being connected to the external thread on the top of the sliding sleeve. The drain hole and valve interface on the flange ensure that the interior of the confining pressure device is completely under water pressure and free of air.

[0008] Preferably, the drain valve is connected to an external pressure sensor to measure the pressure changes inside the confining pressure chamber in real time.

[0009] Furthermore, the displacement sensor support has radial mounting holes and side bolt through holes for adjusting the tightness of the displacement sensor using mounting bolts.

[0010] Furthermore, the sliding sleeve has six holes located at the transition between the upper and lower cavities.

[0011] Furthermore, the positioning sleeve is a three-stage frustum structure with an internal cavity. The outer diameter of the first frustum is the same as the inner diameter of the lower cavity, and a Glyd ring is installed thereon. The second frustum has an external thread that connects to the internal thread of the end interface. The outer diameter of the third frustum is the same as the outer diameter of the sliding sleeve. The inner diameter of the cavity is the same as the outer diameter of the second section of the piston shaft. The end of the positioning sleeve has an internal thread that engages with the external thread on the protrusion of the friction plate.

[0012] Beneficial effects: Compared with the prior art, the significant advantages of this invention are: 1. By reserving a hole in the middle of the sliding sleeve, this invention achieves pressure balance between the displacement transmission device and the confining pressure chamber, avoiding the situation where the piston axis slides outward due to pressure rise rather than sample deformation during confining pressure loading; 2. This invention solves the sealing problem caused by sliding when the piston shaft transmits displacement by installing a Gladley ring in the inner groove of the piston shaft; 3. This invention measures the radial deformation of the sample by installing a displacement sensor, and can connect a corresponding pressure sensor externally through the valve interface to measure the pressure change in the confining pressure chamber in real time. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the structure of the present invention;

[0014] Figure 2 This is a schematic diagram of the displacement transmission device.

[0015] Figure 3 This is a schematic diagram of the piston shaft structure;

[0016] Figure 4 This is a cross-sectional view of the piston shaft;

[0017] Figure 5 This is a schematic diagram of the sliding sleeve.

[0018] Figure 6 This is a cross-sectional view of the sliding sleeve;

[0019] Figure 7 This is a schematic diagram of the positioning sleeve.

[0020] Figure 8 This is a schematic diagram of the friction plate structure;

[0021] Figure 9 This is a schematic diagram of the flange structure;

[0022] Figure 10 This is a cross-sectional view of the flange;

[0023] Figure 11 This is a structural diagram of the fixed base;

[0024] Figure 12 This is a cross-sectional view of the fixed base;

[0025] Figure 13This is a schematic diagram of the displacement sensor support structure;

[0026] Figure 14 This is a schematic diagram of the structure of a Grady ring. Detailed Implementation

[0027] The invention will now be further described with reference to the accompanying drawings.

[0028] The triaxial Hopkinson radial displacement measuring device for bulk materials of the present invention includes a fixed base 100, a displacement transmission device 200, and a displacement sensor 601. The fixed base 100 includes a flange 101, a displacement sensor support 102 disposed on the upper part of the flange 101, and a valve 103 disposed opposite the displacement sensor. The displacement transmission device 200 includes a sliding sleeve 201, a piston shaft 301, a positioning sleeve 202, a friction plate 401, and a Gladley ring 501.

[0029] The flange 101 has two bolt mounting holes 1011 on its top for mounting the displacement sensor support 102; a valve interface 1014 and a drain hole 1015 are provided opposite the bolt holes 1011 on the flange 101; a displacement sensor 601 mounting hole is provided between the bolt holes 1011 and the drain hole 1015 on the flange 101, the mounting hole including a first through hole 1012 and a sliding sleeve interface 1013, the sliding sleeve interface 1013 being connected to the external thread 2012 on the top of the sliding sleeve 201.

[0030] The displacement sensor support 102 has a mounting hole 1021 and two bolt holes 1022 on its top. The mounting hole 1021 is used to install the displacement sensor 601. The bolt holes 1022 are aligned with the bolt mounting holes 1011 on the flange 101, and the displacement sensor support 102 is fixed to the flange 101 by bolts. The side of the displacement sensor support 102 has bolt through holes, and the tightness of the displacement sensor 601 is adjusted by mounting bolts.

[0031] The drain valve 103 is installed at the valve port 1014 on the flange 101, and the drain hole 1015 is located below the drain valve 103.

[0032] Piston shaft 301 includes a first section 3012, a second section 3017, and a third section 3019 with successively decreasing outer diameters. The first section 3012 slides within the sliding sleeve 201 and has the largest outer diameter. The top of the first section 3012 has a first inner groove 3013 to accommodate the Glyd ring 501 for sealing. The bottom of the first section 3012 extends outwards with a first sealing edge 3014 and a second sealing edge 3015. A second inner groove 3016 is located between the two sealing edges to accommodate the Glyd ring 501 for sealing. The second section 3017 slides within... The first section 3012 and the second section 3017 are enclosed within the positioning sleeve 202 and the sliding sleeve 201, with slightly smaller inner and outer diameters. The bottom of the second section 3017 has a third inner groove 3018 for placing the Gladius ring 501 to achieve a sealing effect. The sliding range of the third section 3019 is within the positioning sleeve 202, with the smallest outer diameter to reduce frictional resistance. The first section 3012 and the second section 3017 have cylindrical through cavities 3011 with internal threads, which can adjust the height position of the displacement sensor 601. The third section 3019 has cylindrical cavities 3020 with internal threads, which can be connected to the friction plate 401.

[0033] The top of the sliding sleeve 201 is provided with an external thread 2012, which can be connected to the sliding sleeve interface 1013 at the bottom of the middle of the flange 101. The upper part of the interior is a cylindrical upper cavity 2011. The inner diameter of the top of the sliding sleeve 201 is the same as the outer diameter of the first section 3012 of the piston shaft. The inner diameter of the lower cavity 2014 of the lower part of the sliding sleeve 201 is slightly larger than the outer diameter of the first sealing edge 3014 at the bottom of the first section 3012 of the piston shaft, and six holes 2013 are reserved. The inner diameter of the end interface 2015 of the lower part of the sliding sleeve 201 is the largest and is provided with an internal thread, which can be connected to the top external thread of the positioning sleeve 202.

[0034] The positioning sleeve 202 is a three-stage frustum structure with an internal cavity. The outer diameter of the first frustum 2022 is the same as the inner diameter of the lower cavity 2014, and a Glyd ring 501 is installed to achieve a sealing effect. The outer diameter of the second frustum 2022 is slightly larger and has an external thread, which is connected to the internal thread of the end interface 2015. The outer diameter of the third frustum 2024 is the same as the outer diameter of the sliding sleeve 201. The inner diameter of the cavity is the same as the outer diameter of the second section 3017 of the piston shaft 301. The positioning sleeve 202 has an internal thread at its end, which is connected to the external thread on the protrusion 4012 of the friction plate 401.

[0035] The friction plate 401 includes a contact plate 4011 and a protrusion 4012.

[0036] The piston shaft top 3020 is provided with a linear displacement sensor 601 for detecting radial deformation of the sample; and / or the linear displacement sensor 601 is connected to the piston shaft 301 through the displacement sensor support 102.

[0037] The triaxial Hopkinson radial displacement measuring device for granular materials described in this invention uses a flange instead of a viewing window on the confining pressure device. A displacement transmission device is installed inside the confining pressure device via a fixed base, with the displacement transmission device close to the side of the sample. An external displacement sensor is installed via a displacement sensor support on the fixed base, connecting it to the displacement transmission device. After the sample is compressed, the radial deformation is transmitted to the displacement sensor through the displacement transmission device, thus measuring the radial deformation of the granular material sample in a three-dimensional impact test. Taking an active confining pressure (SHPB) test on sand as an example, the sample is placed in the confining pressure chamber, and then the chamber is sealed and pressurized until the set confining pressure is reached. Then, the piston shaft is lowered, and the contact plate 4011 of the friction plate 401 is brought close to the side of the sample, where the displacement sensor 601 is installed. The SHPB triaxial test begins. During the impact, the sample undergoes radial deformation, which is transmitted to the displacement sensor 601 via the displacement transmission device 200, allowing for the measurement of the radial deformation.

Claims

1. A triaxial Hopkinson radial displacement measuring device for granular materials, installed in a confining pressure device (700), characterized in that, The device includes a fixed base (100) and a displacement sensor (601) and a displacement transmission device (200) mounted thereon. The displacement sensor (601) passes through a through hole in the fixed base (100) and is fixedly connected to the displacement transmission device (200). The displacement transmission device (200) includes a piston shaft (301), a friction plate (401), and a sliding sleeve (201) and a positioning sleeve (202) sequentially fitted onto the piston shaft (301) from top to bottom. The piston shaft (301) includes a first section (3012) and a second section (3017) with successively decreasing outer diameters. The first segment (3012) has a first inner groove (3013) at the top and a first sealing edge (3014) and a second sealing edge (3015) extending vertically and radially from the bottom. A second inner groove (3016) is provided between the two sealing edges. A third inner groove (3018) is provided at the bottom of the second segment (3017). A Glyd ring (501) for sealing is placed in each of the three inner grooves. A through cavity (3011) with internal thread is opened in the first segment (3012) and the second segment (3017) for adjusting displacement. The sensor (601) is positioned at a certain height. A cavity (3020) with internal threads is opened in the third section (3019) for mounting the friction plate (401). The contact plate (4011) of the friction plate (401) is close to the sample. The sliding sleeve (201) includes an upper cavity (2011), a lower cavity (2014), an end interface (2015), and several holes (2013) located at the transition between the upper and lower cavities, with their inner diameters increasing sequentially. The inner diameter of the upper cavity (2011) is the same as the outer diameter of the first section (3012), and the inner diameter of the lower cavity (2014) is... The outer diameter of the first sealing edge (3014) is the same, and the end interface (2015) is threaded to connect with the top external thread of the positioning sleeve (202). During the impact process of the SHPB triaxial test, the sample undergoes radial deformation, which is transmitted to the displacement sensor through the displacement transmission device to measure the radial direction of the sample. The third section (3019) of the piston shaft of the displacement transmission device slides in the positioning sleeve (202), the second section (3017) slides in the positioning sleeve (202) and the sliding sleeve (201), and the first section (3012) slides in the sliding sleeve (201).

2. The triaxial Hopkinson radial displacement measuring device for granular materials according to claim 1, characterized in that, The fixed base (100) includes a flange (101), a displacement sensor support (102) mounted on the flange (101), and a drain valve (103). A drain hole (1015) is also provided below the drain valve (103). The displacement sensor (601) mounting hole on the flange (101) includes a first through hole (1012) and a sliding sleeve interface (1013). The sliding sleeve interface (1013) is connected to the external thread (2012) on the top of the sliding sleeve (201).

3. The triaxial Hopkinson confining pressure radial deformation measuring device for granular materials according to claim 2, characterized in that, The drain valve (103) is connected to an external pressure sensor to measure the pressure change in the confining chamber in real time.

4. The triaxial Hopkinson confining pressure radial deformation measuring device for granular materials according to claim 2, characterized in that, The displacement sensor support (102) has a radial mounting hole (1021) and a bolt through hole (1023) on the side to adjust the tightness of the displacement sensor (601) by means of the mounting bolt.

5. The triaxial Hopkinson radial displacement measuring device for granular materials according to claim 1, characterized in that, The sliding sleeve (201) has 6 holes (2013) located at the transition between the upper and lower cavities.

6. The triaxial Hopkinson radial displacement measuring device for granular materials according to claim 1, characterized in that, The positioning sleeve (202) is a three-stage frustum structure with an internal cavity. The outer diameter of the first frustum (2022) is the same as the inner diameter of the lower cavity (2014), and a Glyd ring (501) is installed thereon. The second frustum (2022) has an external thread that connects to the internal thread of the end interface (2015). The outer diameter of the third frustum (2024) is the same as the outer diameter of the sliding sleeve (201). The inner diameter of the cavity is the same as the outer diameter of the second section (3017) of the piston shaft (301). The end of the positioning sleeve (202) has an internal thread that engages with the external thread on the protrusion (4012) of the friction plate (401).

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