A low-temperature test system applied to a hopkinson bar test and a use method thereof

Abstract

A low-temperature test system applied to a Hopkinson bar test and a use method thereof, comprising a Hopkinson bar test device, the Hopkinson bar test device comprising an incident bar and a transmission bar, further comprising an ice making device for preparing bubble-free cylindrical pure ice; a low-temperature test device for fixing the bubble-free cylindrical pure ice between the incident bar and the transmission bar of the Hopkinson bar test device and providing a low-temperature environment lower than-15 DEG C for the bubble-free cylindrical pure ice, the incident bar and the transmission bar, so as to improve the accuracy of Hopkinson bar test data.

Description

Technical Field

[0001] This invention belongs to the field of rock dynamics technology and relates to a low-temperature testing system for the Hopkinson bar test and its usage method. Background Technology

[0002] my country has a vast distribution of high-altitude and cold regions, with hundreds of large and medium-sized open-pit mines. Due to the presence of natural fissures in the rock mass, groundwater and rainfall cause these fissures near the surface to fill with water. Under the influence of diurnal temperature variations and seasonal temperature changes, the rock and its internal water undergo a continuous freezing-thawing cycle. Slopes formed by open-pit mining are affected by this freeze-thaw environment, impacting their stability. Furthermore, disturbances from mining activities such as blasting can induce landslide risks. Therefore, to evaluate slope stability and prevent landslides, it is necessary to test the dynamic constitutive models of rocks and ice, establish mechanical models of ice-infilled jointed rock masses, and then study the dynamic mechanical properties of these masses.

[0003] The Split Hopkinson Bar (SHPB) is one of the main experimental setups for studying the dynamic mechanical properties of rocks. This setup typically consists of three parts: an impact system, a bar system, and a data acquisition and recording system. High-speed photography is also included to observe crack propagation during rock impact. Conventional SHPB setups use steel bars as both incident and transmission bars. However, due to the low wave impedance of ice, the transmitted wave measured using steel bars is too small for testing and analysis. Therefore, long rock bars made from the same rock as the field material are used instead of steel bars as incident and transmission bars. To reproduce the effects of disturbances in high-altitude open-pit mines, frozen rock bars are used for SHPB tests to measure the dynamic constitutive model of ice. Conventional SHPB setups cannot perform dynamic tests in low-temperature environments. Although some researchers have used liquid nitrogen immersion, alcohol spraying, and freezers for cooling, these methods only place the sample in a certain low-temperature environment, not the entire bar system at both ends of the sample. In addition, if the dynamic constitutive model of ice is to be tested, a pure ice sample with few bubbles and a smooth surface must first be prepared and placed in the SHPB test apparatus to carry out dynamic impact tests. However, the ice samples prepared by the existing ice-making equipment are prone to contain bubbles, and the surface smoothness of the ice does not meet the requirements of the SHPB test. Summary of the Invention

[0004] In view of this, the present invention discloses a low-temperature testing system for the Hopkinson bar test, the specific scheme of which is as follows:

[0005] A low-temperature testing system for the Hopkinson bar test includes a Hopkinson bar testing apparatus, wherein the Hopkinson bar testing apparatus includes an incident bar and a transmission bar, characterized in that it further includes:

[0006] An ice-making apparatus, wherein the ice-making apparatus is used to prepare bubble-free cylindrical pure ice;

[0007] A low-temperature testing device is used to fix bubble-free cylindrical pure ice between the incident rod and the transmission rod of the Hopkinson bar test device, and to provide a low-temperature environment of -25℃ to -15℃ for the bubble-free cylindrical pure ice, the incident rod and the transmission rod;

[0008] The ice-making device includes a silicone container, a cylindrical container, a top cover, a base, an insulation layer, and an insulation lid. The silicone container is a cylindrical container structure with an open top, which is mounted on the base. The cylindrical container is a circular tubular structure with open top and bottom, the inner diameter of the cylindrical container is the same as the outer diameter of the silicone container, and the heights of the cylindrical container and the silicone container are the same. The cylindrical container is fitted around the outer periphery of the silicone container, and the insulation layer covers the outer wall of the cylindrical container.

[0009] The top cover is positioned above the cylindrical container, and the top cover has a vertical pressure relief hole that communicates with the inner cavity of the silicone container; the heat-insulating cover is positioned on the top cover.

[0010] As a supplement to the technical solution of the present invention, the ice-making device also includes bolts and nuts. Through holes are provided on the top cover and the base located on the outside of the cylindrical container. The bolts pass through the through holes on the top cover and the base and are screwed to the nuts. The top cover and the base are connected by the nuts and bolts, and the top cover and the base are clamped on the silicone container by the bolts.

[0011] As a supplement to the technical solution of this invention, the cryogenic testing device includes a Dewar flask, a self-pressurizing liquid nitrogen pump, a liquid nitrogen pump valve, a pressure gauge, a cryogenic conduit, and an insulated cylinder. The self-pressurizing liquid nitrogen pump is connected to the Dewar flask via a pipeline. The pipeline connecting the self-pressurizing liquid nitrogen pump and the Dewar flask is equipped with a liquid nitrogen pump valve and a pressure gauge. The cryogenic conduit connects the Dewar flask to the chamber. The inlet of the cryogenic conduit is connected to the self-pressurizing liquid nitrogen pump, and the outlet of the cryogenic conduit is located inside the chamber.

[0012] Rod holes are provided on the left and right walls of the box. The insulation cylinder is a circular tubular structure. There are two sets of insulation cylinders, which are respectively set on the left and right walls of the box. The insulation cylinder is connected to the rod holes. Insulation cotton is provided on the inner circumference of the end of the insulation cylinder away from the box. The ends of the incident rod and the transmission rod pass through the insulation cylinder and the rod holes in sequence and extend into the box.

[0013] The bottom of the chamber is equipped with a chamber lifting bracket, which can adjust the height of the chamber. Inside the chamber is a sample holder, which includes a bottom support column, a sample support column, and a height adjustment knob. The bottom support adjustment tube is a circular tubular structure. The lower part of the sample support column is located inside the cavity of the bottom support adjustment tube. A screw hole is opened on the side wall of the bottom support adjustment tube. The end of the height adjustment knob is screwed into the screw hole on the bottom support adjustment tube and rests against the side wall of the sample support column. The upper end of the sample support column is equipped with a V-shaped bracket for placing the sample.

[0014] As a supplement to the technical solution of the present invention, the box lifting bracket includes a fine adjustment knob, a fixed support, a lifting support, a guide rail, a rotating shaft, a lifting and rotating component, and a lifting column.

[0015] The fixed support includes a bottom fixed plate, a fixed block, and a base. The fixed block and the base are both disposed on the bottom fixed plate. The fixed block is provided with a threaded through hole for the fine adjustment knob to pass through. The fine adjustment knob is screwed into the threaded through hole of the fixed block. The end of the fine adjustment knob passes through the threaded through hole on the fixed block and is located on the rear side of the fixed block. The length of the end of the fine adjustment knob protruding from the threaded through hole can be adjusted by rotating the fine adjustment knob.

[0016] The lifting support includes a slide top plate and a slide. The slide top plate is located at the upper end of the slide and is fixedly connected to the housing. The slide is located on one side of the base and fits against the base. A guide rail is provided between the slide and the base.

[0017] The lifting and rotating component includes a first arm, a second arm, and an annular ring. The annular ring has a ring structure, and one end of the first and second arms along their length is connected to the outer periphery of the annular ring. A rotating shaft is provided on the base of the fixed support. The lifting and rotating component is fitted onto the rotating shaft through its annular ring and can rotate relative to the rotating shaft. The lifting and rotating component is located behind the fixed block of the fixed support. The end of the fine-tuning knob is in contact with the first arm of the lifting and rotating component. A lifting support column is provided on the lower end surface of the slide top plate of the lifting support. The lifting support column is located above the second arm of the lifting and rotating component. By pushing the first arm of the lifting and rotating component with the end of the fine-tuning knob, the lifting and rotating component rotates, causing the second arm to flip upward and lift the lifting support column on the slide top plate, thus driving the lifting support to move upward along the guide rail.

[0018] As a supplement to the technical solution of the present invention, the box body is a box structure formed by an upper cover plate, a front cover plate, a rear side plate, a left side plate, a right side plate, and a bottom plate. The upper cover plate is provided with a top window, and the front cover plate is provided with a front window. The rear end of the upper cover plate is connected to the upper end of the rear side plate by a hinge. A handle is provided on the upper surface of the upper cover plate. The side surfaces of the left and right side plates near the inside of the box body are provided with sliding grooves. The front cover plate is inserted between the left and right side plates through the sliding grooves on the left and right side plates, so that the left edge of the front cover plate is located in the sliding groove on the left side, and the right edge of the front cover plate is located in the sliding groove on the right side plate. A handle is provided on the front end surface of the front cover plate, and the lower end surface of the upper cover plate is in contact with the upper end surface of the front cover plate. Insulation cotton is provided on the bottom surface of the upper cover plate at the contact positions with the front cover plate, rear side plate, left side plate, and right side plate to improve the sealing between the upper ends of the front cover plate, rear side plate, left side plate, and right side plate and the upper cover plate.

[0019] As a supplement to the technical solution of the present invention, a temperature monitoring system is also included. The temperature monitoring system includes a temperature sensor, a temperature display, and a temperature alarm. The temperature sensor is installed inside the chamber to detect the temperature inside the chamber. The temperature display is installed outside the chamber. The temperature sensor is connected to the temperature display to transmit temperature signals to the temperature display, which displays the temperature value. The temperature alarm is connected to the temperature display and sounds an alarm when the temperature exceeds the set temperature.

[0020] This invention also discloses a method for using a low-temperature testing system applied to the Hopkinson bar test, comprising the following steps:

[0021] S1 uses an ice-making device to prepare bubble-free cylindrical pure ice;

[0022] S2 The incident rod and transmission rod of the Hopkinson rod test device are subjected to a -20℃ low temperature freezing treatment for 48 hours. After the temperature stabilizes, the box of the low temperature test device is assembled with the Hopkinson rod test device. The box lifting bracket at the bottom of the box is adjusted so that the axis of the incident rod, transmission rod, insulation cylinder and rod hole of the Hopkinson rod test device are on the same straight line.

[0023] S3 Adjust the height adjustment knob on the sample holder to ensure that when the bubble-free cylindrical pure ice is placed on the sample holder, the axis of the sample is on the same straight line as the axis of the incident rod and the transmission rod, and turn on the light strip.

[0024] S4 Close the chamber door, set the temperature threshold of the temperature alarm, turn on the self-pressurizing liquid nitrogen pump, so that the liquid nitrogen in the Dewar bottle can continuously and slowly enter the pipeline and be evenly sprayed into the chamber through the spraying device, so that the temperature inside the chamber can drop rapidly. When the temperature inside the chamber is stable below -40℃, turn off the liquid nitrogen pump.

[0025] S5 Quickly open the top cover of the chamber, place the bubble-free cylindrical pure ice on the sample holder inside the chamber, and then close the top cover;

[0026] S6 When the temperature inside the chamber reaches the range of -25℃ to -15℃, the impact test is started using the Hopkinson bar test device, and the incident bar impacts a cylinder of pure ice without bubbles.

[0027] After the S7 test is completed, open the top cover and the front cover to clean and collect the bubble-free cylindrical pure ice fragments inside the chamber.

[0028] As a supplement to the technical solution of the present invention, step S1 includes:

[0029] S1.1 Remove the top cover and insulation cover from the ice-making device. Apply Vaseline to the inner wall of the silicone container of the ice-making device, as well as the upper surface of the silicone container and the cylindrical container.

[0030] S1.2 Boil the purified water and cool it to room temperature. Use a syringe to draw up the purified water and place the tip of the syringe needle against the bottom wall of the silicone mold. Slowly inject the purified water to prevent air from being mixed in during the injection process. When the purified water level in the silicone mold reaches a certain height, keep the syringe needle below the horizontal plane during the water injection process. Stop injecting water when the purified water level reaches 95% of the height of the silicone mold. During the entire water injection process, air bubbles will be generated on the inner wall of the silicone mold. Use the syringe needle to puncture the air bubbles.

[0031] S1.3 After water filling is completed, use bolts and nuts to install the top cover on the upper end of the silicone container, and make the lower end of the top cover fit against the upper end of the silicone container and the cylindrical container. Then place the heat insulation cover on the top cover.

[0032] S1.4 Place the entire ice-making device at the bottom of a -15℃ freezer, where purified water freezes into bubble-free cylindrical pure ice in a silicone mold.

[0033] Beneficial effects: The ice-making structure provided by this invention is simple, quick to operate, economical and practical, with low requirements for laboratory conditions, and can prepare bubble-free pure ice samples; the low-temperature test device provided by this invention uses liquid nitrogen spray cooling, which is economical and environmentally friendly, has high cooling efficiency, and high safety due to its closed spraying. This device provides good low-temperature conditions for a low-temperature test system applied to the Hopkinson bar test, which can improve the accuracy of test data. Attached Figure Description

[0034] Figure 1 This is a three-dimensional structural diagram of the ice-making device of the present invention.

[0035] Figure 2 This is a cross-sectional structural schematic diagram of the ice-making device of the present invention.

[0036] Figure 3 This is a three-dimensional structural diagram of the low-temperature testing device of the present invention.

[0037] Figure 4 This is a rear view schematic diagram of the low-temperature testing device of the present invention.

[0038] Figure 5 This is a cross-sectional structural diagram of the low-temperature testing device of the present invention.

[0039] Figure 6 This is a three-dimensional structural diagram of the box lifting support of the present invention.

[0040] Figure 7 This is a side view of the lifting bracket for the housing of the present invention.

[0041] Figure 8 This is a top view of the lifting bracket structure of the box body of the present invention.

[0042] Figure 9 This is a schematic diagram of the lifting and rotating component structure of the present invention.

[0043] Figure 10 This is a schematic diagram of the main structure of the low-temperature testing system of the present invention.

[0044] In the diagram: 1. Ice-making device; 101. Silicone container; 102. Cylindrical container; 103. Top cover; 104. Base; 105. Insulation layer; 106. Insulation cover; 107. Pressure relief hole; 108. Bolt; 109. Nut.

[0045] 2. Cryogenic testing apparatus, 201. Dewar flask, 202. Self-pressurizing liquid nitrogen pump, 203. Liquid nitrogen pump valve, 204. Pressure gauge, 205. Cryogenic conduit, 206. Chamber, 207. Chamber lifting bracket, 208. Sample holder, 209. Bottom support column, 210. Sample support column, 211. Height adjustment knob, 212. Top cover plate, 213. Front cover plate, 214. Rear side plate, 215. Left side plate, 216. Right side plate, 217. Bottom plate, 218. Top window, 219. Front window, 220. Temperature sensor 221. Sensor; 222. Temperature display; 223. Temperature alarm; 224. Rod hole; 225. LED strip; 226. Fixed support; 227. Lifting support; 228. Guide rail; 229. Rotating shaft; 230. Lifting rotating component; 231. Lifting support column; 232. Bottom fixing plate; 233. Fixing block; 234. Base; 235. Fine adjustment knob; 236. First support arm; 237. Second support arm; 238. Annular ring; 239. Slide top plate; 240. Slide; 241. Insulation cylinder; 242. Impact rod support;

[0046] 301. Incident rod, 302. Transmission rod, 303. Slide rail support, 304. Slide rail. Detailed Implementation

[0047] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0048] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0049] like Figures 1 to 10 As shown, the present invention discloses a low-temperature testing system for the Hopkinson bar test, including a Hopkinson test device. The Hopkinson test device includes an incident rod 301, a transmission rod 302, a slide rail support 303, and a slide rail 304. The slide rail 304 is disposed on the slide rail support 303. The bottom of the incident rod 301 and the transmission rod 302 are provided with supports that cooperate with the slide rail and can slide on the slide rail 304.

[0050] Also includes:

[0051] Ice-making device 1, which is used to prepare bubble-free cylindrical pure ice.

[0052] The low-temperature test device 2 is used to fix bubble-free cylindrical pure ice between the incident rod 301 and the transmission rod 302 of the Hopkinson test device, and to provide a low-temperature environment of -25℃ to -15℃ for the bubble-free cylindrical pure ice.

[0053] The ice-making device 1 includes a silicone container 101, a cylindrical container 102, a top cover 103, a base 104, an insulation layer 105, and an insulation cover 106. The silicone container 101 is a cylindrical container structure with an opening at the top, and it is mounted on the base 104.

[0054] The top cover 103 is disposed above the cylindrical container 102. The top cover 103 is provided with a vertical pressure relief hole 107 that communicates with the inner cavity of the silicone container 101, which is used to relieve pressure during the freezing process of the water in the silicone container 101.

[0055] The cylindrical container 102 is a circular tubular structure with openings at the top and bottom. The inner diameter of the cylindrical container 102 is the same as the outer diameter of the silicone container 101, and the heights of the cylindrical container 102 and the silicone container 101 are the same. The cylindrical container 102 is fitted around the outer circumference of the silicone container 101 and is used to shape the silicone container 101, resisting the frost heave force generated during the freezing process of water into ice, and maintaining the standard shape of the ice.

[0056] The insulation layer 105 covers the outer wall of the cylindrical container 102 for heat preservation. The insulation cover 106 is disposed on the top cover 103. The insulation cover 106 seals the upper outlet of the pressure relief hole 107 by its own weight. When the water in the silicone container 101 freezes, the volume and pressure increase due to the freezing of water, causing the gas in the silicone container 101 to be compressed and released through the pressure relief hole 107. When the pressure in the silicone container 101 reaches a critical value, the gas and water in the silicone container 101 will push up the insulation cover 106 and discharge it from the gap between the insulation cover 106 and the top cover 103, thus achieving the purpose of pressure relief. Both the insulation layer 105 and the insulation cover 106 are made of insulation cotton, which reduces heat exchange between the top and side walls of the silicone container 101 and the outside environment. This allows the water in the silicone container 101 to gradually cool from the bottom down when the entire device is placed in a low-temperature environment. During the cooling process, the water gradually forms ice and expands to the top of the mold. During this process, the air and water in the silicone container are discharged through the pressure relief hole 107 and through the gap between the insulation cover 106 and the top cover 103. Under the combined effect of the freezing heave force and the pressure relief hole 107, the water in the silicone container 101 freezes into a standard cylindrical, bubble-free pure ice. The advantage of using the bottom unidirectional freezing method is that the overall pressure relief effect is good, which can avoid a large number of air bubbles inside the frozen ice. The dynamic impact test can be performed by simply grinding the small protrusions at the pressure relief hole of the ice sample. In the alternative to traditional freezing methods, no insulation is used. Water freezes from the top and bottom of the container and the outer wall, while freezing towards the center of the container. This results in a large number of air bubbles in the center of the frozen ice column, a bulging top, and even internal compression and rupture.

[0057] As a preferred embodiment of the above technical solution, the ice-making device 1 further includes a bolt 108 and a nut 109. The top cover 103 and the base 104 located outside the cylindrical container 102 are provided with through holes. The bolt 108 passes through the through holes on the top cover 103 and the base 104 and is screwed to the nut 109. The top cover 103 and the base 104 are connected by the nut 109 and the bolt 108, so that the top cover 103 and the base 104 can clamp the silicone container 101. The clamping action and the pressure relief action of the pressure relief hole 107 cooperate with each other to avoid the damage to the integrity of the ice caused by the frost heave force generated during the freezing process of water into ice, and always maintain the standard shape of the ice.

[0058] As a preferred embodiment of the above technical solution, the cryogenic testing device 2 includes a Dewar flask 201 for storing liquid nitrogen, a self-pressurizing liquid nitrogen pump 202 for extracting liquid nitrogen spray, a liquid nitrogen pump valve 203, a pressure gauge 204 for monitoring pressure, a cryogenic conduit 205 for transmitting liquid nitrogen, and an insulated cylinder 240 for reducing heat exchange between the incident rod and the transmission rod and the ambient temperature. The self-pressurizing liquid nitrogen pump 202 is connected to the Dewar flask 201 through a pipeline. The pipeline connecting the self-pressurizing liquid nitrogen pump 202 and the Dewar flask 201 is equipped with a liquid nitrogen pump valve 203 and a pressure gauge 204. The cryogenic conduit 205 is used to connect the Dewar flask 201 to the chamber 206. The inlet of the cryogenic conduit 205 is connected to the self-pressurizing liquid nitrogen pump 202, and the outlet of the cryogenic conduit 205 is located inside the chamber 206. The vaporized liquid nitrogen is discharged from the chamber 206 through the cryogenic conduit 205. The self-pressurizing liquid nitrogen pump 202 utilizes the physical property that liquid nitrogen is extremely easy to vaporize. It adopts a negative pressure liquid suction structure to cause a small amount of liquid nitrogen in the Dewar flask 201 to rapidly vaporize in the vaporization chamber, generating a very low pressure ≤0.4Mpa, which automatically discharges the liquid nitrogen from the liquid nitrogen container. The gaseous liquid nitrogen is sprayed into the box 206 through the cryogenic conduit 205, causing the temperature inside the box 206 to drop instantaneously.

[0059] The left and right walls of the housing 206 are provided with rod holes 223 for Hopkinson test rods to pass through. The housing 206 is positioned between the incident rods 301 and the transmission rods 302 of the two Hopkinson test devices. Insulation cotton is provided on the inner circumference of the rod holes 223.

[0060] The bottom of the box 206 is provided with a box lifting bracket 207, which is used to adjust the height and left and right position of the box 206 so that the front end of the Hopkinson rock rod can pass smoothly through the rod hole 223 on the box 206.

[0061] The incident rod 301 and the transmission rod 302 are made of rock and are slender cylinders with a specification of Ф50mm×1000mm. There are no obvious joints or fault structures on the rock rods.

[0062] As a preferred technical solution of the present invention, the box lifting bracket 207 includes a fine adjustment knob 234, a fixed support 225, a lifting support 226, a guide rail 227, a rotating shaft 228, a lifting and rotating component 229, and a lifting support column 230.

[0063] The fixed support 225 includes a bottom fixed plate 231, a fixed block 232, and a base 233. The fixed block 232 and the base 233 are both disposed on the bottom fixed plate 231. The fixed block 232 is provided with a threaded through hole for the fine adjustment knob 234 to pass through. The fine adjustment knob 234 is a cylindrical rod structure with threads on its outer periphery. The fine adjustment knob 234 is screwed into the threaded through hole of the fixed block 232. The end of the fine adjustment knob 234 passes through the threaded through hole on the fixed block 232 and is located on the rear side of the fixed block 232. The length of the end of the fine adjustment knob 234 extending out of the threaded through hole can be adjusted by rotating the fine adjustment knob 234.

[0064] The lifting support 226 includes a slide top plate 238 and a slide 239. The slide top plate 238 is disposed on the upper end of the slide 239 and is fixedly connected to the housing. The slide 239 is disposed on one side of the base 233 and is fitted against the base 233. A guide rail 227 is provided between the slide 239 and the base 233. The guide rail 227 is a cross roller guide rail, which ensures that the vertical lifting of the slide 239 along the cross roller guide rail 227 is more stable and precise.

[0065] The lifting and rotating component 229 includes a first arm 235, a second arm 236, and an annular ring 237. The first arm 235 and the second arm 236 are both long straight rod structures, and the annular ring 237 is an annular structure. One end of the first arm 235 and the second arm 236 in the length direction is connected to the outer periphery of the annular ring 237, and the first arm 235, the second arm 236, and the annular ring 237 form a V-shaped structure.

[0066] The base 233 of the fixed support 225 is provided with a rotating shaft 228. The lifting and rotating component 229 is sleeved on the rotating shaft 228 through its annular ring 237 and can rotate relative to the rotating shaft 228. The lifting and rotating component 229 is located behind the fixed block 232 of the fixed support 225. The end of the fine adjustment knob 234 is in contact with the first arm 235 of the lifting and rotating component 229. By tightening the fine adjustment knob 234, the end of the fine adjustment knob 234 pushes the first arm 235 of the lifting and rotating component 229, so that the lifting and rotating component 229 rotates along the rotating shaft 228.

[0067] The lower end surface of the slide top plate 238 of the lifting support 226 is provided with a lifting column 230. The lifting column 230 is located above the second arm 236 of the lifting and rotating component 229. When the fine adjustment knob 234 pushes the first arm 235 of the lifting and rotating component 229 to rotate the lifting and rotating component 229, the second arm 236 flips upward and lifts the lifting column 230 on the slide top plate 238, causing the lifting support 226 to move upward along the guide rail 227.

[0068] Through the above structural design, the height of the box lifting bracket 207 can be adjusted with high precision, ensuring that the lifting support 226 moves smoothly up and down along the fixed support 225.

[0069] As a preferred embodiment of the present invention, the housing 206 is provided with a sample holder 208 inside. The sample holder 208 is used to support the sample and adjust the height of the sample. It can align the axis of the sample with the axis of the Hopkinson rod according to the sample diameter. The sample holder 208 includes a bottom support column 209, a sample support column 210, and a height adjustment knob 211. The bottom support adjustment tube is a circular tubular structure, and the lower part of the sample support column 210 is a cylindrical structure. The lower part of the sample support column 210 is located inside the cavity of the bottom support adjustment tube. A screw hole is provided on the side wall of the bottom support adjustment tube. The height adjustment knob 211 is a screw-like structure. The end of the height adjustment knob 211 is screwed into the screw hole on the bottom support adjustment tube and rests against the side wall of the sample support column 210. The length of the sample support column 210 inside the bottom support adjustment tube is adjusted by the height adjustment knob 211. The upper end of the sample support column 210 is provided with a V-shaped bracket for placing the sample.

[0070] As a preferred embodiment, the insulating cylinder 240 is a circular tubular structure. Two sets of insulating cylinders 240 are respectively located on the left and right walls of the housing 206. The insulating cylinder 240 communicates with the rod hole 223. The inner diameter of the insulating cylinder 240 is the same as the inner diameter of the impact rod hole 223, and slightly larger than the diameter of the rock rod. Insulating cotton is provided on the inner circumference of the end of the insulating cylinder 240 away from the housing, which can alleviate cold air leakage while ensuring no friction between the impact rod and the inner ring of the insulating cylinder. When assembling the Hopkinson rod testing device with the housing, the ends of the incident rod 301 and the transmission rod 302 pass through the insulating cylinder 240 and the left rod hole 223 in sequence and extend into the housing. The purpose of the insulating cylinder 240 is to reduce heat exchange between the incident rod 301 and the transmission rod 302 and the environment. Before the test begins, the incident rod 301 and the transmission rod 302 should be subjected to low-temperature treatment.

[0071] As a preferred technical solution of the above embodiments, when the cylinder is not added to the outside of the rod hole 223, thermal insulation cotton is added to the inner circumference of the rod hole 223 for low-temperature testing when the impact rod is at room temperature.

[0072] As a preferred embodiment of the present invention, the box 206 is a structure formed by an upper cover plate 212, a front cover plate 213, a rear side plate 214, a left side plate 215, a right side plate 216, and a bottom plate 217. The bottom plate 217 is located at the bottom of the box 206, the upper cover plate 212 is located at the top of the box 206, the front cover plate 213 is located at the front of the box 206, the left side plate 215 is located on the left side of the box 206, the right side plate 216 is located on the right side of the box 206, and the rear side plate 214 is located at the rear of the box 206. The outer dimensions of the box 206 are 400mm*350mm*300mm. The plates constituting the box 206 are made of sandwich materials. The inner and outer surfaces are made of 1mm thick 304 stainless steel with poor thermal conductivity and resistance to rust, and the inner sandwich layer is made of 8mm thick rigid polyurethane foam with good thermal insulation.

[0073] The rear end of the upper cover plate 212 is connected to the upper end of the rear side plate 214 by a hinge. A handle is provided on the upper surface of the upper cover plate 212. By pulling the handle upward, the upper cover plate 212 can be flipped upward around the hinge as the axis.

[0074] The left side panel 215 and the right side panel 216 are both provided with sliding grooves on their side surfaces near the interior of the housing 206. The front cover plate 213 is inserted between the left side panel 215 and the right side panel 216 through the sliding grooves on the left side panel 215 and the right side panel 216, so that the left edge of the front cover plate 213 is located in the sliding groove on the left side, and the right edge of the front cover plate 213 is located in the sliding groove on the right side panel 216. The front end face of the front cover plate 213 is provided with a handle, which is used to insert and pull the front cover plate 213 between the left side panel 215 and the right side panel 216, facilitating the collection of fragments after the test. The lower end face of the upper cover plate 212 is in contact with the upper end face of the front cover plate 213, and after assembly, the upper end of the front cover plate 213 of the housing 206 is in contact with the lower end face of the upper cover plate 212.

[0075] As a preferred technical solution of the above embodiments, in order to balance observation and image acquisition, the upper cover plate 212 is provided with a top window 218, and the front cover plate 213 is provided with a front window 219. Both the top window 218 and the front window 219 are made of wear-resistant and anti-reflective AG glass. Anti-fogging agent is periodically applied to the glass to improve the clarity of high-speed camera shots under photographic lighting. The top window 218 is used by the high-speed camera to capture the internal experimental process of the chamber 206. A light strip 224 is provided around the top window 218 on the lower surface of the upper cover plate 212 to assist observation and enhance image clarity. The front window 219 allows the test personnel to observe the experimental conditions inside the chamber.

[0076] As a preferred embodiment, insulation cotton is provided on the lower bottom surface of the upper cover plate 212 at the contact points with the front cover plate 213, rear side plate 214, left side plate 215, and right side plate 216, and at the contact points between the insulation cylinder 240 and the box body 206. The insulation cotton improves the sealing between the upper ends of the front cover plate 213, rear side plate 214, left side plate 215, and right side plate 216 and the upper cover plate 212, reducing heat exchange between the inside of the box body 206 and the external environment. All joints between the remaining plates are filled with heat-insulating potting compound to enhance sealing and heat insulation.

[0077] As a preferred embodiment of the present invention, the low-temperature testing device 2 further includes a temperature monitoring system. The temperature monitoring system includes a temperature sensor 220, a temperature display 221, and a temperature alarm 222. The temperature sensor 220 is disposed inside the chamber 206 and is used to detect the temperature inside the chamber 206. The temperature display 221 is disposed outside the chamber 206. The temperature sensor 220 is connected to the temperature display 221 and is used to transmit a temperature signal to the temperature display 221, which displays the temperature value. The temperature alarm 222 is connected to the temperature display 221 and will sound an alarm when the temperature exceeds a set temperature.

[0078] The temperature alarm 222 serves only as an alert and includes three lights: red, yellow, and green. The alarm can be set to a temperature threshold of room temperature to -196℃. The optimal test temperature in this embodiment is -20℃. It can be set to illuminate only red when the temperature inside the chamber 206 is below -40℃, only yellow when it is between -40℃ and -25℃, and only green when it is between -25℃ and -15℃.

[0079] The present invention also discloses a method for using the above system, comprising the following steps:

[0080] S1. Preparing bubble-free cylindrical pure ice using ice-making apparatus 1, specifically including the following steps:

[0081] S1.1 Remove the top cover 103 and the insulation cover 106 from the ice-making device 1. Apply Vaseline to the inner wall of the silicone container 101 of the ice-making device 1 to prevent ice columns from sticking to the inner wall of the silicone container 101 after water freezes. Also apply Vaseline to the upper surfaces of the silicone container 101 and the cylindrical container 102 to improve the sealing effect between the top cover 103 and the silicone container 101 and the cylindrical container 102.

[0082] S1.2 Boil the purified water and cool it to room temperature. Use a syringe to draw up the purified water and place the tip of the syringe needle against the bottom wall of the silicone mold. Slowly inject the purified water to prevent air from being mixed in during the injection process. When the purified water level in the silicone mold reaches a certain height, keep the syringe needle below the horizontal plane during the water injection process. Stop injecting water when the purified water level reaches 95% of the height of the silicone mold. During the entire water injection process, air bubbles will be generated on the inner wall of the silicone mold. Use the syringe needle to puncture the air bubbles.

[0083] S1.3 After water filling is completed, use bolts 108 and nuts 109 to install the top cover 103 on the upper end of the silicone container 101, and make the lower end face of the top cover 103 fit against the upper end face of the silicone container 101 and the cylindrical container 102. Then place the heat preservation cover 106 on the top cover 103.

[0084] S1.4 Place the entire ice-making device 1 into the bottom of a -15℃ freezer, where purified water freezes into bubble-free cylindrical pure ice in a silicone mold.

[0085] The S2 low-temperature test apparatus 2's housing 206 is assembled with the Hopkinson bar test apparatus, so that the housing lifting bracket 207 of the low-temperature test apparatus 206 is set on the slide rail 304 of the Hopkinson bar test apparatus. The incident rod 301 and the transmission rod 302 of the Hopkinson bar test apparatus undergo a 48-hour -20℃ low-temperature freezing pretreatment. The incident rod 301 and the transmission rod 302 are then removed and quickly placed on the rod support 24 of the Hopkinson bar test apparatus. 1. The incident rod 301 extends into the box 206 from the rod hole 223 on the left side plate 215 of the box 206, and the transmission rod 302 extends into the box 206 from the rod hole 223 on the right side plate 216 of the box 206. The box lifting bracket 207 at the bottom of the box 206 is adjusted so that the axes of the incident rod 301, transmission rod 302, heat insulation cylinder 240 and rod hole 223 of the box 206 are on the same straight line.

[0086] S3 Adjust the height adjustment knob 211 on the sample holder 208 to ensure that when the bubble-free cylindrical pure ice is placed on the sample holder 208, the axis of the sample is on the same straight line as the axis of the incident rod 301 and the transmission rod 302. Turn on the light strip 224 switch to increase the brightness inside the box 206.

[0087] S4 Close the chamber door, set the temperature threshold of the temperature alarm 222, put on low-temperature gloves, turn on the self-pressurized liquid nitrogen pump 202, so that the liquid nitrogen in the Dewar bottle 201 slowly and continuously enters the pipeline and is evenly sprayed into the chamber through the spraying device, so that the temperature inside the chamber drops rapidly. When the temperature inside the chamber 206 is stable below -40℃, turn off the liquid nitrogen pump.

[0088] S5 Quickly open the top cover 212 of the chamber 206, place the bubble-free cylindrical pure ice on the sample holder 208 inside the chamber 206, and then close the top cover 212.

[0089] S6 When the temperature inside chamber 206 reaches the temperature range of -25℃ to -15℃, the impact test is started using the Hopkinson bar test device, and the incident rod 301 impacts the bubble-free cylindrical pure ice.

[0090] After the S7 test is completed, open the top cover 212, open the front cover 213, clean the bubble-free cylindrical pure ice fragments in the chamber 206, close the front cover 213 and the top cover, and process the test data.

[0091] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A low-temperature testing system for the Hopkinson bar test, comprising a Hopkinson bar testing device, wherein the Hopkinson bar testing device includes an incident bar (301) and a transmission bar (302), characterized in that, Also includes: An ice-making device (1) is used to prepare bubble-free cylindrical pure ice; Low temperature test device (2), the low temperature test device (2) is used to fix bubble-free cylindrical pure ice between the incident rod (301) and the transmission rod (302) of the Hopkinson rod test device, and to provide a low temperature environment of -25℃ to -15℃ for the bubble-free cylindrical pure ice, the incident rod (301) and the transmission rod (302); The ice-making device (1) includes a silicone container (101), a cylindrical container (102), a top cover (103), a base (104), an insulation layer (105), and an insulation cap (106). The silicone container (101) is a cylindrical container structure with an opening at the top, which is mounted on the base (104). The cylindrical container (102) is a circular tubular structure with openings at the top and bottom. The inner diameter of the cylindrical container (102) is the same as the outer diameter of the silicone container (101), and the height of the cylindrical container (102) is the same as that of the silicone container (101). The cylindrical container (102) is fitted around the outer periphery of the silicone container (101), and the insulation layer (105) covers the outer wall of the cylindrical container (102). The top cover (103) is disposed above the cylindrical container (102), and the top cover (103) is provided with a vertical pressure relief hole (107) communicating with the inner cavity of the silicone container (101); the heat preservation cover (106) is disposed on the top cover (103); The ice-making device (1) also includes bolts (108) and nuts (109). The top cover (103) and the base (104) located outside the cylindrical container (102) are provided with through holes. The bolts (108) pass through the through holes on the top cover (103) and the base (104) and are screwed to the nuts (109). The top cover (103) and the base (104) are connected by the nuts (109) and the bolts (108). The top cover (103) and the base (104) are clamped by the bolts (108). The cryogenic testing device (2) includes a Dewar flask (201), a self-pressurizing liquid nitrogen pump (202), a liquid nitrogen pump valve (203), a pressure gauge (204), a cryogenic conduit (205), and an insulated cylinder (240). The self-pressurizing liquid nitrogen pump (202) is connected to the Dewar flask (201) via a pipeline. The pipeline connecting the self-pressurizing liquid nitrogen pump (202) and the Dewar flask (201) is equipped with a liquid nitrogen pump valve (203) and a pressure gauge (204). The cryogenic conduit (205) is used to connect the Dewar flask (201) to the chamber (206). The inlet of the cryogenic conduit (205) is connected to the self-pressurizing liquid nitrogen pump (202), and the outlet of the cryogenic conduit (205) is located inside the chamber (206). The left and right walls of the box (206) are provided with rod holes (223). The heat-insulating cylinder (240) is a circular tubular structure. There are two sets of heat-insulating cylinders (240) and they are respectively set on the left and right walls of the box (206). The heat-insulating cylinder (240) is connected to the rod hole (223). The inner circumference of the end of the heat-insulating cylinder (240) away from the box (206) is provided with heat-insulating cotton. The ends of the incident rod (301) and the transmission rod (302) pass through the heat-insulating cylinder (240) and the rod hole (223) in sequence and extend into the box. The bottom of the box (206) is provided with a box lifting bracket (207), which can adjust the height of the box (206); the box (206) is provided with a sample holder (208) inside, the sample holder (208) includes a bottom support column (209), a sample support column (210), and a height adjustment knob (211). The bottom support adjustment tube is a circular tubular structure. The lower part of the sample support column (210) is located in the cavity of the bottom support adjustment tube. A screw hole is opened on the side wall of the bottom support adjustment tube. The end of the height adjustment knob (211) is screwed into the screw hole on the bottom support adjustment tube and rests against the side wall of the sample support column (210). The upper end of the sample support column (210) is provided with a V-shaped bracket for placing the sample.

2. The low-temperature testing system for the Hopkinson bar test according to claim 1, characterized in that, The box lifting bracket (207) includes a fine adjustment knob (234), a fixed support (225), a lifting support (226), a guide rail (227), a rotating shaft (228), a lifting rotating component (229), and a lifting support column (230). The fixed support (225) includes a bottom fixed plate (231), a fixed block (232), and a base (233). The fixed block (232) and the base (233) are both set on the bottom fixed plate (231). The fixed block (232) is provided with a threaded through hole for the fine adjustment knob (234) to pass through. The fine adjustment knob (234) is screwed into the threaded through hole of the fixed block (232). The end of the fine adjustment knob (234) passes through the threaded through hole on the fixed block (232) and is located on the rear side of the fixed block (232). The length of the end of the fine adjustment knob (234) extending out of the threaded through hole is adjusted by rotating the fine adjustment knob (234). The lifting support (226) includes a slide top plate (238) and a slide (239). The slide top plate (238) is located at the upper end of the slide (239) and is fixedly connected to the housing. The slide (239) is located on one side of the base (233) and is fitted against the base (233). A guide rail (227) is provided between the slide (239) and the base (233). The lifting and rotating component (229) includes a first arm (235), a second arm (236), and an annular ring (237). The annular ring (237) has a ring structure. One end of the first arm (235) and the second arm (236) in the length direction is connected to the outer periphery of the annular ring (237). A rotating shaft (228) is provided on the base (233) of the fixed support (225). The lifting and rotating component (229) is sleeved on the rotating shaft (228) through its annular ring (237) and can rotate relative to the rotating shaft (228). The lifting and rotating component (229) is located behind the fixed block (232) of the fixed support (225). The fine adjustment knob ( The end of 234 is in contact with the first arm (235) of the lifting and rotating component (229); the lower end surface of the slide plate (238) of the lifting support (226) is provided with a lifting column (230), the lifting column (230) is located above the second arm (236) of the lifting and rotating component (229), the first arm (235) of the lifting and rotating component (229) is pushed by the end of the fine adjustment knob (234) to make the lifting and rotating component (229) rotate, so that the second arm (236) flips upward and lifts the lifting column (230) on the slide plate (238), and drives the lifting support (226) to move upward along the guide rail (227).

3. The low-temperature testing system for the Hopkinson bar test according to claim 1, characterized in that, The box (206) is a box structure formed by an upper cover plate (212), a front cover plate (213), a rear side plate (214), a left side plate (215), a right side plate (216), and a bottom plate (217). The upper cover plate (212) is provided with a top window (218), and the front cover plate (213) is provided with a front window (219). The rear end of the upper cover plate (212) is connected to the upper end of the rear side plate (214) by a hinge. The upper end of the upper cover plate (212) is provided with a handle. The side surfaces of the left side plate (215) and the right side plate (216) near the inside of the box (206) are provided with sliding grooves. The front cover plate (213) is inserted through the sliding grooves on the left side plate (215) and the right side plate (216). Insert it between the left side plate (215) and the right side plate (216), so that the left edge of the front cover plate (213) is located in the groove on the left side, and the right edge of the front cover plate (213) is located in the groove on the right side plate (216); the front end face of the front cover plate (213) is provided with a handle, and the lower end face of the upper cover plate (212) is in contact with the upper end face of the front cover plate (213); the lower bottom surface of the upper cover plate (212) is provided with heat insulation cotton at the contact position of the front cover plate (213), the rear side plate (214), the left side plate (215), and the right side plate (216), thereby improving the sealing between the upper end of the front cover plate (213), the rear side plate (214), the left side plate (215), the right side plate (216) and the upper cover plate (212).

4. The low-temperature testing system for the Hopkinson bar test according to claim 2, characterized in that, It also includes a temperature monitoring system, which includes a temperature sensor (220), a temperature display (221), and a temperature alarm (222). The temperature sensor (220) is installed inside the enclosure (206) to detect the temperature inside the enclosure (206). The temperature display (221) is installed outside the enclosure (206). The temperature sensor (220) is connected to the temperature display (221) to transmit temperature signals to the temperature display (221), which displays the temperature value. The temperature alarm (222) is connected to the temperature display (221), and the temperature alarm (222) will sound an alarm when the temperature exceeds the set temperature.

5. The method of using the low-temperature testing system for the Hopkinson bar test according to claim 4, characterized in that, Includes the following steps: S1 uses an ice-making device (1) to prepare bubble-free cylindrical pure ice; S2 The incident rod (301) and transmission rod (302) of the Hopkinson rod test device are subjected to a -20℃ low temperature freezing pretreatment for 48 hours. Then, the box (206) of the low temperature test device (2) is assembled with the Hopkinson rod test device. The box lifting bracket (207) at the bottom of the box (206) is adjusted so that the axis of the incident rod (301), transmission rod (302), heat preservation cylinder (240) and rod hole (223) of the box (206) of the Hopkinson rod test device are on the same straight line. S3 Adjust the height adjustment knob (211) on the sample holder (208) to ensure that when the bubble-free cylindrical pure ice is placed on the sample holder (208), the axis of the sample is on the same straight line as the axis of the incident rod (301) and the transmission rod (302), and turn on the light strip (224). S4 Close the chamber door, set the temperature threshold of the temperature alarm (222), turn on the self-pressurized liquid nitrogen pump (202), so that the liquid nitrogen in the Dewar bottle (201) continuously and slowly enters the pipeline and is evenly sprayed into the chamber through the spraying device, so that the temperature inside the chamber drops rapidly. When the temperature inside the chamber (206) is stable below -40℃, turn off the liquid nitrogen pump. S5 Quickly open the top cover (212) of the chamber (206), place the bubble-free cylindrical pure ice on the sample holder (208) inside the chamber (206), and then close the top cover (212). S6 When the temperature inside the chamber (206) reaches the temperature range of -25℃ to -15℃, the Hopkinson bar test device is used to start the impact test, and the incident rod (301) impacts the bubble-free cylindrical pure ice. After the S7 test is completed, open the top cover (212), open the front cover (213), and clean and collect the bubble-free cylindrical pure ice fragments inside the chamber (206).

6. The method of using the low-temperature testing system for the Hopkinson bar test according to claim 5, characterized in that, Step S1 includes: S1.1 Remove the top cover (103) and the insulation cover (106) from the ice-making device (1), and apply Vaseline to the inner wall of the silicone container (101) of the ice-making device (1), as well as the upper surfaces of the silicone container (101) and the cylindrical container (102). S1.2 Boil the purified water and cool it to room temperature. Use a syringe to draw up the purified water and place the tip of the syringe needle against the bottom wall of the silicone mold. Slowly inject the purified water to prevent air from being mixed in during the injection process. When the purified water level in the silicone mold reaches a certain height, keep the syringe needle below the horizontal plane during the water injection process. Stop injecting water when the purified water level reaches 95% of the height of the silicone mold. During the entire water injection process, air bubbles will be generated on the inner wall of the silicone mold. Use the syringe needle to puncture the air bubbles. S1.3 After water filling is completed, use bolts (108) and nuts (109) to install the top cover (103) on the upper end of the silicone container (101), and make the lower end face of the top cover (103) fit against the upper end face of the silicone container (101) and the cylindrical container (102), and then place the heat preservation cover (106) on the top cover (103); S1.4 Place the ice-making device (1) entirely into the bottom of a -15℃ freezer, where pure water is frozen in a silicone mold into bubble-free cylindrical pure ice.

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