Extremely low temperature environment simulation device for material mechanical property test

Abstract

The invention provides an extremely-low-temperature environment simulation device for testing mechanical properties of materials. The extremely-low-temperature environment simulation device comprises a box body and a heat preservation door hinged to the side edge of the box body. The box body comprises a first thermal insulation layer and a first refrigeration layer group, a mounting sleeve and a lower supporting rod are arranged on the upper side and the lower side in a penetrating manner, an upper sliding rod is arranged in the mounting sleeve, a concave area formed by the first liquid helium layer is a test cavity, and one side, close to the test cavity, of the first liquid helium layer is a corrugated surface; and a temperature sensor penetrates through the box body. By means of the multi-layer cooling and heat preservation structure, the temperature can be effectively reduced to the required low-temperature interval, liquid nitrogen and liquid helium are used for cooling the interior layer by layer, and the cooling effect can be achieved while it is ensured that the liquid nitrogen and the liquid helium are fully utilized.

Description

Technical Field

[0001] This invention relates to an ultra-low temperature environment simulation device for testing the mechanical properties of materials, belonging to the field of materials testing technology. Background Technology

[0002] Fatigue testing is a core method for evaluating the mechanical properties of materials under cyclic loading. Cryogenic fatigue testing focuses on the impact of extreme low-temperature environments (such as liquid helium (-268.9°C) and liquid nitrogen (-196°C), which are commonly used cryogenic media, but direct immersion methods can only stabilize the material near its boiling point. For example, the temperature fluctuation of a liquid helium-immersed specimen is typically less than ±0.5K, but it cannot be actively adjusted to above -196°C. Liquid nitrogen purging relies on cryogenic valves, which are costly and have poor control precision (±2~5°C). Furthermore, the saturated vapor pressure of liquid helium exhibits a strongly nonlinear relationship with temperature; a 100Pa pressure fluctuation can lead to a 1mK temperature change in the 4K temperature range, making it difficult for traditional pressure control methods to achieve millisecond-level response) on the fatigue behavior of materials. The aim is to reveal the crack initiation and propagation mechanism under the coupled effects of temperature and stress, providing crucial data for material design in aerospace, polar engineering, and new energy fields. Its core research content includes cryogenic fatigue strength, crack propagation rate, and microscopic damage mechanisms, directly supporting the reliability assessment of structural components under extreme environments. In the aerospace field, rocket engine tank materials must withstand ultra-low temperatures and high-frequency vibrations caused by liquid hydrogen and liquid oxygen. The lack of low-temperature fatigue data may lead to structural fractures and accidents. In the new energy field, the service safety of wind turbine bearing steel and lithium battery packaging materials in high-altitude and cold regions also depends on accurate low-temperature fatigue testing. In addition, LNG storage tanks, polar equipment and other materials have stringent requirements for low-temperature fatigue resistance, and related research is crucial for extreme environment engineering. Existing low-temperature fatigue testing equipment has significant technical shortcomings in extremely low-temperature environments (such as the -196℃ liquid nitrogen temperature range): Traditional liquid nitrogen spraying technology results in poor temperature field uniformity in the test chamber (vertical temperature difference can reach ±10℃). During cyclic loading, the heat generated by the sample and the heat conduction of the fixture cause a temperature drift rate of 5℃ / min, and the temperature deviates from the target value by ±15℃ within 3 minutes, causing the crack propagation rate test to be distorted by more than 30%. Conventional fixtures take more than 30 minutes to load and unload at a time. When the extremely low-temperature sample is exposed to room temperature, the heat intrusion rate reaches 8℃ / min, and the surface temperature rises to above -150℃ within 5 minutes, causing the surface brittle-ductile transition, resulting in a fatigue life test value that is falsely inflated by 50%. In addition, the impact toughness of aluminum alloy fixtures drops to below 5J / cm² at -196℃, and the sample is easily damaged by bumps during loading and unloading. These issues increase the dispersion of fatigue data for cryogenic materials by more than 40%, leading to engineering misjudgments such as a 25% increase in weight for conservative designs of liquid oxygen components in aerospace and a deviation of more than 40% in the predicted lifespan of steel for LNG storage tanks. They also restrict the research and development of new materials and the reliability assessment of equipment in cryogenic environments. It is urgent to make breakthroughs in key technologies such as cryogenic insulation temperature control and quick-change fixtures to improve testing accuracy. Therefore, a low-temperature environment simulation device for testing the mechanical properties of materials is proposed. Summary of the Invention

[0003] Purpose of the invention: To address the shortcomings of existing technologies, this invention provides an ultra-low temperature environment simulation device for testing the mechanical properties of materials, thereby solving the problems mentioned in the background section.

[0004] Technical solution: A low-temperature environment simulation device for testing the mechanical properties of materials, including a chamber and an insulated door hinged to the side of the chamber; The enclosure includes a first insulation layer and a first cooling layer group. The first insulation layer has a concave structure in the middle, and the first cooling layer group is arranged sequentially in close proximity to the concave structure in the middle of the first insulation layer. The first cooling layer group consists of a first vacuum layer, a first liquid nitrogen layer, a second vacuum layer, and a first liquid helium layer from the outside to the inside. The first liquid nitrogen layer and the first liquid helium layer are each provided with an independent input pipe and an output pipe that communicate with the outside of the enclosure. The contact points between the input pipe and the output pipe of any layer in the cooling layer group and other layers outside that layer are sealed by welding. Mounting sleeves and lower support rods are respectively provided on the upper and lower sides, penetrating the box body, the first vacuum layer, the first liquid nitrogen layer, the second vacuum layer and the first liquid helium layer. An upper sliding rod is provided inside the mounting sleeve. The lower support rod is fixedly connected to the box body. The upper sliding rod and the mounting sleeve are connected by a multi-stage heat insulation ring group fixedly connected to the inner wall of the mounting sleeve. Both the first vacuum layer and the second vacuum layer are provided with support plates perpendicular to both sides; The concave region formed by the first liquid helium layer is the test cavity, and the upper sliding rod and the lower support rod extend towards the center of the test cavity to clamp the sample to be tested; the side of the first liquid helium layer near the test cavity is set as a corrugated surface; Temperature sensors are installed in the upper, middle, and lower regions of the test chamber, penetrating the chamber body, the first vacuum layer, the first liquid nitrogen layer, the second vacuum layer, and the first liquid helium layer.

[0005] This invention utilizes a multi-layer cooling and insulation structure to effectively reduce the temperature to the required low-temperature range. Cooling is achieved layer by layer from liquid nitrogen to liquid helium, ensuring full utilization of the liquid nitrogen and helium while achieving the cooling effect. The inner cavity uses thermal radiation for cooling, which, compared to conventional methods of immersion in liquid helium or spraying liquid helium, avoids the vaporization and fogging of liquid helium, thus preventing the observation of samples. This ensures uniform and stable temperature inside the chamber, while also making temperature control more precise and stable. The multi-stage insulation ring system ensures that the gas inside the test chamber does not exchange with the outside air when the upper sliding rod moves, which helps to maintain a constant temperature inside the test chamber. The first liquid helium layer has a corrugated surface on the side closest to the test chamber, which can effectively increase the heat transfer area of ​​liquid helium, improve cooling efficiency, and achieve rapid cooling.

[0006] The first liquid helium layer is set as an arc-shaped corrugated surface on the side near the test chamber, with its center located on the vertical line between the upper sliding rod and the lower support rod.

[0007] The arc-shaped test chamber minimizes the distance between most of the liquid helium layer walls and the sample under test, and the spacing is uniform. When a cooling effect is generated, the sample under test can be cooled quickly.

[0008] The insulated door includes a second insulation layer and a second refrigeration layer group. The second insulation layer has a concave structure in the middle, and the second refrigeration layer group is arranged sequentially and closely adjacent to the concave structure in the middle of the second insulation layer. The second refrigeration layer group includes a third vacuum layer, a second liquid nitrogen layer, a fourth vacuum layer, and a second liquid helium layer arranged sequentially from the outside to the inside. The second liquid nitrogen layer and the second liquid helium layer are each provided with an independent input pipe and an output pipe that communicate with the outside of the box. The contact points between the input pipe and the output pipe of any layer and other layers outside the layer are sealed by welding.

[0009] To further ensure the cooling effect of the test chamber, a cooling layer group with the same layer structure is set in the insulation door, so that the insulation door also maintains a low temperature, thus avoiding the influence of the temperature of the insulation door on the temperature inside the test chamber during the test.

[0010] A sealing groove is formed along the edge of the box near the insulated door. A first sealing protrusion is provided on the side of the insulated door near the box, corresponding to the position of the sealing groove. The first sealing protrusion is set in the shape of a trapezoid, and the cross-section of any edge segment of the first sealing protrusion is an isosceles trapezoid. The width of the bottom edge of the first sealing protrusion is the same as the width of the sealing groove.

[0011] To achieve better insulation, a matching sealing protrusion and sealing groove are designed to ensure a tight seal between the insulation door and the cabinet after the insulation door is closed, preventing cold air leakage and further improving the cooling effect.

[0012] A magnetic strip is embedded and fixed at the inner edge of the insulated door, which attracts the metal box after the insulated door is closed to assist in positioning.

[0013] To ensure stable closing of the insulated door, a magnetic strip is installed. After the insulated door is closed, the magnetic strip attracts the door to the metal casing. Due to the sealing effect of the sealing groove and sealing protrusion, as well as the heat insulation effect of the insulation layer of the insulated door and casing, the magnetism of the magnetic strip is not affected, and it can stably exert its magnetic attraction effect. It is also easy to replace.

[0014] The upper sliding rod is configured as an assembly, including a sliding rod with a threaded hole at the lower end, a pressure rod threadedly connected to the threaded hole at the lower end of the sliding rod, and a heat insulation sleeve provided at the upper end of the sliding rod; The insulation sleeve is positioned at a certain distance from the outside of the chamber, and this distance is greater than the stroke of the pressure bar from its upper limit position to the sample to be tested. The pressure rod includes a limiting platform whose outer diameter is clearance-fitted with the inner diameter of the mounting sleeve, and a positioning rod for positioning the sample to be tested. The gap between the limiting platform and the inner diameter of the mounting sleeve is between 0.08 mm and 0.12 mm.

[0015] The modular design of the slide bar makes it easier to install and replace the pressure bar. The appropriate pressure bar can be replaced according to the shape and specifications of different test samples. The distance setting of the insulation sleeve can ensure the effective stroke of the slide bar, which is not affected by the structure of the insulation sleeve. The limiting stage can prevent the slide bar stroke from being too large and affecting the airtightness between the upper slide bar and the mounting sleeve, thus ensuring the temperature maintenance effect of the test chamber.

[0016] The multi-stage insulation ring includes at least two polytetrafluoroethylene (PTFE) rings disposed inside the mounting sleeve. The two PTFE rings are respectively disposed at the upper edge of the mounting sleeve and near the lower edge. The distance between the PTFE ring disposed at the lower end and the lower edge of the mounting sleeve is set according to the maximum size of the sample to be tested.

[0017] Utilizing the thermal insulation properties of polytetrafluoroethylene (PTFE), and with the PTFE ring at the lower end also serving as a limiting structure, this design achieves a multi-functional effect, reducing production costs. In practical use, multiple designs can be installed to ensure a better sealing effect.

[0018] The insulation sleeve includes a shell fixedly connected to the slide rod, a liquid nitrogen tube spirally attached to the slide rod, and insulation filler filling the shell; the liquid nitrogen tube has an inlet pipe that passes through the shell from the side near the upper end and communicates with an external liquid nitrogen storage container, and a return pipe that passes through the shell from the side near the lower end and communicates with an external liquid nitrogen storage container.

[0019] A surrounding liquid nitrogen tube is installed in the insulation sleeve to keep the slide rod at a low temperature, thereby reducing the temperature difference between the part of the connecting rod that enters the test chamber and the test chamber. At the same time, it prevents the external room temperature from being transferred to the test chamber through the slide rod and affecting the temperature uniformity of the test chamber.

[0020] The first and second insulation layers are the same as the cavity of the insulation sleeve, and are both filled with insulation filler to achieve the insulation effect. The insulation filler includes, but is not limited to, any one of polyester fiber cotton, aerogel composite cotton, rigid polyether polyurethane foam, foam glass, rock wool, or glass wool.

[0021] By filling with insulating material, the overall weight of the device is reduced while achieving good thermal insulation. The thickness of the insulation layer is greater than that of the refrigeration layer, which reduces the amount of refrigerant used, lowers experimental and production costs, and makes the device more economical.

[0022] The insulation door is provided with an observation window assembly that runs vertically through the insulation door in the middle of the test chamber. The observation window assembly includes an observation frame near the outside of the insulation door, and an observation channel is provided in the area where the observation frame communicates with the inside of the insulation door. The observation frame is equipped with an outer glass slot and an inner glass slot near the inner and outer sides of the frame, respectively, both made of transparent and colorless quartz glass. A vacuum is created between the two layers of quartz glass. It also includes a spotlight frame set between the outer glass slot and the outer surface of the observation frame, and a spotlight assembly perpendicular to the quartz glass is set on the spotlight frame; The observation frame is equipped with a heating wire channel and a built-in electric heating wire to prevent excessive temperature difference between the inside and outside from causing frost to form on the glass. Near the inner opening of the observation channel, a second sealing protrusion is provided around the opening. The second sealing protrusion is shaped like a trapezoid, and its cross-section is a right trapezoid at any edge segment. The bottom edge of the second sealing protrusion matches the outer edge of the test chamber.

[0023] By setting up a heated observation window assembly, the impact of fogging on observation caused by temperature differences between the inside and outside of the glass is reduced. In addition, LED spotlights are installed on the outside of the window to enable clear observation of the internal state of the test chamber and ensure a bright field of view. During the test, a high-speed camera can also be used to record the changes of the sample during loading, providing a clearer observation environment for camera recording.

[0024] Beneficial effects: The multi-layer cooling and insulation structure can effectively reduce the temperature to the required low temperature range. Cooling is achieved layer by layer from liquid nitrogen to liquid helium, ensuring full utilization of liquid nitrogen and helium while achieving the cooling effect. The internal cavity uses thermal radiation for cooling, which also solves two problems: First, conventional cooling methods such as immersion in liquid helium or spraying liquid helium can cause fogging and frost formation due to liquid helium vaporization, making it impossible to observe the samples; second, spraying methods are difficult to achieve uniform and stable temperature inside the chamber, while this method can achieve more precise and stable temperature control.

[0025] The polytetrafluoroethylene insulation ring between the upper sliding rod and the chamber ensures that the gas inside the test chamber does not exchange with the outside air when the upper sliding rod moves, which helps to maintain a constant temperature inside the test chamber.

[0026] By introducing liquid nitrogen into the insulation sleeve to cool the slide rod, the connecting rod is kept at a low temperature, which reduces the temperature difference between the part of the connecting rod that enters the test chamber and the test chamber, thus minimizing the factors that affect the temperature change inside the test chamber.

[0027] The insulation door is designed with the same multi-layer cooling and insulation structure as the chamber body, which effectively ensures that the temperature of the part in contact with the test chamber is consistent with that of the test chamber, reduces the impact of temperature on the test chamber, and ensures the stability of the experiment.

[0028] A double-layered glass heated viewing window is installed on the outside of the insulated door passage to reduce the impact of fogging caused by temperature differences between the inside and outside of the glass on observation. In addition, an LED spotlight is installed on the outside of the viewing window to enable clear observation of the internal state of the test chamber.

[0029] This device is capable of testing the mechanical properties of materials at extremely low temperatures and reduces experimental errors caused by small temperature variations through a powerful temperature maintenance function. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0031] Figure 1This is a schematic diagram of the overall structure of the present invention.

[0032] Figure 2 This is a cross-sectional structural diagram of the housing of the present invention.

[0033] Figure 3 This is a right view of the box structure of the present invention.

[0034] Figure 4 This is a schematic diagram of the connecting rod structure of the present invention.

[0035] Figure 5 This is a schematic cross-sectional view of the housing of the present invention.

[0036] Figure 6 This is a schematic diagram of the structure of the heat-insulating door of the present invention.

[0037] Figure 7 This is a schematic diagram of the cross-section of the insulated door of the present invention.

[0038] Figure 8 This is a schematic diagram of the window structure of the present invention.

[0039] Figure 9 This is a schematic cross-sectional view of the window of the present invention. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0042] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0043] A low-temperature environment simulation device for testing the mechanical properties of materials includes a chamber 1 and an insulated door 2 hinged to the side of the chamber 1. The enclosure 1 includes a first insulation layer 3 and a first cooling layer group 4. The first insulation layer 3 has a concave structure in the middle, and the first cooling layer group 4 is arranged sequentially in close contact with the concave structure in the middle of the first insulation layer 3. The first cooling layer group 4 consists of a first vacuum layer 41, a first liquid nitrogen layer 42, a second vacuum layer 43, and a first liquid helium layer 44 from the outside to the inside. The first liquid nitrogen layer 42 and the first liquid helium layer 44 are each provided with an independent input pipe and an output pipe that communicate with the outside of the enclosure 1. The contact points between the input pipe and the output pipe of any layer in the cooling layer group and other layers outside the layer are sealed by welding. Mounting sleeves 5 and lower support rods 6 are respectively provided on the upper and lower sides of the box body 1, the first vacuum layer 41, the first liquid nitrogen layer 42, the second vacuum layer 43 and the first liquid helium layer 44. An upper sliding rod 7 is provided inside the mounting sleeve 5. The lower support rod 6 is fixedly connected to the box body 1. The upper sliding rod 7 and the mounting sleeve 5 are connected by a multi-stage heat insulation ring group 8 fixedly connected to the inner wall of the mounting sleeve 5. Both the first vacuum layer 41 and the second vacuum layer 43 are provided with support plates 9 perpendicular to both sides; The concave region formed by the first liquid helium layer 44 is a test cavity. The upper sliding rod 7 and the lower support rod 6 extend towards the center of the test cavity to clamp the sample to be tested. The side of the first liquid helium layer 44 near the test cavity is set with a corrugated surface. Temperature sensors 10 are installed in the upper, middle and lower regions of the test chamber, respectively, through the chamber 1, the first vacuum layer 41, the first liquid nitrogen layer 42, the second vacuum layer 43 and the first liquid helium layer 44.

[0044] This invention utilizes a multi-layer cooling and insulation structure to effectively reduce the temperature to the required low-temperature range. Cooling is achieved layer by layer from liquid nitrogen to liquid helium, ensuring full utilization of the liquid nitrogen and helium while achieving the cooling effect. The inner cavity uses thermal radiation for cooling, which, compared to conventional methods of immersion in liquid helium or spraying liquid helium, avoids the vaporization and fogging of liquid helium, thus preventing the observation of samples. This ensures uniform and stable temperature inside the chamber, while also making temperature control more precise and stable. The multi-stage heat preservation ring group 8 ensures that the gas inside the test chamber does not exchange with the outside air when the upper sliding rod 7 moves, which helps to maintain a constant temperature inside the test chamber. The first liquid helium layer 44 has a corrugated surface on the side near the test chamber, which can effectively increase the heat transfer area of ​​liquid helium, improve cooling efficiency, and achieve rapid cooling.

[0045] The first liquid helium layer 44 is set with an arc-shaped corrugated surface on the side near the test chamber, and its center is located on the vertical line between the upper sliding rod 7 and the lower support rod 6.

[0046] The arc-shaped test chamber minimizes the distance between most of the liquid helium layer walls and the sample under test, and the spacing is uniform. When a cooling effect is generated, the sample under test can be cooled quickly.

[0047] The insulated door 2 includes a second insulation layer 11 and a second refrigeration layer group 12. The second insulation layer 11 has a concave structure in the middle, and the second refrigeration layer group 12 is arranged sequentially close to the concave structure in the middle of the second insulation layer 11. The second refrigeration layer group 12 includes a third vacuum layer 121, a second liquid nitrogen layer 122, a fourth vacuum layer 123, and a second liquid helium layer 124 arranged sequentially from the outside to the inside. The second liquid nitrogen layer 122 and the second liquid helium layer 124 are each provided with an input pipe and an output pipe that are connected to the outside of the box 1 and are independent of each other. The contact position between the input pipe and the output pipe of any layer and other layers outside the layer is sealed by welding.

[0048] To further ensure the cooling effect of the test chamber, a cooling layer group with the same layer structure is set in the insulation door 2, so that the insulation door 2 also maintains a low temperature state, and the temperature of the insulation door 2 avoids affecting the temperature inside the test chamber during the test.

[0049] A sealing groove 13 is formed along the edge of the box body 1 near the heat preservation door 2. A first sealing protrusion 14 corresponding to the sealing groove 13 is provided on the side of the heat preservation door 2 near the box body 1. The first sealing protrusion 14 is set in the shape of a trapezoid, and the cross-section of any edge segment of the first sealing protrusion 14 is an isosceles trapezoid. The width of the bottom edge of the first sealing protrusion 14 is the same as the width of the sealing groove 13.

[0050] To achieve better insulation, a matching sealing protrusion and sealing groove 13 are designed to ensure airtightness between the insulation door 2 and the cabinet 1 after the insulation door 2 is closed, preventing cold air leakage and further improving the cooling effect.

[0051] A magnetic strip is embedded and fixed at the inner edge of the heat-insulating door 2. After the heat-insulating door 2 is closed, it attracts the metal box 1 to achieve the function of auxiliary positioning.

[0052] In order to achieve stable closing of the insulated door 2, a magnetic strip is set. After the insulated door 2 is closed, the magnetic strip will stably attract the insulated door 2 to the metal box 1. Due to the sealing effect of the sealing groove 13 and the sealing protrusion, as well as the heat insulation effect of the insulation layer of the insulated door 2 and the box 1, the magnetism of the magnetic strip is not affected, and it can stably exert the magnetic attraction effect. It is also easy to replace.

[0053] The upper sliding rod 7 is configured as an assembly, including a sliding rod 71 with a threaded hole at the lower end, a pressure rod 72 threadedly connected to the threaded hole at the lower end of the sliding rod 71, and a heat insulation sleeve 15 disposed at the upper end of the sliding rod 71. The insulation sleeve 15 is positioned at a certain distance from the outside of the box 1, and this distance is greater than the stroke of the pressure rod 72 from its upper limit position to the sample to be tested. The pressure rod 72 includes a limiting platform 721 whose outer diameter is clearance-fitted with the inner diameter of the mounting sleeve 5, and a positioning rod 722 for positioning the sample to be tested. The gap between the limiting platform 721 and the inner diameter of the mounting sleeve 5 is between 0.08 mm and 0.12 mm.

[0054] The modular design of the slide bar 71 makes it easier to install and replace the pressure bar 72. The appropriate pressure bar 72 can be replaced according to the shape and specifications of different test samples. The distance setting of the insulation sleeve 15 can ensure the effective stroke of the slide bar 71, which is not affected by the structure of the insulation sleeve 15. The limiting stage 721 can prevent the slide bar 71 from having too large a stroke, which would affect the airtightness between the upper slide bar 7 and the mounting sleeve 5, and ensure the temperature maintenance effect of the test chamber.

[0055] The multi-stage insulation ring assembly 8 includes at least two polytetrafluoroethylene (PTFE) rings disposed inside the mounting sleeve 5. The two PTFE rings are respectively disposed at the upper edge and near the lower edge of the mounting sleeve 5. The distance between the PTFE ring disposed at the lower end and the lower edge of the mounting sleeve 5 is set according to the maximum size of the sample to be tested.

[0056] Utilizing the thermal insulation properties of polytetrafluoroethylene (PTFE), and with the PTFE ring at the lower end also serving as a limiting structure, this design achieves a multi-functional effect, reducing production costs. In practical use, multiple designs can be installed to ensure a better sealing effect.

[0057] The insulation sleeve 15 includes a shell 151 fixedly connected to the slide rod 71, a liquid nitrogen tube 152 spirally attached to the slide rod 71, and insulation filler filling the shell 151; the liquid inlet pipe of the liquid nitrogen tube 152 passes through the shell 151 from the side near the upper end and communicates with the external liquid nitrogen storage container, and the liquid return pipe passes through the shell 151 from the side near the lower end and communicates with the external liquid nitrogen storage container.

[0058] The insulation sleeve 15 is equipped with a surrounding liquid nitrogen tube 152 to keep the slide rod 71 at a low temperature, thereby reducing the temperature difference between the part of the connecting rod that enters the test chamber and the test chamber, and at the same time preventing the external room temperature from being transferred to the test chamber through the slide rod 71 and affecting the temperature balance of the test chamber.

[0059] The first insulation layer 3 and the second insulation layer 11 have the same cavity as the insulation sleeve 15, and are all filled with insulation filler to achieve the insulation effect. The insulation filler includes, but is not limited to, any one of polyester fiber cotton, aerogel composite cotton, rigid polyether polyurethane foam, foam glass, rock wool, or glass wool.

[0060] By filling with insulating material, the overall weight of the device is reduced while achieving good thermal insulation. The thickness of the insulation layer is greater than that of the refrigeration layer, which reduces the amount of refrigerant used, lowers experimental and production costs, and makes the device more economical.

[0061] The heat preservation door 2 is provided with an observation window assembly 16 that is vertically penetrating the center of the test chamber. The observation window assembly 16 includes an observation frame 161 near the outside of the heat preservation door 2, and an observation channel 162 is provided in the area where the observation frame 161 communicates with the inside of the heat preservation door 2. The observation frame 161 is provided with an outer glass slot 163 and an inner glass slot 164 near the inner and outer sides of the observation frame 161, respectively, and both are made of transparent and colorless quartz glass. The space between the inner and outer layers of quartz glass is set as a vacuum. It also includes a spotlight frame 165 disposed between the outer glass slot 163 and the outer surface of the observation frame 161, and a spotlight assembly 166 perpendicular to the quartz glass is disposed on the spotlight frame 165. The observation frame 161 is provided with a heating wire channel 167, which contains an electric heating wire to prevent excessive temperature difference between the inside and outside from causing frost to form on the glass. Near the inner opening of the insulation door 2, the observation channel 162 is provided with a second sealing protrusion 168 surrounding the opening. The second sealing protrusion 168 is shaped like a trapezoid, and the cross-section of any edge segment is a right trapezoid. The bottom edge of the second sealing protrusion 168 matches the outer edge of the test chamber.

[0062] By setting up a heated observation window assembly 16, the impact of fogging on observation caused by temperature differences between the inside and outside of the glass is reduced. Furthermore, an LED spotlight is installed on the outside of the window to enable clear observation of the internal state of the test chamber, ensuring a bright field of view. During the test, a high-speed camera can also be used to record the changes in the sample during loading, providing a clearer observation environment for camera recording.

[0063] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0064] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A low-temperature environment simulation device for testing the mechanical properties of materials, comprising a chamber (1) and an insulated door (2) hinged to the side of the chamber (1). The box (1) includes a first insulation layer (3) and a first cooling layer group (4). The first insulation layer (3) has a concave structure in the middle. The first cooling layer group (4) is arranged in sequence close to the concave structure in the middle of the first insulation layer (3). The first cooling layer group (4) consists of a first vacuum layer (41), a first liquid nitrogen layer (42), a second vacuum layer (43), and a first liquid helium layer (44) from the outside to the inside. The first liquid nitrogen layer (42) and the first liquid helium layer (44) are provided with input pipes and output pipes that are connected to the outside of the box (1) and are independent of each other. The input pipes and output pipes of any layer in the cooling layer group are sealed with welding at the contact points with other layers outside the layer. An installation sleeve (5) and a lower support rod (6) are respectively provided on the upper and lower sides of the box body (1), the first vacuum layer (41), the first liquid nitrogen layer (42), the second vacuum layer (43) and the first liquid helium layer (44). An upper sliding rod (7) is provided inside the installation sleeve (5). The lower support rod (6) is fixedly connected to the box body (1). The upper sliding rod (7) and the installation sleeve (5) are connected by a multi-stage heat insulation ring group (8) fixedly connected to the inner wall of the installation sleeve (5). Both the first vacuum layer (41) and the second vacuum layer (43) are provided with support plates (9) perpendicular to both sides. The concave region formed by the first liquid helium layer (44) is the test cavity. The upper sliding rod (7) and the lower support rod (6) extend towards the middle of the test cavity to clamp the sample to be tested. The side of the first liquid helium layer (44) near the test cavity is set as a corrugated surface. Temperature sensors (10) are installed in the upper, middle and lower regions of the test chamber, respectively, through the box (1), the first vacuum layer (41), the first liquid nitrogen layer (42), the second vacuum layer (43) and the first liquid helium layer (44).

2. The ultra-low temperature environment simulation device for testing the mechanical properties of materials according to claim 1, characterized in that: The first liquid helium layer (44) is set as an arc-shaped corrugated surface on the side near the test cavity, and its center is located on the vertical line between the upper sliding rod (7) and the lower support rod (6).

3. The ultra-low temperature environment simulation device for testing the mechanical properties of materials according to claim 1, characterized in that: The insulated door (2) includes a second insulation layer (11) and a second refrigeration layer group (12). The second insulation layer (11) has a concave structure in the middle. The second refrigeration layer group (12) is arranged in sequence close to the concave structure in the middle of the second insulation layer (11). The second refrigeration layer group (12) includes a third vacuum layer (121), a second liquid nitrogen layer (122), a fourth vacuum layer (123), and a second liquid helium layer (124) arranged in sequence from the outside to the inside. The second liquid nitrogen layer (122) and the second liquid helium layer (124) are each provided with an input pipe and an output pipe that are connected to the outside of the box (1) and are independent of each other. The contact position of the input pipe and output pipe of any layer with other layers outside the layer is sealed by welding.

4. The ultra-low temperature environment simulation device for testing the mechanical properties of materials according to claim 1, characterized in that: A sealing groove (13) is provided on the side of the box (1) near the heat-insulating door (2) along the edge of the box (1). A first sealing protrusion (14) is provided on the side of the heat-insulating door (2) near the box (1) corresponding to the position of the sealing groove (13). The first sealing protrusion (14) is set in the shape of a trapezoid. The cross-section of any edge segment of the first sealing protrusion (14) is an isosceles trapezoid. The width of the bottom edge of the first sealing protrusion (14) is the same as the width of the sealing groove (13).

5. The ultra-low temperature environment simulation device for testing the mechanical properties of materials according to claim 4, characterized in that: A magnetic strip is embedded and fixed at the inner edge of the heat-insulating door (2). After the heat-insulating door (2) is closed, it attracts the metal box (1) to achieve the function of auxiliary positioning.

6. The ultra-low temperature environment simulation device for testing the mechanical properties of materials according to claim 3, characterized in that: The upper sliding rod (7) is assembled and includes a sliding rod (71) with a threaded hole at the lower end, a pressure rod (72) threadedly connected to the threaded hole at the lower end of the sliding rod (71), and a heat insulation sleeve (15) provided at the upper end of the sliding rod (71). The insulation sleeve (15) is set at a certain distance from the outside of the box (1), which is greater than the stroke of the pressure rod (72) from the upper limit position to press the sample to be tested; The pressure bar (72) includes a limiting platform (721) whose outer diameter is clearance-fitted with the inner diameter of the mounting sleeve (5) and a positioning rod (722) for positioning the sample to be tested. The gap between the limiting platform (721) and the inner diameter of the mounting sleeve (5) is between 0.08 mm and 0.12 mm.

7. The ultra-low temperature environment simulation device for testing the mechanical properties of materials according to claim 6, characterized in that: The multi-stage insulation ring group (8) includes at least two polytetrafluoroethylene (PTFE) rings disposed inside the mounting sleeve (5). The two PTFE rings are respectively disposed at the upper edge of the mounting sleeve (5) and near the lower edge. The distance between the PTFE ring disposed at the lower end and the lower edge of the mounting sleeve (5) is set according to the maximum size of the sample to be tested.

8. The ultra-low temperature environment simulation device for testing the mechanical properties of materials according to claim 6, characterized in that: The insulation sleeve (15) includes a shell (151) fixedly connected to the slide rod (71), a liquid nitrogen tube (152) spirally attached to the slide rod (71), and insulation filler filling the shell (151); the liquid inlet pipe of the liquid nitrogen tube (152) passes through the shell (151) from the side near the upper end and communicates with the external liquid nitrogen storage container, and the liquid return pipe passes through the shell (151) from the side near the lower end and communicates with the external liquid nitrogen storage container.

9. The ultra-low temperature environment simulation device for testing the mechanical properties of materials according to claim 7, characterized in that: The first insulation layer (3) and the second insulation layer (11) have the same cavity as the insulation sleeve (15), and are both filled with insulation filler to achieve the insulation effect. The insulation filler includes, but is not limited to, any one of polyester fiber cotton, aerogel composite cotton, rigid polyether polyurethane foam, foam glass, rock wool, or glass wool.

10. The ultra-low temperature environment simulation device for testing the mechanical properties of materials according to claim 1, characterized in that: The heat preservation door (2) is provided with an observation window assembly (16) that penetrates vertically through the heat preservation door (2) in the middle of the test chamber. The observation window assembly (16) includes an observation frame (161) near the outside of the heat preservation door (2) and an observation channel (162) is provided in the area where the observation frame (161) communicates with the inside of the heat preservation door (2). The observation frame (161) is provided with an outer glass slot (163) and an inner glass slot (164) on the inner and outer sides near the observation frame (161), respectively, and both are made of transparent and colorless quartz glass. The space between the inner and outer layers of quartz glass is set as a vacuum. It also includes a spotlight frame (165) disposed between the outer glass slot (163) and the outer surface of the observation frame (161), and a spotlight assembly (166) perpendicular to the quartz glass is disposed on the spotlight frame (165). The observation frame (161) is provided with a heating wire channel (167) and an internal electric heating wire to avoid excessive temperature difference between the inside and outside leading to frost on the glass; The observation channel (162) is located near the inner channel opening of the insulation door (2), and a second sealing protrusion (168) is provided around the channel opening. The second sealing protrusion (168) is set in the shape of a trapezoid, and the cross-section of any edge segment is a right trapezoid. The bottom edge of the second sealing protrusion (168) matches the outer edge of the test chamber.

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