Cold nitrogen refrigerating system suitable for in-situ CT uniaxial tensile test

Abstract

The invention discloses a cold nitrogen refrigerating system suitable for an in-situ CT (computed tomography) uniaxial tensile test, which is characterized by comprising a tensile device and a cold nitrogen refrigerating device arranged on the tensile device, the stretching device comprises an upper clamp expansion joint, a supporting cylinder, a light-transmitting cylinder, a lower clamp, a tension bar and a loading mechanism. The cold nitrogen refrigerating device comprises a gas guide pipe, an upper refrigerating clamp heat insulation shell, a light-transmitting cylinder heat insulation shell, a supporting cylinder heat insulation shell and a supporting cylinder inner heat preservation part. According to the invention, the stretching device is connected with the cold nitrogen refrigeration device, so that each test temperature of the uniaxial stretching test at low temperature can be guaranteed, and the test temperature requirement can be well met.

Description

Technical Field

[0001] The invention relates to the technical field of characterization of material microstructures in a low-temperature environment, and in particular to a cold nitrogen refrigeration system suitable for an in-situ CT uniaxial tensile test. Background Art

[0002] In low temperature environment, the failure mechanism and damage fireworks law of materials often show significant differences compared with those in normal temperature environment. To study the failure mechanism and damage evolution law of materials, it is necessary to observe the internal microstructure and damage morphology of materials under in-situ loading in low temperature environment. Therefore, in order to better evaluate the reliability of materials, a cold nitrogen refrigeration system based on X-ray suitable for in-situ CT uniaxial tensile test is of great significance to study the internal microstructure and damage morphology of materials under in-situ loading in low temperature environment.

[0003] The use of cold nitrogen refrigeration can quickly achieve the low-temperature environment required for the experiment, and the supply rate of cold nitrogen can be adjusted by negative feedback based on the temperature in the experimental chamber measured by the temperature measuring element, so as to accurately control the temperature in the experimental chamber at one time. When the temperature in the experimental chamber is higher than the set temperature, the supply rate of cold nitrogen is increased, but when the temperature in the experimental chamber is lower than the set temperature, the supply rate of cold nitrogen is reduced.

[0004] As researchers continue to expand the application of X-rays, X-rays have received widespread attention as a powerful detection tool. X-rays not only play a vital role in the medical field, but also serve as an industrial flaw detection method in the industrial field to ensure the quality of product production and improve production processes. However, in the field of materials research, static X-ray 3D imaging can no longer meet its needs. The industry has developed a variety of in-situ devices, such as high-temperature stretching, stress corrosion, hot pressing sintering, etc., to study the failure process and mechanism of materials in service environments, thereby further providing a theoretical basis for improving material performance. However, there is still no in-situ CT uniaxial tensile specimen device based on X-rays at low temperatures on the market. Therefore, it is necessary to design a uniaxial tensile test device that can perform in-situ CT in a low-temperature environment to solve the above technical problems. Summary of the invention

[0005] The purpose of the present invention is to provide a cold nitrogen refrigeration system based on X-rays suitable for in-situ CT uniaxial tensile testing, so as to solve the problem raised in the above background technology that there is currently no in-situ CT uniaxial tensile specimen device based on X-rays at low temperature on the market.

[0006] In order to achieve the above purpose, the present invention provides the following technical solutions:

[0007] A cold nitrogen refrigeration system based on X-ray suitable for in-situ CT uniaxial tensile test, characterized by comprising a stretching device and a cold nitrogen refrigeration device arranged on the stretching device;

[0008] The stretching device includes an upper clamp expansion joint, a support tube, a light-transmitting tube, a lower clamp, a tension rod and a loading mechanism; the lower end of the tension rod is connected to the loading mechanism, and the lower clamp is connected to the upper end of the tension rod; the lower end of the upper clamp expansion joint is limitedly matched with the upper end of the light-transmitting tube, the lower end of the light-transmitting tube is limitedly matched with the upper end of the support tube, and the lower end of the support tube is fixed to the upper plate of the loading mechanism;

[0009] Furthermore, the stretching device also includes an upper fixture bearing cover, the outer side of the upper fixture bearing cover is tightly attached to the inner side of the upper refrigeration fixture insulation shell, and the internal thread at the lower end of the upper fixture bearing cover is connected to the external thread at the upper end of the upper fixture expansion joint, so as to realize axial fixation of the air guide tube and the bearing.

[0010] Furthermore, the stretching device also includes a guide sleeve, which is sleeved on the outside of the tension rod, and the lower end of the guide sleeve is fixed to the upper plate of the loading mechanism.

[0011] The cold nitrogen refrigeration device comprises an air duct, an upper refrigeration fixture insulation shell, a light-transmitting tube insulation shell, a support tube insulation shell and a support tube inner insulation sleeve; the inner side of the upper refrigeration fixture insulation shell is sleeved on the upper end of the upper fixture expansion joint; the light-transmitting tube insulation shell is sleeved on the outer side of the light-transmitting tube; the support tube insulation shell is sleeved on the outer side of the support tube; the outer side of the support tube inner insulation sleeve is tightly attached to the inner side of the support tube, and the inner side of the support tube inner insulation sleeve is sleeved on the outer side of the tension rod; the support tube insulation shell, the support tube and the support tube inner insulation sleeve are provided with air inlet holes for introducing cold nitrogen at corresponding positions of the side walls, and the support tube air inlet hole is provided with threads to ensure tight connection with the air pipe to prevent leakage of cold nitrogen.

[0012] Furthermore, the cold nitrogen refrigeration device also includes a bearing and a clamping nut. The bearing is arranged in the bearing cover of the upper clamp. The upper end of the bearing is limitedly matched with the annular portion arranged at the middle end of the air guide pipe, and the lower end of the bearing is limitedly matched with the upper end of the expansion joint of the upper clamp. The lower end of the air guide pipe is provided with a thread. After the air guide pipe passes through the bearing, it is axially fixed on the expansion joint of the upper clamp by the clamping nut.

[0013] Furthermore, the bearing is a low-temperature bearing.

[0014] Furthermore, four waist-shaped groove gas channels for letting in cold nitrogen are provided at the middle and upper end of the inner part of the insulation sleeve in the support tube, and are connected with the air inlet holes on the side walls, so that the cold nitrogen enters the waist-shaped groove from the air inlet holes and is discharged through the exhaust holes provided by the expansion joint of the upper clamp. A channel for placing a low-temperature thermocouple is reserved in one of the waist-shaped groove gas channels of the insulation sleeve in the support tube.

[0015] Furthermore, a step is provided inside the lower end of the insulation sleeve in the support tube, which cooperates with the upper end of the guide sleeve.

[0016] Furthermore, seven exhaust holes are arranged inside the upper clamp expansion joint, which has the function of an expansion joint.

[0017] The present invention connects the stretching device with the cold nitrogen refrigeration device, which can ensure various test temperatures at low temperatures in the uniaxial stretching test and can well meet the experimental temperature requirements.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: the existing X-ray-based in-situ stretching device cannot meet the requirements of low-temperature in-situ stretching experimental research. The present device adopts cold nitrogen refrigeration, which avoids the problem of unclear imaging caused by vibration of the experimental instrument caused by air cooling, and provides important stability guarantee for high-quality imaging; the cold nitrogen refrigeration used in the refrigeration system can ensure that the experiment is at the required experimental temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is the general assembly drawing of the present invention;

[0020] Figure 2 It is a general cross-sectional view of the present invention;

[0021] Figure 3 It is a cross-sectional view of the thermal insulation sleeve in the support tube of the present invention;

[0022] Figure 4 It is a cross-sectional view of the air guide pipe, the bearing and the upper fixture expansion joint of the present invention;

[0023] In the figure: 1. air guide tube; 2. bearing; 3. upper fixture bearing cover; 4. clamping nut; 5. upper refrigeration fixture insulation shell; 6. light-transmitting tube insulation shell; 7. support tube insulation shell; 8. upper fixture expansion joint; 9. lower fixture; 10. tension rod; 11. guide sleeve; 12. support tube; 13. insulation sleeve in support tube; 14. light-transmitting tube; 15. loading mechanism; 16. upper plate. DETAILED DESCRIPTION

[0024] The following will be combined with the accompanying drawings in the examples of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] See also Figure 1-4A cold nitrogen refrigeration system suitable for in-situ CT uniaxial tensile test, including an air guide pipe 1, a bearing 2, an upper fixture bearing cover 3, a clamping nut 4, an upper refrigeration fixture insulation shell 5, a light-transmitting tube insulation shell 6, a support tube insulation shell 7, an upper fixture expansion joint 8, a lower fixture 9, a tension rod 10, a guide sleeve 11, a support tube system 12, insulation inside the support tube 13, a light-transmitting tube 14, and a loading mechanism 15.

[0026] In this embodiment: the upper fixture bearing cover 3, the upper fixture expansion joint 8, the lower fixture 9, the tension rod 10, the guide sleeve 11, the support tube 12, the light-transmitting tube 14, and the loading mechanism 15 constitute a stretching device;

[0027] The tension rod 10 of the stretching device is fixed on the loading mechanism 15 to realize the loading of the tensile test tension.

[0028] The guide sleeve 11 is fixed to the upper plate 16 of the loading mechanism 15 through the flange at the lower end thereof and screws, and is sleeved on the outer side of the tension rod 10 to play a supporting and guiding role.

[0029] The lower end of the lower clamp 9 is provided with a thread, which cooperates with the external thread on the upper end of the tension rod 10 to achieve a tight connection.

[0030] The upper fixture bearing cover 3 is provided with an internal thread, which cooperates with the external thread of the step at the upper end of the upper fixture expansion joint 8 to achieve a tight connection, thereby realizing the limited installation of the bearing.

[0031] The flange provided at the lower end of the support tube 12 is fixed to the upper plate 16 of the loading mechanism 15 by screws, and is closely attached to the outer side of the guide sleeve 11, playing a supporting and fixing role.

[0032] The lower end of the light-transmitting tube 14 is connected to the step provided at the upper end of the supporting tube 12 by cooperation.

[0033] The upper clamp expansion joint 8 has seven funnel-shaped exhaust holes inside for the outlet of cold nitrogen, and has the function of an expansion joint to make the cold nitrogen flow more smoothly; the lower end step of the upper clamp expansion joint 8 cooperates with the upper end of the light-transmitting tube 14 to achieve connection.

[0034] In this embodiment: the air guide pipe 1, the bearing 2, the pressing nut 4, the upper refrigeration fixture insulation shell 5, the light-transmitting tube insulation shell 6, the support tube insulation shell 7 and the support tube inner insulation sleeve 13 constitute a cold nitrogen refrigeration device.

[0035] The insulation sleeve 13 in the support cylinder of the cold nitrogen refrigeration device is relatively fixed on the outside of the tension rod 10 to isolate the experimental refrigeration environment from the external temperature and achieve preliminary insulation of the tensile test chamber.

[0036] The inner side of the heat-insulating outer shell 7 of the support tube is in close contact with the outer side of the support tube 12, so as to reduce the heat exchange between the cold nitrogen gas intake part and the external environment, thereby achieving further heat preservation of the test.

[0037] The inner side of the light-transmitting tube heat-insulating shell 6 is in close contact with the outer side of the light-transmitting tube 14, so as to further reduce the heat exchange between the experimental environment and the external environment, and keep the ambient temperature in the tensile test chamber further stable.

[0038] The inner side of the upper refrigeration fixture insulation shell 5 is sleeved on the upper end of the upper fixture expansion joint 8 and connected to the outer side of the upper fixture bearing cover 3 to prevent frost from direct contact between the upper fixture expansion joint and the external environment, thereby maintaining further stability of the test environment temperature.

[0039] An annular portion is provided at the middle end of the air guide tube 1 to press against the upper end of the bearing 2 , and axial fixation is achieved through a compression nut 4 and an external thread provided at the lower end of the air guide tube 1 .

[0040] The low-temperature resistant bearing used in the bearing 2 can prevent frost at the connection point from affecting the tensile test temperature at low temperatures. The lower end of the bearing 2 fits with the step provided inside the upper clamp expansion joint 8 to achieve connection.

[0041] The side wall of the support tube 12 is provided with four air inlet holes with built-in threads, which cooperate with the air pipe for introducing cold nitrogen to achieve a tight connection to prevent leakage of cold nitrogen.

[0042] The side walls of the inner insulation sleeve 13 of the support tube and the heat-insulating outer shell 7 of the support tube are provided with four air inlet holes, the centers of which are on the same axis.

[0043] Four waist-shaped grooves are provided at the middle and upper end of the inner insulating sleeve 13 of the support tube, and are connected to the four waist-shaped grooves of the inner insulating sleeve 13 of the support tube for introducing cold nitrogen to create the required refrigeration environment and realize uniform refrigeration of the material.

[0044] A channel for a low-temperature thermocouple is reserved at the lower end of a waist-shaped groove of the insulation sleeve 13 in the support tube, so as to facilitate the insertion of the low-temperature thermocouple and realize accurate measurement of the test environment temperature.

[0045] A step is provided inside the lower end of the heat-insulating sleeve 13 in the support tube, and is matched with the upper end of the guide sleeve 11 to achieve connection.

[0046] Working principle:

[0047] The liquid ammonia tank is connected with the argon pressure reducing valve, the air pipe and the cold nitrogen refrigeration system. The liquid nitrogen is gasified to form cold nitrogen. The cold nitrogen is passed through the air pipe into the waist-shaped groove of the insulation sleeve in the support tube to achieve a low-temperature environment. The low-temperature thermocouple is inserted into the flush position of the tensile sample through the reserved channel in the waist-shaped groove of the support tube to measure the experimental temperature. The flow rate of the cold nitrogen and the temperature measured by the low-temperature thermocouple are controlled by adjusting the argon pressure reducing valve to achieve the low-temperature environment required for the experiment. The cold nitrogen is discharged through the exhaust hole set in the expansion joint of the upper fixture, and finally discharged into the external environment through the air guide pipe. The bearing connected to the air guide pipe adopts a low-temperature bearing. The purpose is to prevent the temperature from being too low during the discharge of the cold nitrogen, which causes frost on the outside and hinders the smooth discharge of the cold nitrogen.

[0048] Working process:

[0049] Prepare the plate-shaped tensile specimen specified by the tensile fixture, fix the tensile specimen at the corresponding position of the expansion joint of the upper fixture, and adjust the position of the lower fixture on the tension rod through the loading mechanism so that the tensile specimen is just installed between the fixtures.

[0050] According to the requirements, the low-temperature test is carried out, the air pipe is connected with the thread of the air hole set in the support tube, and cold nitrogen is introduced. The cold nitrogen passes through the insulation sleeve of the support tube and the air hole of the support tube, and flows into the waist-shaped groove of the insulation sleeve in the support tube, so that the cold nitrogen fills the surrounding of the tensile specimen and cools it evenly. The low-temperature thermocouple is extended into the surrounding of the tensile specimen through the reserved channel in the support tube. The experimental environment realizes real-time display of temperature through the low-temperature thermocouple. At this time, the flow rate of the cold nitrogen is controlled by adjusting the argon pressure reducing valve to achieve the low-temperature environment required for the experiment. The cold nitrogen is discharged through the exhaust hole set in the expansion joint of the upper fixture, and finally discharged into the external environment through the air guide pipe.

[0051] After the test temperature parameters are determined, the device can be placed in an X-ray microscope for loading and in-situ observation, and the various parameters of the X-ray can be set to start the X-ray CT scan. After the experiment, the captured images can be post-processed to obtain a 3D image of the experimental object, and relevant analysis and research can be performed on it. The contents not described in detail in this manual belong to the prior art known to professional and technical personnel in this field.

[0052] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A cold nitrogen refrigeration system suitable for in-situ CT uniaxial tensile testing, characterized in that: It includes a stretching device and a cold nitrogen refrigeration device arranged on the stretching device; The stretching device comprises an upper clamp expansion joint (8), a support tube (12), a light-transmitting tube (14), a lower clamp (9), a tension rod (10), a guide sleeve (11) and a loading mechanism (15); the lower end of the tension rod (10) is connected to the loading mechanism (15), and the lower clamp is connected to the upper end of the tension rod (10); the upper end of the light-transmitting tube (14) is limitedly matched with the lower end of the upper clamp expansion joint (8) and is limitedly matched with the upper end of the support tube, and the lower end of the support tube (12) is fixed to the upper plate of the loading mechanism (15); The cold nitrogen refrigeration device comprises an air guide tube (1), a bearing (2), a clamping nut (4), an upper refrigeration fixture heat-insulating shell (5), a light-transmitting tube heat-insulating shell (6), a support tube heat-insulating shell (7) and a support tube inner insulation sleeve (13); the bearing (2) is connected to the air guide tube (1) through the clamping nut (4) and is limitedly matched with the upper end of the upper fixture expansion joint; the inner side of the upper refrigeration fixture heat-insulating shell (5) is sleeved on the upper end of the upper fixture expansion joint (8); the light-transmitting tube heat-insulating shell (6) is sleeved on the outer side of the light-transmitting tube (14); the support tube heat-insulating shell (7) is sleeved on the outer side of the support tube (12); the outer side of the support tube inner insulation sleeve (13) is tightly attached to the inner side of the support tube (12), and the inner side of the support tube inner insulation sleeve (13) is sleeved on the outer side of the guide sleeve (11); Air inlet holes for introducing cold nitrogen are provided at corresponding positions on the side walls of the support tube heat-insulating outer shell (7), the support tube (12) and the support tube inner heat-insulating shell (13), and threads are provided at the position of the air inlet hole of the support tube (12).

2. A cold nitrogen refrigeration system suitable for in-situ CT uniaxial tensile test according to claim 1, characterized in that: The middle and upper end of the inner insulating sleeve (13) of the support tube is provided with four waist-shaped groove gas passages for introducing cold nitrogen, and the four waist-shaped groove gas passages are connected to the air inlet holes on the side wall, so that the cold nitrogen can enter the waist-shaped grooves from the air inlet holes. A channel for placing a low-temperature thermocouple is reserved in one of the waist-shaped groove gas passages of the inner insulating sleeve (13) of the support tube.

3. A cold nitrogen refrigeration system suitable for in-situ CT uniaxial tensile test according to claim 1, characterized in that: The middle end of the air guide tube (1) is provided with an annular portion which is limitedly matched with the upper end of the bearing (2), and the lower end of the bearing (2) is limitedly matched with the upper end of the upper clamp expansion joint (8). The lower end of the air guide tube (1) is provided with a thread, and after passing through the bearing (2), it is axially fixed on the upper clamp expansion joint (8) by a clamping nut (4).

4. A cold nitrogen refrigeration system suitable for in-situ CT uniaxial tensile test according to claim 1, characterized in that: The stretching device also includes an upper fixture bearing cover (3), the lower end of which is provided with an internal thread, which is connected to the external thread provided at the upper end of the upper fixture expansion joint (8) to achieve axial fixation of the air guide tube and the bearing, and the outer side of the upper fixture bearing cover (3) is tightly attached to the inner side of the upper refrigeration and heat insulation shell (5).

5. The cold nitrogen refrigeration system suitable for in-situ CT uniaxial tensile test according to claim 1, characterized in that: The stretching device also includes a guide sleeve (11), which is sleeved on the outside of the tension rod (10), and the lower end of the guide sleeve (11) is fixed to the upper plate of the loading mechanism (15).

6. A cold nitrogen refrigeration system suitable for in-situ CT uniaxial tensile test according to claim 5, characterized in that: A step is provided inside the lower end of the heat-insulating sleeve (13) in the support tube, which matches the upper end of the guide sleeve (11).

7. The cold nitrogen refrigeration system suitable for in-situ CT uniaxial tensile test according to claim 1, characterized in that: A group of funnel-shaped exhaust holes are arranged inside the upper clamp expansion joint (8), which has the function of an expansion joint and makes the cold nitrogen flow more smoothly.

8. The cold nitrogen refrigeration system suitable for in-situ CT uniaxial tensile test according to claim 1, characterized in that: The bearing (2) is a low-temperature resistant bearing.

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