Ultra-Cryogenic Chamber for Impact Testing

Abstract

The present invention provides an ultra-low temperature chamber for impact testing, comprising a rectangular container having at least double side walls and an open top, the side walls including a first side wall and a second side wall formed in a shape surrounding the first side wall, the first side wall defines a first space in which a test specimen can be placed, the second side wall defines a second space such that thermal insulation can be performed between the first side wall and the second side wall, the second space has a structure with an upper part closed, and a first cooling medium is continuously supplied to the second space to block heat transfer between the first space and the outside, and a second cooling medium is continuously supplied to the first space to cool the test specimen.

Description

[Technical field]

[0001] The present invention relates to an ultra-cryogenic chamber for impact testing, and more particularly to an ultra-cryogenic chamber capable of cooling a test piece for impact testing to a desired temperature within a short period of time using a cooling medium. [Background technology]

[0002] In general, in order to perform high-speed testing of a device under test (DUT), a cryogenic chamber for shock testing operates not only the device under test but also a system for testing the device within the chamber.

[0003] Korean Patent Publication No. 10-2010-0000666 discloses a chamber for preparing impact test specimens. In the case of conventional chambers, the test specimens are cooled using vaporized liquefied nitrogen, and impact testing is performed when the test specimen reaches a target temperature after being cooled. However, in conventional systems, the cooling limit of the test specimen is only -196°C. This is because it is somewhat difficult to lower the temperature of the test specimen to the service temperature (20K in liquefied hydrogen environment) due to the considerable heat loss inside the low-temperature chamber and the connecting piping.

[0004] Recently, there has been an increasing need to modify the system so that materials can be evaluated under the operating environment of hydrogen tank materials (20K, -253℃). Therefore, it is necessary to create a chamber that can perform shock tests under ultra-low temperature environments through changes in the chamber design.

[0005] Meanwhile, in the past, the chamber was maintained in a vacuum atmosphere to reduce the use of cooling media, but since the manufacturing and maintenance costs of the vacuum chamber are relatively high, it is necessary to manufacture a chamber capable of cryogenically cooling test pieces in an inexpensive manner. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention is intended to solve various problems including those mentioned above, and aims to provide an ultra-low temperature chamber for impact testing that can effectively cool a test piece to an ultra-low temperature while reducing the manufacturing and maintenance costs of the chamber. However, these problems are merely examples and are not intended to limit the scope of the present invention. [Means for solving the problem]

[0007] According to one embodiment of the present invention, there is provided an ultra-cryogenic chamber for impact testing, the ultra-cryogenic chamber for impact testing includes a rectangular container having at least double side walls and an open top, the side walls include a first side wall and a second side wall formed in a shape surrounding the first side wall, the first side wall defines a first space in which a test specimen can be placed, the second side wall defines a second space such that thermal insulation can be performed between the first side wall and the second side wall, the second space has a structure with an upper part closed, a first cooling medium is continuously supplied to the second space to block heat transfer between the first space and the outside, and a second cooling medium is continuously supplied to the first space to cool the test specimen.

[0008] In the ultra-cryogenic chamber for impact testing, a portion of the second side wall may include a first cooling medium supply portion capable of supplying the first cooling medium.

[0009] In the ultra-cryogenic chamber for impact testing, a portion of the second side wall may include a first cooling medium discharge portion capable of discharging the first cooling medium.

[0010] In the ultra-cryogenic chamber for impact testing, the first cooling medium discharge portion may have a diameter of 3 mm to 10 mm.

[0011] The ultra-low temperature chamber for impact testing may include a second cooling medium supply portion formed in a portion of the first side wall penetrating a portion of the second side wall to supply the second cooling medium to the first space.

[0012] In the ultra-low temperature chamber for impact testing, the bottom surface of the container may be knurled to facilitate attachment and detachment of the test specimen.

[0013] In the impact test ultra-cryogenic chamber, the first cooling medium may include liquefied nitrogen (LN2).

[0014] In the shock test ultra-cryogenic chamber, the second cooling medium may include liquefied helium (LHe).

[0015] In the ultra-low temperature chamber for impact testing, a shielding cover may be formed on an upper portion of the container to seal the first space.

[0016] In the ultra-low temperature chamber for impact testing, the container may include SUS316 material.

[0017] In the ultra-cryogenic chamber for impact testing, the first side wall and the second side wall may have a thickness of 2 mm to 10 mm. Effect of the Invention

[0018] According to one embodiment of the present invention as described above, it is possible to realize an ultra-low temperature chamber for impact testing that can effectively cool a test piece to an ultra-low temperature while reducing the manufacturing and maintenance costs of the chamber, although the scope of the present invention is not limited by such effects. [Brief description of the drawings]

[0019] [Figure 1] 1 is a perspective view illustrating a schematic structure of an ultra-low temperature chamber for impact testing according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a perspective view illustrating a schematic structure of the container shown in FIG. 1. [Diagram 3] FIG. 3 is a cutaway view of the container shown in FIG. 2. [Figure 4] 1 is a photograph of an ultra-cryogenic chamber for impact testing according to an example of the present invention. [Diagram 5] 1 is a graph showing the results of a cooling test of a test piece sample for an impact test according to an experimental example of the present invention. [Figure 6] 1 is a graph showing the results of a cooling test of a test piece sample for an impact test according to an experimental example of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Various preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0021] The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art, and the following embodiments may be modified into various other forms, and the scope of the present invention is not limited to the following embodiments. Rather, these embodiments are provided to make the present disclosure more complete and complete, and to fully convey the concept of the present invention to those skilled in the art. Hereinafter, the embodiments of the present invention will be described with reference to the drawings that show an ideal embodiment of the present invention.

[0022] FIG. 1 is a perspective view that illustrates the structure of an ultra-low temperature chamber for impact testing according to one embodiment of the present invention, and FIG. 2 is a perspective view that illustrates the structure of a container shown in FIG.

[0023] 1, an ultra-cryogenic chamber 100 for impact testing according to an embodiment of the present invention includes a rectangular container 10 having at least two side walls and an open top, and a cover 20 that is placed on the top of the container to shield the inside of the container 10 from the outside. A handle may be formed on a part of the cover 20 for easy operation. In this case, the shape of the handle may be made such that an operator can easily move the cover 20.

[0024] Specifically, the container 10 may include a first cooling medium supply unit 12 capable of supplying the first cooling medium to the inside of the container 10, and a first cooling medium discharge unit 14 capable of discharging the first cooling medium to the outside.

[0025] The container 10 may include a second cooling medium supply unit 16 capable of supplying the second cooling medium to the inside of the container 10. Here, since the vaporization of the second cooling medium is performed at a very fast speed, it is only necessary to supply the second cooling medium to the inside of the container 10, and there is no need to form a separate structure for discharging the second cooling medium.

[0026] Referring to FIG. 2, the test piece 30 is placed in the empty space 11A formed inside the container 10. A predetermined pattern may be formed on the bottom surface 18 of the container so that the bottom of the container 10 and the test piece 30 do not stick to each other due to evaporation. For example, the predetermined pattern includes the bottom surface of the container 10 that has been knurled. Also, even if the bottom surface is processed to have an uneven shape, the test piece 30 can be easily attached and detached. The predetermined pattern may be manufactured by various pattern processing methods other than knurling. Also, since the cooling medium according to the embodiment of the present invention circulates from the bottom to the top, the bottom surface of the container 10 does not need to be separately insulated.

[0027] FIG. 3 is a cutaway view of the container shown in FIG.

[0028] Referring to Fig. 3, which shows a sidewall of the container 10 cut from the bottom to the top of the container 10 shown in Fig. 2 based on the first cooling medium supply unit 12, the first cooling medium discharge unit 14, and the second cooling medium supply unit 16, the container 10 may include at least a double sidewall. The container 10 may include, for example, SUS316 material. In addition to the SUS316 material, any material may be used as long as it can prevent distortion and shrinkage of the chamber due to the cooling medium.

[0029] For example, the side walls may include a first side wall 10A and a second side wall 10B formed in a shape surrounding the first side wall 10A. The first side wall 10A defines a first space 11A in which the test piece 30 can be placed. The second side wall 10B defines a second space 11B in which a thermal insulation treatment can be performed between the first side wall 10A and the second side wall 10B. At this time, as shown in FIG. 2, the second space 11B has a structure in which the upper part is closed.

[0030] The thickness of the first side wall 10A and the second side wall 10B may be 2 mm to 10 mm. If the thickness of the first side wall 10A and the second side wall 10B is out of this range, heat loss occurs, which may cause a problem of a significant decrease in the cooling efficiency of the chamber.

[0031] For example, when the thickness of the first side wall 10A and the second side wall 10B is less than 2 mm, condensation of the first cooling medium occurs at the corners of the first space 11A due to the influence of the first cooling medium, which may reduce the cooling efficiency of the first space 11A. On the other hand, when the thickness of the first side wall 10A and the second side wall 10B exceeds 10 mm, a problem occurs in which the heat insulating effect of the first cooling medium is reduced, and a problem occurs in which the cooling of the test piece 30 cannot be controlled to a desired temperature by the second cooling medium. Therefore, the thickness of the first side wall 10A and the second side wall 10B may be 2 mm to 10 mm, preferably 3 mm to 6 mm, and more preferably 3 mm to 4 mm.

[0032] The second space 11B can be continuously supplied with the first cooling medium to block heat transfer between the first space 11A and the outside. The first cooling medium can include, for example, liquefied nitrogen (LN2).

[0033] In order to continuously supply the first cooling medium to the second space 11B at a constant flow rate, a first cooling medium supply unit 12 is provided at a portion of the second side wall 10B. Also, a first cooling medium discharge unit 14 is provided at a portion of the second side wall 10B so that the first cooling medium can be discharged from the second space 11B to the outside.

[0034] The first cooling medium supply unit 12 and the first cooling medium discharge unit 14 may be formed on the same level line, although they are formed in a part of the second side wall 10B. In this case, only one first cooling medium supply unit 12 may be disposed, and at least two or more first cooling medium discharge units 14 may be disposed so that the first cooling medium can be appropriately discharged according to the flow rate of the first cooling medium in order to maintain the level inside the container 10. No artificial discharge device such as a vacuum pump is formed in a part of the first cooling medium discharge unit 14.

[0035] Since the first cooling medium is prone to vaporization, if the amount is greater than the allowable amount used for thermal insulation, there may be a high risk of explosion of the container 10. To solve this, a part of the first cooling medium is discharged to the outside of the container 10, whereby the container 10 can be stably controlled.

[0036] Here, the diameter of the first cooling medium discharge portion 14 may be 3 mm to 10 mm. If the diameter of the first cooling medium discharge portion 14 is less than 3 mm, the first cooling medium is not smoothly discharged to the outside. On the other hand, if the diameter of the first cooling medium discharge portion 14 exceeds 10 mm, the amount of the first cooling medium discharged to the outside of the container 10 increases, causing heat loss and causing a problem that the insulation of the first space 11A cannot be appropriately controlled. Therefore, the diameter of the first cooling medium discharge portion 14 must be controlled to 3 mm to 10 mm, preferably 3 mm to 5 mm, and more preferably 4 mm to 5 mm.

[0037] Meanwhile, a second cooling medium can be continuously supplied to the first space 11A to cool the test piece 30. The second cooling medium can include, for example, liquefied helium (LHe). In order to supply the second cooling medium to the first space 11A, a second cooling medium supply part 16 is provided which is formed in a part of the first side wall 10A by penetrating a part of the second side wall 10B.

[0038] When liquefied helium is used as the second cooling medium, it is impossible to cool it by immersion at an ultra-low temperature environment of 20K (-253°C) because of its extremely high vaporizability. Therefore, a gas cooling method can be adopted to control the gas by directly contacting the test piece 30. For this purpose, the second cooling medium supply unit 16 must be formed in the vicinity of the area where the test piece 30 is placed.

[0039] Hereinafter, the configuration and operation of the present invention will be described in more detail with reference to preferred embodiments of the present invention, which are presented as preferred examples of the present invention and should not be construed as limiting the present invention in any sense.

[0040] As samples of the experimental examples of the present invention, steel test pieces for impact testing having the compositions summarized in Table 1 below were prepared in a size of 10 mm x 10 mm x 55 mm, and then placed in a space provided in an ultra-low temperature chamber for impact testing shown in Fig. 4. Then, liquid nitrogen was injected into an empty space in the shape of a square tube for insulation provided on the outer wall of the chamber in an atmospheric pressure atmosphere, and the temperature of the chamber was cooled to -196°C. At this time, the temperature inside the chamber and the temperature of the sample were continuously monitored using a thermocouple connected by spot welding.

[0041] The temperature inside the chamber was cooled to -196°C and maintained for a certain period of time, after which liquefied helium was supplied to the space in which the test specimen was placed and directly sprayed onto the test specimen. The liquefied helium was supplied at 3 bar or less. At this time, liquefied nitrogen was continuously supplied to insulate the inside of the chamber. After the temperature of the chamber was cooled to -253°C, the test specimen was cooled to an ultra-low temperature while maintaining the temperature for about 30 minutes, and an impact test was performed.

[0042] [Table 1] 5 and 6 are graphs showing the results of a cooling test of a test piece sample for an impact test according to an experimental example of the present invention.

[0043] First, referring to FIG. 5, when liquid nitrogen was initially poured into the ultra-low temperature chamber for impact testing to cool the temperature inside the chamber to -196°C, it was confirmed that the temperature of the test piece sample was maintained at around -196°C after 30 minutes.

[0044] Referring to FIG. 6, when liquefied nitrogen was continuously introduced to keep the chamber insulated from the outside, and liquefied helium was secondarily introduced to cool the temperature inside the chamber to an ultra-low temperature state of -253°C, it was confirmed that the temperature of the test piece sample was maintained at around -253°C from about 80 minutes later.

[0045] As mentioned above, as the demand for cryogenic environment materials increases due to the expansion of the natural energy business field, no chambers capable of producing test pieces that can be subjected to impact tests at temperatures below 20K have been developed.

[0046] According to one embodiment of the present invention, liquid helium is directly injected into the chamber to cool the test specimen, but in order to prevent the temperature of the chamber from rising during the required maintenance time in the cryogenic test, liquid nitrogen is continuously supplied to the outer wall of the chamber for insulation, thereby maximizing the decrease in the internal temperature of the test specimen even in a normal pressure environment.

[0047] The present invention has been described with reference to the embodiments shown in the drawings, but these are merely illustrative, and those skilled in the art will appreciate that various modifications and equivalent embodiments are possible. Therefore, the true technical scope of protection of the present invention should be determined by the technical ideas of the appended claims.

Claims

1. The container has at least two side walls and is rectangular and open at the top. The sidewall includes a first sidewall and a second sidewall formed in a shape surrounding the first sidewall, the first side wall defines a first space in which a test strip can be placed; The second side wall defines a second space between the first side wall and the second side wall so that a thermal insulation treatment can be performed, and the second space has a structure with an upper portion closed, a first cooling medium is continuously supplied to the second space to block heat transfer between the first space and the outside; a second cooling medium is continuously supplied to the first space to cool the test piece;

2. 2. The impact testing ultra-cryogenic chamber of claim 1, wherein a portion of the second side wall includes a first cooling medium supply portion capable of supplying the first cooling medium.

3. The ultra-cryogenic chamber for impact testing according to claim 1 , wherein a portion of the second side wall includes a first cooling medium discharge portion through which the first cooling medium can be discharged.

4. 4. The ultra-cryogenic chamber for impact testing according to claim 3, wherein the diameter of the first cooling medium discharge portion is 3 mm to 10 mm.

5. 2. The ultra-cryogenic chamber for impact testing according to claim 1, further comprising a second cooling medium supply portion formed in a portion of the first side wall penetrating a portion of the second side wall to supply the second cooling medium to the first space.

6. 2. The ultra-low temperature chamber for impact testing according to claim 1, wherein the bottom surface of the container is knurled to facilitate attachment and detachment of the test specimen.

7. The first cooling medium is liquefied nitrogen (LN ２ 2. The shock testing ultra-cryogenic chamber of claim 1, comprising:

8. 10. The shock testing ultra-cryogenic chamber of claim 1, wherein the second cooling medium comprises liquefied helium (LHe).

9. The ultra-low temperature chamber for impact testing according to claim 1 , wherein a shielding cover is formed on an upper portion of the container to seal the first space.

10. The impact test ultra-cryogenic chamber of claim 1 , wherein the container comprises SUS316 material.

11. 2. The impact test ultra-cryogenic chamber of claim 1, wherein the first and second side walls have a thickness of 2 mm to 10 mm.

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