Coupling device using shape memory alloy and method for manufacturing same

Abstract

The present invention relates to a coupling device using a shape memory alloy. More specifically, the coupling device comprises a coupler unit for retaining at least two pipes. The coupler unit is made of a shape memory alloy such that pipes are inserted into both ends of the coupler unit, respectively, in a cooled state, and then heated so as to restore the shape, thereby retaining the two pipes. In addition, a method for manufacturing a coupling device using a shape memory alloy according to a preferred embodiment of the present invention comprises: an arrangement step of arranging a raw material having a quadrangular shape on a lower mold; a lower bending step of pressing and bending the raw material between an intermediate mold and the lower mold after the arrangement step; an upper bending step of pressing and bending the raw material between an upper mold and the intermediate mold after the lower bending step; and a welding step of separating the raw material from the intermediate mold and then welding end portions thereof after the upper bending step. The coupler unit is manufactured accordingly.

Description

A bonding device using a shape memory alloy and a manufacturing method thereof

[0001] The present invention relates to a joining device using a shape memory alloy and a method for manufacturing the same, and more specifically, to a joining device using a shape memory alloy and a method for manufacturing the same, which can fix two pipes by inducing shape restoration only by heating using a shape memory coupler to which deformation has been added in advance.

[0002] Welding, currently in widespread use, offers advantages over other joining methods, such as casting or riveting, including reduced work processes, reduced raw material consumption, and improved performance and lifespan. However, it also has several drawbacks. For example, Republic of Korea Patent No. 10-2311789 (October 13, 2021) discloses a welding ring for pipe joining and a pipe welding method using the same.

[0003] However, welding for pipe fastening still presents the following challenges. First, because the surrounding area is heated to a high temperature and melted to join, the material deteriorates, and residual stresses are likely to develop at the joint upon cooling. Second, welding defects such as pores or cracks can develop in the welded area depending on the working conditions, requiring non-destructive testing. Third, the strength and quality of the joint depend on the worker's skill, requiring skilled workers. Fourth, preliminary preparations, such as welding machine installation, and non-destructive testing are time-consuming and costly. Fifth, connecting pipes composed of dissimilar metals and non-ferrous metals is difficult. Sixth, sufficient space is required for the welding tool to access the pipe to be welded. Considering the above-mentioned drawbacks of welding, welding has been difficult to perform when connecting pipes composed of various materials, including dissimilar metals, non-ferrous metals, and other plastics, or when welding tools are inaccessible in compact, integrated workspaces.

[0004] The present invention has been devised to solve the problems of the prior art as described above, and its purpose is to provide a joining device using a shape memory alloy and a manufacturing method thereof that can easily fix two pipes by inducing shape restoration only by heating using a shape memory coupler to which deformation has been added in advance.

[0005] The problems to be solved by the present invention are not limited to the problems mentioned above, and other problems to be solved by the present invention that are not mentioned herein will be clearly understood by a person having ordinary skill in the technical field to which the present invention pertains from the description below.

[0006] In a preferred embodiment of the present invention, a coupling device using a shape memory alloy comprises a coupler portion for fixing at least two pipes, wherein the coupler portion is manufactured from a shape memory alloy, and is characterized in that the two pipes are fixed by inserting pipes into each end of the coupler portion in a cooled state and then heating to restore their shape.

[0007] In addition, the shape memory alloy according to a preferred embodiment of the present invention is characterized by having a composition of, in wt%, iron (Fe): 16 to 18%, manganese (Mn): 4.5 to 5.5%, silicon (Si): 9 to 11%, chromium (Cr): 3.5 to 4.5%, nickel (Ni): 0.6 to 0.8%, vanadium (V): 0.25 to 0.35%, the remainder carbon (C) and other unavoidable impurities.

[0008] In addition, the coupler part according to a preferred embodiment of the present invention is characterized in that it is formed in a cylindrical shape with a hollow portion.

[0009] In addition, in a method for manufacturing a coupling device using a shape memory alloy according to a preferred embodiment of the present invention, the coupler part is manufactured by including a placing step in which a raw material in the shape of a square plate is placed in a lower mold, a lower bending step in which the raw material is bent by being pressed between an intermediate mold and the lower mold after the placing step, an upper bending step in which the raw material is bent by being pressed between an upper mold and the intermediate mold after the lower bending step, and a welding step in which the raw material is separated from the intermediate mold and an end is welded after the upper bending step.

[0010] In addition, the coupler part according to a preferred embodiment of the present invention is characterized in that it is manufactured in a heated state.

[0011] By means of solving the above problem, the present invention's shape memory alloy-based coupling device and its manufacturing method utilize a shape memory alloy coupling (CryoFit Coupling) whose shape changes depending on the ambient temperature, thereby enabling a work process easier than welding and reliably connecting pipes in a short period of time.

[0012] The effects of the present invention are not limited to the effects mentioned above, and effects of the present invention not mentioned herein will be clearly understood by those skilled in the art to which the present invention pertains from the description below.

[0013] FIG. 1 (a) is a drawing showing a state in which a coupler part of a coupling device using a shape memory alloy according to an embodiment of the present invention is cooled, and FIG. 1 (b) is a drawing showing a state in which a coupler part according to an embodiment of the present invention is heated and restored to its original state.

[0014] Figure 2 is a flowchart showing a method for manufacturing a bonding device using a shape memory alloy according to one embodiment of the present invention.

[0015] FIG. 3 is a drawing showing a mold used in manufacturing a bonding device using a shape memory alloy according to one embodiment of the present invention.

[0016] Figure 4 is a conceptual diagram showing a method for manufacturing a bonding device using a shape memory alloy according to one embodiment of the present invention.

[0017] Figure 5 is a diagram showing the results of a finite element simulation for calculating the bending load requirement of an Fe-SMA plate.

[0018] Figure 6 is a drawing showing the Fe-SMA coupler welding application area and the mold bending press.

[0019] Fig. 7 is a drawing showing a CNC machine for removing internal weld protrusions and machining uneven portions of an Fe-SMA coupler.

[0020] Figure 8 is a schematic diagram for theoretically calculating the pressure required to increase the inner diameter.

[0021] Figure 9 is a schematic diagram showing the 3D design and pre-deformation process of the Fe-SMA coupler pre-deformation device mold.

[0022] Figure 10 is a schematic diagram showing the principle of pre-strain application of the Fe-SMA coupler.

[0023] The terms used in this specification will be briefly explained, and the present invention will be described in detail.

[0024] The terms used in this invention have been selected from widely used, common terms, taking into account their functions. However, these terms may vary depending on the intentions of those skilled in the art, precedents, the emergence of new technologies, etc. Therefore, the terms used in this invention should be defined based on their meaning and the overall content of the invention, rather than simply their names.

[0025] When a part of a specification is said to “include” a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise stated.

[0026] Below, with reference to the attached drawings, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0027] Specific details, including the problems to be solved, means of solving them, and the effects of the invention, are included in the embodiments and drawings described below. The advantages and features of the present invention, and methods for achieving them, will become clearer with reference to the embodiments described below in detail, along with the accompanying drawings.

[0028] Hereinafter, the present invention will be described in more detail with reference to the attached drawings.

[0029] In a preferred embodiment of the present invention, a coupling device using a shape memory alloy comprises a coupler part (100) for fixing at least two pipes (10), and the coupler part (100) is made of a shape memory alloy, and when a pipe (10) is inserted into each of both ends of the coupler part (100) in a cooled state, the coupler part (100) is heated to restore its shape, thereby fixing the two pipes (10).

[0030] More specifically, referring to FIG. 1, the coupler part (100) is a shape memory coupler to which deformation has been added in advance, and as the shape is restored only by heating with a torch or the like, the diameter is reduced, thereby pressurizing and fixing the pipe (10) inserted inside.

[0031] For example, the coupler part (100) is formed in a cylindrical shape with a hollow space formed therein, and the pipes (10) are inserted into the hollow space at both ends and the ends are in contact. When the worker heats the coupler part (100), the hollow space is minimized, and the two pipes (10) inserted are fixed in a state where the inner surface of the coupler part (100) is in contact with the outer surface of the pipe (10).

[0032] That is, in the case of conventional manual couplings using welding or bolting, workability is low, construction speed and reliability are low, and quality is greatly affected by the skill of the worker, whereas the coupling device using the shape memory alloy of the present invention has the advantage of faster construction speed and higher workability through a simple and easy process.

[0033] In addition, the shape memory alloy is formed to have a composition of, in wt%, iron (Fe): 16 to 18%, manganese (Mn): 4.5 to 5.5%, silicon (Si): 9 to 11%, chromium (Cr): 3.5 to 4.5%, nickel (Ni): 0.6 to 0.8%, vanadium (V): 0.25 to 0.35%, the remainder carbon (C) and other unavoidable impurities, so that shape restoration is achieved in a short time when heated using a torch or the like.

[0034] Hereinafter, a method for manufacturing a bonding device using a shape memory alloy according to a preferred embodiment of the present invention will be described in detail with reference to the attached drawings.

[0035] Referring to FIGS. 2 to 4, the coupler part (100) is manufactured by including a placement step (S100) in which a square plate-shaped raw material (200) is placed in a lower mold (210), a lower bending step (S200) in which the raw material (200) is bent by being pressed between an intermediate mold (220) and the lower mold (210) after the placement step (S100), an upper bending step (S300) in which the raw material (200) is bent by being pressed between an upper mold (230) and the intermediate mold (220) after the lower bending step (S200), and a welding step (S400) in which the raw material (200) is separated from the intermediate mold (220) and an end is welded after the upper bending step (S300).

[0036] Here, the lower mold (210) is a die provided with a groove formed to have a semicircular cross-section therein, the upper mold (230) is a die formed in a shape symmetrical to the lower mold (210), and the intermediate mold (220) is a die provided in a cylindrical shape. That is, the manufacture of the coupler portion (100) is performed by placing an Fe-SMA plate on the lower mold (210), and then placing the cylindrical intermediate mold (220) on the plate and applying pressure through a press, thereby bending the plate. In other words, the lower shape of the plate is bent in the shape of an empty space between the lower mold (210) and the intermediate mold (220), and the lower part of the Fe-SMA coupler is plastically worked into a cylindrical shape. Thereafter, the upper part of the plate, in which the lower bending has been performed, is pressed by the upper mold to bend the upper part. At this time, if the circumference of the Fe-SMA coupler is small or bent, making it difficult to position the unformed portion between the upper mold (230) and the intermediate mold (220), the lower mold (310) can be used to solve the problem through multi-stage molding. Afterwards, while the upper mold (230), the intermediate mold (220), and the lower mold (210) are in contact, the intermediate mold (220) is removed, and welding is performed through a space prepared in advance between the upper mold (230) and the lower mold (210).

[0037] As a result, the coupler part (100) is manufactured in a heated state, and when the pipes (10) are inserted into each end of the coupler part (100) in a cooled state, the pipes (10) are heated and restored to their original state, thereby clamping the pipes (10). That is, when the pipes (10) are inserted into each end of the coupler part (100) in a cooled state and the ends of the two pipes (10) are in contact, the hollow space is minimized as the worker heats the coupler part (100), and the two inserted pipes (10) are fixed in a state where the inner surface of the coupler part (100) is in contact with the outer surface of the pipes (10).

[0038] Meanwhile, the shape memory alloy described in the present invention refers to an alloy that remembers its original shape even when deformed by applying force and immediately returns to its original shape when heated slightly. Since the crystal arrangement of the shape memory alloy is significantly different on the high-temperature side (mother phase) and the low-temperature side (martensite phase), even if the shape is deformed on the low-temperature side, it returns to its original shape (mother phase) when heated above a certain temperature (reverse transformation temperature).

[0039] On the other hand, referring to FIGS. 5 and 6, a finite element simulation was performed to obtain the required load required for bending the raw material (200) plate, and the condition under which the intermediate mold (220) presses the Fe-SMA plate was simulated to derive the required load required for forming.

[0040] The forming conditions of the above raw material (100) were simulated to form a Fe-SMA plate with a width of 120 mm and a thickness of 1.5 mm, and the final forming radius R was set to 60.5 mm, which is the outer diameter of the pipe (10). For the simulation, the yield strength and elastic modulus of Fe-SMA were calculated to be 400 MPa and 150 GPa, respectively. In order to confirm whether forming was possible with the pressure of a 7-ton hydraulic press, a finite element analysis was performed assuming a condition of applying a load of 7 tons and simulating the condition. Referring to Fig. 5, as can be seen from the finite element simulation results, when a load is applied with our 7-ton hydraulic press, a load of approximately 500 MPa, which is far higher than the yield strength of 400 MPa of the material, is applied, and it can be confirmed that the material is sufficiently formed without any unformed portions.

[0041] In addition, referring to Fig. 7, if necessary after machining, the interior can be CNC machined for the purpose of removing the welding protrusion and machining the internal unevenness, and the prototype Fe-SMA coupler of the currently designed design has an inner diameter of approximately 60.5 to 61 mm when pre-strained after welding, and a width of not exceeding 120 mm.

[0042] Also, referring to Fig. 8, for the jig design for pre-deformation, the pressure and additional load required to expand the inner diameter of the Fe-SMA coupler in the theoretically given design are first calculated using a simple theoretical mechanics model as follows. The theoretical calculation schematic diagram represents the balance of forces in the process of expanding the inner diameter by applying a load to the inside of the Fe-SMA machined into a cylindrical shape after welding, and shows a cross-sectional view of the cylindrical coupler as viewed from above. At this time, if a load is added to expand the inner diameter by applying a uniform load to the inside of the Fe-SMA coupler, it can be approximated as pressure P if the load is uniform, and when considering only half of the coupler as shown in Fig. 8, if only the component of force in the vertical direction is considered, the sum of the components corresponding to the vertical direction of the pressure P is balanced with the force F1 added to the coupler cross-section. If the total vertical component of the load added to the inside of the coupler is F2, F2 has a force twice as large as the force added to the coupler cross-section, and when a load of about 500 MPa is added, a sufficient degree of pre-deformation (more than 4% in the tensile direction) can be applied. Therefore, if the maximum load to be added to the Fe-SMA plate is calculated as 500 MPa, when a coupler with an inner diameter of 60.5 mm is manufactured by bending and then welding a Fe-SMA plate with a width of 120 mm and a thickness of 1.5 mm, the total force (F1 * 2) added to the coupler cross-section is as follows. It is calculated as follows: (F1 * 2) = 1.5 (mm) * 120 (mm) * 500 (N / mm2) * 2 = 180,000 N

[0043] Meanwhile, the total vertical component force F2 of the pressure applied inside the Fe-SMA cross-section can be calculated as (P2 * area of ​​the vertical cross-section to which the pressure is applied), and therefore P2 is calculated as follows. P2 = (F1 * 2) / (60.5 (mm) * 120 (mm)) = 24.8 MPa

[0044] Referring to Fig. 9, a pre-strain application device for a Fe-SMA coupler in a drawing form is designed based on such theoretical calculations. That is, as illustrated in Fig. 9, the Fe-SMA coupler pre-strain application device has a drawing form and is composed of jigs 1-3 and a tray for fixing the jigs. In order to easily apply pre-strain to increase the inner diameter of the Fe-SMA coupler, jigs 1 and 2 are first arranged on the tray so that the jigs are fixed, and then the Fe-SMA coupler (pipe-shaped) is inserted and fixed in a form surrounding jigs 1 and 2. Afterwards, a cone-shaped jig 3 is inserted, and when jig 3 is pressed vertically with a strong load, jigs 1 and 2 form the Fe-SMA toward the outside of the pipe and increase the inner diameter.

[0045] Referring to Fig. 10, when jig 3 is inserted into the designed pre-strain device and pressed with a strong load, the previously installed jigs 1 and 2 expand outward, and at this time, an almost uniform load can be applied. It is expected that such a design can precisely control the degree of inner diameter expansion from the design of jigs 1-3 and the insertion amount of jig 3, and the amount of pre-strain applied can be freely controlled through the jig design, and rapid pre-strain application is also possible. In the preceding theoretical calculation, the load for applying sufficient pre-strain is ideally to create a pressure of 24.8 MPa or more inside the Fe-SMA coupler, so when calculating the required load, the area of ​​the inner cross section of the Fe-SMA coupler with an inner diameter of 60.5 mm is approximately 2,873 mm. 2Therefore, the required vertical load is 71,258 N. Since the vertical load of 71,258 N is close to the maximum load of the press, the calculated value shows that if the width of the Fe-SMA coupler is set to the maximum (120 mm), it can be formed with the maximum load of the press, and if the width is reduced to 100 mm or 80 mm, it can be formed without any problems.

[0046] As a result, the coupling device using the shape memory alloy of the present invention has the advantage of being easier to work with than welding and being able to reliably connect pipes in a short period of time by using a shape memory alloy coupling (CryoFit Coupling) that changes shape depending on the ambient temperature.

[0047] In this way, it will be understood by those skilled in the art that the technical configuration of the present invention described above can be implemented in other specific forms without changing the technical idea or essential features of the present invention.

[0048] Therefore, the embodiments described above should be understood as being exemplary and not restrictive in all respects, and the scope of the present invention is indicated by the claims described below rather than the detailed description above, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

[0049] [Explanation of symbols]

[0050] 100: Coupler section

[0051] 200: Raw materials

[0052] 210: Lower mold

[0053] 220: Intermediate mold

[0054] 230: Upper mold

[0055] 10: Pipe

[0056] S100: Deployment stage

[0057] S200: Lower bending stage

[0058] S300: Upper bending stage

[0059] S400: Welding stage

Claims

1. Includes a coupler section for fixing at least two pipes; The above coupler part is manufactured from a shape memory alloy, A joint device using a shape memory alloy, characterized in that the two pipes are fixed by inserting pipes into each end of the coupler portion in a cooled state and then heating to restore their shape.

2. In paragraph 1, The above shape memory alloy is, A bonding device using a shape memory alloy, characterized by having a composition of, in weight %, iron (Fe): 16 to 18%, manganese (Mn): 4.5 to 5.5%, silicon (Si): 9 to 11%, chromium (Cr): 3.5 to 4.5%, nickel (Ni): 0.6 to 0.8%, vanadium (V): 0.25 to 0.35%, the remainder being carbon (C) and other unavoidable impurities.

3. In paragraph 1, A coupling device using a shape memory alloy, characterized in that the above coupler part is formed in a cylindrical shape with a hollow portion.

4. In the manufacturing method of a joining device using the shaped alloy of paragraph 1, A placement step in which a square plate-shaped raw material is placed in the lower mold; After the above-mentioned placement step, a lower bending step in which the raw material is bent by being pressed between the middle mold and the lower mold; After the lower bending step, an upper bending step in which the raw material is bent by being pressed between the upper mold and the intermediate mold; and A method for manufacturing a coupling device using a shape memory alloy, characterized in that the coupler part is manufactured by including a welding step in which, after the upper bending step, the raw material is separated from the intermediate mold and the end is welded.

5. In paragraph 4, A method for manufacturing a coupling device using a shape memory alloy, characterized in that the coupler part is manufactured in a heated state.

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