Fastening member, method for manufacturing fastening member, and method for releasing fastening

Abstract

To provide a fastening material, a manufacturing method of the fastening material, and a fastening release method capable of compatibly securing fastening strength and facilitating fastening release at low cost.SOLUTION: The fastening material 1 does not foam when fastening the plurality of members 21,22, and exhibits the same fastening strength as that of a fastening material made of a normal metal body. On the other hand, the fastening material 1 is foamed and made porous by heating. As a result, the strength of the fastening material 1 is reduced, and the fastening of the plurality of members 21,22 can be easily released by breaking the fastening material 1. The foam precursor 10 is inexpensive as compared with a shape memory alloy, and according to the fastening material 1, it is possible to achieve both securing of fastening strength and ease of fastening release at low cost.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to fasteners, methods for manufacturing fasteners, and methods for unfastening. [Background technology]

[0002] Conventional fastening materials include those that use shape memory alloys (see, for example, Patent Document 1). The fastening device (fastening material) in Patent Document 1 includes leg portions made of shape memory alloy, which are inserted into insertion holes in the fastening target component. At room temperature, an engaging claw portion formed on the end of the leg portion engages with a shoulder of a step formed in the insertion hole. At high temperatures, the shape memory effect causes the outer shape of the engaging claw portion to deform slightly, releasing it from engagement with the shoulder of the step. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-304020 Summary of the Invention [Problem to be solved by the invention]

[0004] The above-mentioned fastening materials can ensure both fastening strength and ease of fastening / unfastening, but the inclusion of shape memory alloys increases the cost of each fastening material, which is a problem. For this reason, it is thought that they are unlikely to be adopted in fields that require fastening multiple components, such as buildings, automobiles, ships, and aircraft. Therefore, there is a need for a material that can ensure both fastening strength and ease of fastening / unfastening at a low cost.

[0005] The present disclosure provides a fastening material, a method for manufacturing a fastening material, and a method for fastening and unfastening that can both ensure fastening strength and be easily released at low cost. [Means for solving the problem]

[0006] The gist of the present disclosure is as follows.

[0007] [1] A fastener made from a foam precursor that expands when heated.

[0008] This fastening material does not foam when fastening multiple components, and exhibits the same level of fastening strength as fastening materials made of ordinary metal bodies. However, this fastening material foams and becomes porous when heated. As a result, the strength of the fastening material decreases, and by breaking the fastening material, the fastening of multiple components can be easily released. The foam precursor is less expensive than shape memory alloys, and this fastening material can both ensure fastening strength and make it easy to release the fastening at a low cost.

[0009] [2] The fastening material according to [1], which is configured to contain a foaming agent and a thickener. According to this, the thickener contained in the fastening material can suppress the release of gas to the outside and the segregation of pores when the foaming agent is decomposed by heating and gas is generated inside the fastening material. Therefore, the porosity of the fastening material can be promoted and made uniform.

[0010] [3] The fastening material according to [1] or [2], which contains aluminum as a main metal component. By using an aluminum foam precursor, a lightweight and easily processable fastening material can be obtained.

[0011] [4] The fastening material according to any one of [1] to [3], which contains iron as a main metal component. By using an iron foam precursor, a fastening material with excellent strength can be obtained.

[0012] [5] The method for producing a fastening material according to any one of [1] to [4], comprising: a preparation step of preparing a metal material and a foaming agent; a foaming precursor formation step of forming a foaming precursor by mixing the foaming agent with a metal constituting the metal material; and a cutting step of cutting a fastening material of a desired shape from the foaming precursor. This method for producing a fastening material can produce a foaming precursor in which the foaming agent is mixed with the metal. The fastening material described above can be easily produced by cutting a fastening material of a desired shape from the obtained foaming precursor.

[0013] [6] The method for manufacturing a fastening material according to [5], wherein the preparation step further includes a laminate formation step of preparing a pair of metal plates as the metal material, and forming a laminate having a foaming agent sandwiched between the pair of metal plates after the preparation step, and the foam precursor formation step includes friction stirring the laminate to form the foam precursor. According to this method, by performing friction stirring on the laminate having a foaming agent sandwiched between the pair of metal plates, a foam precursor in which the foaming agent is uniformly mixed in the metal can be obtained.

[0014] [7] The method for manufacturing a fastening material according to [6], wherein the preparation step further includes preparing a thickener, the laminate formation step includes forming the laminate in which the foaming agent and the thickener are sandwiched between the pair of metal plates, and the foam precursor formation step includes forming the foam precursor by mixing the foaming agent and the thickener with the metal constituting the metal material. According to this method, by performing friction stirring on the laminate in which the foaming agent and the thickener are sandwiched between the pair of metal plates, a foam precursor in which the foaming agent and the thickener are uniformly mixed in the metal can be obtained.

[0015] [8] In the method for manufacturing a fastening material according to [5], the preparing step includes preparing a metal powder as the metal material, and the foam precursor forming step includes a mixing step of mixing the metal powder and the foaming agent, and a molding step of molding the mixed metal powder and the foaming agent to form the foam precursor. This method makes it possible to easily obtain a foam precursor in which a foaming agent is mixed in a metal.

[0016] [9] The method for producing a fastening material according to [8], wherein the preparing step further comprises preparing a thickener, the mixing step comprises mixing the metal powder, the foaming agent, and the thickener, and the molding step comprises molding the mixed metal powder, the foaming agent, and the thickener. This method makes it possible to easily obtain a foam precursor in which the foaming agent and the thickener are mixed in the metal.

[0017]

[10] A method for releasing a fastened body in which multiple components are fastened together with the fastening material according to any one of [1] to [9], comprising: a foaming step of heating the fastening material to cause it to foam; and a releasing step of breaking the foamed fastening material and releasing the fastening of the multiple components together. According to this fastening releasing method, the fastening material foams when heated, reducing its strength, and the multiple components that have been mechanically fastened can be easily disassembled.

[0018]

[11] The method for releasing fastening material according to

[10] , wherein the foaming step uses a halogen lamp to heat the fastening material. By using a halogen lamp, the fastening material can be heated locally, reducing the impact of heating on other components. This makes it easier to recycle the other components.

[0019]

[12] The method for releasing fastening according to

[10] or

[11] , wherein in the foaming step, the fastening material is heated so that the porosity of the fastening material is 60% or more. By allowing foaming of the fastening material to proceed until the porosity of the fastening material is 60% or more, the fastening material becomes sufficiently easy to break. [Effects of the Invention]

[0020] According to the present disclosure, it is possible to provide a fastening material, a method for manufacturing a fastening material, and a method for fastening and unfastening that can both ensure fastening strength and facilitate unfastening at low cost. [Brief explanation of the drawings]

[0021] [Figure 1] Fig. 1(a) is a schematic perspective view of a fastening material according to one embodiment, and Fig. 1(b) is a schematic cross-sectional view showing a state in which the fastening material fastens a plurality of members. [Figure 2] Fig. 2(a) is a schematic cross-sectional view of the fastened body in the foaming step, and Fig. 2(b) is a schematic cross-sectional view of the fastened body in the releasing step. [Figure 3] Fig. 3(a) is a schematic perspective view of the laminate in the laminate forming step, and Fig. 3(b) is a schematic perspective view of the laminate in the foam precursor forming step. [Figure 4] Fig. 4(a) is a schematic perspective view of the laminate in a foam precursor forming step, and Fig. 4(b) is a schematic perspective view of the laminate in a cutting step. [Figure 5] 1 is a photograph of a fastener and a pair of metal plates. [Figure 6] This is a photograph of the fastener. [Figure 7] Figure 7(a) is a photograph of the fastening material before foaming, and Figure 7(b) is a photograph of the fastening material after foaming. [Figure 8] Figure 8(a) is a photograph of the fastener placed in the tensile shear tester, and Figure 8(b) is a photograph of the fastener at the time of fracture. [Figure 9] Figure 9 is a photograph of the fastener after shearing. [Figure 10] FIG. 10 is a graph of a load-displacement curve obtained by measuring the shear load of a fastener in a tensile shear test. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, a preferred embodiment of a fastening material according to an embodiment of the present disclosure will be described in detail with reference to the drawings.

[0023] [Fastening material configuration] FIG. 1(a) is a schematic perspective view of a fastening material according to one embodiment. The fastening material 1 is a material for mechanically fastening multiple members. The fastening material 1 can be used in fields that require fastening multiple members, such as buildings, automobiles, ships, and aircraft. The fastening material 1 is, for example, a rivet, a screw, or a thread. In this embodiment, the fastening material 1 will be described as a rivet. In the example of FIG. 1(a), the fastening material 1 has a cylindrical shape.

[0024] The fastening material 1 is composed of a foaming precursor that foams when heated. The fastening material 1 contains aluminum as its main metal component. In addition to the metal material, the fastening material 1 also contains, for example, a foaming agent and a thickener. An example of a foaming agent is titanium hydride (TiH2) with a particle size of 45 μm or less. Other examples of foaming agents include zirconium hydride (ZrH2) and calcium carbonate (CaCO3). An example of a thickener is alumina (Al2O3) with a particle size of 1 μm or less. Other examples of thickeners include silicon carbide (SiC), silicon dioxide (SiO2), and magnesium oxide (MgO).

[0025] [Tightening method] An example of a method for fastening multiple members 21 and 22 using a fastening material 1 will be described. The fastening material 1 described above does not foam at room temperature and has a predetermined strength. At room temperature, the fastening material 1 forms a fastened body 100 in which multiple members 21 and 22 are fastened together, as shown in FIG. 1(b). The fastened body 100 is a structure in which multiple members 21 and 22 are fixed so that they are in close contact with each other using the fastening material 1. The members 21 and 22 are, for example, metal plates. The member 21 includes a through hole 21a for passing the fastening material 1 therethrough. Similarly, the member 22 includes a through hole 22a for passing the fastening material 1 therethrough. The diameter of the through hole 21a is the same as the diameter of the through hole 22a. The length of the fastening material 1 is longer than the thickness of the members 21 and 22 when they are stacked together. 1(b), fastening material 1 is passed through through holes 21a and 22a in a state in which member 21 and member 22 are stacked so that the center of through hole 21a and the center of through hole 22a are aligned. In this state, end 11 of fastening material 1 on the member 21 side protrudes from member 21, and end 12 of fastening material 1 on the member 22 side protrudes from member 22.

[0026] After fastener 1 is passed through through holes 21a and 22a, end 11 and end 12 of fastener 1 are each crimped. End 11 and end 12 are each deformed using, for example, a hammer or a rivet gun. As shown in FIG. 1(b), end 11 is deformed so as to come into close contact with the surface of member 21. The diameter of end 11 after deformation becomes larger than the diameter of insertion portion 13, which is the portion of fastener 1 that passes through through holes 21a and 22a. Similarly, end 12 is deformed so as to come into close contact with the surface of member 22. The diameter of end 12 after deformation becomes larger than the diameter of insertion portion 13.

[0027] [How to release the connection] Next, an example of a method for releasing the fastening material 1 will be described. The method for releasing the fastening material 1 includes a foaming step and a releasing step. FIG. 2(a) is a schematic cross-sectional view of the fastened body 100 during the foaming step. The fastening material 1 is foamed and made porous by heating. As shown in FIG. 2(a), the porous state occurs when the foaming agent decomposes due to heating, generating gas inside the fastening material 1 and creating multiple pores 14. The foaming process may increase the volume of the fastening material 1, causing the fastening material 1 to expand. Specifically, gas is generated at multiple locations inside the fastening material 1, causing the fastening material 1 to expand at multiple locations. However, the inclusion of a thickener in the fastening material 1 prevents the generated gas from being released outside the fastening material 1 and prevents the locations where pores are created from segregating.

[0028] The fastening material 1 is heated to, for example, 700°C. In the foaming process, the fastening material 1 is heated, for example, using a halogen lamp. In the foaming process, the fastening material 1 of the fastened body 100 is locally heated by the halogen lamp so that the heating effect on the components 21 and 22 other than the fastening material 1 is minimized. When a halogen lamp is used as a heating method, for example, the focus of light from the halogen lamp is adjusted to the center in the height direction of the fastening material 1. For example, light from the halogen lamp may be irradiated from the end 11 side and then from the end 12 side. Alternatively, two halogen lamps may be prepared and end 11 and end 12 may be heated simultaneously. Alternatively, end 11 and end 12 may be heated only from one side without heating both sides. The heating time depends on the irradiation intensity of the halogen lamp, but is, for example, about 30 seconds.

[0029] In the foaming process, for example, the fastening material 1 may be heated so that the porosity of the fastening material 1 becomes 40% or more, the fastening material 1 may be heated so that the porosity of the fastening material 1 becomes 60% or more, or the fastening material 1 may be heated so that the porosity of the fastening material 1 becomes 80% or more. The porosity p is calculated, for example, as a percentage by the following formula (1) where ρ is the density of the fastening material 1 before foaming and ρf is the density of the fastening material 1 after foaming. p={1―(ρf / ρ)}×100···(1) When the fastening material 1 is foamed, the porosity of the fastening material 1 increases while the density of the fastening material 1 decreases. As a result, the strength of the fastening material 1 decreases. The strength of the fastening material 1 after foaming may decrease to, for example, one-third or one-half of the strength of the fastening material 1 before foaming.

[0030] By reducing the strength of the fastening material 1, it becomes possible to easily break the fastening material 1. FIG. 2(b) is a schematic cross-sectional view of the fastened body 100 in the release step. In the release step illustrated in FIG. 2, the fastening material 1 is broken by shearing by pulling the members 21 and 22 in opposite directions. The method for breaking the fastening material 1 is not limited to this, and the fastening material 1 may also be broken with a hammer or the like. In the release step, the fastening material 1 is broken, and it becomes possible to easily release the fastening between the multiple members 21 and 22.

[0031] [Method of manufacturing fastening materials] Next, a method for manufacturing the fastening material 1 will be described with reference to Figures 3 and 4. The manufacturing method includes a preparation step, a foam precursor formation step, and a cutting step. In the preparation step, a metal material, a foaming agent, and a thickener, which are constituent materials of the fastening material 1, are prepared. In this embodiment, the fastening material 1 is manufactured using a friction stir process. The manufacturing method using the friction stir process further includes a laminate formation step.

[0032] In a manufacturing method using friction stir welding, a pair of metal plates 31 and 32 are prepared as metal materials in a preparation step. FIG. 3(a) is a schematic perspective view of a laminate 3 in a laminate formation step. The laminate formation step is performed after the preparation step. In the laminate formation step, a laminate 3 is formed by sandwiching a foaming agent 4 and a thickener 5 between a pair of metal plates 31 and 32. Each of the pair of metal plates 31 and 32 is, for example, an aluminum plate. In the example of FIG. 3(a), each of the pair of metal plates 31 and 32 has a rectangular shape including a pair of long sides and a pair of short sides in a plan view. The outer edges of the metal plates 31 and 32 are aligned in a plan view. The foaming agent 4 is, for example, titanium hydride (TiH2) powder, and the thickener 5 is, for example, alumina (Al2O3) powder.

[0033] 3(b) and 4(a) are schematic perspective views of the laminate 3 in the foam precursor forming step. In the foam precursor forming step, friction stirring is performed on the laminate 3 to form a foam precursor 10 by mixing the metal constituting the metal plates 31 and 32 with the foaming agent 4 and thickener 5. Friction stirring is performed using a friction stir tool 6 consisting of a cylindrical tool 61 and a rod-shaped probe 62 attached to the tip of the tool 61. In the foam precursor forming step, the tool 61 and the probe 62 are pressed in the thickness direction B of the laminate 3 while rotating at a predetermined rotation speed in a rotation direction A about the center of the friction stir tool 6. This causes the probe 62 to penetrate the metal plates 31 and 32. Then, the friction stir tool 6 is moved at a constant speed from one of a pair of short sides to the other in a direction C parallel to the pair of long sides of the metal plate 31.

[0034] When the friction stir tool 6 reaches the other of the pair of short sides, the friction stir tool 6 is shifted a predetermined distance in a direction perpendicular to direction C (a direction parallel to the pair of short sides), and the friction stir tool 6 is again moved from one of the pair of short sides toward the other. As shown in FIG. 4(a), this movement operation is repeated multiple times. As a result, in the portion R where the friction stir tool 6 has moved, the foaming agent 4 and the thickener 5 are uniformly mixed in the metal of the pair of metal plates 31, 32, and the metal plates 31 and 32 are joined together, thereby obtaining a foam precursor 10.

[0035] 4(b) is a schematic perspective view of the laminate in the cutting step. In the cutting step, the fastening material 1 is cut out in a desired shape from the foam precursor 10. The desired shape is, for example, a cylindrical shape. As a cutting method, for example, electric discharge machining is used. In the electric discharge machining, the fastening material 1 may be cut out by generating an electric discharge between a thin, wire-shaped electrode and the foam precursor 10 and moving the electrode along the outer edge of the desired shape.

[0036] [Action and effect] The fastening material 1 described above does not foam when fastening multiple components 21, 22 together, and exhibits the same level of fastening strength as a fastening material made of a normal metal body. However, this fastening material 1 foams and becomes porous when heated. As a result, the strength of the fastening material 1 decreases, and by breaking the fastening material 1, the fastening of multiple components 21, 22 can be easily released. The foam precursor 10 is less expensive than a shape memory alloy, and this fastening material 1 can both ensure fastening strength and facilitate release at a low cost.

[0037] The fastening material 1 is configured to contain a foaming agent 4 and a thickener 5. By containing the thickener 5, when the foaming agent 4 is decomposed by heating and gas is generated inside the fastening material 1, the release of gas to the outside and segregation of pores can be suppressed. This promotes and uniforms the porosity of the fastening material 1.

[0038] The fastening material 1 contains aluminum as a main metal component. By using the foam precursor 10 made of aluminum, the fastening material 1 can be obtained which is lightweight and easy to process.

[0039] The method for manufacturing the fastening material 1 includes a preparation step of preparing a metal material, a foaming agent 4, and a thickener 5, a foam precursor formation step of forming a foam precursor 10 by mixing the foaming agent 4 and the thickener 5 with a metal that constitutes the metal material, and a cutting step of cutting out a fastening material 1 having a desired shape from the foam precursor 10. This method for manufacturing the fastening material 1 makes it possible to obtain a foam precursor 10 in which the foaming agent 4 and the thickener 5 are mixed in a metal. The fastening material 1 described above can be easily manufactured by cutting out a fastening material 1 having a desired shape from the obtained foam precursor 10.

[0040] The preparation step includes preparing a pair of metal plates 31, 32 as a metal material, and after the preparation step, a laminate formation step is included in which a laminate 3 is formed in which a foaming agent 4 and a thickener 5 are sandwiched between the pair of metal plates 31, 32. The foam precursor formation step includes friction stirring the laminate 3 to form a foam precursor 10. According to this, by performing friction stirring on the laminate 3 in which the foaming agent 4 and the thickener 5 are sandwiched between the pair of metal plates 31, 32, a foam precursor 10 in which the foaming agent 4 and the thickener 5 are uniformly mixed in the metal can be obtained.

[0041] The fastening release method includes a foaming step of heating and foaming the fastening material 1 in a fastened body 100 in which multiple members 21, 22 are fastened together with the fastening material 1, and a release step of breaking the foamed fastening material 1 to release the fastening of the multiple members 21, 22. According to this fastening release method, the fastening material 1 is foamed by heating and its strength is reduced, allowing the multiple members 21, 22 that have been mechanically fastened to be easily disassembled.

[0042] In the foaming process, a halogen lamp is used to heat the fastening material 1. By using a halogen lamp, the fastening material 1 can be heated locally, and the influence of heating on the other members 21 and 22 can be reduced. This makes it easier to recycle the other members 21 and 22.

[0043] In the foaming process, the fastening material 1 is heated, for example, so that the porosity of the fastening material 1 becomes 80% or more. By allowing the foaming of the fastening material 1 to proceed until the porosity of the fastening material 1 becomes 80% or more, the fastening material 1 becomes sufficiently easy to break.

[0044] [Variations] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments.

[0045] The manufacturing method of the fastening material 1 is not limited to a manufacturing method using the friction stir welding method, and may be a manufacturing method using powder metallurgy instead of the friction stir welding method. In a manufacturing method using powder metallurgy, a metal powder is prepared as a metal material in a preparation step. For example, aluminum powder is prepared in the preparation step.

[0046] The foam precursor forming process in the powder metallurgy manufacturing method includes a mixing process and a molding process. In the mixing process, a metal powder, a foaming agent 4, and a thickener 5 are mixed together. In the mixing process, for example, the metal powder, the foaming agent 4, and the thickener 5 are uniformly mixed together. The mixing process may be performed using a mechanical mixer.

[0047] The molding process includes a consolidation process and a hot extrusion process. In the consolidation process, the powder mixed in the mixing process is solidified. In the consolidation process, for example, the mixed powder is compression-molded into a predetermined shape to form a solid form. Subsequently, in the hot extrusion process, the solidified mixture is fed into a hot extruder and extruded into a predetermined shape. Through the hot extrusion process, a foam precursor 10 can be obtained in which the foaming agent 4 and the thickener 5 are uniformly mixed in the metal. Then, in the cutting process, the fastening material 1 is cut out into a desired shape from the obtained foam precursor 10. This allows the fastening material 1 to be easily manufactured.

[0048] The fastening material 1 may be manufactured by a casting precursor method. In the casting precursor method, for example, a thickener 5 and a foaming agent 4 are added to molten aluminum, followed by stirring and cooling to obtain a foam precursor 10.

[0049] Although the above-described method for manufacturing a fastening material includes a thickener, it is not necessary to include a thickener. In the foaming step of the fastening / unfastening method, other heating methods may be used instead of heating with a halogen lamp. For example, the fastening material 1 may be heated with an infrared heater or a laser. Alternatively, the fastened body 100, including the fastening material 1, may be heated in an electric furnace. Furthermore, the fastening material 1 may contain other metal components as its main component instead of aluminum. For example, the main metal component of the fastening material 1 may be iron. When the main metal component of the fastening material 1 is iron, a fastening material 1 with excellent strength is obtained. When the fastening material 1 is a rivet, it does not have to be cylindrical. For example, the fastening material 1 may be a rivet with a flange.

[0050] The fastening material 1 may be a screw instead of a rivet. In this case, in the cutting step of the manufacturing method, a desired shape may be cut out from the head of the screw along the shank. After cutting, a thread may be formed on the shank. Furthermore, in the cutting step, cutting using, for example, a blade may be performed instead of electrical discharge machining. In addition, in the present embodiment, an example has been described in which the entire fastening material 1 is composed of a foam precursor. However, the fastening material 1 may be composed of a portion that contains a metal foam body and a portion that does not. For example, after manufacturing the fastening material 1, a metal that does not contain a foam precursor may be joined to both ends of the fastening material 1. In this case, when the fastening material 1 is passed through the through holes 21a and 22a and the end portions 11 and 12 of the fastening material 1 are respectively crimped, the end portions 11 and 12 may not contain a foam precursor.

[0051] [Example] Hereinafter, examples of the present disclosure will be described.

[0052] [Manufacturing of fastening materials] First, a fastening material was manufactured using the manufacturing method described with reference to FIGS. 3 and 4. Two sheets of commercially pure aluminum (alloy number A1050) measuring 210 mm in length, 80 mm in width, and 6 mm in thickness were prepared as a pair of metal plates. Titanium hydride (TiH) powder with a particle diameter of 45 μm or less was prepared as the foaming agent, and alumina (AlO) powder with a particle diameter of 1 μm or less was prepared as the thickening agent. A foam precursor in which the foaming agent and thickening agent were uniformly mixed in the metal was obtained by friction stirring a laminate composed of the above materials. Specifically, a foam precursor in which 1 mass % titanium hydride powder and 5 mass % alumina powder were mixed with the aluminum plate was obtained. Then, a cylindrical rivet with a diameter of 6 mm and a height of 7 mm was obtained as the fastening material by electrical discharge machining from the foam precursor, as shown in FIG. 5.

[0053] [Formation of fastener] Next, two steel plates measuring 60 mm in length, 30 mm in width, and 1.6 mm in thickness were prepared as the multiple components to be fastened with fastening materials. A through hole with a diameter of 6.1 mm was formed in each steel plate at the center in the width direction and 6 mm from one end in the length direction, as shown in Figure 5. The two steel plates were overlapped so that the centers of the through holes were aligned, and then fastening materials were inserted into the through holes.

[0054] Next, as shown in Figure 6, a riveter was used to deform both ends of the fastener to fasten the two steel plates together to form a fastened body. Here, it was found that even the fastener containing the foam precursor can undergo plastic deformation in the same way as a fastener not containing the foam precursor (composed only of commercially pure aluminum), and can fasten two steel plates together.

[0055] [Foaming of fastening materials] Next, the foaming process in the fastening / unfastening method described in Figure 2 was carried out. A halogen lamp was used as the heat source. The distance between the fastening material and the halogen lamp was adjusted so that the focal point of the halogen lamp's light was aligned with the center position in the height direction of the fastening material. The power of the halogen lamp was 1600 W. In the foaming process, with the fastened body placed on a support stand, the fastening material was heated from one side of a pair of metal plates (the side of the metal plate opposite the metal plate placed on the support stand) for about 30 seconds.

[0056] 7(a) is a photograph of the fastening material before foaming, and FIG. 7(b) is a photograph of the fastening material after foaming. In the example of FIG. 7(b), the fastening material expands toward one side of the pair of metal plates. Note that in the foaming process, the fastening material may be heated without placing the fastener on a support base, or the fastening material may be heated from both sides of the pair of metal plates, causing the fastening material to expand toward both sides of the pair of metal plates.

[0057] Next, the release step of the fastening release method described in FIG. 2 was performed. In this example, a tensile shear test was performed on the fastening material, and the pair of metal plates were pulled in opposite directions to shear and fracture the fastening material. FIG. 8(a) is a photograph of the fastened body placed in a tensile shear testing machine, and FIG. 8(b) is a photograph of the fastening material at fracture. FIG. 9 is a photograph of the fastened body after shear. A universal testing machine was used as the tensile shear testing machine. FIG. 9 shows the fracture surface of the fastening material in the metal body placed on the right. Porosity is observed on the fracture surface. In other words, it is assumed that the fastening material fractured at the location where the porosity occurred.

[0058] Figure 10 shows a graph of a load-displacement curve obtained by measuring the shear load of a fastener in a tensile shear test. The vertical axis of Figure 10 shows shear load in units of N (Newtons). The horizontal axis of Figure 10 shows displacement in units of mm (millimeters). The displacement is the length to which the fastener is pulled from its initial length, assuming that the length of the fastener when it is installed in the tensile shear tester is the initial length.

[0059] FIG. 10 shows the shear load measurement results for the fastener after foaming, as well as the shear load measurement results for the fastener before foaming as a comparative example. First, in the load-displacement curve for the fastener before foaming, the load increases rapidly from the initial position, and shear deformation progresses in the fastener. At the displacement of maximum load Tm1, the load reaches the maximum load Nm1. At maximum load Tm1, shear progresses further in the fastener, and for example, the fastener may develop a crack. However, the fastener has not yet fractured. At the displacement after maximum load Tm1, the load gradually decreases, and shear progresses further. Finally, at fracture time Tb1, the fastener fractures.

[0060] In contrast, in the load-displacement curve of the fastener after foaming, the load increases rapidly from the initial position, and shear deformation progresses in the fastener. The load reaches the maximum load Nm2 at the displacement Tm2 at the maximum load. Then, at displacements after the maximum load Tm2, ​​shear progresses further, and the fastener fractures at the displacement Tb2 at the fracture point. In the load-displacement curve after foaming, the load decreases in stages. This is thought to be because as shear progresses, cracks form connecting multiple pores within the fastener. When a crack reaches a pore, the crack formation progresses rapidly, causing a sudden decrease in load. Meanwhile, the load gradually decreases until the crack reaches the next pore. It is assumed that the presence of pores causes repeated sudden and gradual load decreases, resulting in a gradual load decrease.

[0061] As shown in Figure 10, the maximum load Nm1 of the fastener before foaming is greater than the maximum load Nm2 of the fastener after foaming. This result shows that the foaming process reduces the maximum load required to shear the fastener. As a result, foaming the fastener reduces its strength, and by breaking the fastener, it is possible to easily release the fastening of multiple components. [Explanation of symbols]

[0062] 1...fastening material, 3...laminate, 4...foaming agent, 5...thickener, 10...foam precursor, 21, 22...member, 31, 32...metal plate, 100...fastening body, p...porosity.

Claims

1. A fastening material made from a foam precursor that expands when heated.

2. The fastening material of claim 1 , further comprising a foaming agent and a thickening agent.

3. The fastener of claim 1 , comprising aluminum as a primary metallic component.

4. The fastener of claim 1 , comprising iron as a primary metallic component.

5. A method for manufacturing a fastening material according to any one of claims 1 to 4, a preparation step of preparing a metal material and a foaming agent; a foam precursor forming step of forming a foam precursor by mixing the foaming agent with a metal constituting the metal material; a cutting step of cutting a fastening material of a desired shape from the foam precursor.

6. In the preparation step, a pair of metal plates is prepared as the metal material; The method further includes, after the preparation step, a laminate formation step of forming a laminate in which a foaming agent is sandwiched between the pair of metal plates, The method for manufacturing a fastening material according to claim 5 , wherein the foam precursor forming step comprises friction stirring the laminate to form the foam precursor.

7. In the preparation step, a thickener is further prepared, In the laminate formation step, the laminate is formed by sandwiching the foaming agent and the thickener between the pair of metal plates, The method for manufacturing a fastening material according to claim 6 , wherein the foam precursor forming step comprises mixing the foaming agent and the thickener with the metal constituting the metal material to form the foam precursor.

8. In the preparation step, a metal powder is prepared as the metal material, The foam precursor forming step includes: a mixing step of mixing the metal powder and the foaming agent; and forming the foam precursor by molding the mixed metal powder and foaming agent.

9. In the preparation step, a thickener is further prepared, In the mixing step, the metal powder, the foaming agent, and the thickener are mixed together, The method for manufacturing a fastening material according to claim 8 , wherein the molding step includes molding the mixed metal powder, the foaming agent, and the thickener.

10. a foaming step of foaming the fastening material by heating the fastening material in a fastened body in which a plurality of members are fastened together using the fastening material according to any one of claims 1 to 4; and a releasing step of breaking the fastening material after foaming and releasing the fastening between the plurality of members.

11. The fastening release method according to claim 10 , wherein the foaming step heats the fastening material using a halogen lamp.

12. The fastening release method according to claim 10 , wherein in the foaming step, the fastening material is heated so that the porosity of the fastening material becomes 60% or more.

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