Preparation method of test piece for flame-resistance evaluation, and test piece for flame-resistance evaluation

Abstract

[Problem] Even when an object to be evaluated is a composite member made from a combination of members having different material properties, it is made possible to properly evaluate the composite member as a whole on the assumption of actual use. [Solution] Provided is a preparation method of a test piece 100 of an axle beam bush formed from metal and rubber, which have different material properties, whereby: a predetermined region is set which is exposed to a heat source located at a predetermined position and where a part exhibiting the lowest flame resistance has the largest surface area when the axle beam bush is actually used; the surface area ratios of members present in the region are calculated; and a test piece 100 is prepared by using a metal member 103 and a rubber member 104 having the same material properties as those of said members in the region, the metal member and the rubber member being exposed at the same ratios as the calculated surface area ratios.

Description

Method for preparing test specimens for evaluating flame retardancy and test specimens for evaluating flame retardancy

[0001] The present disclosure relates to a method for producing a test piece for evaluating flame retardancy suitable for evaluation tests based on European flame retardancy standard EN45545-2, and to a test piece for evaluating flame retardancy produced by the method.

[0002] The European flame retardancy standard EN 45545-2 is a unified European standard established to unify fire protection standards across countries, and is required for all parts related to railway vehicles. This standard is being adopted not only in Europe but also around the world, and evaluations based on this standard are also being conducted in Japan. For example, Patent Document 1 discloses a method for evaluating the maximum average heat release rate in accordance with EN 45545-2 by cutting sheet-shaped test specimens from molded articles made of resin compositions used in interior materials for railway vehicles, etc. Patent Document 2 discloses a method for evaluating the heat release characteristics and smoke generation characteristics of synthetic leather used in vehicle seats in accordance with EN 45545-2. Patent Document 3 discloses a method for evaluating flame retardancy by cutting flexible members used in air springs for railway vehicles into a predetermined shape and performing a heat release test as specified in EN 45545-2 on the resulting test specimens.

[0003] JP 2019-38895 A JP 2020-12252 A Japanese Patent No. 7014562 A

[0004] EN45545-2 clause 5.3.2 states that evaluation tests must be conducted under the same exposed surface conditions as those under actual use. If the test specimens disclosed in Patent Documents 1-3 are molded articles made of the same components, or sheets or components that are made of the same material no matter which part is cut out, then flame retardancy evaluation using test specimens can be conducted under the same exposed surface conditions as those under actual use. However, if the test specimens are composite components made of different materials (e.g., metal and rubber), such as bushings and axle springs used in railway bogies, it is not possible to cut out test specimens from specific parts, making it difficult to properly evaluate the composite component as a whole.

[0005] Therefore, the present disclosure aims to provide a method for preparing a test piece for evaluating flame retardancy, and a test piece for evaluating flame retardancy, which allows appropriate evaluation of the composite member as a whole, assuming actual use, even if the object to be evaluated is a composite member made by combining components of different materials.

[0006] To achieve the above object, a first aspect of the present disclosure is a method for preparing a test specimen for evaluating the flame retardancy of a composite member made of multiple components of different materials, comprising: setting a predetermined region in the composite member's actual use state where the composite member will be exposed to a heat source at a predetermined position and the surface area of ​​the portion with the weakest fire resistance will be the largest; calculating the surface area ratio of each component in the predetermined region; and preparing the test specimen using multiple test components made of the same material as each component in the predetermined region so that the test components are exposed at the same ratio as the calculated surface area ratio. Another aspect of the first aspect is characterized in that the test specimen has a predetermined shape with a flat surface, with one test component placed on the outer side of the flat surface and another test component placed on the inner side of the flat surface. Another aspect of the first aspect is characterized in that the test specimen is prepared using each test component so that one side of the test specimen is exposed at the same ratio. Another aspect of the first configuration is characterized in that, in the above configuration, both sides of the test piece are created using each test member so that they are exposed to the same extent. Another aspect of the first configuration is characterized in that, in the above configuration, if the composite member has a cavity on the inside of the surface, a cavity is also formed on the inside of the surface of the test piece. Another aspect of the first configuration is characterized in that, in the above configuration, if the composite member is made of metal and rubber, the test piece is created by setting a predetermined area so that the surface area of ​​the rubber is maximized. To achieve the above object, a second aspect of the present disclosure is a test piece for evaluating the flame retardancy of a composite member made of multiple members made of different materials, characterized in that it is created by any of the methods for creating a test piece for flame retardancy evaluation described in the first configuration.

[0007] According to the present disclosure, even if the evaluation target is a composite member made of a combination of components of different materials, appropriate evaluation of the composite member as a whole can be performed by using a flame retardancy evaluation test piece that reproduces the actual use. According to another aspect of the present disclosure, in addition to the above-mentioned effect, the arrangement of each test component in the test piece is the same as the arrangement of each component in a predetermined region, thereby enabling the creation of a test piece that more closely resembles the actual use condition of the composite member. According to another aspect of the present disclosure, in addition to the above-mentioned effect, the test piece is formed into a predetermined shape with a flat surface, with one test component arranged on the outer side of the flat surface and the other test component arranged on the inner side of the surface, thereby enabling the creation of a test piece that more closely resembles the actual use condition of the composite member. According to another aspect of the present disclosure, in addition to the above-mentioned effect, one side of the test piece is created so that the same proportions are exposed using each test component, thereby making it easy to create a test piece that reproduces the actual use condition. According to another aspect of the present disclosure, in addition to the above-mentioned effect, both sides of the test piece are created so that the same proportions are exposed using each test component, thereby enabling the test piece to be set without paying attention to the orientation of the front and back during evaluation testing, eliminating setting errors. According to another aspect of the present disclosure, in addition to the above effects, when a composite member has cavities on the inside of its surface, cavities are also formed on the inside of the surface of the test piece, making it possible to create a test piece that more closely resembles the actual use condition of a composite member having cavities. According to another aspect of the present disclosure, in addition to the above effects, when a composite member is made of metal and rubber, a test piece is created by setting a predetermined area so that the surface area of ​​the rubber is maximized, making it possible to obtain a test piece that reproduces the most unfavorable actual use condition.

[0008] 1 is an explanatory diagram showing the actual use state of the axle spring bushing of Example 1. An explanatory diagram of a test piece for evaluating flame retardancy of Example 1, where (A) is a plan view, (B) is a cross section along line A-A, and (C) is a cross section along line A-A of a modified example. An explanatory diagram showing the actual use state of the single link bushing of Example 2. An explanatory diagram of a test piece for evaluating flame retardancy of Example 2, where (A) is a plan view, (B) is a cross section along line B-B, (C) is a cross section along line B-B of a modified example, and (D) is a plan view of the modified example. An explanatory diagram showing the actual use state of the axle spring of Example 3. An explanatory diagram of a test piece for evaluating flame retardancy of Example 3, where (A) is a plan view, (B) is a cross section along line C-C, (C) is a cross section along line C-C of a modified example, and (D) is a plan view of the modified example. An explanatory diagram showing the actual use state of the axle spring of Example 4. 1 is an explanatory diagram of a test specimen for evaluating flame retardancy in Example 4, where (A) is a plan view and (B) is a cross section taken along line D-D. 2 is an explanatory diagram of a modified example of the test specimen for evaluating flame retardancy in Example 4, where (A) is a plan view and (B) is a cross section taken along line E-E. 3 is an explanatory diagram of a modified example of the test specimen for evaluating flame retardancy in which a coating layer is formed on the surface of the sample layer, where (A) is a plan view and (B) is a cross section taken along line F-F. 4 is an explanatory diagram of a modified example of the test specimen for evaluating flame retardancy showing another example of the arrangement of the metal member and the rubber member, where (A) is a plan view and (B) is a cross section taken along line G-G.

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0010] FIG. 1 shows an axle beam bushing 1 used in a railroad vehicle axle beam bogie. The axle beam bogie is designed so that vertical loads are borne by springs on the axle box and longitudinal loads are borne by axle beams connecting the axle box and the bogie frame. The axle beam bushing 1 is incorporated into the connection between the axle beam 10 and the bogie frame 11, transmitting the load and providing vibration isolation. FIG. 1 shows the actual use of the axle beam bushing 1, the subject of evaluation, from below. The axle beam bushing 1 comprises a shaft-shaped inner metal fitting 2 located in the center, a rubber member 3 bonded to the outer surface of the inner metal fitting 2, and an outer metal fitting 4 bonded to the outer surface of the rubber member 3. Bosses 5, 5 provided at both axial ends of the inner metal fitting 2 are supported by the bogie frame 11, and the middle portion of the axle beam bushing 1, including the outer metal fitting 4, is supported by a tubular portion 10a provided at the end of the axle beam 10. Therefore, assuming that the heat source is on the ground (near the rail), the lower half of each of the metal tubular portion 10a, the ends 3a, 3a of the rubber 3 protruding from the tubular portion 10a, and the boss portions 5, 5 of the metal inner fitting 2 will be exposed to the heat source.

[0011] A method for preparing a test specimen for evaluating flame retardancy (hereinafter simply referred to as "test specimen") will be described below, taking into account the actual use state of this axial beam bushing 1. First, a region is set where the surface area of ​​the rubber 3, which is exposed to the heat source below and has the weakest fire resistance, is maximized. In this case, a region S surrounded by a dashed line is set. Next, the surface area ratios of the exposed portions of the cylindrical portion 10a of the axial beam 10, which is metal, the left and right boss portions 5, 5, and the end portions 3a, 3a of the rubber 3 in region S are calculated. For example, the ratios are as shown below.

[0012] [Surface area ratio] Axial beam (tubular part): 25,000 mm ２ (47%) Boss part: 20,000 mm ２ (38%) Rubber: 8000mm ２ (15%) == ... ２

[0013] Next, a test specimen (e.g., 75 mm (length) × 75 mm (width) × 25 mm (thickness)) specified in EN45545-2 is prepared. At this time, as shown in FIGS. 2A and 2B, the test specimen 100 has a sample layer 102 formed on the surface of the main rubber 101, which serves as the lower layer, using two test members: a metal (e.g., iron) and a rubber (e.g., natural rubber) made of the same materials as the components in region S. The main rubber 101 may be made of the same material as the rubber in the sample layer 102, or a different material. In the sample layer 102, the metal and rubber are exposed in the same proportions as the surface area calculated in region S. The arrangement of both components is also adjusted to match the actual use conditions. Therefore, the sample layer 102 is formed so that the metal member 103 accounts for 85% or less of the central area, and the rubber members 104, 104 account for a combined proportion of 15% or more on either side of it. In this way, a test specimen 100 is obtained having a sample layer 102 on its surface that reproduces the actual use conditions.

[0014] However, as shown in FIG. 2(C), the sample layer 102 may be formed on both the front and back surfaces of the test specimen 100, rather than on just one surface. By creating both surfaces of the test specimen 100 in this manner, with the metal member 103 and the rubber member 104 exposed in equal proportions, the test specimen 100 can be set without paying attention to the orientation of the front and back surfaces during evaluation testing, eliminating errors during setting. Note that EN 45545-2 specifies the thickness of the metal portion of the test specimen. For example, steel plate is 0.8 mm, and aluminum plate is 1.0 mm. Therefore, the thickness of the metal portion of the sample layer 102 is also set based on EN 45545-2. By conducting a test using the test specimen 100 with the sample layer 102 formed on its surface, flame retardancy evaluation can be performed under exposed surface conditions equivalent to those in actual use.

[0015] Thus, in Example 1, a method for preparing a test piece 100 for a shaft beam bushing 1 (an example of a composite material) made of different materials, metal and rubber (an example of multiple materials), involves setting a predetermined region S in which the surface area of ​​the portion with the weakest fire resistance is greatest and exposed to a heat source at a predetermined position when the shaft beam bushing 1 is in actual use, calculating the surface area ratio of each member in region S, and preparing a test piece 100 using metal members 103 and rubber members 104 (an example of multiple test members) made of the same material as each member in region S, so that the test piece 100 is exposed at the same ratio of surface area as the calculated ratio. With this configuration, even if the shaft beam bushing 1, which is the evaluation target, is a composite material made by combining members made of different materials, appropriate evaluation of the composite material as a whole can be performed by using a test piece 100 that is reproduced assuming actual use.

[0016] In particular, the arrangement of the metal member 103 and the rubber member 104 in the test piece 100 is the same as the arrangement of each member in the region S. Therefore, it is possible to create a test piece 100 that more closely resembles the actual use condition of the axial beam bushing 1. One side of the test piece 100 is created so that the metal member 103 and the rubber member 104 are exposed in equal proportions. Therefore, it is possible to easily create a sample layer 102 that reproduces the actual use condition. For the axial beam bushing 1 made of metal and rubber, the region S is set so that the surface area of ​​the rubber is maximized when the test piece 100 is created. Therefore, it is possible to obtain a test piece 100 that reproduces the actual use condition under the most unfavorable circumstances.

[0017] FIG. 3 shows a single-link bushing 20 used in a traction device for railway vehicles. The single-link bushing 20 is incorporated into the connection portions at both ends of a single link (monolink) 30 that connects the bogie and the carbody, transmitting loads and providing vibration isolation. FIG. 3 shows a side view of the single-link bushing 20 being evaluated in actual use. The single-link bushing 20 is incorporated into the end of the single link and includes a shaft-shaped inner metal fitting 21 located at the center, a cylindrical outer metal fitting 22 located outside the inner metal fitting 21, and a cylindrical rubber 23 bonded to the inner metal fitting 21 and outer metal fitting 22 between them. A connection portion 24 protruding laterally from the end of the inner metal fitting 21 is connected to the bogie frame 31 with a bolt 25. Therefore, assuming that the heat source is located to the side of the connection part 24 (in front of the plane of the paper in Figure 3), the metal bogie frame 31, connection part 24, bolt 25, inner metal fitting 21, and the outer rubber 23 and outer metal fitting 22 will all be exposed to the heat source.

[0018] A method for preparing a test specimen will be described below, taking into account the actual usage conditions of this single-link bushing 20. First, a region S (surrounded by a dashed line) is set, which is exposed to the heat source and has the largest surface area of ​​the rubber 23, which is the part with the weakest fire resistance. Next, the proportions of the exposed surface area of ​​each of the metal parts in region S, namely the bogie frame 31, the connection part 24, the bolt 25, the inner metal fitting 21, the rubber 23 (the C-shaped part that does not overlap with the bogie frame 31), and the outer metal fitting 22, are calculated. For example, the proportions are as shown below. The bogie frame 31, the connection part 24, the bolt 25, the inner metal fitting 21, and the outer metal fitting 22 are calculated collectively as metal parts.

[0019] [Surface area ratio] Metal part: 20,000 mm ２ (66.6%) Rubber: 10,000 mm ２ (33.3%) == ... ２

[0020] Next, a test specimen (e.g., 75 mm (length) × 75 mm (width) × 25 mm (thickness)) specified in EN45545-2 is prepared. At this time, as shown in FIGS. 4(A) and 4(B), the test specimen 100A has a sample layer 102A formed on the surface of the main rubber 101, which is the lower layer, using two test members: a metal (e.g., iron) and a rubber (e.g., natural rubber) made of the same materials as the components in region S. In the sample layer 102A, the metal and rubber are exposed in the same proportions as the calculated surface area proportions in region S. The thickness of the metal portion is set based on EN45545-2. In this sample layer 102A, the metal member 103 is formed in the center, which is the inner side in the surface direction, at a proportion of 66.6% or less, and the rubber member 104 is formed around the outer periphery of the metal member 103, which is the outer side in the surface direction, at a proportion of 33.3% or more. In this way, a test specimen 100A having a sample layer 102A on its surface that reproduces actual use conditions is obtained. However, as shown in Fig. 4(C), the sample layer 102A may be formed not only on the front surface but also on both the front and back surfaces. Also, in consideration of the C-shaped exposure of the rubber 23, the sample layer 102A may be formed by extending the metal member 103 to one side and cutting out one side of the rubber member 104, as shown in Fig. 4(D). By conducting a test using the test piece 100A in which the sample layer 102A is reproduced on the surface in this way, it is possible to evaluate flame retardancy under exposed surface conditions that are the same as those in actual use.

[0021] Thus, in Example 2 described above, the method for preparing test piece 100A for single link bushing 20 (an example of a composite member) made of different materials, metal and rubber (an example of a plurality of members), involves the following steps: setting a predetermined region S in which the surface area of ​​the portion of single link bushing 20 that is exposed to a heat source at a predetermined position and has the weakest fire resistance is maximized when actually used; calculating the surface area ratio of each member in region S; and preparing test piece 100A using metal member 103 and rubber member 104 (an example of a plurality of test members) made of the same material as each member in region S, so that the exposed surface area is the same as the calculated surface area ratio. With this configuration, even if single link bushing 20, which is the object to be evaluated, is a composite member made by combining members made of different materials, by using test piece 100A that is reproduced assuming actual use, it is possible to appropriately evaluate the composite member as a whole, and the same effects as those of Example 1 described above can be achieved.

[0022] In particular, the test piece 100A is formed into a predetermined shape with a flat surface, with the rubber member 104 (an example of the first test member) disposed on the outer side of the flat surface and the metal member 103 (an example of the other test member) disposed on the inner side of the surface in the planar direction. This makes it possible to create a test piece 100A that more closely resembles the actual use state of the single-link bushing 20.

[0023] Figure 5 shows an axle spring 40 used at the connection between an axle box and a bogie frame of a railway vehicle. The axle spring 40 elastically supports a bogie frame 51 on an axle box 50, transmitting the load from the bogie frame 51 to the axle box 50 while also providing vibration isolation. Figure 5 shows the axle spring 40, the object being evaluated, in actual use from the side. The axle spring 40 includes a cylindrical upper metal fitting 41 fixed to the bogie frame 51, a lower metal fitting 42 fixed to the axle box 50, and a conical laminated rubber 43 connecting the upper metal fitting 41 and the lower metal fitting 42. Therefore, assuming a heat source is located in front or to the side, the entire circumference or half circumference of the metal upper metal fitting 41, lower metal fitting 42, and laminated rubber 43 will be exposed to the heat source.

[0024] A method for preparing a test specimen will be described below, taking into account the actual usage conditions of this axle spring 40. First, a region S (region surrounded by a dashed line) is set, which is exposed to the heat source and has the largest surface area of ​​the laminated rubber 43, which is the part with the weakest fire resistance. Next, the ratio of the surface area of ​​the exposed parts of the upper metal fitting 41 and lower metal fitting 42, which are metal, to the laminated rubber 43 in region S is calculated. For example, the ratios are as shown below. Here, the calculation is performed for the entire circumference. The upper metal fitting 41 and lower metal fitting 42 are calculated together as metal parts.

[0025] [Surface area ratio] Metal part: 100,000 mm ２ (41%) Laminated rubber: 140,000 mm ２ (59%) == ... ２

[0026] Next, a test specimen (e.g., 75 mm (length) × 75 mm (width) × 25 mm (thickness)) specified in EN45545-2 is prepared. At this time, as shown in FIGS. 6A and 6B, the test specimen 100B has a sample layer 102B formed on the surface of the main rubber 101, which is the lower layer, using two test members: a metal (e.g., iron) and a rubber (e.g., natural rubber) made of the same materials as the components in region S. In the sample layer 102B, the metal and rubber are exposed in the same proportions as the calculated surface area proportions in region S. The thickness of the metal portion is set based on EN45545-2. In this sample layer 102B, the metal member 103 is formed in the center, which is the inner side in the surface direction, at a proportion of 41% or less, and the rubber member 104 is formed around the outer periphery of the metal member 103, which is the outer side in the surface direction, at a proportion of 59% or more. In this way, the test specimen 100B having the sample layer 102B on its surface, which reproduces actual use conditions, is obtained. However, as shown in Fig. 6(C), the sample layer 102B may be formed not only on the front surface but also on both the front and back surfaces. Also, the sample layer 102B is not limited to a form in which the metal member 103 is surrounded by the rubber member 104, but may be half made of the metal member 103 and half made of the rubber member 104, as shown in Fig. 6(D). By conducting a test using the test piece 100B in which the sample layer 102B is reproduced on the surface in this way, it is possible to evaluate flame retardancy under exposed surface conditions that are the same as those in actual use.

[0027] Thus, in Example 3, the method for preparing test piece 100B for axle spring 40 (an example of a composite member) made of different materials, metal and rubber (an example of a plurality of members), involves the following steps: setting a predetermined region S in which the surface area of ​​the portion of axle spring 40 that is exposed to a heat source at a predetermined position and has the weakest fire resistance is maximized when actually used; calculating the surface area ratio for each member in region S; and preparing test piece 100B using metal member 103 and rubber member 104 (an example of a plurality of test members) made of the same material as each member in region S, so that the test piece 100B is exposed at the same ratio as the calculated surface area ratio. With this configuration, even if axle spring 40, which is the evaluation target, is a composite member made by combining members made of different materials, appropriate evaluation of the composite member as a whole can be performed by using test piece 100B reproduced assuming actual use, and the same effects as those of Examples 1 and 2 can be achieved.

[0028] 7 also shows the same axle spring 40 as in Example 3, but differs from Example 3 in that a flame-retardant rubber cover 45 is attached to cover the entire laminated rubber 43. A cylindrical cavity (gap) 46 is formed around the entire circumference between the cover 45 and the laminated rubber 43. Therefore, assuming that a heat source is located in front or to the side, the entire circumference or half circumference of the metal upper metal fitting 41 and lower metal fitting 42 and the cover 45 will be exposed to the heat source.

[0029] A method for preparing a test specimen will be described below, taking into account the actual usage conditions of this axle spring 40. First, a region S (region surrounded by a dashed line) is set, which is exposed to the heat source and has the largest surface area of ​​the cover 45, which is the part with the weakest fire resistance. Next, the ratio of the surface area of ​​each of the exposed parts of the metal upper metal fitting 41 and lower metal fitting 42 and the cover 45 (rubber) in region S is calculated. For example, the ratios are as shown below. Here, the calculation is performed for the entire circumference. The upper metal fitting 41 and lower metal fitting 42 are calculated together as metal parts.

[0030] [Surface area ratio] Metal part: 100,000 mm ２ (50%) Rubber: 100,000 mm ２(50%) == ... ２

[0031] Next, a test specimen (e.g., 75 mm (length) × 75 mm (width) × 25 mm (thickness)) specified in EN45545-2 is prepared. At this time, as shown in FIGS. 8A and 8B , the test specimen 100C has a sample layer 102C formed on the surface of the main rubber 101, which is the lower layer, using two test members: a metal (e.g., iron) and a rubber (e.g., CSM rubber) made of the same materials as the members in the region S. In the sample layer 102C, the metal and rubber are exposed in the same proportions as the calculated surface area proportions in the region S. The thickness of the metal portion is set based on EN45545-2. In this sample layer 102C, the metal member 103 is formed in the center, which is the inner side in the surface direction, at a proportion of 50% or less, and the rubber member 104 is formed around the outer periphery of the metal member 103, which is the outer side in the surface direction, at a proportion of 50% or more. Furthermore, in consideration of the formation of a cavity 46 between the laminated rubber 43 and the cover 45, as shown in Fig. 8(B), a cavity (e.g., 6 mm thick) 105 is formed between the metal member 103 and rubber member 104 and the main rubber 101. The size (area and depth) of this cavity 105 can be set, taking into account the extent of the cavity 46 in the actual axle spring 40, based on, for example, the ratio to the total volume of the laminated rubber 43, the average distance between the cover 45 and the laminated rubber 43, the dimension between the cover 45 and the laminated rubber 43 at the location most likely to be affected by a heat source, etc.

[0032] In the case of Fig. 8, the sample layer 102C and the cavity 105 may be formed on both the front and back surfaces if possible. However, in order to evaluate the test piece 100C under unfavorable conditions, the sample layer 102C can be formed using only the rubber member 104, omitting the metal member, as shown in Fig. 9. By conducting a test using the test piece 100C in which the sample layer 102C is reproduced on the surface in this way, it is possible to evaluate the flame retardancy under exposed surface conditions that are the same as those in actual use.

[0033] Thus, in Example 4, the method for preparing test piece 100C for axle spring 40 (an example of a composite member) made of different materials, metal and rubber (an example of multiple members), involves the following steps: setting a predetermined region S in which the surface area of ​​the portion of axle spring 40 that is exposed to a heat source at a predetermined position and has the weakest fire resistance is maximized when actually used; calculating the surface area ratio for each member in region S; and preparing test piece 100C using metal member 103 and rubber member 104 (an example of multiple test members) made of the same material as each member in region S, so that the metal member 103 and rubber member 104 are exposed at the same ratio as the calculated surface area ratio. With this configuration, even if axle spring 40, which is the evaluation target, is a composite member made by combining members made of different materials, appropriate evaluation of the composite member as a whole can be performed by using test piece 100C reproduced assuming actual use, and the same effects as those of Examples 1 to 3 can be achieved.

[0034] In particular, since the axle spring 40 has a cavity 46 on the inside of the surface, a cavity 105 is also formed on the inside of the surface of the test piece 100C. Therefore, it is possible to create a test piece 100C that is closer to the actual use state of the axle spring 40 having the cavity 46.

[0035] Below, we will explain modifications common to each example. When a coating layer is formed on the surface of an evaluation object, such as by applying a flame-retardant paint, a coating layer 106 can be formed on the surface of the sample layer 102D of a test piece 100D, which is made up of a metal member 103 and a rubber member 104, as shown in Figures 10(A) and 10(B). However, the configuration of the sample layer 102D itself is not limited to that shown in Figure 10. The arrangement of the metal member and the rubber member can be modified as appropriate to match the structure of the evaluation object. The planar shape of the member located at the center of the sample layer, as shown in Figure 4, is not limited to a square or rectangular shape, and may be other shapes such as a circle. The arrangement of the metal member and the rubber member may be reversed from that of the above examples. As shown in Figure 11, a test piece 100E may have multiple band-shaped rubber members 104 arranged in parallel inside the metal member 103. The shape and size of the test piece can also be modified as appropriate, as long as it can be used in evaluation tests based on EN45545-2. For example, the test specimen may be circular in plan view, the thickness of the main rubber may be reduced, or only the sample layer may be used to create the test specimen. If the exposed surface of the object to be evaluated has irregularities or steps, the irregularities or steps may also be reproduced in the sample layer. If the depressions exceed the thickness of the test specimen, a through hole may be formed in the test specimen. The number of components forming the composite member is not limited to two, and test specimens according to the present disclosure can be created using three or more components. In other words, the test specimen may be created using the number of test components that matches the number of composite members.

[0036] 1...Axle beam bushing, 2, 21...Inner metal fittings, 3, 23...Rubber, 3a...End portion, 4, 22...Outer metal fittings, 5...Boss portion, 10...Axle beam, 10a...Cylinder portion, 11, 31, 51...Bogie frame, 20...Single link bushing, 24...Connection portion, 25...Bolt, 30...Single link, 40...Axle spring, 41...Upper metal fitting, 42...Lower metal fitting, 43...Laminated rubber, 45...Cover, 46, 105...Space, 50...Axle box, 100, 100A, 100B, 100C...Test piece for flame retardancy evaluation, 101...Main body rubber, 102, 102A, 102B, 102C...Sample layer, 103...Metal member, 104...Rubber member, S...Area.

Claims

1. A method for producing a test piece for evaluating flame retardancy of a composite member made of a plurality of members made of different materials, comprising the steps of: A predetermined region is set in which a surface area of ​​a portion exposed to a heat source at a predetermined position and having the weakest fire resistance is maximized in an actual use state of the composite member; Calculating the proportion of the surface area of ​​each of the members in the predetermined region; A method for preparing a test piece for evaluating flame retardancy, characterized in that the test piece is prepared using a plurality of test members made of the same material as each of the members in the specified area, so that the test piece is exposed at the same ratio as the calculated ratio of surface area.

2. 2. The method for producing a test specimen for evaluating flame retardancy according to claim 1, wherein the arrangement of the test members in the test specimen is the same as the arrangement of the members in the predetermined region.

3. 3. A method for preparing a test piece for evaluating flame retardancy according to claim 1 or 2, characterized in that the test piece is formed into a predetermined shape with a flat surface, one of the test members is arranged on the outer side of the flat surface in the planar direction, and another of the test members is arranged on the inner side of the planar surface in the planar direction.

4. 2. The method for preparing a test piece for evaluating flame retardancy according to claim 1, wherein one side of the test piece is prepared so as to be exposed at the same ratio using each of the test members.

5. 2. The method for preparing a test piece for evaluating flame retardancy according to claim 1, wherein both sides of the test piece are prepared so as to be exposed at the same ratio using each of the test members.

6. The method for producing a test specimen for evaluating flame retardancy according to claim 1, wherein, when the composite member has a cavity on the inside of its surface, a cavity is also formed on the inside of the surface of the test specimen.

7. The method for preparing a test specimen for evaluating flame retardancy according to claim 1, characterized in that, when the composite member is made of metal and rubber, the test specimen is prepared by setting the specified area so that the surface area of ​​the rubber is maximized.

8. A test piece for evaluating the flame retardancy of a composite member made of a plurality of members made of different materials, A test piece for evaluating flame retardancy, produced by the method for producing a test piece for evaluating flame retardancy according to claim 1.