Hollow test piece

Abstract

To provide a hollow test piece capable of reducing a volume of a fluid which is introduced into the hollow test piece.SOLUTION: A hollow test piece extending in a length direction includes: one side large diameter part which is formed at one side in the length direction; the other side large diameter part which is formed at the other side in the length direction; and a parallel part which is formed between the one side large diameter part and the other side large diameter part and which has the outer diameter smaller than the one side large diameter part and the other side large diameter part. The parallel part includes an outer peripheral surface, an inner peripheral surface, and a stress concentration portion which is formed on the inner peripheral surface and extends in a circumferential direction of the inner peripheral surface. In a case where an inner diameter of the parallel part is defined as D1 and a length of the parallel part in the length direction is defined as L1, the length L1 of the parallel part satisfies the condition of 0.5×D1≤L1≤3×D1.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to hollow specimens. [Background technology]

[0002] Autoclave-type material testing machines are known that perform material testing by placing test pieces, which are samples for material testing, in a pressure vessel filled with gas such as hydrogen gas. When performing material testing in a hydrogen gas environment using an autoclave-type material testing machine, a large amount of hydrogen is used, making it difficult to carry out the test, and therefore testing laboratories that can do this are limited.

[0003] Patent Document 1 discloses a hollow test piece into which a fluid can be introduced, the hollow test piece having a notch formed on the inner surface of the center in the longitudinal direction to increase the inner diameter. In material testing using the hollow test piece, the amount of hydrogen used can be reduced compared to autoclave testing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4817253 Summary of the Invention [Problem to be solved by the invention]

[0005] A hollow test piece having a notch (stress concentration portion) as described in Patent Document 1 has a problem in that a specific shape that allows material testing, for example, fatigue testing of the stress concentration portion, to be performed with high accuracy has not been determined. In addition, since processing of the stress concentration portion involves processing of a narrow portion, there is a problem in ensuring the processing accuracy of the stress concentration portion. There is a problem in that if the internal shape of the hollow test piece is enlarged so that the stress concentration portion can be processed, the amount of fluid used in the hollow portion increases. In the case where the fluid is hydrogen gas or the like that has a risk of explosion, the increased amount of fluid used will cause safety management issues.

[0006] In view of the above circumstances, an object of at least one embodiment of the present disclosure is to provide a hollow test piece that can reduce the volume of fluid introduced into the hollow test piece. [Means for solving the problem]

[0007] The hollow specimen according to at least one embodiment of the present disclosure comprises: A hollow test specimen extending along a longitudinal direction, a large diameter portion formed on one side in the longitudinal direction; an other-side large diameter portion formed on the other side in the longitudinal direction; a parallel portion formed between the one-side large diameter portion and the other-side large diameter portion, the parallel portion having an outer diameter smaller than that of the one-side large diameter portion and the other-side large diameter portion, The parallel portion is The outer periphery and An inner circumferential surface; a stress concentration portion formed on the inner circumferential surface and extending along a circumferential direction of the inner circumferential surface, When the inner diameter of the parallel portion is defined as D1 and the length of the parallel portion in the longitudinal direction is defined as L1, the length L1 of the parallel portion satisfies the condition 0.5×D1≦L1≦3×D1. Effect of the Invention

[0008] In accordance with at least one embodiment of the present disclosure, a hollow test specimen is provided that allows for a reduced volume of fluid introduced into the hollow test specimen. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram of a materials testing system including a hollow specimen according to one embodiment of the present disclosure. [Diagram 2] FIG. 2 is a schematic cross-sectional view of a hollow test piece according to an embodiment of the present disclosure taken along the central axis direction. [Diagram 3] FIG. 3 is a schematic cross-sectional view of the cut-out portion of the hollow specimen shown in FIG. 2. [Figure 4] FIG. 3 is a schematic cross-sectional view showing a state in which a connector and a stopper are connected to the hollow test piece shown in FIG. 2. [Diagram 5] FIG. 2 is a schematic cross-sectional view of a hollow test piece according to an embodiment of the present disclosure taken along the central axis direction. [Figure 6] FIG. 2 is a schematic cross-sectional view of a hollow test piece according to an embodiment of the present disclosure taken along the central axis direction. [Figure 7] FIG. 2 is a schematic cross-sectional view of a hollow test piece according to an embodiment of the present disclosure taken along the central axis direction. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as the embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present disclosure.

[0011] (Materials Testing System) Fig. 1 is a schematic diagram of a material testing system 100 including a hollow specimen 1 according to an embodiment of the present disclosure. Fig. 2 is a schematic cross-sectional view along the central axis CA of the hollow specimen 1 according to an embodiment of the present disclosure. As shown in Figs. 1 and 2, the hollow specimen 1 according to some embodiments has a longitudinal direction along the extension direction of the central axis CA of the hollow specimen 1. The hollow specimen 1 is formed in a cylindrical shape extending along the longitudinal direction, and a hollow portion 11 in which a fluid can exist is formed inside the hollow specimen 1.

[0012] The hollow test piece 1 is used for material testing, and is attached to a material testing machine 110. Specifically, the hollow test piece 1 is supported on both longitudinal sides by the material testing machine 110, and a load L is applied along the longitudinal direction by the material testing machine 110. In the illustrated embodiment, the hollow test piece 1 attached to the material testing machine 110 is arranged so that the longitudinal direction is along the vertical direction, with the large diameter portion 2 on one side positioned below in the vertical direction and the large diameter portion 3 on the other side positioned inside in the vertical direction.

[0013] (Materials Testing System) The material testing system 100 includes a hollow test piece 1, a material testing machine 110, and a fluid switching device 120 configured to be able to switch the fluid filled in the hollow portion 11 of the hollow test piece 1. The material testing machine 110 is suitable for use as a fatigue testing machine, a tensile testing machine, a compression testing machine, or the like.

[0014] (Material testing machine) 1, the material testing machine 110 includes a one-side support section 111, an other-side support section 112, a load applying section (actuator) 113, and a load cell 114. The one-side support section 111 supports one side in the longitudinal direction of the hollow test piece 1, specifically the one-side large diameter section 2. The other-side support section 112 supports the other side in the longitudinal direction of the hollow test piece 1, specifically the other-side large diameter section 3.

[0015] The load applying section 113 is configured to apply a load L to the hollow test piece 1 along the longitudinal direction, for example, by separating at least one of the one-side support section 111 or the other-side support section 112 from the other. In the illustrated embodiment, the load L is applied to the hollow test piece 1 by the load applying section 113 toward one side in the longitudinal direction, i.e., toward the downward side in the vertical direction. The load cell 114 is configured to measure the load L applied to the hollow test piece 1 by the load applying section 113. The load cell 114 is configured to convert the load L applied to the hollow test piece 1 into an electric signal.

[0016] (Fluid switching device) In some embodiments, the fluid switching device 120 includes a first fluid inlet line 121 for introducing a first fluid into the hollow portion 11, a second fluid inlet line 122 for introducing a second fluid into the hollow portion 11, and a fluid outlet line 123 for discharging fluid from the hollow portion 11, as shown in FIG. 1. One end of the first fluid inlet line 121, the second fluid inlet line 122, and the fluid outlet line 123 is connected to the hollow portion 11. The other end of the first fluid inlet line 121 is connected to a first tank 124 that stores the first fluid. The other end of the second fluid inlet line 122 is connected to a second tank 125 that stores the second fluid. The other end of the fluid outlet line 123 is connected to a vacuum pump 126 for sucking fluid from the hollow portion 11.

[0017] In the illustrated embodiment, the first fluid introduction line 121 and the second fluid introduction line 122 join at a first junction P1, and the downstream side (one end side) of the first junction P1 becomes a shared line 127. The fluid discharge line 123 joins with the shared line 127 at a second junction P2.

[0018] In the illustrated embodiment, the fluid switching device 120 further includes a discharge line 128 for discharging the fluid from the shared line 127 to the outside of the fluid switching device 120, and a compressor 129 for pressurizing the fluid guided to the hollow portion 11. In the embodiment illustrated in Fig. 1, the discharge line 128 has one end connected to the shared line 127 at the second junction P2, and the other end open to the atmosphere. The compressor 129 is provided upstream of the second junction P2 of the shared line 127.

[0019] When the test fluid filled in the hollow portion 11 during the material test is a first fluid (e.g., hydrogen gas), the first fluid is introduced from a first tank 124 to the hollow portion 11 through a first fluid introduction line 121. When the test fluid is a second fluid (e.g., an inert gas), the second fluid is introduced from a second tank 125 to the hollow portion 11 through a second fluid introduction line 122. When the test fluid is air, the other end of the fluid introduction line (121 or 122) for introducing air into the hollow portion 11 may be open to the atmosphere. When switching the test fluid, it is preferable to drive a vacuum pump 126. The fluid in the hollow portion 11 is drawn into a fluid discharge line 123 by the negative pressure of the vacuum pump 126, and is discharged to the outside of the fluid switching device 120 through the fluid discharge line 123. By removing the test fluid before switching from hollow portion 11 by vacuum drawing, the purity of the test fluid in hollow portion 11 after switching can be increased, and the influence of the environment (test fluid) on the material test can be appropriately controlled.

[0020] As shown in Fig. 1, a strain measuring device (e.g., a strain gauge) 130 may be attached to the outer surface of the hollow test piece 1. As shown in Fig. 1, a pressure measuring device (e.g., a pressure gauge) 140 may be used to monitor the pressure of the fluid guided to the hollow portion 11. In the embodiment shown in Fig. 1, the pressure measuring device 140 is provided downstream (one end side) of the compressor 129 of the shared line 127.

[0021] (Hollow test piece) 2, the hollow test piece 1 includes a one-side large diameter portion 2 formed on one side in the longitudinal direction (lower side in the figure), an other-side large diameter portion 3 formed on the other side in the longitudinal direction (upper side in the figure), and a parallel portion 4 formed in the longitudinal direction between the one-side large diameter portion 2 and the other-side large diameter portion 3. The parallel portion 4 has an outer diameter smaller than the one-side large diameter portion 2 and the other-side large diameter portion 3.

[0022] In the illustrated embodiment, the hollow test piece 1 further includes a one-side expanded diameter portion 5 formed between the one-side large diameter portion 2 and the parallel portion 4 in the longitudinal direction, and an other-side expanded diameter portion 6 formed between the other-side large diameter portion 3 and the parallel portion 4 in the longitudinal direction. The one-side large diameter portion 2, the other-side large diameter portion 3, the parallel portion 4, the one-side expanded diameter portion 5, and the other-side expanded diameter portion 6 each have an outer peripheral surface 21, 31, 41, 51, 61 and an inner peripheral surface 22, 32, 42, 52, 62. The hollow portion 11 is defined by the inner peripheral surfaces 22, 32, 42, 52, 62.

[0023] The one-side expanded diameter section 5 has a larger diameter toward the one side in the longitudinal direction, i.e., toward the one-side large diameter section 2. The one-side expanded diameter section 5 has an outer peripheral surface 51 with an R-shape that convex radially inward. The other-side expanded diameter section 6 has a larger diameter toward the other side in the longitudinal direction, i.e., toward the other-side large diameter section 3. The other-side expanded diameter section 6 has an outer peripheral surface 61 with an R-shape that convex radially inward.

[0024] (Stress concentration area) 2, the hollow test piece 1 has a stress concentration portion 43 formed on the inner peripheral surface 42 of the parallel portion 4 and extending along the circumferential direction of the inner peripheral surface 42. The stress concentration portion 43 is a portion where stress concentration occurs when a load is applied by a material testing machine 110. Portions of the hollow test piece 1 other than the stress concentration portion 43 are designed so that stress concentration does not occur as much as in the stress concentration portion 43 when a load is applied by the material testing machine 110.

[0025] (length of parallel part) 2, the parallel portion 4 of the hollow test piece 1 according to some embodiments has the above-mentioned outer peripheral surface 41, the above-mentioned inner peripheral surface 42, and the above-mentioned stress concentration portion 43. When the inner diameter of the parallel portion 4 is defined as D1 and the length of the parallel portion 4 in the longitudinal direction is defined as L1, the length L1 of the parallel portion 4 satisfies the condition 0.5×D1≦L1≦3×D1.

[0026] In the embodiment shown in FIG. 2, the inner diameter D1 of the parallel portion 4 is the diameter of a portion of the inner circumferential surface 42 where the annular cutout portion 44 (stress concentration portion 43) is not formed. The inner diameter D1 of the parallel portion 4 of the hollow test piece 1 is restricted by a machining tool for forming the stress concentration portion 43 on the inner circumferential surface 42. The parallel portion 4 can homogenize the stress generated during material testing by satisfying the condition of 0.5×D1≦L1≦3×D1 for the length L1. The hollow test piece 1 including such a parallel portion 4 can reduce the internal volume of the parallel portion 4, and therefore the volume of the fluid introduced into the hollow test piece 1 can be reduced.

[0027] Furthermore, since the length L of the parallel portion 4 satisfies the condition 0.5×D1≦L1≦3×D1, an area can be secured on the outer surface 41 for attaching a strain gauge for balancing the axial center of the hollow test piece 1 attached to the material testing machine 110 before the start of the material test.

[0028] (Notch) Fig. 3 is a schematic cross-sectional view of the notch 44 of the hollow specimen 1 shown in Fig. 2. In the hollow specimen 1 according to some embodiments, the above-mentioned stress concentration portion 43 includes an annular notch 44 having a V-shaped cross section formed on the inner circumferential surface 42 of the parallel portion 4.

[0029] In the illustrated embodiment, the cutout portion 44 includes a first inclined surface 441 that is inclined so as to be positioned radially outward as it approaches one side in the longitudinal direction, a second inclined surface 442 that is inclined so as to be positioned radially outward as it approaches the other side in the longitudinal direction, and an R-shaped portion 443 that connects the outer circumferential end of the first inclined surface 441 and the second inclined surface 442 and is curved concavely radially outward. The inclination angle θ between the first inclined surface 441 and the second inclined surface 442 is preferably within a range of 50° to 70°, and more preferably within a range of 55° to 65°. In this case, the cutout portion 44 can be well machined by a machining tool. When the inner diameter of the parallel portion 4 is defined as D1, the curvature radius R1 of the R-shaped portion 443 satisfies the condition of 0.1×D1≦R1≦0.2×D1. The stress concentration coefficient can be changed by changing the curvature radius R1 of the R-shaped portion 443. In order to change the stress concentration factor, the depth ND of the cutout portion 44 may be changed instead of the curvature radius R1 of the R-shaped portion 443.

[0030] The shape of the cutout 44 can be determined according to a desired stress intensity factor to be applied to the hollow test piece 1 during material testing. The cutout 44 having a V-shaped annular cross section can be machined well using a machining tool, so machining precision can be ensured. Note that the cutout 44 is not limited to a V-shaped annular cross section. The cutout 44 may be, for example, a U-shaped annular cross section.

[0031] (connector) Fig. 4 is a schematic cross-sectional view showing a state in which the connector 23 and the stopper plug 24 are connected to the hollow test piece 1 shown in Fig. 2. The connector 23 has an inserted portion 231 inserted into the inside of the inner circumferential surface 32 of the other-side large diameter portion 3, a flange portion 232 protruding radially outward from the inserted portion 231, and a through-hole 233 penetrating the connector 23 along the longitudinal direction of the hollow test piece 1 and communicating the hollow portion 11 with the outside of the hollow test piece 1 (for example, the shared line 127). The other-side end of the hollow test piece 1 and the flange portion 232 are joined by welding, and a welded portion W1 is formed between the other-side end of the hollow test piece 1 and the flange portion 232.

[0032] (Shut-off valve) The closure plug 24 has an inserted portion 241 that is inserted into the inside of the inner circumferential surface 22 of the one-side large diameter portion 2, and a flange portion 242 that protrudes radially outward from the inserted portion 241. The end portion of the one side of the hollow test piece 1 and the flange portion 242 are joined by welding, and the one side of the hollow portion 11 is closed by the closure plug 24. A welded portion W2 is formed between the end portion of the one side of the hollow test piece 1 and the flange portion 242.

[0033] (Step surface) 5 is a schematic cross-sectional view along the central axis of a hollow test piece 1 according to an embodiment of the present disclosure. In the hollow test piece 1 according to some embodiments, as shown in FIG. 5, the inner peripheral surface 42 of the parallel portion 4 includes a first inner peripheral surface 421 having an inner diameter D1, a second inner peripheral surface 422 having an inner diameter smaller than that of the first inner peripheral surface 421, and a step surface 423 connecting the first inner peripheral surface 421 and the second inner peripheral surface 422. The stress concentration portion 43 includes an outer peripheral edge 424 of the step surface 423. The step surface 423 is an annular surface extending along a direction perpendicular to the central axis CA of the hollow test piece 1.

[0034] According to the above configuration, the hollow test piece 1 has a structure in which the first inner peripheral surface 421 and the step surface 423 can be formed by drilling, so that the processing for forming the stress concentration portion 43 is easier than the cutout portion 44. In addition, the outer peripheral edge 424 of the step surface 423 that becomes the stress concentration portion 43 can be accessed from the outside, so that visual confirmation of the state and finishing processing by polishing are possible. Therefore, it is possible to ensure the processing accuracy of the stress concentration portion 43. In the illustrated embodiment, the second inner peripheral surface 422 is formed on the other side in the longitudinal direction from the first inner peripheral surface 421, but it may be formed on the one side in the longitudinal direction from the first inner peripheral surface 421.

[0035] (Solid member) 6 and 7 are schematic cross-sectional views taken along the central axis of a hollow test piece 1 according to one embodiment of the present disclosure. As shown in Fig. 6 and Fig. 7, the hollow test piece 1 according to some embodiments has at least one solid member 7 disposed in the above-mentioned hollow portion 11. By disposing the solid member 7 in the hollow portion 11, the volume into which a fluid can be introduced in the hollow portion 11 can be substantially reduced, and therefore the volume of the fluid introduced into the hollow test piece 1 can be reduced.

[0036] (Rod-shaped member) In some embodiments of the hollow test specimen 1, as shown in FIG. 6, the at least one solid member 7 described above includes a rod-shaped member 8 having an outer peripheral surface 81 that faces the inner peripheral surface 42 of the hollow test specimen 1 with a gap between them.

[0037] In the illustrated embodiment, the rod-shaped member 8 has an outer circumferential surface 81 and includes a central portion 82 extending along the longitudinal direction of the hollow test piece 1, a first fitting portion 83, and a second fitting portion 84. The first fitting portion 83 is located on one side in the longitudinal direction from the central portion 82 and is formed integrally with the central portion 82. The first fitting portion 83 is formed with a larger diameter than the central portion 82, and is fixed to the one-side large diameter portion 2 by fitting its outer circumferential surface into the inner circumferential surface 22 of the one-side large diameter portion 2. The second fitting portion 84 is located on the other side in the longitudinal direction from the central portion 82 and is formed integrally with the central portion 82. The second fitting portion 84 is formed with a larger diameter than the central portion 82, and is fixed to the other-side large diameter portion 3 by fitting its outer circumferential surface into the inner circumferential surface 32 of the other-side large diameter portion 3.

[0038] The first fitting portion 83 has at least one through hole 831 that penetrates the first fitting portion 83 along the longitudinal direction of the hollow test piece 1 and communicates between the hollow portion 11 and the outside of the hollow test piece 1 (e.g., the shared line 127). The second fitting portion 84 has at least one through hole 841 that penetrates the second fitting portion 84 along the longitudinal direction of the hollow test piece 1 and communicates between the hollow portion 11 and the outside of the hollow test piece 1. In the illustrated example, the at least one through hole 831, 841 includes a plurality of through holes 831, 841 formed at intervals along the circumferential direction of the hollow test piece 1.

[0039] According to the above configuration, the rod-shaped member 8 is disposed with a gap between it and the inner circumferential surface 42 on which the stress concentration portion 43 of the parallel portion 4 is formed, and therefore does not affect the stress concentration portion 43. The hollow test piece 1 having the rod-shaped member 8 is capable of filling a fluid into the space facing the stress concentration portion 43 in the hollow portion 11 while reducing the volume in the hollow portion 11 into which a fluid can be introduced.

[0040] (sphere) In the hollow test piece 1 according to some embodiments, the at least one solid member 7 described above includes a plurality of spheres 9 that are filled in the hollow portion 11, as shown in FIG.

[0041] In the illustrated embodiment, the outer diameter D5 of the plurality of spherical bodies 9 is set to a size such that the spherical bodies 9 do not enter the cutout portion 44. Each of the plurality of spherical bodies 9 does not have to be a perfect sphere. The hollow portion 11 includes a central hollow portion 11A defined by the inner peripheral surface 42 of the parallel portion 4, a first hollow portion 11B defined by the inner peripheral surface 22 of the first large diameter portion 2, and an second hollow portion 11C defined by the inner peripheral surface 32 of the second large diameter portion 3. It is preferable that the plurality of spherical bodies 9 are filled not only in the central hollow portion 11A, but also in the first hollow portion 11B and the second hollow portion 11C.

[0042] According to the above-mentioned configuration, by filling the hollow portion 11 of the hollow test piece 1 with a plurality of spherical bodies 9, the volume of the hollow portion 11 into which a fluid can be introduced can be effectively reduced.

[0043] (Outer diameter of parallel part) In the hollow test piece 1 according to some embodiments, as shown in FIG. 2, when the inner diameter of the parallel portion 4 is defined as D1 and the outer diameter of the parallel portion 4 is defined as D2, the outer diameter D2 of the parallel portion 4 satisfies the condition of 1.5×D1≦D2≦2×D1. By making the outer diameter D2 of the parallel portion 4 satisfy the condition of 1.5×D1≦D2≦2×D1, the thickness of the parallel portion 4 required for the material test can be secured while preventing the thickness of the parallel portion 4 from becoming excessive. Here, when a relatively high stress is applied to the stress concentration portion 43 in the material test, it is necessary to make the thickness of the one-side large diameter portion 2 and the other-side large diameter portion 3 sufficiently larger than the thickness of the parallel portion 4. By preventing the thickness of the parallel portion 4 from becoming excessive, it is possible to prevent the thickness of the one-side large diameter portion 2 and the other-side large diameter portion 3 from becoming excessive, which leads to an increase in size and weight of the hollow test piece 1.

[0044] (Outer diameter of large diameter part on one side) 2, in the hollow test piece 1 according to some embodiments, when the inner diameter of the parallel portion 4 described above is defined as D1 and the outer diameter of the one-side large diameter portion 2 described above is defined as D3, the outer diameter D3 of the one-side large diameter portion 2 satisfies the condition 2×D1≦D3≦3×D1. By making the outer diameter D3 of the one-side large diameter portion 2 satisfy the condition 2×D1≦D3≦3×D1, the thickness of the one-side large diameter portion 2 can be made sufficiently larger than the thickness of the parallel portion 4, and the thickness of the one-side large diameter portion 2 can be prevented from becoming excessively large.

[0045] (Outer diameter of the large diameter part on the other side) 2, in the hollow test piece 1 according to some embodiments, when the inner diameter of the above-mentioned parallel portion 4 is defined as D1 and the outer diameter of the above-mentioned other-side large diameter portion 3 is defined as D4, the outer diameter D4 of the other-side large diameter portion 3 satisfies the condition 2×D1≦D4≦3×D1. By making the outer diameter D4 of the other-side large diameter portion 3 satisfy the condition 2×D1≦D4≦3×D1, the thickness of the other-side large diameter portion 3 can be made sufficiently larger than the thickness of the parallel portion 4, and the thickness of the other-side large diameter portion 3 can be prevented from becoming excessively large.

[0046] (Support structure for large diameter portion on one side and large diameter portion on the other side) In some embodiments of the hollow test piece 1, as shown in FIG. 2, the above-mentioned one-side large diameter portion 2 and the other-side large diameter portion 3 have threaded portions 211, 311 formed on at least a portion of the outer circumferential surfaces 21, 31 in the longitudinal direction.

[0047] The one-side support part 111 has a threaded portion 115 that screws into the threaded portion 211 of the one-side large diameter part 2. The one-side large diameter part 2 is supported by the one-side support part 111 by screwing the threaded portion 211 into the threaded portion 115 of the one-side support part 111. The other-side support part 112 has a threaded portion 116 that screws into the threaded portion 311 of the other-side large diameter part 3. The other-side large diameter part 3 is supported by the other-side support part 112 by screwing the threaded portion 311 into the threaded portion 116 of the other-side support part 112.

[0048] According to the above configuration, the hollow test piece 1 is fixed to the material testing machine 110 via the threaded portions 211, 311 formed on the outer circumferential surfaces 21, 31 of the one-side large diameter portion 2 and the other-side large diameter portion 3. This hollow test piece 1 does not have an enlarged diameter portion such as a flange for fixing the one-side large diameter portion 2 and the other-side large diameter portion 3 of the hollow test piece 1 to the material testing machine 110, so that a material with a relatively small outer diameter can be used as the base material for the hollow test piece 1.

[0049] (Length of large diameter part on one side) 2, in the hollow test piece 1 according to some embodiments, when the inner diameter of the parallel portion 4 described above is defined as D1 and the longitudinal length of the one-side large diameter portion 2 described above is defined as L4, the length L4 of the one-side large diameter portion 2 satisfies the condition 3×D1≦L4≦6×D1. By making the length L4 of the one-side large diameter portion 2 satisfy the condition 3×D1≦L4≦6×D1, it is possible to prevent the length L4 of the one-side large diameter portion 2 from becoming excessively large while ensuring the length necessary for supporting the one-side large diameter portion 2 on the one-side support portion 111 of the material testing machine 110.

[0050] (Length of the large diameter part on the other side) 2, in the hollow test piece 1 according to some embodiments, when the inner diameter of the parallel portion 4 described above is defined as D1 and the longitudinal length of the other-side large diameter portion 3 described above is defined as L5, the length L5 of the other-side large diameter portion 3 satisfies the condition 3×D1≦L5≦6×D1. By making the length L5 of the other-side large diameter portion 3 satisfy the condition 3×D1≦L5≦6×D1, it is possible to prevent the length L5 of the other-side large diameter portion 3 from becoming excessively large while ensuring the length necessary for supporting the other-side large diameter portion 3 on the other-side support portion 112 of the material testing machine 110.

[0051] (One side expanded diameter part, other side expanded diameter part) As shown in Figures 2, 6 and 7, the hollow test piece 1 according to some embodiments includes the above-mentioned one-side large diameter portion 2, the other-side large diameter portion 3, the parallel portion 4, the one-side expanded diameter portion 5 and the other-side expanded diameter portion 6.

[0052] The outer peripheral surface 51 of the one-side expanded diameter portion 5 smoothly continues to the outer peripheral surface 41 of the parallel portion 4 without any steps, and is connected to the outer peripheral surface 21 of the one-side large diameter portion 2 so as to have a predetermined inclination angle with respect to the outer peripheral surface 21. The outer diameter of the outer peripheral surface 51 is smallest at the connection portion with the outer peripheral surface 41, and is largest at the connection portion with the outer peripheral surface 21.

[0053] The outer peripheral surface 61 of the other-side expanded diameter portion 6 smoothly continues to the outer peripheral surface 41 of the parallel portion 4 without any steps, and is connected to the outer peripheral surface 31 of the other-side large diameter portion 3 so as to have a predetermined inclination angle with respect to the outer peripheral surface 41. The outer diameter of the outer peripheral surface 61 is smallest at the connection portion with the outer peripheral surface 41, and is largest at the connection portion with the outer peripheral surface 31.

[0054] According to the above configuration, when a load L is applied by the material testing machine 110, the hollow test piece 1 can suppress stress concentration from occurring in areas other than the parallel portion 4 of the hollow test piece 1, such as the one-side enlarged diameter portion 5 and the other-side enlarged diameter portion 6.

[0055] (Length of enlarged part on one side) 2, in the hollow test piece 1 according to some embodiments, when the longitudinal length of the parallel portion 4 described above is defined as L1 and the longitudinal length of the one-side expanded diameter portion 5 described above is defined as L2, the length L2 of the one-side expanded diameter portion 5 satisfies the condition 1 / 3×L1≦L2≦1 / 2×L1. By making the length L2 of the one-side expanded diameter portion 5 satisfy the condition 1 / 3×L1≦L2≦1 / 2×L1, the R-shape of the outer peripheral surface of the one-side expanded diameter portion 5 can be made to have a curvature that does not cause stress concentration, and the length L2 of the one-side expanded diameter portion 5 can be prevented from becoming excessively large.

[0056] (Length of the other side expansion part) 2, in the hollow test piece 1 according to some embodiments, when the longitudinal length of the parallel portion 4 described above is defined as L1 and the longitudinal length of the other-side expanded diameter portion 6 described above is defined as L3, the length L3 of the other-side expanded diameter portion 6 satisfies the condition 1 / 3×L1≦L3≦1 / 2×L1. By making the length L3 of the other-side expanded diameter portion 6 satisfy the condition 1 / 3×L1≦L3≦1 / 2×L1, the R-shape of the outer peripheral surface of the other-side expanded diameter portion 6 can be made to have a curvature that does not cause stress concentration, and the length L3 of the other-side expanded diameter portion 6 can be prevented from becoming excessively large.

[0057] In this specification, expressions expressing relative or absolute configuration, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," do not only strictly represent such a configuration, but also represent a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions indicating that things are in an equal state, such as "identical," "equal," and "homogeneous," not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained. Furthermore, in this specification, expressions describing shapes such as a rectangular shape or a cylindrical shape do not only refer to shapes such as a rectangular shape or a cylindrical shape in the strict geometric sense, but also refer to shapes that include uneven portions, chamfered portions, etc., to the extent that the same effect can be obtained. In addition, in this specification, the expressions "comprise," "include," or "have" a certain element are not exclusive expressions that exclude the presence of other elements.

[0058] The present disclosure is not limited to the above-described embodiments, and includes modifications to the above-described embodiments and appropriate combinations of these modifications.

[0059] The contents described in the above-mentioned embodiments can be understood, for example, as follows.

[0060] 1) The hollow test piece (1) according to at least one embodiment of the present disclosure is A hollow test specimen (1) extending along a longitudinal direction, A large diameter portion (2) formed on one side in the longitudinal direction; an other-side large diameter portion (3) formed on the other side in the longitudinal direction; a parallel portion (4) formed between the one-side large diameter portion (2) and the other-side large diameter portion (3), the parallel portion (4) having an outer diameter smaller than the one-side large diameter portion (2) and the other-side large diameter portion (3), The parallel portion (4) is An outer circumferential surface (41); An inner circumferential surface (42); a stress concentration portion (43) formed on the inner peripheral surface (42) and extending along the circumferential direction of the inner peripheral surface (42), When the inner diameter of the parallel portion (4) is defined as D1 and the length of the parallel portion (4) in the longitudinal direction is defined as L1, the length L1 of the parallel portion (4) satisfies the condition 0.5×D1≦L1≦3×D1.

[0061] According to the above configuration 1), the parallel portion (4) of the hollow test piece (1) is restricted in its inner diameter D1 by a machining tool for forming the stress concentration portion (43) on the inner peripheral surface (42). The parallel portion (4) can homogenize the stress generated during material testing by making the length L of the parallel portion (4) satisfy the condition 0.5×D1≦L1≦3×D1. The hollow test piece (1) including such a parallel portion (4) can have a small internal volume of the parallel portion (4), and therefore can reduce the volume of the fluid introduced into the hollow test piece (1).

[0062] 2) In some embodiments, the hollow test piece (1) described in 1) above, The stress concentration portion (43) is The parallel portion (4) has an annular cutout portion (44) formed in the inner circumferential surface (42) thereof, the cutout portion (44) including an annular cutout portion (44) having a V-shaped cross section.

[0063] According to the above configuration 2), the shape of the cutout portion (44) can be determined according to the desired stress intensity factor to be applied to the hollow test piece (1) during material testing. The cutout portion (44) having a V-shaped annular cross section can be machined well by the above machining tool, so that machining precision can be ensured.

[0064] 3) In some embodiments, the hollow test piece (1) described in 1) above, The inner peripheral surface (42) of the parallel portion (4) is A first inner circumferential surface (421) having the inner diameter D1; a second inner circumferential surface (422) having an inner diameter smaller than that of the first inner circumferential surface (421); a step surface (423) connecting the first inner circumferential surface (421) and the second inner circumferential surface (422), The stress concentrating portion (43) includes an outer peripheral edge (424) of the step surface (423).

[0065] According to the above configuration 3), the hollow test piece (1) has a structure in which the first inner peripheral surface (421) and the step surface (423) can be formed by drilling, so that the processing for forming the stress concentration portion (43) is easier than that of the notch portion (44) or the like. In addition, the outer peripheral edge (424) of the step surface (423) which becomes the stress concentration portion (43) is accessible from the outside, so that the state can be visually confirmed and finishing processing can be performed by polishing. This makes it possible to ensure the processing accuracy of the stress concentration portion (43).

[0066] 4) In some embodiments, the hollow test piece (1) according to any one of 1) to 3) above, The hollow test piece (1) has at least one solid member (7) disposed in the hollow portion (11).

[0067] According to the above configuration 4), by disposing the solid member (7) in the hollow portion (11), the volume into which the fluid can be introduced into the hollow portion (11) can be substantially reduced, and therefore the volume of the fluid introduced into the hollow test piece (1) can be reduced.

[0068] 5) In some embodiments, the hollow test piece (1) according to 4) above, The at least one solid member (7) The hollow test piece (1) includes a rod-shaped member (8) having an outer peripheral surface (81) facing the inner peripheral surface (42) of the hollow test piece (1) with a gap therebetween.

[0069] According to the above configuration 5), the rod-shaped member (8) is disposed with a gap between it and the inner peripheral surface (42) on which the stress concentration portion (43) of the parallel portion (4) is formed, and therefore does not affect the stress concentration portion (43). The hollow test piece (1) having the rod-shaped member (8) can fill the space facing the stress concentration portion (43) in the hollow portion (11) with a fluid while reducing the volume in the hollow portion (11) into which a fluid can be introduced.

[0070] 6) In some embodiments, the hollow test piece (1) according to 4) above, The at least one solid member (7) The hollow portion (11) contains a plurality of spherical bodies (9).

[0071] According to the above configuration 6), by filling the hollow portion (11) of the hollow test piece (1) with a plurality of spherical bodies (9), the volume into which a fluid can be introduced in the hollow portion (11) can be effectively reduced.

[0072] 7) In some embodiments, the hollow test piece (1) according to any one of 1) to 6) above, When the outer diameter of the parallel portion (4) is defined as D2, the outer diameter D2 of the parallel portion (4) satisfies the condition 1.5×D1≦D2≦2×D1.

[0073] According to the above configuration 7), by making the outer diameter D2 of the parallel portion (4) satisfy the condition 1.5×D1≦D2≦2×D1, it is possible to ensure the thickness of the parallel portion (4) required for the material test while preventing the thickness of the parallel portion (4) from becoming excessive. Here, when a relatively high stress is applied to the stress concentration portion (43) in the material test, it is necessary to make the thickness of the one-side large diameter portion (2) and the other-side large diameter portion (3) sufficiently larger than the thickness of the parallel portion (4). By preventing the thickness of the parallel portion (4) from becoming excessive, it is possible to prevent the thickness of the one-side large diameter portion (2) and the other-side large diameter portion (3) from becoming excessive, which would lead to an increase in size and weight of the hollow test piece (1).

[0074] 8) In some embodiments, the hollow test piece (1) according to 7) above, When the outer diameter of the one-side large diameter portion (1) is defined as D3, the outer diameter D3 of the one-side large diameter portion (1) satisfies the condition 2×D1≦D3≦3×D1.

[0075] According to the above configuration 8), by making the outer diameter D3 of the one-side large diameter portion (1) satisfy the condition 2×D1≦D3≦3×D1, the thickness of the one-side large diameter portion (2) can be made sufficiently larger than the thickness of the parallel portion (4), and the thickness of the one-side large diameter portion (2) can be prevented from becoming excessively large.

[0076] 9) In some embodiments, the hollow test piece (1) according to any one of 1) to 8) above, a one-side expanded diameter portion formed between the one-side large diameter portion and the parallel portion, the one-side expanded diameter portion having a diameter increasing toward the one-side large diameter portion, the one-side expanded diameter portion having an outer circumferential surface with an R-shape that is convex toward an inner side in a radial direction; The other-side expanded diameter portion is formed between the other-side large diameter portion and the parallel portion, and the diameter of the other-side expanded diameter portion increases toward the other-side large diameter portion, the other-side expanded diameter portion having an R-shape that convexly extends radially inward on its outer circumferential surface.

[0077] According to the above configuration 9), when stress is applied to the hollow test piece (1) during material testing, stress concentration can be suppressed in parts other than the parallel part (4) of the hollow test piece (1), such as the one-side enlarged diameter part and the other-side enlarged diameter part.

[0078] 10) In some embodiments, the hollow test piece (1) according to 9) above, When the length of the one-side expanded diameter portion (4) in the longitudinal direction is defined as L2, the length L2 of the one-side expanded diameter portion (4) satisfies the condition 1 / 3×L1≦L2≦1 / 2×L1.

[0079] According to the configuration of 10) above, by making the length L2 of the one-side expanded diameter portion (4) satisfy the condition 1 / 3 × L1 ≦ L2 ≦ 1 / 2 × L1, the R-shape of the outer peripheral surface of the one-side expanded diameter portion (4) can be made to have a curvature that does not cause stress concentration, and the length L2 of the one-side expanded diameter portion (4) can be prevented from becoming excessively large.

[0080] 11) In some embodiments, the hollow test piece (1) according to any one of 1) to 10) above, The one-side large diameter portion (2) and the other-side large diameter portion (3) have threads (211, 311) formed on at least a portion of the outer circumferential surface (21, 31) in the longitudinal direction.

[0081] According to the above configuration 11), the hollow test piece (1) is fixed to the material testing machine (110) via the threaded portions (211, 311) formed on the outer circumferential surfaces (21, 31) of the one-side large diameter portion (2) and the other-side large diameter portion (3). This hollow test piece (1) does not have an enlarged diameter portion such as a flange for fixing the one-side large diameter portion (2) and the other-side large diameter portion (3) of the hollow test piece (1) to the material testing machine, so that a material having a relatively small outer diameter can be used as the base material for the hollow test piece (1). [Explanation of symbols]

[0082] 1 Hollow test piece 2 Large diameter part on one side 3 Large diameter part on the other side 4 Parallel section 5. Enlarged diameter part on one side 6 Expanded diameter part on other side 7 Solid parts 8 Rod-shaped member 9. Spherical body 11 Hollow part 11A Center hollow part 11B Hollow part on one side 11C Hollow part on other side 21,31,41,51,61,81 Outer surface 22,32,42,52,62 Inner surface 23 Connector 24 Stopcock 43 Stress concentration area 44 Cutout 82 Central part 83 First fitting part 84 Second fitting part 100 Materials Testing Systems 110 Material testing machine 111 One side support part 112 Other side support part 113 Load bearing section 114 Load Cell 115,116,211,311 Threaded part 120 Fluid Switching Device 121 First fluid introduction line 122 Second fluid introduction line 123 Fluid discharge line 124 First Tank 125 Second Tank 126 Vacuum Pump 127 Shared Line 128 Release Line 129 Compressor 140 Pressure measuring device 231,241 Inserted part 232,242 Tsuba 233,831 Through holes 421 1st inner surface 422 2nd inner peripheral surface 423 Step surface 424 Outer edge 441 1st slope 442 2nd slope 443 R-shaped part CA center axis D1 Inner diameter D2, D3, D4, D5 Outer diameter L load P1 First Junction P2 2nd confluence R1 radius of curvature W1, W2 welded section

Claims

1. A hollow test specimen extending along a longitudinal direction, a large diameter portion formed on one side in the longitudinal direction; an other-side large diameter portion formed on the other side in the longitudinal direction; a parallel portion formed between the one-side large diameter portion and the other-side large diameter portion, the parallel portion having an outer diameter smaller than that of the one-side large diameter portion and the other-side large diameter portion, The parallel portion is The outer periphery and An inner circumferential surface; a stress concentration portion formed on the inner circumferential surface and extending along a circumferential direction of the inner circumferential surface, When the inner diameter of the parallel portion is defined as D1 and the length of the parallel portion in the longitudinal direction is defined as L1, the length L1 of the parallel portion satisfies the condition of 0.5×D1≦L1≦3×D1. Hollow specimen.

2. The stress concentration portion is An annular cutout portion formed on the inner circumferential surface of the parallel portion includes an annular cutout portion having a V-shaped cross section.

2. The hollow test specimen according to claim 1.

3. The inner circumferential surface of the parallel portion is A first inner circumferential surface having the inner diameter D1; A second inner circumferential surface having an inner diameter smaller than that of the first inner circumferential surface; a step surface connecting the first inner circumferential surface and the second inner circumferential surface, The stress concentration portion includes an outer circumferential edge of the step surface.

2. The hollow test specimen according to claim 1.

4. At least one solid member is disposed in the hollow portion of the hollow test specimen. The hollow test piece according to any one of claims 1 to 3.

5. The at least one solid member comprises: The hollow test piece further includes a rod-shaped member having an outer circumferential surface facing the inner circumferential surface of the hollow test piece with a gap therebetween.

5. The hollow test piece according to claim 4.

6. The at least one solid member comprises: A plurality of spherical bodies are filled in the hollow portion.

5. The hollow test piece according to claim 4.

7. When the outer diameter of the parallel portion is defined as D2, the outer diameter D2 of the parallel portion satisfies the condition of 1.5×D1≦D2≦2×D1. The hollow test piece according to any one of claims 1 to 3.

8. When the outer diameter of the one-side large diameter portion is defined as D3, the outer diameter D3 of the one-side large diameter portion satisfies the condition of 2×D1≦D3≦3×D1.

8. The hollow test piece according to claim 7.

9. a first-side expanded diameter portion formed between the first-side large diameter portion and the parallel portion, the first-side expanded diameter portion having a diameter increasing toward the first-side large diameter portion, the first-side expanded diameter portion having an outer circumferential surface with an R-shape that is convex toward an inner side in a radial direction; The other-side expanded diameter portion is formed between the other-side large diameter portion and the parallel portion, and the other-side expanded diameter portion has a diameter that increases toward the other-side large diameter portion, and the other-side expanded diameter portion has an R shape that is convex toward the inside in the radial direction on an outer circumferential surface. The hollow test piece according to any one of claims 1 to 3.

10. When the length of the one-side expanded diameter portion in the longitudinal direction is defined as L2, the length L2 of the one-side expanded diameter portion satisfies the condition of 1 / 3×L1≦L2≦1 / 2×L1.

10. The hollow test specimen according to claim 9.

11. The one-side large diameter portion and the other-side large diameter portion have a threaded portion formed on at least a part of an outer circumferential surface in the longitudinal direction. The hollow test piece according to any one of claims 1 to 3.

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