Test fixture for columnar tensile sample and use method of test fixture

Abstract

The invention discloses a test fixture for a columnar tensile sample and a use method of the test fixture, and belongs to the technical field of mechanical property testing of high-temperature materials. In order to solve the technical problems that an existing clamp is complex in operation, a brittle sample cannot be clamped by means of friction or occlusal force, and materials of the clamp are limited in a high-temperature environment, the structural design of the sleeve and the two clamping blocks is mainly adopted, and stable clamping of a sample shaft shoulder is achieved in the mode that the clamping blocks are spliced in the sleeve and rotate by 90 degrees. The device is simple and convenient to operate, and is suitable for stable and reliable axial tension test of a brittle sample in a high-temperature environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of mechanical property testing of high-temperature materials, and particularly relates to a testing fixture for columnar tensile specimens and a using method thereof. Background Art

[0002] Composite materials such as graphite, carbon-carbon, and ceramics (CMC) have unique advantages in applications under high-temperature environments, and their mechanical properties directly affect the service life and safety of components. At the same time, due to the influence of composition and process on such materials, the probability of defects is relatively high. Therefore, it is necessary to test and characterize the mechanical properties of such materials to provide key data support for the research, production of materials, and design of components. Currently, for columnar graphite tensile specimens, a method of combining a collar + two semi-rings is given in Standard JB / T 8133.9 to perform axial tensile loading on the specimens, but this clamping method is not very convenient in actual operation.

[0003] For columnar tensile metal specimens, mechanical and hydraulic fixtures can generally be used to clamp the specimens by utilizing the frictional force and biting force between the cylindrical ends of the specimens and the clamping surfaces. However, for brittle materials such as graphite and carbon-carbon composites, this clamping method is not advisable. At the same time, for test environments above 500°C, due to the radiation effect of high temperature on the materials of mechanical and hydraulic fixtures, this clamping method also has great limitations in high-temperature tests. Summary of the Invention

[0004] The purpose of the present invention is to provide a testing fixture for columnar tensile specimens and a using method thereof, so as to solve problems such as complex operation of existing fixtures, inability to clamp brittle specimens relying on friction or biting force, and limited fixture materials in high-temperature environments, and to achieve reliable and convenient specimen clamping and axial tensile testing.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A testing fixture for columnar tensile specimens includes an upper connecting rod assembly and a lower connecting rod assembly;

[0007] The upper connecting rod assembly includes an upper connecting rod, an upper sleeve, a first upper clamping block, and a second upper clamping block; the upper sleeve includes a cylindrical chamber, as well as an upper circular hole, a lower circular hole, and two side windows that communicate with the cylindrical chamber; the upper sleeve is detachably connected to the lower end of the upper connecting rod through the upper circular hole, the lower circular hole is used for passing the upper end of the specimen, and the side windows are used for passing the first upper clamping block and the second upper clamping block; both the first upper clamping block and the second upper clamping block include semi-circular holes, the first upper clamping block and the second upper clamping block are placed in the cylindrical chamber of the upper sleeve, and the semi-circular holes are made into a complete circular hole by splicing with each other and are clamped at the shoulder below the upper end of the specimen;

[0008] The lower link assembly includes a lower link, a lower sleeve, a first lower clamping block, and a second lower clamping block; the lower sleeve includes a cylindrical chamber, as well as an upper circular hole, a lower circular hole, and a side window that communicate with the cylindrical chamber; the lower sleeve is detachably connected to the upper end of the lower link through the lower circular hole, the upper circular hole is used for introducing the lower end of the specimen, and the side window is used for passing through the first lower clamping block and the second lower clamping block; both the first lower clamping block and the second lower clamping block include semi-circular holes, the first lower clamping block and the second lower clamping block are placed in the cylindrical chamber of the lower sleeve, and the semi-circular holes are made into a complete circular hole by splicing with each other and are stuck at the shoulder above the lower end of the specimen.

[0009] Further, the upper end of the upper link is a spherical hinge surface for connecting to the testing machine base with a concave spherical surface; the lower end of the lower link is a spherical hinge surface for connecting to the testing machine base with a concave spherical surface.

[0010] Further, the lower end of the upper link is a threaded end with an external thread, the upper circular hole of the upper sleeve is provided with an internal thread, and the threaded end of the upper link is threadedly connected to the upper circular hole of the upper sleeve; the upper end of the lower link is a threaded end with an external thread, the lower circular hole of the lower sleeve is provided with an internal thread, and the threaded end of the lower link is threadedly connected to the lower circular hole of the lower sleeve.

[0011] Further, the back of the side where the semi-circular holes of the first upper clamping block and the second upper clamping block are located is a flat surface, and the two connecting surfaces between the side where the semi-circular holes are located and the flat surface are arc surfaces; the back of the side where the semi-circular holes of the first lower clamping block and the second lower clamping block are located is a flat surface, and the two connecting surfaces between the side where the semi-circular holes are located and the flat surface are arc surfaces.

[0012] Further, there are two concave arc surfaces on the side wall of the cylindrical chamber of the upper sleeve that are symmetric about the center of the upper sleeve, the directions of the two concave arc surfaces are perpendicular to the directions of the two side windows, and the two concave arc surfaces are used to accommodate the arc surfaces on both sides after the first upper clamping block and the second upper clamping block are spliced; there are two concave arc surfaces on the side wall of the cylindrical chamber of the lower sleeve that are symmetric about the center line, the directions of the two concave arc surfaces are perpendicular to the directions of the two side windows, and the two concave arc surfaces are used to accommodate the arc surfaces on both sides after the first lower clamping block and the second lower clamping block are spliced.

[0013] Further, the upper link assembly and the lower link assembly are made of superalloy materials, refractory metal materials, high-strength graphite materials, or C / C composite materials.

[0014] A method for using a test fixture for a columnar tensile specimen includes the following steps:

[0015] 1) Connect the spherical hinge surfaces of the upper link and the lower link to the testing machine base, and respectively connect the threaded ends of the upper link and the lower link to the upper circular hole and the lower circular hole of the upper sleeve;

[0016] 2) Insert the upper end of the specimen into the lower circular hole of the upper sleeve, insert the first upper clamping block and the second upper clamping block into the upper sleeve, and clamp the shoulder of the upper end of the specimen through the two semi-circular holes;

[0017] 3) Join the first upper clamping block and the second upper clamping block together, and the two semi-circular holes form a complete circular hole to completely clamp the shoulder of the upper end of the specimen;

[0018] 4) Rotate the joined first upper clamping block and second upper clamping block 90° around the center of the upper sleeve to clamp the upper end of the specimen;

[0019] 5) Move the upper connecting rod assembly downward so that the lower end of the specimen extends into the upper circular hole of the lower sleeve, insert the first lower clamping block and the second lower clamping block into the lower sleeve, and clamp the shoulder of the lower end of the specimen through the two semi-circular holes;

[0020] 6) Join the first lower clamping block and the second lower clamping block together, and the two semi-circular holes form a complete circular hole to completely clamp the shoulder of the lower end of the specimen;

[0021] 7) Rotate the joined first lower clamping block and second lower clamping block 90° around the center of the lower sleeve to clamp the lower end of the specimen, completing the clamping and installation of the specimen.

[0022] The beneficial effects achieved by the present invention are as follows:

[0023] 1. The present invention adopts a structural design of "sleeve + two clamping blocks". By splicing the two clamping blocks inside the sleeve and rotating them 90°, the stable clamping of the specimen is realized, with simple operation and quick installation, improving the test efficiency.

[0024] 2. The present invention clamps the shoulder of the specimen through the semi-circular holes of the clamping blocks, avoiding relying on friction or bite force for clamping, and is applicable to brittle graphite materials, carbon-carbon composite materials, etc., improving the applicability and stability of the test.

[0025] 3. The present invention adopts a detachable connection structure. Threaded connections are used between the upper connecting rod and the upper sleeve, and between the lower connecting rod and the lower sleeve, facilitating the installation, replacement, and maintenance of the fixture, and improving the convenience and durability of use.

[0026] 4. A mating concave arc surface is provided between the clamping block and the sleeve of the present invention to ensure reliable positioning of the clamping block after rotation, prevent the specimen from shifting under force, and improve the accuracy and stability of the test.

[0027] 5. The end of the connecting rod assembly of the present invention adopts a spherical hinge surface design, which can be connected to the concave spherical surface of the testing machine base, reducing the clamping error, optimizing the axial alignment, and improving the accuracy of the test.

[0028] 6. The present invention can select superalloy, refractory metal, high-strength graphite or C / C composite material as the fixture material according to the test requirements, and can be stably used in the range of room temperature to 2500°C, meeting the tensile test requirements under high-temperature environment. Description of the Drawings

[0029] Figure 1 It is a schematic assembly diagram of the test fixture in the embodiment of the present invention.

[0030] Figure 2 It is a schematic exploded view of the test fixture in the embodiment of the present invention.

[0031] Figure 3 It is a structural diagram of the upper clamping block in the embodiment of the present invention.

[0032] Figure 4 It is a structural diagram of the upper sleeve in the embodiment of the present invention.

[0033] Figure 5 It is a schematic diagram of the specimen extending into the sleeve in the embodiment of the present invention.

[0034] Figure 6 It is a schematic diagram of the first upper clamping block inserted into the sleeve in the embodiment of the present invention.

[0035] Figure 7 It is a schematic diagram of the second upper clamping block inserted into the sleeve in the embodiment of the present invention.

[0036] Figure 8 It is a schematic diagram of the splicing of two upper clamping blocks in the embodiment of the present invention.

[0037] Figure 9 It is a schematic diagram of the two upper clamping blocks rotated 90° in the embodiment of the present invention.

[0038] Description of the Reference Numerals:

[0039] 110: upper connecting rod; 111: spherical hinge surface;

[0040] 112: threaded end; 120: upper sleeve;

[0041] 121: side window; 122: upper circular hole;

[0042] 123: lower circular hole; 124: concave arc surface;

[0043] 130: first upper clamping block; 131: semi-circular hole;

[0044] 132: flat straight surface; 133: arc surface;

[0045] 140: second upper clamping block; 210: lower connecting rod;

[0046] 211: Ball hinge surface; 212: Threaded end;

[0047] 220: Lower sleeve; 230: First lower clamping block;

[0048] 240: Second lower clamping block. Detailed implementation mode

[0049] To make the technical features, advantages or technical effects in the above technical solutions of the present invention more obvious and understandable, the following will be described in detail through embodiments.

[0050] The embodiment of the present invention specifically discloses a test fixture for a columnar tensile specimen. As Figure 1-2 shown, it includes an upper link assembly and a lower link assembly. The upper link assembly includes an upper link 110, an upper sleeve 120, a first upper clamping block 130 and a second upper clamping block 140; the lower link assembly includes a lower link 210, a lower sleeve 220, a first lower clamping block 230 and a second lower clamping block 240. The compositional structures of the upper link assembly and the lower link assembly are exactly the same, except that they are symmetrically arranged up and down. The upper end of the upper link 110 is a ball hinge surface 111 for connecting to the test machine base with a concave spherical surface; the lower end is a threaded end 112 with an external thread for threaded connection to the upper sleeve 120. Similarly, the lower end of the lower link 210 is a ball hinge surface 211 for connecting to the test machine base with a concave spherical surface; the upper end is a threaded end 212 with an external thread for threaded connection to the lower sleeve 220.

[0051] The structures of the four clamping blocks, namely the first upper clamping block 130, the second upper clamping block 140, the first lower clamping block 230 and the second lower clamping block 240, are exactly the same. Therefore, to avoid repetition, the structure of the first upper clamping block 130 will be described as an example, and the connection relationship between the first upper clamping block 130 and the second upper clamping block 140 will be described as an example. As Figure 3 shown, taking the first upper clamping block 130 as an example, it includes a semi-circular hole 131. The back surface on the side where the semi-circular hole 131 is located is a flat surface 132, and the two connecting surfaces between the side where the semi-circular hole 131 is located and the flat surface 132 are arc surfaces 133. The first upper clamping block 130 and the second upper clamping block 140 are placed in the cylindrical cavity of the upper sleeve 120, and the semi-circular holes are made into a complete circular hole by splicing and clamped at the lower shaft shoulder of the upper end of the specimen.

[0052] The structures of the upper sleeve 120 and the lower sleeve 220 are exactly the same, except that they are symmetrically arranged up and down during use. Therefore, to avoid repetition, the upper sleeve 120 will be described as an example. As Figure 4As shown in the figure, the upper sleeve 120 includes a cylindrical chamber, as well as an upper circular hole 122, a lower circular hole 123, and two side windows 121 that communicate with the cylindrical chamber. The upper sleeve 120 is detachably connected to the lower end of the upper connecting rod 110 through the upper circular hole 122. The lower circular hole 123 is used for introducing the upper end of the specimen, and the side windows 121 are used for passing through the first upper clamping block 130 and the second upper clamping block 140. The upper circular hole 122 of the upper sleeve 120 is provided with internal threads, and the threaded end of the upper connecting rod 110 is threadedly connected to the upper circular hole 122 of the upper sleeve 120. On the side wall of the cylindrical chamber of the upper sleeve 120, there are two concave arc surfaces 124 that are centrosymmetric with respect to the center of the upper sleeve 120. The directions of the two concave arc surfaces 124 are perpendicular to the directions of the two side windows 121. The two concave arc surfaces 124 are used to accommodate the two side arc surfaces 133 after the first upper clamping block 130 and the second upper clamping block 140 are spliced together.

[0053] This test fixture can be made of superalloy materials and, in combination with a high-temperature atmospheric furnace, can meet the test requirements up to 1100°C. This test fixture can also be made of refractory metal materials (such as pure tungsten and its alloys, pure molybdenum and its alloys) and, in combination with a high-temperature vacuum furnace, can meet the test requirements up to 1600°C. This test fixture can also be made of high-strength graphite or C / C composite materials and, in combination with a high-temperature vacuum furnace, can meet the test requirements up to 2500°C.

[0054] The embodiment of the present invention also provides a method for using a test fixture for a columnar tensile specimen, including the following steps:

[0055] 1) The spherical hinge surfaces 111 at the upper end of the upper connecting rod 110 and the spherical hinge surfaces 211 at the lower end of the lower connecting rod 210 are both connected to the test machine base with concave spherical surfaces. The diameter of the spherical hinge surface is related to the load.

[0056] 2) By means of threaded connection, screw the lower end of the upper connecting rod 110 into the upper circular hole 122 (i.e., the internal threaded hole) of the upper sleeve 120, and perform the same operation on the lower connecting rod 210.

[0057] 3) Install the specimen, insert the upper end of the specimen into the cylindrical chamber from the lower circular hole 123 of the upper sleeve 120, as Figure 5 shown.

[0058] 4) Insert the first upper clamping block 130 into the side window 121 of the upper sleeve 120, as Figure 6 shown. Then insert the second upper clamping block 140 into the side window 121 of the upper sleeve 120, so that the two semi-circular holes are stuck at the upper end shoulder of the specimen, as Figure 7 shown. Then splice the first upper clamping block 130 and the second upper clamping block 140 together to form a complete circular hole, clamping the upper end of the specimen. After splicing, the first upper clamping block 130 and the second upper clamping block 140 can restrict the axial movement of the upper end of the specimen, asFigure 8 as shown

[0059] 5) The first upper clamping block 130 and the second upper clamping block 140 after splicing then rotate 90° around the center of the upper sleeve 120, so that they enter the concave arc surface 124 on the side wall of the upper sleeve 120, and thus are completely limited in the horizontal direction, as Figure 9 shown

[0060] 6) Slowly move the upper connecting rod assembly downward so that the lower end of the specimen extends into the upper circular hole of the lower sleeve 220. Then repeat the same operations as in steps 4) to 5) for the lower connecting rod assembly, that is, insert the first lower clamping block 230 and the second lower clamping block 240 into the lower sleeve 220, clamp the shoulder at the lower end of the specimen and splice it into a complete circular hole, and then rotate 90° around the center of the lower sleeve 220 to complete the final clamping and installation of the specimen.

[0061] Although the present invention has been disclosed above with embodiments, it is not intended to limit the present invention. Any appropriate modification or equivalent replacement of the technical solutions of the present invention by those of ordinary skill in the art shall be covered within the protection scope of the present invention. The protection scope of the present invention shall be defined by the claims.

Claims

1. A test fixture for a columnar tensile specimen, characterized in that It includes an upper connecting rod assembly and a lower connecting rod assembly; The upper connecting rod assembly includes an upper connecting rod, an upper sleeve, a first upper clamping block and a second upper clamping block; the upper sleeve includes a cylindrical chamber, as well as an upper end round hole, a lower end round hole and two side windows communicating with the cylindrical chamber; the upper sleeve is detachably connected to the lower end of the upper connecting rod through the upper end round hole, the lower end round hole is used for introducing the upper end of the specimen, and the side windows are used for passing through the first upper clamping block and the second upper clamping block; both the first upper clamping block and the second upper clamping block include semi-circular holes, the first upper clamping block and the second upper clamping block are placed in the cylindrical chamber of the upper sleeve, and the semi-circular holes are made into a complete round hole by splicing with each other and are stuck at the shoulder below the upper end of the specimen; The lower connecting rod assembly includes a lower connecting rod, a lower sleeve, a first lower clamping block and a second lower clamping block; the lower sleeve includes a cylindrical chamber, as well as an upper end round hole, a lower end round hole and a side window communicating with the cylindrical chamber; the lower sleeve is detachably connected to the upper end of the lower connecting rod through the lower end round hole, the upper end round hole is used for introducing the lower end of the specimen, and the side window is used for passing through the first lower clamping block and the second lower clamping block; both the first lower clamping block and the second lower clamping block include semi-circular holes, the first lower clamping block and the second lower clamping block are placed in the cylindrical chamber of the lower sleeve, and the semi-circular holes are made into a complete round hole by splicing with each other and are stuck at the shoulder above the lower end of the specimen.

2. The test fixture for columnar tensile specimens according to claim 1, wherein, The upper end of the upper connecting rod is a spherical hinge surface for connecting the testing machine base with a concave spherical surface; the lower end of the lower connecting rod is a spherical hinge surface for connecting the testing machine base with a concave spherical surface.

3. The test fixture for columnar tensile specimens according to claim 1, characterized in that, The lower end of the upper connecting rod is a threaded end with an external thread, the upper end round hole of the upper sleeve is provided with an internal thread, and the threaded end of the upper connecting rod and the upper end round hole of the upper sleeve adopt a threaded connection method; the upper end of the lower connecting rod is a threaded end with an external thread, the lower end round hole of the lower sleeve is provided with an internal thread, and the threaded end of the lower connecting rod and the lower end round hole of the lower sleeve adopt a threaded connection method.

4. The test fixture for columnar tensile specimens according to claim 1, characterized in that, The back of the side where the semi-circular holes of the first upper clamping block and the second upper clamping block are located is a flat surface, and the two connecting surfaces between the side where the semi-circular holes are located and the flat surface are arc surfaces; the back of the side where the semi-circular holes of the first lower clamping block and the second lower clamping block are located is a flat surface, and the two connecting surfaces between the side where the semi-circular holes are located and the flat surface are arc surfaces.

5. The test fixture for columnar tensile specimens according to claim 4, characterized in that, There are two concave arc surfaces symmetric about the center of the upper sleeve on the side wall of the cylindrical chamber of the upper sleeve, the directions of the two concave arc surfaces are perpendicular to the directions of the two side windows, and the two concave arc surfaces are used for accommodating the arc surfaces on both sides after the first upper clamping block and the second upper clamping block are spliced; there are two concave arc surfaces symmetric about the center line on the side wall of the cylindrical chamber of the lower sleeve, the directions of the two concave arc surfaces are perpendicular to the directions of the two side windows, and the two concave arc surfaces are used for accommodating the arc surfaces on both sides after the first lower clamping block and the second lower clamping block are spliced.

6. The test fixture for columnar tensile specimens according to claim 1, characterized in that, The upper connecting rod assembly and the lower connecting rod assembly are made of superalloy materials, refractory metal materials, high-strength graphite materials or C / C composite materials.

7. A method for using the test fixture for columnar tensile specimens according to any one of claims 1-6, characterized in that, It includes the following steps: 1) Connect the spherical hinge surfaces of the upper connecting rod and the lower connecting rod to the testing machine base, and connect the threaded ends of the upper connecting rod and the lower connecting rod to the upper end round hole and the lower end round hole of the upper sleeve respectively; 2) Insert the upper end of the specimen into the lower end round hole of the upper sleeve, insert the first upper clamping block and the second upper clamping block into the upper sleeve and clamp the shoulder at the upper end of the specimen through the two semi-circular holes; 3) Join the first upper clamping block and the second upper clamping block together. The two semi-circular holes become a complete circular hole and completely clamp the upper shaft shoulder of the specimen. 4) Rotate the joined first upper clamping block and second upper clamping block 90° around the center of the upper sleeve to clamp the upper end of the specimen. 5) Move the upper connecting rod assembly downward so that the lower end of the specimen extends into the upper circular hole of the lower sleeve. Insert the first lower clamping block and the second lower clamping block into the lower sleeve and clamp the lower shaft shoulder of the specimen through the two semi-circular holes. 6) Join the first lower clamping block and the second lower clamping block together. The two semi-circular holes become a complete circular hole and completely clamp the lower shaft shoulder of the specimen. 7) Rotate the joined first lower clamping block and second lower clamping block 90° around the center of the lower sleeve to clamp the lower end of the specimen, completing the clamping and installation of the specimen.

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