Device for tensile test of ultra-high performance concrete test piece

Abstract

The utility model relates to the technical field of concrete tensile testing, in particular to an ultra-high performance concrete test piece tensile testing device which comprises an upper clamping assembly and a lower clamping assembly, the size of the upper clamping assembly and the size of the lower clamping assembly are adjustable, and the upper clamping assembly, the lower clamping assembly and a test piece are vertically and coaxially arranged. The upper clamping assembly, the lower clamping assembly and the test piece are vertically and coaxially arranged, so that the technical problem of inaccurate tensile test caused by eccentricity of the test piece due to tension load is solved. Through cooperation of the upper and lower clamping assembly structures in a rotating and sliding connection mode and cooperative clamping of the upper and lower clamping assemblies and the test piece, the clamping assembly and the test piece are high in adaptability, and the technical effect of stable clamping is achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of concrete tensile test, in particular to a device for tensile test of ultra-high performance concrete specimens. Background Art

[0002] The tensile property of concrete is one of its basic mechanical properties. It is not only an important part of the research on concrete strength theory and failure mechanism, but also directly affects the crack resistance of reinforced concrete structures. The usual test method is to first prepare strip-shaped concrete specimens, and then clamp the two ends of the strip-shaped concrete specimens by using clamps, and use a tensile machine or a certain amount of weights to apply force for testing. In the prior art, there is a problem that the concrete specimen and the clamp are not on the same axis in the commonly used concrete tensile test clamp, so that the load of the concrete specimen is not fully applied along the axial direction; in addition, there is also a problem that the clamping force of the concrete tensile clamp is insufficient, the concrete specimen cannot be effectively fixed, and it is easy to produce sliding that affects the results, and it is easy to produce concentrated loads, making the applied load unstable and uneven.

[0003] After retrieval, a Chinese patent with the authorization announcement number of CN 207095976 U discloses a specimen clamp for tensile test of concrete-like materials. The clamp includes an upper clamping member and a lower clamping member. The upper clamping member includes a connecting rod, a clamping groove, a fastening bolt and a nut, and the lower clamping member includes a base, a clamping groove, a fastening bolt and a nut. One end of the clamping part is provided with a quarter-circular clamping groove for clamping the end of the specimen, and the clamping parts are separated and need to be tightened with bolts and nuts during use. Compared with the existing domestic and foreign clamps for tensile test of concrete-like materials of the utility model, in the direct tensile test, the phenomenon of strain concentration at the end of the specimen is avoided, and it is not necessary to carry out densification treatment on the end of the specimen, making the tensile test result more accurate and reliable. It can also effectively ensure that the specimen is axially tensioned, making the load action line coincide with the tensile specimen as much as possible, with the advantages of simple structure and convenient clamping, and has high use value.

[0004] However, when installing the specimen with the above-mentioned specimen clamp for tensile test of concrete-like materials, it is necessary to fully open the upper clamping member and the lower clamping member, and after putting the specimen into the clamping member, it is necessary to fix the clamping member with nuts again. The operation is relatively troublesome, and it is necessary to match the size and height of the clamping opening of the clamping member with the specimen, otherwise there will be problems such as inability to install or instability. Summary of the Utility Model

[0005] Aiming at the technical problem that when installing the specimen with the above-mentioned specimen clamp for tensile test of concrete-like materials, it is necessary to fully open the upper clamping member and the lower clamping member, and after putting the specimen into the clamping member, it is necessary to fix the clamping member with nuts again. The operation is relatively troublesome, and it is necessary to match the size and height of the clamping opening of the clamping member with the specimen, otherwise there will be problems such as inability to install or instability.

[0006] Technical idea: Starting from the problems of the prior art, this application provides a device for tensile testing of ultra-high performance concrete specimens. By vertically co-aligning the upper clamping assembly, the lower clamping assembly, and the specimen, the eccentric tensile load on the specimen is avoided. Through the cooperation of the rotational and sliding connection methods between the upper and lower clamping assemblies, and the cooperative clamping of the upper and lower clamping assemblies and the specimen, the adaptability between the clamping assembly and the specimen is high, achieving the technical effects of stable clamping and easy disassembly.

[0007] To achieve the above object, the technical solution adopted by the present utility model is:

[0008] This application provides a device for tensile testing of ultra-high performance concrete specimens, including an upper clamping assembly and a lower clamping assembly. The sizes of the upper clamping assembly and the lower clamping assembly are adjustable, and the upper clamping assembly, the lower clamping assembly, and the specimen are vertically coaxial.

[0009] Further, the upper clamping assembly includes a clamping top seat connected to the testing machine. Rotating connection blocks are provided on both the left and right sides of the clamping top seat, and each rotating connection block is provided with an upper clamping block that cooperates with the specimen.

[0010] Furthermore, the lower clamping assembly includes a clamping base. Lower clamping blocks that cooperate with the specimen are provided on both the left and right sides of the clamping base. A fastening block is connected to each lower clamping block, and the fastening block is connected to the clamping base.

[0011] Specifically, the head end of the rotating connection block is movably connected to the clamping top seat through a shaft, the middle part of the rotating connection block is fixed to the clamping top seat through a locking nut, and the tail end of the rotating connection block is fixedly connected to the upper clamping block through a locking screw.

[0012] In particular, the specimen has a dog-bone shape structure.

[0013] Specifically, the overall width of the specimen is 100 mm, the length is 500 mm, the thickness is 50 mm, and the chamfer radius of the variable cross-section is 62.5 mm.

[0014] Specifically, both the upper clamping block and the lower clamping block are cuboid structures, and the surfaces in contact with the specimen are arc-shaped curved surfaces. The arc-shaped curved surfaces cooperate with the curved surfaces on the side of the specimen, and the upper clamping block and the lower clamping block clamp and fix the specimen.

[0015] Further, movable slot openings are provided through both the left and right sides of the clamping base, and the lower clamping block abuts against the specimen through the movable slot openings.

[0016] Furthermore, the front and rear surfaces of the clamping base and the front and rear surfaces of the lower clamping block are fixed by lock nuts. A fastener is fixedly connected to the lower clamping block, and the fastener is connected to the clamping base by a lock nut.

[0017] Preferably, auxiliary fixing components for clamping and fixing the specimen in the front and rear directions are provided on both the front and rear sides of the clamping base.

[0018] In the above technical solution, C-shaped notch openings are respectively formed through the front and rear surfaces of the clamping top seat and the clamping base, and the width of the C-shaped notch opening matches the width of the specimen.

[0019] Further, the auxiliary fixing component includes fixing plates respectively fixedly connected to the front and rear surfaces of the clamping base, and movable plates slidably connected to the side walls of the C-shaped notch openings formed in the clamping base. The fixing plates and the movable plates are connected by connecting rods.

[0020] Compared with the prior art, the beneficial effects of the present utility model are as follows:

[0021] 1. By vertically coaxially arranging the upper clamping component, the lower clamping component and the specimen, the present utility model avoids the eccentricity of the tensile load on the specimen. Through the cooperation of the rotational and sliding connection methods between the structures of the upper and lower clamping components, the technical effect of adjustable sizes of the upper clamping component and the lower clamping component is achieved. And through the clamping cooperation between the upper and lower clamping components and the specimen, the adaptability between the clamping component and the specimen is high, and the technical effect of stable clamping is achieved.

[0022] 2. Through the setting of the clamping base, the present utility model facilitates the support and fixation of the specimen. The C-shaped notch opening structures formed through the front and rear surfaces of the clamping base facilitate the installation and placement of the specimen. And the lower clamping blocks arranged on both side surfaces of the clamping base facilitate the clamping and fixing of the specimen. And through the connection setting of the fasteners on the lower clamping blocks, the further clamping and fixing of the specimen is realized, making the clamping of the specimen more stable and avoiding the problem that the specimen moves during the tensile test and affects the test result.

[0023] 3. Through the movable connection between the clamping top seat and the movable clamping block, the present utility model facilitates the installation of the specimen. Then, the clamping top seat and the movable clamping block are fixed to realize the clamping of the specimen. Further, through the cooperative setting of the upper clamping block and the specimen, the clamping and fixing of the applied force are realized, making the clamping more stable.

[0024] 4. By respectively fixedly connecting fixing plates to the front and rear surfaces of the clamping base, and having movable plates slidably connected to the side walls of the C-shaped notch openings formed in the clamping base, and connecting the fixing plates and the movable plates by connecting rods, through the setting of the fixing plates and the movable plates, the further clamping and fixing of the front and rear surfaces of the specimen are realized, making the specimen more stable. Description of the Drawings

[0025] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation of the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0026] Figure 1 It is a schematic diagram of the overall structure of the present utility model;

[0027] Figure 2 It is a top view of the present utility model;

[0028] Figure 3 For the present utility model Figure 2 A cross-sectional view in the A-A direction;

[0029] Figure 4 For the present utility model Figure 2 A cross-sectional view in the B-B direction;

[0030] Figure 5 It is a schematic diagram of the specimen structure of the present utility model;

[0031] In the figure: 1. Upper clamping assembly; 11. Clamping top seat; 12. Movable clamping block; 13. Upper clamping block; 2. Lower clamping assembly; 21. Clamping base; 22. Lower clamping block; 23. Fastening block; 3. Specimen; 4. Auxiliary fixing assembly; 41. Movable plate; 42. Connecting rod; 43. Fixed plate; 44. Locking bolt. Specific embodiments

[0032] In order to enable those of ordinary skill in the art to better understand the technical solutions of the present utility model, the following will further describe the technical solutions of the present utility model in conjunction with the drawings and embodiments.

[0033] In the description of the present utility model, it should be understood that the orientation or positional relationship indicated by terms such as "upper", "lower", "front", "rear", "left", "right", "front end", "rear end", "inner side", "outer side", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present utility model.

[0034] In the description of the present application, it should also be noted that, unless otherwise clearly specified and defined, the terms "set", "installed", "connected", and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0035] The inventors' research found that in the tensile test experiment of concrete specimens, it is necessary to use specimen fixtures to clamp and fix the specimens, and the specimens and the fixtures should be coaxially arranged to avoid the problem of eccentric tensile load on the specimens, resulting in inaccurate test results; and the height of the fixture and the specimen should be cooperatively clamped to make the clamping stable. The existing specimen fixtures have the technical problems of inconvenient installation, unstable clamping and easy eccentricity, which in turn cause inaccurate test results.

[0036] Based on the above findings, the present application provides a device for tensile testing of ultra-high performance concrete specimens, including an upper clamping assembly 1 and a lower clamping assembly 2. The sizes of the upper clamping assembly 1 and the lower clamping assembly 2 are adjustable, and the upper clamping assembly 1, the lower clamping assembly 2 and the specimen 3 are vertically coaxially arranged. Embodiment 1

[0037] Refer to Figures 1-5 As shown, the present application provides a device for tensile testing of ultra-high performance concrete specimens, including an upper clamping assembly 1 and a lower clamping assembly 2. The sizes of the upper clamping assembly 1 and the lower clamping assembly 2 are adjustable, and the upper clamping assembly 1, the lower clamping assembly 2 and the specimen 3 are vertically coaxially arranged.

[0038] It should be noted that by arranging the upper clamping assembly 1, the lower clamping assembly 2 and the specimen 3 vertically coaxially, the problem of eccentric tensile load on the specimen 3, resulting in inaccurate test results, is avoided.

[0039] Furthermore, the upper clamping assembly 1 includes a clamping top seat 11 connected to the testing machine. Movable clamping blocks 12 are rotatably connected to the left and right sides of the clamping top seat 11, and upper clamping blocks 13 cooperating with the specimen 3 are arranged on each of the movable clamping blocks 12.

[0040] As an example, the clamping top seat 11 and the movable clamping block 12 are axially movably connected, and can also be rotatably connected by means of hinges. Through the rotational connection method, it is convenient to install the specimen 3 between the clamping base 21 and the clamping top seat 11.

[0041] After the installation of Specimen 3 is completed, the clamping top seat 11 and the movable clamping block 12 are fixed by tightening nuts, so that the clamping top seat 11 and the movable clamping block 12 are in close contact with Specimen 3, making the clamping more stable.

[0042] Furthermore, through the setting of the upper clamping block 13, the arc-shaped curved surface of the upper clamping block 13 is in mating contact with the curved surface on the side of Specimen 3, further enhancing the stability of the clamping.

[0043] Specifically, the lower clamping assembly 2 includes a clamping base 21. Lower clamping blocks 22 that cooperate with Specimen 3 are arranged on both the left and right sides of the clamping base 21. A fastening block 23 is connected to each lower clamping block 22, and the fastening block 23 is connected to the clamping base 21.

[0044] It should be noted that movable slot openings are formed through both the left and right sides of the clamping base 21, and the lower clamping blocks 22 are in contact with Specimen 3 through the movable slot openings. The arc-shaped curved surface of the lower clamping block 22 is in mating contact with the curved surface on the side of Specimen 3, further enhancing the stability of the clamping.

[0045] As an example, C-shaped slot openings are formed through both the front and rear surfaces of the clamping top seat 11 and the clamping base 21, and the width of the C-shaped slot openings matches the width of Specimen 3. Embodiment Two

[0046] On the basis of Embodiment One, with reference to Figure 1 As shown, in order to further clamp and fix the front and rear sides of Specimen 3, auxiliary fixing components 4 for clamping and fixing Specimen 3 in the front and rear directions are provided on both the front and rear sides of the clamping base 21.

[0047] Specifically, the auxiliary fixing component 4 includes fixing plates 43 fixedly connected to the front and rear surfaces of the clamping base 21 respectively, and movable plates 41 slidably connected to the side walls of the C-shaped slot openings formed in the clamping base 21. The fixing plates 43 and the movable plates 41 are connected by connecting rods 42.

[0048] As an example, the fixing plates 43 are fixed to the clamping base 21 by tightening nuts. The connecting rods 42 are fixedly connected to the movable plates 41, and the connecting rods 42 are movably connected to the fixing plates 43. The fixing of the connecting rods 42 and the fixing plates 43 is achieved through locking bolts 44.

[0049] Specific application cases:

[0050] Taking the tensile test of ultra-high performance concrete specimens as an example, the specific application of a device for tensile testing of ultra-high performance concrete specimens in this application is specifically analyzed.

[0051] Ultra-high performance concrete is a cement-based composite material made from raw materials such as cement, admixtures, aggregates, reinforcing fibers, water reducers, and water, which has ultra-high mechanical properties, ultra-high resistance to erosion medium penetration performance, and also has the characteristics of improving brittleness.

[0052] During the tensile test of the ultra-high performance concrete specimen, first, before reaching the test age, the specimen 3 is taken out of the curing room. After the surface moisture is dried, the specimen 3 is installed in the fixture.

[0053] Specifically, the specimen 3 is placed into the clamping base 21 through the C-shaped notch provided on the clamping base 21. Further, the fastening block 23 is pushed to drive the lower clamping block 22 to move, so that the arc-shaped curved surface of the lower clamping block 22 abuts against the curved surface of the side of the specimen 3, realizing the restricted fixation of the specimen 3. Further, the clamping base 21 and the lower clamping block 22 are fixed by a locking nut, and the clamping base 21 and the fastening block 23 are fixed by a locking nut, completing the clamping fixation between the specimen 3 and the lower clamping assembly 2.

[0054] Further, the specimen 3 is placed in the clamping top seat 11, and the specimen 3 is abutted and fixed by the movable clamping block 12 and the upper clamping block 13. The middle part of the movable clamping block 12 is fixed to the clamping top seat 11 by a locking nut, and the tail end of the movable clamping block 12 is fixedly connected to the upper clamping block 13 by a locking screw. The clamping fixation between the specimen 3 and the upper clamping assembly 1 is realized.

[0055] The specimen 3, the upper clamping assembly 1, and the lower clamping assembly 2 are in a vertical coaxial position. The testing machine is connected to the clamping top seat 11 to ensure that the central axes of the upper clamping assembly 1 and the lower clamping assembly 2 are consistent with and centered on the central axis of the specimen 3.

[0056] Further, the connecting rod 42 is pushed to make the movable plate 41 abut tightly against the specimen 3, and then the position of the connecting rod 42 and the fixed plate 43 is fixed by a locking bolt 44, realizing the clamping fixation of the front and back surfaces of the specimen 3, making the fixation more stable.

[0057] When using a displacement sensor to measure deformation, the displacement sensor should be fixed on the deformation measurement frame and positioned by the gauge positioning rod, and then the deformation measurement frame is fixed to the middle part of the specimen 3 by fastening screws. When using resistance strain gauges to measure deformation, after the specimen 3 is taken out of the curing room, the surface should be dried as soon as possible with a hair dryer in the middle parts on both sides of the specimen 3, and then the resistance strain gauges are pasted with glue. The time from taking out the specimen 3 to the end of the test should not exceed 4 h. The preparatory work for deformation measurement should be done in advance.

[0058] Start the testing machine for pre-tensioning. The pre-tensioning load shall be equivalent to 15% - 20% of the failure load. During pre-tensioning, the strain values shall be measured and the eccentricity shall be calculated. The calculation method shall refer to the axial tension test method in GB / T50081. When the eccentricity of the test block is greater than 15%, the test block shall be re-centered and adjusted.

[0059] After pre-tensioning, the measuring instruments shall be re-adjusted for formal testing. During the tensile test, continuous and uniform loading shall be applied to Specimen 3. Displacement control loading is preferably adopted, and the loading rate shall be controlled at 0.2 mm / min. When a displacement sensor is used to measure the deformation, the deformation within the measuring gauge length of Specimen 3 shall be automatically recorded by the data acquisition system, and the load-displacement curve shall be plotted.

[0060] When one of the following conditions is met, the loading shall be terminated and the test shall be stopped:

[0061] (1) When the residual tensile strength is lower than 30% of the ultimate tensile strength;

[0062] (2) When the tensile strain of the test piece is greater than 10000 με;

[0063] (3) When it is broken.

[0064] In summary, although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A device for tensile testing of ultra-high performance concrete specimens, comprising an upper clamping assembly (1) and a lower clamping assembly (2), characterized in that: The sizes of the upper clamping assembly (1) and the lower clamping assembly (2) are both adjustable, and the upper clamping assembly (1), the lower clamping assembly (2) and the test piece (3) are vertically coaxially arranged.

2. The device for tensile testing of ultra-high performance concrete specimens according to claim 1, characterized in that: The upper clamping assembly (1) comprises a clamping top seat (11) connected to the testing machine, and both left and right sides of the clamping top seat (11) are rotatably connected to movable clamping blocks (12), and each movable clamping block (12) is provided with an upper clamping block (13) that cooperates with the test piece (3).

3. The device for tensile testing of ultra-high performance concrete specimens according to claim 2, characterized in that: The lower clamping assembly (2) comprises a clamping base (21), and lower clamping blocks (22) matching the test piece (3) are arranged on the left and right sides of the clamping base (21), and each of the lower clamping blocks (22) is connected to a fastening block (23), and the fastening block (23) is connected to the clamping base (21).

4. The device for tensile testing of ultra-high performance concrete specimens according to claim 3, characterized in that: Auxiliary fixing components (4) for clamping and fixing the test piece (3) in the front and rear directions are provided on both the front and rear sides of the clamping base (21).

5. The device for tensile testing of ultra-high performance concrete specimens according to claim 4, characterized in that: C-shaped notches are provided through the front and rear surfaces of the clamping top seat (11) and the clamping base (21), and the width of the C-shaped notches matches the width of the test piece (3).

6. The device for tensile testing of ultra-high performance concrete specimens according to claim 5, characterized in that: The auxiliary fixing assembly (4) comprises a fixing plate (43) fixedly connected to the front and rear surfaces of the clamping base (21) respectively, and a movable plate (41) slidably connected to the side wall of a C-shaped notch provided on the clamping base (21); the fixing plate (43) and the movable plate (41) are connected via a connecting rod (42).

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