A composite material fatigue test anti-instability clamp

Abstract

The application provides a composite material fatigue test anti-instability clamp, which comprises two anti-instability components and two clamping components arranged in parallel, each anti-instability component comprises two anti-instability plates; each anti-instability plate comprises a base plate and a forked jaw connected to the base plate, a forked groove is formed between the two adjacent forked jaws, the forked jaws and the forked grooves of the two anti-instability plates of the same anti-instability component are inserted together, the two anti-instability components are oppositely arranged, the two clamping components clamp the two anti-instability components together towards the same end, and the sample is located between the two clamping components. The first forked jaw and the second forked jaw are alternately arranged, the length direction of the sample is limited, and the overall instability or local buckling is avoided during the test, so that the test can be smoothly carried out.

Description

Technical Field

[0001] This application specifically relates to an anti-instability fixture for composite material fatigue testing. Background Technology

[0002] In fatigue testing of non-metallic composite materials, thin-sheet specimens are often used. Due to their thinness, overall instability or local buckling often occurs during the test, leading to test failure. To avoid test failure, clamps are needed to support the specimens and prevent instability. However, when existing ballast fatigue testing machines perform ballast tests on composite material specimens, the specimens bend away from the ballast direction under pressure load, which seriously affects the accuracy and reliability of the test.

[0003] The utility model patent with announcement number CN217111756U discloses a composite material fatigue testing machine, including a base and a ballast unit. The top of the base has two hydraulic cylinders symmetrically fixedly connected by a fixing sleeve. The output ends of the two hydraulic cylinders are fixedly connected to the same pressure plate. A lower shell is placed on the base. The top of the lower shell is fixedly connected to an upper shell by bolts. Two cavities are symmetrically opened on the sides of the upper and lower shells that are close to each other. Two side restraint plates are symmetrically slidably connected in the two cavities by an elastic clamping unit. A sample piece is clamped between the two side restraint plates.

[0004] This composite material fatigue testing machine effectively limits and restrains the upper and lower sides of the specimen through its elastic clamping unit and two side restraint plates. This prevents the specimen from bending away from the bearing force during the compressive fatigue test, ensuring that the specimen can only move along the bearing force direction, thus greatly improving the testing accuracy and reliability of the machine. The device, with its telescopic springs, smooth rods, and sliding plates, allows the two side restraint plates to move vertically. This provides sufficient cushioning when the specimen breaks and generates a huge impact force, effectively preventing damage to the side restraint plates during impact and ensuring their safety. This allows the testing machine to operate normally for extended periods. However, the large area of ​​the first and second observation slots in this composite material fatigue testing machine results in a large area of ​​the specimen being unrestrained. During the test, local instability or buckling can still occur, leading to test failure. Utility Model Content

[0005] To address the instability or buckling problems of composite materials during fatigue testing in the prior art, this application proposes an anti-instability fixture for composite material fatigue testing, which includes two anti-instability components and two clamping components arranged in parallel. Each anti-instability component includes a first anti-instability plate and a second anti-instability plate, both of which extend in a vertical direction. The two anti-instability components are spaced apart along a first axis.

[0006] The first anti-instability plate includes a first base plate and at least two downwardly extending first forks connected to the lower end face of the first base plate, with a first fork groove formed between two adjacent first forks. The second anti-instability plate includes a second base plate and at least two upwardly extending second forks connected to the upper end face of the second base plate, with a second fork groove formed between two adjacent second forks. The first forks in the same anti-instability assembly are inserted into the second fork groove, and the second forks are inserted into the first fork groove. There is a first distance between the end of the first fork and the bottom of the second fork groove, and a second distance between the end of the second fork and the bottom of the first fork groove. Both the first distance and the second distance are 1-2 mm larger than the deformation size of the sample when compressed.

[0007] Two first anti-instability plates are arranged opposite each other, and two second anti-instability plates are arranged opposite each other. Each clamping assembly includes two clamping plates arranged opposite each other along a first axis. The two clamping plates of the same clamping assembly are connected together by connecting bolts. The two clamping plates of one clamping assembly are used to clamp the first substrates of the two first anti-instability plates together, and the two clamping plates of the other clamping assembly are used to clamp the second substrates of the two second anti-instability plates together. The sample is located between the two clamping assemblies. The first axis extends horizontally.

[0008] In operation, this application first clamps both sides of one end of the specimen into the first specimen groove of a first anti-instability plate, and fixes the two first anti-instability plates to the specimen using a first clamping assembly. Then, both sides of the other end of the specimen are clamped into the second specimen groove of a second anti-instability plate, and the two second anti-instability plates are fixed to the specimen using a second clamping assembly. The first fork is inserted into the second fork groove, and the second fork is inserted into the first fork groove, forming a specimen assembly. When installing the first and second clamping assemblies, the torque of the nut is controlled at 3.2 ± 0.1 N·m. Then, both ends of the specimen assembly are clamped onto the two fixtures of the testing equipment for fatigue testing. To facilitate the determination of the first and second distances, it is necessary to estimate the deformation size of the specimen based on experience or conduct preliminary tests. After the deformation size of the specimen is roughly determined, a formal fatigue test is then conducted.

[0009] In this application, the entire sample is clamped between two anti-instability components, and the first fork and the second fork are alternately arranged, which restricts the length of the sample. During the test, overall instability or local buckling is avoided. Furthermore, since there is a first distance between the end of the first fork and the bottom of the second fork groove, and a second distance between the end of the second fork and the bottom of the first fork groove, the sample can be stretched and compressed, so that the test can be carried out smoothly.

[0010] Furthermore, to prevent tilting during installation, each anti-instability component has a vertically extending sample slot on the side facing another anti-instability component, with the depth of the sample slot being 30-45% of the sample thickness. Specifically, each first anti-instability plate has a vertically extending first sample slot on the side facing another first anti-instability plate, and each second anti-instability plate has a vertically extending second sample slot on the side facing another second second anti-instability plate. The first and second sample slots of the same anti-instability component together form a sample slot, and the depth of the first and second sample slots of the same anti-instability component is the same.

[0011] Furthermore, to avoid friction between adjacent first and second forks during the test, which could affect the accuracy of the test data, there is a 1-2mm gap between adjacent first and second forks in the same anti-instability component.

[0012] Furthermore, to prevent the edges of the first and second forks from scratching the surface of the sample, the edges of the first and second forks have rounded chamfers.

[0013] Furthermore, to facilitate the installation of the connectors onto the fixtures of the testing equipment, two connectors are included: a first connector and a second connector. Each first substrate has a first protrusion on its outer side at the end opposite to the first fork, and each second substrate has a second protrusion on its outer side at the end opposite to the second fork. Each connector includes a claw and a clamping head connected to the claw. The claw of the first connector clamps onto the two first protrusions, and the claw of the second connector clamps onto the two second protrusions. Specifically, the claw includes a crossbeam and claw hooks formed at both ends of the crossbeam. Each claw hook forms a groove with the crossbeam. The first protrusion is inserted into the groove of the first connector, and the second protrusion is inserted into the groove of the second connector. The clamping head is connected to the middle part of the crossbeam. This connector does not affect the clamping force between the two anti-instability components and can simultaneously apply force to both the first and second anti-instability plates, ensuring the smooth progress of the test.

[0014] Furthermore, to prevent the first protrusion from moving freely within the slot of the first connector and to prevent the second protrusion from moving freely within the slot of the second connector, two clamping bolts are screwed onto the crossbeam of each claw. The two clamping bolts are located on both sides of the clamping head and pass through the connected crossbeam. The clamping bolt on the first connector passes through the connected crossbeam and presses against the first protrusion, and the clamping bolt on the second connector passes through the connected crossbeam and presses against the second protrusion. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of an embodiment of this application.

[0016] Figure 2 for Figure 1 The left view.

[0017] Figure 3 This is the main view of the clamping component.

[0018] Figure 4 for Figure 2 A view from the center AA direction.

[0019] Figure 5 for Figure 2 A view from the center (BB direction).

[0020] Figure 6 A view of the anti-instability clamp holding the sample. Detailed Implementation

[0021] Please see Figures 1-6 In the accompanying drawings, the first arrow Z points in the vertical direction, and the second arrow X points in the direction of the first axis, which extends horizontally. The following describes the anti-instability fixture for composite material fatigue testing in this application. This anti-instability fixture includes two parallel anti-instability components and two clamping components. For ease of description, the two anti-instability components are referred to as the first anti-instability component 10 and the second anti-instability component 20, respectively. The two anti-instability components are spaced apart along the first axis.

[0022] The two anti-instability components have the same structure. The following description uses the first anti-instability component 10 as an example to illustrate its structure. The first anti-instability component 10 includes a first anti-instability plate 11 and a second anti-instability plate 14. Both the first and second anti-instability plates extend vertically. The first anti-instability plate 11 includes a first substrate 111 and two downwardly extending first forks 112 connected to the lower end face of the first substrate. A first fork groove 113 is formed between adjacent first forks. The second anti-instability plate 14 includes a second substrate 14. 1. Three upwardly extending second forks 142 connected to the upper surface of the second substrate, with a second fork groove 143 formed between adjacent second forks; the first fork of the first anti-instability component is inserted into the second fork groove, and the second fork is inserted into the first fork groove, with a first distance H1 between the end of the first fork and the bottom of the second fork groove, and a second distance H2 between the end of the second fork and the bottom of the first fork groove. Both the first and second distances are 1.5 mm larger than the deformation size of the sample during compression to ensure the normal conduct of the test. Two first anti-instability plates are arranged opposite each other, and two second anti-instability plates are arranged opposite each other.

[0023] In this embodiment, to avoid friction between adjacent first and second forks that could interfere with the test data, a 1.5mm gap is provided between adjacent first and second forks in the same anti-instability assembly. To prevent the edges of the first and second forks from scratching the sample surface, in this embodiment, the edge of the first fork has a first rounded chamfer of 115°, and the edge of the second fork has a second rounded chamfer of 145°.

[0024] For ease of description, the two clamping components are referred to as the first clamping component 30 and the second clamping component 50, respectively. The two clamping components have the same structure. The following description uses the first clamping component 30 as an example to illustrate the structure of the clamping component. The first clamping component 30 includes two clamping plates 31 arranged opposite to each other along the first axis. A connecting bolt 32 passes through the two clamping plates of the same clamping component and is screwed with a nut 33 to connect the two clamping plates together. The first clamping component 30 has four connecting bolts 32. Among the four connecting bolts, every two connecting bolts form a bolt group. The two bolt groups are respectively installed on both sides of the clamping plate in the horizontal direction.

[0025] The two clamping plates of the first clamping assembly 30 are used to clamp the first substrates of the two first anti-instability plates together, and the two clamping plates of the second clamping assembly 50 are used to clamp the second substrates of the two second anti-instability plates together. The sample 51 is located between the two clamping assemblies.

[0026] To facilitate sample clamping, each first anti-instability plate has a first sample groove 114 extending vertically on the side facing the other first anti-instability plate, and each second anti-instability plate has a second sample groove 144 extending vertically on the side facing the other second anti-instability plate. The first sample groove and the second sample groove of the same anti-instability component together form a sample clamping slot, that is, each anti-instability component has a sample clamping slot extending vertically on the side facing the other anti-instability component.

[0027] The first and second sample slots of the same anti-instability component have the same depth, and the depth of both the first and second sample slots is 40% of the sample thickness. It can be understood that in other embodiments, the depth of the first and second sample slots can also be 30%, 35% or 45% of the sample thickness, or other proportions between 30% and 45%.

[0028] To facilitate clamping the anti-instability fixture onto the fixture of the test equipment, this embodiment also provides two connecting parts. For ease of description, the two connecting parts are referred to as the first connecting part 40 and the second connecting part 60, respectively. The two connecting parts have the same structure. The specific structure of the connecting parts will be described below using the first connecting part 40 as an example.

[0029] The first connector 40 includes a jaw and a clamping head 42 connected to the jaw. The jaw includes a crossbeam 41 and claw hooks 43 formed at both ends of the crossbeam. Each claw hook forms a groove 44 between itself and the crossbeam. The clamping head is connected to the middle part of the crossbeam and is located on the side of the crossbeam away from the claw hooks.

[0030] Each first substrate has a first protrusion 16 on the outer side of the end opposite to the first fork, and each second substrate has a second protrusion 18 on the outer side of the end opposite to the second fork. The two first protrusions are respectively inserted into the two slots of the first connector, and the two second protrusions are respectively inserted into the two slots of the second connector.

[0031] Two clamping bolts 45 are screwed onto the crossbeam of each jaw. The two clamping bolts are located on both sides of the clamping head and pass through the connected crossbeam. The clamping bolt on the first connector passes through the connected crossbeam and presses against the first protrusion. The clamping bolt on the second connector passes through the connected crossbeam and presses against the second protrusion.

[0032] In this embodiment, during operation, firstly, both sides of one end of the sample 51 are respectively clamped into the first sample groove 114 of a first anti-instability plate 11, and the two first anti-instability plates are fixed to the sample using the first clamping assembly 30. Then, both sides of the other end of the sample are respectively clamped into the second sample groove 144 of a second anti-instability plate 14, and the two second anti-instability plates are fixed to the sample using the second clamping assembly 50, with the first fork inserted into the second fork groove and the second fork inserted into the first fork groove. When installing the first clamping assembly and the second clamping assembly, the torque of the nut 33 is controlled at 3.2±0.1 N·m. The first protrusion on the first anti-instability plate is inserted into the two grooves of the first connector, and the clamping bolt is tightened so that the clamping bolt presses against the first protrusion, thus completing the installation of the first connector. Then, the second protrusion on the second anti-instability plate is inserted into the two grooves of the second connector, and the clamping bolt is tightened so that the clamping bolt presses against the second protrusion, thus completing the installation of the second connector. Then, the clamping heads of the first and second connectors are clamped onto the two fixtures of the testing equipment for fatigue testing.

Claims

1. A buckling prevention fixture for composite material fatigue testing, characterized in that, It includes two anti-instability components and two clamping components arranged in parallel. Each anti-instability component includes a first anti-instability plate and a second anti-instability plate. Both the first and second anti-instability plates extend in the vertical direction. The two anti-instability components are spaced apart along the first axis. The first anti-instability plate includes a first base plate and at least two downwardly extending first forks connected to the lower end face of the first base plate, with a first fork groove formed between two adjacent first forks. The second anti-instability plate includes a second base plate and at least two upwardly extending second forks connected to the upper end face of the second base plate, with a second fork groove formed between two adjacent second forks. The first forks in the same anti-instability assembly are inserted into the second fork groove, and the second forks are inserted into the first fork groove. There is a first distance between the end of the first fork and the bottom of the second fork groove, and a second distance between the end of the second fork and the bottom of the first fork groove. Both the first distance and the second distance are 1-2 mm larger than the deformation size of the sample when compressed. Two first anti-instability plates are arranged opposite each other, and two second anti-instability plates are arranged opposite each other. Each clamping assembly includes two clamping plates arranged opposite each other along a first axis. The two clamping plates of the same clamping assembly are connected together by connecting bolts. The two clamping plates of one clamping assembly are used to clamp the first substrates of the two first anti-instability plates together, and the two clamping plates of the other clamping assembly are used to clamp the second substrates of the two second anti-instability plates together. The sample is located between the two clamping assemblies. The first axis extends horizontally.

2. The anti-instability clamp according to claim 1, characterized in that, Each anti-instability component has a vertically extending sample slot on the side facing the other anti-instability component, and the depth of the sample slot is 30-45% of the sample thickness.

3. The anti-instability clamp according to claim 2, characterized in that, Each first anti-instability plate has a first sample groove extending vertically on one side facing another first anti-instability plate, and each second anti-instability plate has a second sample groove extending vertically on one side facing another second anti-instability plate. The first sample groove and the second sample groove of the same anti-instability component together form a sample slot, and the first sample groove and the second sample groove of the same anti-instability component have the same depth.

4. The anti-instability clamp according to claim 1, characterized in that, In the same anti-instability assembly, there is a gap of 1-2mm between adjacent first forks and second forks.

5. The anti-instability clamp according to claim 1, characterized in that, The edges of the first and second forks have rounded chamfers.

6. The anti-instability clamp according to claim 1, characterized in that, It also includes two connectors, the two first connectors being a first connector and a second connector; each first substrate has a first protrusion on the outer side of the end opposite to the first fork, and each second substrate has a second protrusion on the outer side of the end opposite to the second fork. Each connector includes a pawl and a clamping head connected to the pawl, wherein the pawl of the first connector is clamped on the two first protrusions, and the pawl of the second connector is clamped on the two second protrusions.

7. The anti-instability clamp according to claim 6, characterized in that, The chuck includes a crossbeam and claw hooks formed at both ends of the crossbeam. Each claw hook forms a groove with the crossbeam. A first protrusion is inserted into the groove of the first connector, a second protrusion is inserted into the groove of the second connector, and a clamping head is connected to the middle part of the crossbeam.

8. The anti-instability clamp according to claim 7, characterized in that, Two clamping bolts are screwed onto the crossbeam of each jaw. The two clamping bolts are located on both sides of the clamping head and pass through the connected crossbeam. The clamping bolt on the first connector passes through the connected crossbeam and presses against the first protrusion. The clamping bolt on the second connector passes through the connected crossbeam and presses against the second protrusion.

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