Three-point bending fatigue testing device for composite material

Abstract

The invention belongs to the technical field of airplane strength tests, and particularly relates to a three-point bending fatigue testing device for a composite material. The device comprises an upper pressing head, supporting blocks and a lower supporting base, the two supporting blocks are arranged at the two ends of the lower supporting base in a sliding mode respectively, each supporting block comprises a base, a V-shaped groove is formed in the upper end of each base, a cylindrical roller is arranged in each V-shaped groove, the bottom of a test piece is supported by the cylindrical rollers of the two supporting blocks, and pressure is applied to the upper portion of the test piece through the upper pressing head. The opposite inner sides of the two bases are respectively connected with two longitudinal limiting strips, the two longitudinal limiting strips clamp the test piece on the two sides of the test piece, the outer sides of the two bases are respectively connected with a transverse limiting strip, and the two transverse limiting strips of the two bases clamp the test piece at the front end and the rear end of the test piece. According to the invention, the accuracy of long-time fatigue test can be ensured, and test errors can be reduced.

Description

Technical Field

[0001] The present application belongs to the technical field of aircraft strength testing, and in particular relates to a three-point bending fatigue testing device for composite materials. Background Art

[0002] Composite materials have been widely used in the aerospace field due to their high specific strength, specific modulus, excellent fatigue resistance, and corrosion resistance. During their service life, composite laminates are often subjected to bending fatigue loads, so accurately obtaining the bending fatigue characteristics of composite laminates is of great significance.

[0003] The bending properties of composite materials are usually tested using a three-point bending static test fixture, such as Figure 1 As shown in the figure, this device can meet the requirements of static testing, but it can encounter problems during long-term fatigue testing. For example, without front, back, left, and right constraints on the test piece, it can easily deviate from its initial position during fatigue testing. The fixture base is placed on a platform without fixed constraints, which can easily cause the base to move and cause misalignment during fatigue testing. These issues can affect the accuracy of test results, and base movement can also pose safety risks. Summary of the Invention

[0004] In order to solve the above problems, the present application provides a three-point bending fatigue testing device for composite materials, which is used to accurately obtain the bending fatigue performance of composite materials.

[0005] The composite material three-point bending fatigue testing device provided in the present application mainly includes an upper pressure head, a support block and a lower support base. The two support blocks are slidably arranged at both ends of the lower support base respectively. Each support block includes a base. A V-shaped groove is arranged on the upper end of the base. A cylindrical roller is arranged in the V-shaped groove. The bottom of the test piece is supported by the cylindrical rollers of the two support blocks. Pressure is applied to the top of the test piece by the upper pressure head. Two longitudinal limit bars are connected to the opposite inner sides of the two bases. The two longitudinal limit bars clamp the test piece on both sides of the test piece. A transverse limit bar is connected to the outer sides of the two bases. The two transverse limit bars of the two bases clamp the test piece at the front and rear ends of the test piece.

[0006] Preferably, a hook is provided on each side of the base, and each hook is connected to the two ends of the cylindrical roller via a tension spring.

[0007] Preferably, the hook is a bolt detachably connected to the base.

[0008] Preferably, the upper pressure head and the lower support base each include a clamping plate, and the clamping plate can be clamped by the hydraulic head of the testing machine.

[0009] Preferably, the lower support base is provided with a T-shaped groove with a scale, a base locking block is slidably provided in the T-shaped groove, a locking bolt passes through the base of the support block, and the locking bolt passes through the base and is threadedly connected to the base locking block.

[0010] Preferably, a transverse limiting support is fixed on the outer side of the base, a strip hole is provided on the transverse limiting support, and the transverse limiting strip is tightened at the strip hole of the transverse limiting support by tightening bolts and nuts.

[0011] The present application can ensure that the positions of the test device and the test piece do not change during the fatigue test of the test piece, thereby ensuring the accuracy of long-term fatigue testing and reducing test errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a structural diagram of an existing fatigue testing device.

[0013] Figure 2 It is a structural schematic diagram of a preferred embodiment of the composite material three-point bending fatigue testing device of the present application.

[0014] Figure 3 for Figure 2 Schematic diagram of the support block structure of the illustrated embodiment.

[0015] Among them, 1-upper pressure head, 2-test piece, 3-support block, 4-lower support base, 5-base locking block, 31-base, 32-cylindrical roller, 33-tensioning spring, 34-tightening bolt, 35-nut, 36-longitudinal limit bar, 37-transverse limit support, 38-transverse limit bar, 39-locking bolt. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solutions and advantages of the implementation of this application clearer, the technical solutions in the implementation of this application will be described in more detail below in conjunction with the drawings in the implementation of this application. In the drawings, the same or similar numbers throughout represent the same or similar elements or elements with the same or similar functions. The described implementation is a part of the implementation of this application, not all of the implementations. The implementation described below with reference to the drawings is exemplary and is intended to be used to explain this application, and should not be understood as a limitation on this application. Based on the implementation in this application, all other implementations obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. The implementation of this application is described in detail below in conjunction with the drawings.

[0017] This application provides a composite material three-point bending fatigue test device, such as Figure 2-Figure 3As shown, it mainly includes an upper pressure head 1, a support block 3 and a lower support base 4. The two support blocks 3 are respectively slidably arranged at the two ends of the lower support base 4. Each support block 3 includes a base 31. The upper end of the base 31 is provided with a V-shaped groove, and a cylindrical roller 32 is provided in the V-shaped groove. The bottom of the test piece 2 is supported by the cylindrical roller 32 of the two support blocks 3. Pressure is applied from above the test piece 2 by the upper pressure head 1. Two longitudinal limit bars 36 are respectively connected to the opposite inner sides of the two bases 31. The two longitudinal limit bars 36 clamp the test piece 2 on both sides of the test piece 2. The outer sides of the two bases 31 are respectively connected to a transverse limit bar 38. The two transverse limit bars 38 of the two bases 31 clamp the test piece 2 at the front and rear ends of the test piece 2.

[0018] In this embodiment, the positions of the two longitudinal limit bars 36 are calculated based on the width of the test specimen 2 and the width of the base 31. Tightening the bolts of the longitudinal limit bars 36 secures them, allowing the test specimen 2 to be positioned exactly in the middle of the cylindrical roller 32. At this point, the longitudinal limit is adjusted. After adjusting the span, the test specimen 2 is centered on the cylindrical roller 32. The left and right positions of the transverse limit bars 38 are adjusted so that they just contact the left and right end surfaces of the test specimen 2 without exerting pressure. The fixing nuts at the bottom of the transverse limit bars are tightened to restrict the lateral movement of the test specimen 2. At this point, the transverse limit is adjusted.

[0019] This application adds longitudinal and transverse limit bars at the position where the test piece is placed. The longitudinal limit bars can effectively limit the forward and backward displacement of the test piece on the cylindrical roller during the test, and the transverse limit bars can limit the left and right movement of the test piece. This support method can ensure the consistency of the position of the test piece during long-term fatigue testing and reduce test errors.

[0020] On the other hand, the present application can replace supporting cylindrical rollers of different radii by arranging the cylindrical rollers 32 in the V-grooves to meet the test methods of different standards.

[0021] In some optional embodiments, a hook is provided on each side of the base 31, and each hook is connected to both ends of the cylindrical roller 32 via a tension spring 33. This embodiment is used to reliably fix the cylindrical roller 32 in the V-shaped groove, and the tension spring 33 is used to tighten the cylindrical roller so that it is tightly attached to the inner wall of the V-shaped groove.

[0022] In some optional embodiments, the hook is a bolt detachably connected to the base 31 .

[0023] This embodiment uses bolt connections to facilitate replacement of various components.

[0024] In addition to the detachable cylindrical roller 32 on the base 31, the present application can also set a cylindrical roller at the bottom of the upper pressure head 1 in the same way, such as Figure 2shown.

[0025] In some optional embodiments, the upper pressure head 1 and the lower support base 4 each include a clamping plate, which can be clamped by the hydraulic head of the testing machine.

[0026] In this embodiment, the upper pressure head 1 and the lower support base 4 are fixed to the chuck position of the testing machine in the form of a splint. This splint can achieve a good centering effect by relying on the centering accuracy of the testing machine. In addition, during the fatigue test, the lower support base is not prone to loosening or shaking by adopting the hydraulic head of the testing machine, thereby improving the stability of long-term testing.

[0027] In some optional embodiments, a T-shaped groove with a scale is provided on the lower support base 4, and a base locking block 5 is slidably provided in the T-shaped groove. A locking bolt 39 passes through the base 31 of the support block 3, and the locking bolt 39 passes through the base 31 and is threadedly connected to the base locking block 5.

[0028] In some optional embodiments, a transverse limit support 37 is fixed to the outer side of the base 31 , and a strip hole is provided on the transverse limit support 37 . The transverse limit strip 38 is tightened at the strip hole of the transverse limit support 37 by tightening the bolt 34 and the nut 35 .

[0029] The steps for installing the test piece based on the above composite material three-point bending fatigue test device are as follows:

[0030] Step 1: Replace the cylindrical roller size specifications of the upper pressure head and support block according to the test standards;

[0031] Step 2: Clamp the upper pressure head and the lower support base into the wedge-shaped chuck of the hydraulic head of the testing machine and adjust the appropriate clamping force;

[0032] Step 3: According to the test requirements, adjust the support block spacing to meet the required span, make the support blocks symmetrical on the left and right, and lock the two support blocks with the locking bolts;

[0033] Step 4: Place the test piece on the cylindrical roller so that the test piece is centered in the front, back, left and right directions;

[0034] Step 5: Move the longitudinal limit bars to the two sides of the test piece and tighten the bolts to limit the deviation of the test piece to the sides;

[0035] Step 6: Move the lateral limit bars to fit the front and rear ends of the test piece, tighten the bolts and nuts to limit the forward and backward movement of the test piece;

[0036] Step 7: Adjust the crossbeam of the testing machine so that the upper pressure head contacts the test piece, apply fatigue load, and carry out the test.

[0037] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A composite material three-point bending fatigue testing device, characterized in that: The test piece (2) comprises an upper pressure head (1), a support block (3) and a lower support base (4), wherein the two support blocks (3) are respectively slidably arranged at the two ends of the lower support base (4), each support block (3) comprises a base (31), a V-shaped groove is arranged at the upper end of the base (31), a cylindrical roller (32) is arranged in the V-shaped groove, the bottom of the test piece (2) is supported by the cylindrical rollers (32) of the two support blocks (3), and pressure is applied to the upper part of the test piece (2) by the upper pressure head (1), two longitudinal limit bars (36) are connected to the opposite inner sides of the two bases (31), and the two longitudinal limit bars (36) clamp the test piece (2) at both sides of the test piece (2), and a transverse limit bar (38) is connected to the outer sides of the two bases (31), and the two transverse limit bars (38) of the two bases (31) clamp the test piece (2) at the front and rear ends of the test piece (2).

2. The composite material three-point bending fatigue testing device according to claim 1, characterized in that: A hook is provided on each side of the base (31), and each hook is connected to both ends of the cylindrical roller (32) via a tension spring (33).

3. The composite material three-point bending fatigue testing device according to claim 2, characterized in that: The hook is a bolt detachably connected to the base (31).

4. The composite material three-point bending fatigue testing device according to claim 1, characterized in that: The upper pressure head (1) and the lower support base (4) each comprise a clamping plate, and the clamping plate can be clamped by the hydraulic head of the testing machine.

5. The composite material three-point bending fatigue testing device according to claim 1, characterized in that: The lower support base (4) is provided with a T-shaped sliding groove with a scale, and a base locking block (5) is slidably provided in the T-shaped sliding groove. A locking bolt (39) is passed through the base (31) of the support block (3), and the locking bolt (39) passes through the base (31) and is threadedly connected to the base locking block (5).

6. The composite material three-point bending fatigue testing device according to claim 1, characterized in that: A transverse limiting support (37) is fixed on the outer side of the base (31), and a strip hole is provided on the transverse limiting support (37). The transverse limiting strip (38) is tightened at the strip hole of the transverse limiting support (37) by tightening the bolt (34) and the nut (35).

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