Fatigue test piece anti-bending device

Abstract

The invention provides an anti-bending device for a fatigue test piece. The anti-bending device comprises two pull rods (2) and two fixed bases (3), one side of the fixed base (3) is a bottom plate and is fixed on a test frame, and the other side of the fixed base (3) is of a lug structure; the pull rod (2) is a round rod, one end of the pull rod (2) is connected with a lug structure single-double lug on the fatigue test piece (1), and the other end of the pull rod (2) is connected with a lug structure single-double lug on the fixed base (3); the two pull rods (2) are symmetrically arranged on the two sides of the fatigue test piece (1), and the axial direction of the two pull rods (2) is the additional bending direction of the fatigue test piece (1). The anti-bending device overcomes the defects in the prior art, is low in cost, designable, high in universality, good in anti-bending effect and free of looseness in the testing process, and a size calculation method of the anti-bending device is provided.

Description

Technical Field

[0001] The invention belongs to the technical field of aviation technical structure design and relates to an anti-bending device for a fatigue test piece. Background Art

[0002] When fatigue testing is performed on long or cantilevered specimens, due to the asymmetry of the structure / load or insufficient stiffness of the specimen in the non-load-bearing direction, the specimen will produce unreal additional bending stress, causing premature failure of the specimen.

[0003] In order to minimize the unreal additional bending stress of the test piece, an anti-bending device is usually designed to reduce the additional bending stress of the test piece without affecting the stress in the test area.

[0004] At present, the anti-bending device is generally a pallet or a top wheel. In fatigue tests, the pallet and the top wheel will cause wear in the contact area, and will loosen as the test progresses, resulting in poor anti-bending effect; the pallet and the top wheel have complex structures and need to be customized according to the test, which is costly. Summary of the invention

[0005] The invention provides a fatigue test piece anti-bending device, which has low cost, is designable, has strong versatility and will not loosen during the test process.

[0006] The present invention provides a fatigue test piece anti-bending device, comprising: two pull rods 2 and two fixed bases 3;

[0007] One side of the fixed base 3 is a bottom plate fixed on the test frame, and the other side is an ear piece structure;

[0008] The pull rod 2 is a round rod, one end of which is connected to the single or double ears of the ear structure on the fatigue test piece 1, and the other end is connected to the single or double ears of the ear structure on the fixed base 3;

[0009] The two tie rods 2 are symmetrically arranged on both sides of the fatigue test piece 1 , and the axial directions of the two tie rods 2 are the additional bending directions of the fatigue test piece 1 .

[0010] Optionally, the pull rod 2 is a round rod with double-ear joints at both ends.

[0011] Optionally, the plane where the lug of the pull rod 2 is located is parallel to the load loading direction of the fatigue test piece 1 to prevent the pull rod 2 from bending.

[0012] Optionally, the length and cross-sectional area of ​​the tie rod 2 conform to the following formula:

[0013] EAF1 / (LK1) 2 <1%

[0014] Among them, the load F1 applied at the loading end, the displacement of the anti-bending support point △y, the length L of the pull rod 2, the cross-sectional area A, and the elastic modulus E of the pull rod 2.

[0015] Optionally, the anti-bending support point displacement Δy is determined according to the formula K1=F1 / Δy;

[0016] Among them, K1 is the stiffness of the anti-bending support point of the test piece.

[0017] Optionally, the stiffness of the anti-bending support point of the test piece is obtained through finite element modeling simulation or actual measurement through a displacement sensor and a force sensor.

[0018] Optionally, the fatigue test piece 1 is a cantilever test piece.

[0019] Optionally, the connection point of the pull rod 2 on the fatigue test piece 1 is located at the center of the area of ​​the fatigue test piece 1 where the additional deformation exists.

[0020] Optionally, the fatigue test piece 1 is a cantilever bracket with a triangular frame;

[0021] The triangle frame is equipped with reinforcing ribs.

[0022] The connection point of the tension rod 2 on the fatigue test piece 1 is arranged on the reinforcing rib.

[0023] The present invention provides a fatigue test piece anti-bending device, comprising: two pull rods 2 and two fixed bases 3; one side of the fixed base 3 is a bottom plate fixed on a test frame, and the other side is an ear structure; the pull rod 2 is a round rod, one end of which is connected to the ear structure on the fatigue test piece 1 with a single or double ear, and the other end is connected to the ear structure on the fixed base 3 with a single or double ear; the two pull rods 2 are symmetrically arranged on both sides of the fatigue test piece 1, and the axial directions of the two pull rods 2 are additional bending directions of the fatigue test piece 1, which overcomes the shortcomings of the prior art, provides a low-cost, designable, highly versatile, good anti-bending effect, and no loosening during the test process anti-bending device, and provides a size calculation method for the anti-bending device. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. It is obvious that the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 is an isometric view of the anti-bending device;

[0026] Figure 2 is a top view of the anti-bending device;

[0027] Figure 3 It is a schematic diagram of the force analysis of the anti-bending device;

[0028] Description of reference numerals:

[0029] 1. Test piece, 2. Pull rod, 3. Fixed base. DETAILED DESCRIPTION

[0030] The simple test platform for the aircraft tail provided by the present invention is described in detail below with reference to the accompanying drawings.

[0031] like Figure 1-2 As shown, a fatigue test piece anti-bending device includes: a test piece 1, a pull rod 2, and a fixed base 3.

[0032] The tie rod 2 is a round rod with double-ear joints at both ends, one end of which is connected to a single ear on the fatigue test piece, and the other end is fixed to the test frame through a fixed base 3. The tie rod 2 provides lateral support to the test piece by pulling on both sides, reducing the additional bending moment during the loading process of the test piece.

[0033] The opening direction of the two ears of the tie rod is along the load loading direction of the fatigue test piece to prevent the tie rod from bending.

[0034] By analyzing and calculating the area and length of the tie rod, the influence of the component force generated by the deformation coordination of the tie rod on the load of the fatigue test piece can be reduced. The calculation method of the area and length of the tie rod is as follows:

[0035] a) Calculate the stiffness of the anti-bending support point of the test piece: Figure 1 As shown, a finite element model of the test piece is established, a fatigue test piece load F1 is applied to the loading end, and the anti-bending support point is displaced Δy, then the anti-bending support point stiffness of the test piece K1=F1 / Δy;

[0036] b) Calculate the rod stiffness: the rod length L, area A, elastic modulus E, then the rod stiffness K2 = EA / L;

[0037] c) Calculate the vertical additional tension of the tie rod when the anti-bending support point of the test piece is displaced Δy: F2≈K2Δy 2 / L;

[0038] d) The influence of the vertical additional tension of the tie rod on the test piece load F1: F2 / F1≈((K2 / K1)(Δy / L);

[0039] e) Calculate the length L and area A of the pull rod: F2 / F1<1%; substitute into the above formula to determine the rod length L and area A.

[0040] The present invention provides a fatigue test piece anti-bending device, comprising: two pull rods 2 and two fixed bases 3;

[0041] One side of the fixed base 3 is a bottom plate fixed on the test frame, and the other side is an ear piece structure;

[0042] The pull rod 2 is a round rod, one end of which is connected to the single or double ears of the ear structure on the fatigue test piece 1, and the other end is connected to the single or double ears of the ear structure on the fixed base 3;

[0043] The two tie rods 2 are symmetrically arranged on both sides of the fatigue test piece 1 , and the axial directions of the two tie rods 2 are the additional bending directions of the fatigue test piece 1 .

[0044] Optionally, the pull rod 2 is a round rod with double-ear joints at both ends.

[0045] Optionally, the plane where the lug of the pull rod 2 is located is parallel to the load loading direction of the fatigue test piece 1 to prevent the pull rod 2 from bending.

[0046] Optionally, the length and cross-sectional area of ​​the tie rod 2 conform to the following formula:

[0047] EAF1 / (LK1) 2 <1%

[0048] Among them, the fatigue load F1 applied at the loading end, the length L of the pull rod 2, the cross-sectional area A, and the elastic modulus E of the pull rod 2.

[0049] Optionally, the anti-bending support point displacement Δy is determined according to the formula K1=F1 / Δy;

[0050] Among them, K1 is the stiffness of the anti-bending support point of the test piece.

[0051] Optionally, the stiffness of the anti-bending support point of the test piece is obtained through finite element modeling simulation or actual measurement through a displacement sensor and a force sensor.

[0052] Optionally, the fatigue test piece 1 is a cantilever test piece.

[0053] Optionally, the connection point of the pull rod 2 on the fatigue test piece 1 is located at the center of the area of ​​the fatigue test piece 1 where the additional deformation exists.

[0054] Optionally, the fatigue test piece 1 is a cantilever bracket with a triangular frame;

[0055] The triangle frame is equipped with reinforcing ribs.

[0056] The connection point of the pull rod 2 on the fatigue test piece 1 is arranged on the reinforcing rib.

[0057] The present invention provides a fatigue test piece anti-bending device, comprising: two pull rods 2 and two fixed bases 3; one side of the fixed base 3 is a bottom plate fixed on a test frame, and the other side is an ear structure; the pull rod 2 is a round rod, one end of which is connected to the ear structure on the fatigue test piece 1 with a single or double ear, and the other end is connected to the ear structure on the fixed base 3 with a single or double ear; the two pull rods 2 are symmetrically arranged on both sides of the fatigue test piece 1, and the axial directions of the two pull rods 2 are additional bending directions of the fatigue test piece 1, which overcomes the shortcomings of the prior art, provides a low-cost, designable, highly versatile, good anti-bending effect, and no loosening during the test process anti-bending device, and provides a size calculation method for the anti-bending device.

[0058] The above embodiments are only used to illustrate the technical solutions of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the field can easily think of various equivalent modifications or substitutions within the technical scope disclosed by the present invention, and these modifications or substitutions should all be covered within the protection scope of the present invention.

Claims

1. A fatigue test piece anti-bending device, characterized in that: include: Two pull rods (2) and two fixed bases (3); One side of the fixed base (3) is a bottom plate fixed on the test frame, and the other side is an ear plate structure; The pull rod (2) is a round rod, one end of which is connected to the single or double ears of the ear structure on the fatigue test piece (1), and the other end is connected to the single or double ears of the ear structure on the fixed base (3); The two tie rods (2) are symmetrically arranged on both sides of the fatigue test piece (1), and the axial directions of the two tie rods (2) are the additional bending directions of the fatigue test piece (1).

2. The anti-bending device for fatigue test piece according to claim 1, characterized in that: The pull rod (2) is a round rod with double-ear joints at both ends.

3. The fatigue test piece anti-bending device according to claim 1, characterized in that: The plane where the ear piece of the pull rod (2) is located is parallel to the load loading direction of the fatigue test piece (1), so as to prevent the pull rod (2) from being bent.

4. The fatigue test piece anti-bending device according to claim 1, characterized in that: The length and cross-sectional area of ​​the tie rod (2) conform to the following formula: EAF1 / (LK1) 2 <1% Among them, the load F1 applied at the loading end, the length L of the pull rod (2), the cross-sectional area A, and the elastic modulus E of the pull rod (2).

5. The fatigue test piece anti-bending device according to claim 4, characterized in that: The stiffness of the anti-bending support point K1 is determined according to the formula K1 = F1 / Δy; Wherein, Δy is the displacement of the anti-bending support point of the specimen under load F1.

6. The anti-bending device for fatigue test piece according to claim 1, characterized in that: The stiffness of the anti-bending support point of the test piece is obtained through finite element modeling simulation or through test load application and displacement sensor measurement.

7. The anti-bending device for fatigue test piece according to claim 6, characterized in that: The fatigue test piece (1) is a cantilever test piece.

8. The fatigue test piece anti-bending device according to claim 7, characterized in that: The connection point of the tension rod (2) on the fatigue test piece (1) is located at the center of the area of ​​the fatigue test piece (1) where additional deformation exists.

9. The fatigue test piece anti-bending device according to claim 8, characterized in that: The fatigue test piece (1) is a cantilever bracket with a triangular frame; The triangle frame is equipped with reinforcing ribs. The connection point of the pull rod (2) on the fatigue test piece (1) is arranged on the reinforcing rib.

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