Method for determining proportion of friction force of rivet connection structure

Abstract

The invention belongs to the field of comprehensive strength design, and relates to a method for determining the proportion of friction force of a rivet connection structure. The method comprises the following steps: determining a rivet connection mode and number; designing two groups of comparison test pieces; wherein the first group of test pieces are test pieces with friction force, and the second group of test pieces are test pieces without friction force; the second plate in the first group of test pieces with friction force is a flat plate, and the rivet connection area of the second plate adopts flat plate surface contact; carrying out a fatigue performance test, namely obtaining the fatigue limit of each test piece through the test; and according to the fatigue limit of the first group of test pieces and the fatigue limit of the second group of test pieces, the proportion of the friction force relative to the external load is analyzed, so that the shear load before rivet correction is obtained.

Description

Technical Field

[0001] The invention belongs to the field of comprehensive strength design and relates to a method for determining the proportion of friction force in a rivet connection structure. Background Art

[0002] Riveted joints, as mechanical connections, are widely used in structural design, particularly for helicopter structures. Riveted joints are a key area of ​​focus in strength design, particularly in fatigue-critical areas. Therefore, the study and application of failure modes and calculation methods for rivet joints have become a key focus of strength design. For rivet-joined structures, rivets primarily bear shear loads. Under these loads, the primary failure modes of the rivet joint structure are extrusion, shearing, and fatigue. Calculation methods exist for each of these failure modes.

[0003] Defects of background technology:

[0004] The conventional calculation method of failure modes does not take into account the influence of friction. Generally speaking, the existence of friction can increase the allowable strength values ​​of different failure modes. The conventional calculation method does not take into account the influence of friction, and the allowable strength value given by this method is conservative. Summary of the Invention

[0005] Purpose of the invention: The invention obtains the rivet shear correction load, which can effectively improve the structural utilization efficiency, achieve the purpose of weight reduction and effectively deal with external field problems.

[0006] Technical solution:

[0007] A method for determining the proportion of friction force in a rivet connection structure is provided, comprising:

[0008] Determine the rivet connection method and number;

[0009] Two groups of comparative test pieces were designed; the first group of test pieces were test pieces with friction, and the second group of test pieces were test pieces without friction. In the first group of test pieces with friction, the second plate was a flat plate, and the rivet connection area of ​​the second plate adopted flat-plate surface contact. In the second group of test pieces with friction, a boss structure corresponding to the position was provided on the second plate, and the rivet connection area of ​​the second plate adopted boss surface contact. The number of test pieces in each group was n, and n was 4, 5, or 6.

[0010] Conduct fatigue performance tests, that is, obtain the fatigue limit of each test piece through tests;

[0011] According to the fatigue limits of the first and second groups of test pieces, the proportion of friction force to external load is analyzed to obtain the shear load before rivet correction.

[0012] Furthermore, based on the fatigue limits of the first group of test pieces and the second group of test pieces, the proportion of friction force to external load is analyzed, including:

[0013] The fatigue limits of each specimen in the first group of specimens are: P 11 、P 12 ,…,P 1n , take the logarithmic values ​​with base 10 as follows: Q 11 , Q 12 ,…,Q 1n ;

[0014] Take the average value Q 1av for: The average fatigue limit P of the first group of test pieces is 1av for:

[0015] The fatigue limits of each specimen in the second group of specimens are: P 21 、P 22 ,…,P 2n , take the logarithmic values ​​with base 10 as follows: Q 21 , Q 22 ,…,Q 2n ,

[0016] Take the average value Q 2av for: The average fatigue limit P of the first group of test pieces is 2av for:

[0017] The friction force ratio λ is obtained based on the average fatigue limit of the two groups of test pieces.

[0018] Furthermore, the calculation formula of λ is:

[0019]

[0020] Furthermore, the shear load before rivet correction T xz The calculation formula is:

[0021] T xz =T×(1-λ);

[0022] Among them, T is the shear load before rivet correction, that is, the external load.

[0023] Furthermore, when the rivet connection method is a lap connection, a boss structure corresponding to the number of rivets is set on the connection surface of any one of the connection plates.

[0024] Furthermore, when the rivet connection method is butt connection, boss structures corresponding to the number of rivets are respectively provided on both sides of the middle plate.

[0025] Furthermore, the diameter of the boss surface is 2 to 3 times the diameter of the rivet.

[0026] Furthermore, the boss thickness δ needs to satisfy 0.3 mm ≤ δ ≤ 0.5 mm.

[0027] Beneficial effects: The present invention obtains the proportion of friction force through relevant methods, and then corrects the allowable value of structural destruction strength, which is of great significance for structural weight reduction and external field problem processing; determines the proportion of friction force in the rivet connection structure, and improves the structural bearing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of a typical lap joint.

[0029] Figure 2 Schematic diagram of a typical docking connection.

[0030] Figure 3 It is a side view of the boss structure.

[0031] Figure 4 It is a top view of the boss structure. DETAILED DESCRIPTION

[0032] 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.

[0033] In the description of the present invention, it should be understood that the terms "center", "axial", "vertical", "up", "down", "upper end", "bottom end", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention 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 cannot be understood as limiting the scope of protection of the present invention.

[0034] The main method of the present invention for determining the proportion of friction force in a rivet connection structure is to design comparative test pieces, determine fatigue properties of test pieces in different groups, and obtain the proportion of friction force by comparing fatigue properties.

[0035] The present invention provides a method for determining the proportion of friction force in a rivet connection structure, the specific steps of which are as follows:

[0036] a) Determine the connection type of the rivet connection area, that is, determine whether the rivet connection area is a lap connection (rivet is single shear) or a butt connection (rivet is double shear);

[0037] b) Design a typical connection test piece of corresponding connection type. The structural type is shown in Figure 1-2 As shown, the number of rivets can be arranged according to the number of areas of interest.

[0038] c) Based on a) and b) above, two groups of comparative test pieces are designed. The first group of test pieces are friction test pieces, and the second group of test pieces are non-friction test pieces.

[0039] d) The number of test pieces in each group is 6;

[0040] e) The rivet connection area of ​​the first group of friction test pieces adopts flat surface contact and is riveted in accordance with the structural design requirements;

[0041] f) The second group of test pieces was divided into two cases: when the connection was overlapped, a boss structure was set on any one of the connecting plates in the connection area; when the connection was butt-jointed, a boss structure was set on the middle plate in the connection area;

[0042] g) Boss structure see Figure 3-4 As shown, its thickness δ needs to satisfy 0.3mm≤δ≤0.5mm, and its radius R needs to satisfy R=2D, where D is the rivet diameter.

[0043] h) After the above test pieces are designed, fatigue performance tests are carried out to obtain the fatigue limit of each test piece through tests;

[0044] i) The fatigue limits of each test piece in the first group are: P 11 、P 12 、P 13 、P 14 、P 15 、P 16 , take the logarithmic values ​​with base 10 as follows: Q 11 , Q 12 , Q 13 , Q 14 , Q 15 , Q 16 ;

[0045] The average value is: The average fatigue limit of the first group of test pieces is:

[0046]

[0047] j) The fatigue limits of each specimen in the second group are: P 21 、P 22 、P 23 、P 24 、P 25 、P 26 , take the logarithmic values ​​with base 10 as follows: Q 21 , Q 22 , Q 23 , Q 24 , Q 25 , Q 26 ;

[0048] k) Take the average value as: The average fatigue limit of the first group of test pieces is:

[0049] l) Based on the average fatigue limit of each group of test pieces obtained in i) and j), the friction force ratio can be calculated as:

[0050]

[0051] The main reason for selecting the average fatigue limit as the characteristic load to characterize the friction force ratio analysis is: One reason: Under the same loading method, configuration, and material, the main factor affecting the different fatigue limits of the two groups of test pieces is friction. Therefore, there is a strong correlation between fatigue limit and friction. Differential design is performed on the two groups of test pieces to form a comparative relationship between the presence and absence of friction. The fatigue limit caused by the influence of friction is obtained through fatigue performance testing;

[0052] The second reason is that if static strength tests are conducted on two groups of test pieces, the static strength bearing capacity is correlated with the material's ultimate allowable stress and configuration. Friction has little effect on bearing capacity, so the friction contribution cannot be determined through static strength tests.

[0053] Reason three: The current test methods for fatigue performance testing of small test pieces are mature, the test plan is simple to formulate, and the test cycle is controllable. Therefore, the risk of using fatigue performance testing of small test pieces as a test for friction force ratio analysis is controllable.

[0054] Reason 4: The method of obtaining fatigue limit through fatigue test data of small test pieces is mature, reliable, and has high accuracy, which meets the analytical accuracy requirements for obtaining the friction force ratio.

[0055] m) According to the obtained λ value, the shear load on the rivet can be corrected, that is, the shear load on the rivet can be corrected to:

[0056] T xz =T×(1-λ),

[0057] Where T is the shear load before rivet correction;

[0058] n) Carry out strength design of connection area and handle external field problems based on the corrected shear load.

[0059] Other embodiments of the present disclosure will readily occur to those skilled in the art after considering the specification and practicing the disclosure herein. This application is intended to cover any variations, uses, or adaptations of the present disclosure that follow the general principles of the present disclosure and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered as exemplary only, with the true scope and spirit of the present disclosure being indicated by the following claims.

[0060] It should be understood that the present disclosure is not limited to the exact structures that have been described above and shown in the drawings, and that various modifications and changes can be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.

Claims

1. A method for determining the proportion of friction force in a rivet connection structure, characterized in that: include: Determine the rivet connection method and number; Design two groups of comparative test pieces; the first group of test pieces are test pieces with friction, and the second group of test pieces are test pieces without friction; In the first set of friction test pieces, the second plate is a flat plate, and the rivet connection area of ​​the second plate adopts flat plate surface contact; in the second set of friction test pieces, a boss structure corresponding to the position is provided on the second plate, and the rivet connection area of ​​the second plate adopts boss surface contact; the number of test pieces in each set is n; n is 4, 5, or 6; Conduct fatigue performance tests, that is, obtain the fatigue limit of each test piece through tests; According to the fatigue limits of the first and second groups of test pieces, the proportion of friction force to external load is analyzed to obtain the shear load before rivet correction.

2. The method according to claim 1, characterized in that Based on the fatigue limits of the first and second groups of test pieces, analyze the proportion of friction force relative to external load, including: The fatigue limits of each specimen in the first group of specimens are: P 11 、P 12 ,…,P 1n , take the logarithmic values ​​with base 10 as follows: Q 11 , Q 12 ,…,Q 1n ; Take the average value Q 1av for: Then the average fatigue limit P of the first group of test pieces is 1av for: The fatigue limits of each specimen in the second group of specimens are: P 21 、P 22 ,…,P 2n , take the logarithmic values ​​with base 10 as follows: Q 21 , Q 22 ,…,Q 2n , Take the average value Q 2av for: Then the average fatigue limit P of the first group of test pieces is 2av for: The friction force ratio λ is obtained based on the average fatigue limit of the two groups of test pieces.

3. The method according to claim 1, characterized in that The calculation formula for λ is:

4. The method according to claim 2 or 3, characterized in that Rivet shear load before correction T xz The calculation formula is: T xz =T×(1-λ); Among them, T is the shear load before rivet correction, that is, the external load.

5. The method according to claim 1, wherein When the rivet connection method is a lap connection, a connecting surface of any one of the connecting plates is selected to set a boss structure corresponding to the number of rivets.

6. The method according to claim 1, characterized in that When the rivet connection method is butt connection, boss structures corresponding to the number of rivets are respectively provided on both sides of the middle plate.

7. The method according to claim 1, characterized in that The diameter of the boss surface is 2 to 3 times the diameter of the rivet.

8. The method according to claim 1, characterized in that The boss thickness δ must satisfy 0.3mm≤δ≤0.5mm.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 8 is implemented.

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