Aircraft connecting structure fastener load distribution method

Abstract

The invention belongs to the technical field of aircraft strength, and discloses an aircraft connecting structure fastener load distribution method, which comprises the following steps of: determining external load force and torque required to be transmitted by a connecting structure, determining a load transmission mode of fasteners, and determining a load distribution mode of the fasteners according to the material of each fastener, the size of a connected piece and material extrusion performance data; determining the minimum allowable load of each fastener on the connecting part, calculating the total torque borne by all the fasteners, the load of the external force distributed under each fastener and the load of the corresponding fastener under the torque acting on the single fastener, and finally obtaining the total load borne by each fastener under the action of the external load. The ultimate bearing capacity of the structure can be fully excavated, and the weight of the structure can be reduced; for the situation that the fastener bears double shears, the load of the fastener can be distributed based on the allowable value of the double shears; meanwhile, the load distribution device is suitable for load distribution of connecting structure fasteners between parts made of various different materials, and the application range is wide.

Description

Technical Field

[0001] This invention belongs to the field of aircraft strength technology, and relates to a load calculation method for aircraft connection structures, specifically a load distribution method for fasteners in aircraft connection structures. Background Technology

[0002] Strength analysis of aircraft connection structures is an important part of aircraft strength design. In connection strength analysis, the distribution of fastener loads is the foundation of the analysis. Therefore, it is necessary to focus on the distribution of fastener loads.

[0003] Conventional fastener load distribution methods primarily rely on the cross-sectional area of ​​the fastener to distribute the load. Patent CN111797480B provides a method for load distribution based on stiffness. However, this method does not consider the load-bearing capacity of fasteners and the fastener holes of the connected parts during the distribution process, failing to fully exploit the ultimate load-bearing capacity of the structure and hindering the reduction of the weight of the connected structure. Furthermore, this method only considers the elastic range; as the load increases, the metal structure gradually enters the plastic stage, and this method cannot account for the redistribution of fastener loads after the structure enters the plastic stage, raising doubts about the accuracy of the load distribution results in the high-load stage. Additionally, fasteners exhibit better stiffness when subjected to double shear than when subjected to single shear, a difference that this patent fails to reflect. Finally, this patent only applies to situations where the two connected parts have the same elastic modulus. However, aircraft structures often feature connections such as alloy steel and aluminum alloy parts, titanium alloy and aluminum alloy parts, and composite material and aluminum alloy parts, where the elastic moduli of the two connected parts differ significantly. The method for calculating the compressive or tensile stiffness of the connected parts provided in this patent does not specify a method for calculating stiffness in such cases and is not applicable to situations where the elastic moduli of the connected parts differ. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for load distribution of fasteners in aircraft connection structures, which can fully exploit the ultimate load-bearing capacity of the structure and minimize the weight of the connection structure.

[0005] The technical solution of the present invention is as follows: A method for load distribution of fasteners in aircraft connection structures, comprising the following steps, involves analyzing connection structures equipped with fasteners: S1, determine the external load force and torque that the connection structure needs to transmit; S2, determines the method by which the fastener transmits load; S3, based on the material of each fastener, the size of the connected parts, and the material extrusion performance data, determine the minimum allowable load of each fastener at the connection point; S4. Based on the minimum allowable load of each fastener at the connection point and the coordinates of each fastener in the same coordinate system, determine the common centroid coordinates of all fasteners, calculate the torque generated by translating the external load to the common centroid, and then calculate the total torque borne by all fasteners. S5. Based on the minimum allowable load of each fastener at the connection point, determine the load distribution equation under the action of external force, and obtain the load equation F(F) under the distribution of external force on each fastener. S6. Based on the minimum allowable load of each fastener at the connection point, the distance of each fastener from the common centroid, and the load distribution equation under the total torque, the load equation F(M) of the fastener corresponding to the torque acting on the individual fastener is obtained. S7. Calculate the vector sum of the load equations F(F) and F(M) to obtain the total load borne by each fastener under the external load.

[0006] Furthermore, in S1, all external load forces are combined into a single external load concentrated force F, and all external load moments are combined into a single external load concentrated moment M0.

[0007] Furthermore, in S3, the minimum allowable load is the smaller of the allowable load of the fastener itself and the allowable compressive load of the connected parts.

[0008] Furthermore, in S4, after determining the common centroid coordinates of all fasteners, the x, y, and z values ​​of each fastener in the coordinate system are the center coordinates of the intersection surface between the fastener's cross-section and the neutral surface of the structure subjected to the external load; based on the distance of the common centroid from the concentrated external load F, the moment component M that moves F to the common centroid is calculated. F Then, the concentrated torques M0 and M of the external load are... F By superimposing these forces, we obtain the total torque M experienced by all fasteners.

[0009] Furthermore, in S5, the load F(F) of each fastener under the action of the external load concentrated force F is calculated by multiplying the minimum allowable load of the corresponding fastener by the external load concentrated force F and then dividing by the sum of the minimum allowable loads of all fasteners.

[0010] Furthermore, in S6, the fastener load F(M) under the action of the total moment M is calculated by multiplying the minimum allowable load of the corresponding fastener by the total moment M, and then dividing by the distance between the center of the corresponding fastener and the common centroid and the sum of the minimum allowable loads of all fasteners.

[0011] Furthermore, the F(F) and F(M) vectors of all fasteners are superimposed, and then the vectors in different directions are merged to obtain the total load of the fasteners.

[0012] Furthermore, the load type in S2 includes shear load.

[0013] Technical effects: This invention proposes a method for fastener load distribution in aircraft connection structures based on the load-bearing capacity of fasteners and the fastener holes of connected parts. Using this patent for fastener load distribution can fully explore the ultimate load-bearing capacity of the structure, which is beneficial to reducing the structural weight. For fasteners subjected to double shear, this patent can distribute the fastener load based on the allowable double shear value. At the same time, this patent is applicable to the fastener load distribution of connection structures between parts made of various materials, and has a wide range of applications. Attached Figure Description

[0014] Figure 1 This is a schematic diagram illustrating a specific embodiment of the present invention.

[0015] Figure 2 This is a schematic diagram of a static strength test of the vertical tail joint connection area of ​​a certain type of aircraft using the method of the present invention for static strength analysis. Detailed Implementation

[0016] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. Numerous specific design details are set forth in the following detailed description to provide a more complete understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setup and method set forth below, but covers any improvements, substitutions, and modifications to the structures, methods, and devices without departing from the spirit of the invention. In the drawings and the following description, any parts not exhaustively described are considered to be common knowledge or conventional practices in the art.

[0017] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited in each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0018] Example 1: A method for load distribution of fasteners in aircraft connection structures, comprising the following steps, involves analyzing connection structures equipped with fasteners: S1, determine the external load force and torque that the connection structure needs to transmit; S2, determines the method by which the fastener transmits load; S3, based on the material of each fastener, the size of the connected parts, and the material extrusion performance data, determine the minimum allowable load of each fastener at the connection point; S4. Based on the minimum allowable load of each fastener at the connection point and the coordinates of each fastener in the same coordinate system, determine the common centroid coordinates of all fasteners, calculate the torque generated by translating the external load to the common centroid, and then calculate the total torque borne by all fasteners. S5. Based on the minimum allowable load of each fastener at the connection point, determine the load distribution equation under the action of external force, and obtain the load equation F(F) under the distribution of external force on each fastener. S6. Based on the minimum allowable load of each fastener at the connection point, the distance of each fastener from the common centroid, and the load distribution equation under the total torque, the load equation F(M) of the fastener corresponding to the torque acting on the individual fastener is obtained. S7. Calculate the vector sum of the load equations F(F) and F(M) to obtain the total load borne by each fastener under the external load.

[0019] In S1, all external load forces are combined into a single external load concentrated force F, and all external load moments are combined into a single external load concentrated moment M0.

[0020] In S3, the minimum allowable load is the smaller of the allowable load of the fastener itself and the allowable compressive load of the connected parts.

[0021] In S4, after determining the common centroid coordinates of all fasteners, the x, y, and z values ​​of each fastener in the coordinate system are the center coordinates of the intersection surface between the fastener's cross-section and the neutral plane of the structure subjected to the external load. Based on the distance between the common centroid and the concentrated external load force F, the moment M that moves F to the common centroid is calculated. F Then, the concentrated torques M0 and M of the external load are... F By superimposing these forces, we obtain the total torque M experienced by all fasteners.

[0022] In S5, the load F(F) of each fastener under the action of the external load concentrated force F is calculated by multiplying the minimum allowable load of the corresponding fastener by the external load concentrated force F and then dividing by the sum of the minimum allowable loads of all fasteners.

[0023] In S6, the fastener load F(M) under the action of the total moment M is calculated by multiplying the minimum allowable load of the corresponding fastener by the total moment M, and then dividing by the distance between the center of the corresponding fastener and the common centroid and the sum of the minimum allowable loads of all fasteners.

[0024] The F(F) and F(M) vectors of all fasteners are superimposed, and then the vectors in different directions are merged to obtain the total load of the fasteners.

[0025] The load type in S2 includes shear load.

[0026] Example 2: This invention provides a load distribution method for fasteners in aircraft connection structures, which can fully exploit the ultimate bearing capacity of the structure and reduce the weight of the connection structure as much as possible.

[0027] This invention provides a method for load distribution of fasteners in aircraft connection structures, which mainly includes the following steps; Step 1: Determine the external load force F and torque M0 that the connection structure needs to transmit; Step 2: Determine the load transfer method of the fastener; Step 3: Determine the minimum allowable load for each fastener connection based on the fastener grade, the dimensions of the connected parts, and the material extrusion performance data. Step 4: Based on the minimum allowable load of each fastener connection and the coordinates of each fastener in the same coordinate system, determine the centroid coordinates O of the fastener group, and calculate the torque M generated by translating the external load to the centroid of the fastener group. F Therefore, the total torque borne by the fastener group is M = M0 + M F ; Step 5: Based on the minimum allowable load P of each fastener connection. imin Determine the load distribution equation f(F) under the action of force F, and obtain the load distribution equation f(F) under the action of force F. i The load F(Fi) of each fastener under action; Step 6: Based on the minimum allowable load P of each fastener connection. imin And the distance d between the center of the fastener and the centroid of the fastener group. i And the load distribution equation f(M) under the action of moment M, to obtain the load distribution equation f(M) under the action of moment M. i The load F(M) of each fastener under action; Step 7: Calculate the vector sum of F(F) and F(M) to obtain the total load F(i) borne by each fastener under the external load.

[0028] Example 3: This invention provides a method for load distribution of fasteners in aircraft connection structures, comprising: Step 1: Determine that the external loads borne by the connection structure are concentrated force F and concentrated moment M0; Step 2: Based on the structural form shown in the figure, determine that the fastener transmits load by shear load. Step 3: Since the load transfer method determined in the previous step is shear transfer, based on the fastener grade, the dimensions of the connected parts, and the material properties, determine the minimum allowable load P for each fastener connection. imin i = 1~4, and the magnitude is the allowable shear load P of the fastener itself. jgjAllowable compressive load P of the connected structure jg The value that is determined by both factors is the smaller of the two:

[0029] Step 4: Based on the coordinates of each fastener and the minimum allowable load P at each fastener connection point. i The coordinates of the centroid of the fastener group are calculated using the following formula:

[0030] In the formula: —The X-coordinate of the centroid of the fastener group; —The Y-coordinate of the centroid of the fastener group; —The Z-coordinate of the centroid of the fastener group; — The X-coordinate of the center of the shear plane of the i-th fastener is, in the case of single shear, the center coordinate of the interface between the two layers of the structure connected by the fastener; in the case of double shear, the center coordinate of the interface between the cross section of the fastener and the neutral plane of the structure subjected to double shear. — The Y-coordinate of the center of the shear plane of the i-th fastener is, in the case of single shear, the center coordinate of the interface between the two layers of the structure connected by the fastener; in the case of double shear, the center coordinate of the interface between the cross section of the fastener and the neutral plane of the structure subjected to double shear. — The Z-coordinate of the center of the shear plane of the i-th fastener is, in the case of single shear, the center coordinate of the interface between the two layers of the structure connected by the fastener; in the case of double shear, the center coordinate of the interface between the cross section of the fastener and the neutral plane of the structure subjected to double shear. Based on the distance d from the centroid of the fastener group to the line of concentrated force F. m The moment component M that translates force F to the centroid of the fastener group is calculated. F :

[0031] Based on the force conditions shown in the attached diagram, the concentrated moments M0 and M F The torques will be superimposed, and the total torque borne by the fastener group can be calculated as follows:

[0032] Step 5: Calculate the fastener load under concentrated force F

[0033] In the formula: —The load borne by each fastener under the action of force F; —The sum of the minimum allowable loads of all fasteners, that is, the sum of the load-bearing capacities of all fasteners.

[0034] As can be seen from the attached figure, the concentrated force F is in the Y-axis direction, so the fastener load under the concentrated force is also in the Y-axis direction.

[0035] Step 6: Calculate the fastener load under the total moment M.

[0036] In the formula: —The load borne by each fastener under the action of torque M; —The distance between the center of the fastener and the centroid of the fastener group; —The sum of the minimum allowable loads of all fasteners.

[0037] To facilitate data processing and the synthesis of the total load on the fastener, the X and Y loads on the fastener under the action of torque M can be solved separately:

[0038]

[0039] In the formula: —The load in the X direction borne by each fastener under the action of torque M; —The Y-direction load borne by each fastener under the action of torque M; — The Y-axis distance between the center of the fastener and the centroid of the fastener group; — The X-axis distance between the center of the fastener and the centroid of the fastener group.

[0040] Step 7: Calculate the total load on the fasteners Based on steps 5 and 6, the total loads of the fastener in the X and Y directions can be obtained as follows:

[0041]

[0042] The final total load of the fasteners is

[0043] During the development of a large amphibious aircraft, the method described in this patent was used to conduct load distribution on the fasteners between the vertical tail boom flange and the vertical tail joint. Static strength analysis was then performed based on this, and an ultimate load static test was conducted on the connection between the vertical tail joint and the vertical tail boom flange. The vertical tail joint of this aircraft is made of 4340 alloy steel, and the T-shaped boom flange is made of 7050-T7451 aluminum alloy. The connection between the joint and the horizontal edge (bottom edge of the T-shape) of the boom flange adopts a variable thickness design. The fasteners in the connection area are 8 HST11AG12 high-strength bolts. The maximum thickness of the joint is 8.8 mm, and the minimum thickness is 5.3 mm. The maximum thickness of the boom flange is 11.3 mm, and the minimum thickness is 7.7 mm. The connection between the joint and the vertical edge (vertical edge of the T-shape) of the boom flange adopts a uniform thickness design. The fasteners in the connection area are 6 HST10AG10 and 2 HST10AG8 high-strength bolts. The joint thickness is 6 mm, and the boom flange thickness is 7 mm. Under the ultimate load of the vertical tail fuselage docking joint, the fastener load distribution according to the method of this patent yielded a minimum static strength margin of 0.00 in the connection area, which just meets the static strength requirements. An ultimate load static test was conducted on the vertical tail fuselage joint area. The results showed that the bearing capacity of the joint connection with the beam flange was not less than the ultimate load, indicating that the fastener load obtained using this method is reliable.

[0044] The above static test schematic diagram and physical diagram are shown below. Figure 2 .

[0045] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements without departing from the principle of the present invention, and these improvements should also be considered within the scope of protection of the present invention.

Claims

1. A method for load distribution of fasteners in aircraft connection structures, characterized in that, The analysis of connection structures with fasteners includes the following steps: S1, determine the external load force and torque that the connection structure needs to transmit; S2, determines the method by which the fastener transmits load; S3, based on the material of each fastener, the size of the connected parts, and the material extrusion performance data, determine the minimum allowable load of each fastener at the connection point; S4. Based on the minimum allowable load of each fastener at the connection point and the coordinates of each fastener in the same coordinate system, determine the common centroid coordinates of all fasteners, calculate the torque generated by translating the external load to the common centroid, and then calculate the total torque borne by all fasteners. S5. Based on the minimum allowable load of each fastener at the connection point, determine the load distribution equation under the action of external force, and obtain the load equation F(F) under the distribution of external force on each fastener. S6. Based on the minimum allowable load of each fastener at the connection point, the distance of each fastener from the common centroid, and the load distribution equation under the total torque, the load equation F(M) of the fastener corresponding to the torque acting on the individual fastener is obtained. S7. Calculate the vector sum of the load equations F(F) and F(M) to obtain the total load borne by each fastener under the external load.

2. The method for load distribution of fasteners in an aircraft connection structure according to claim 1, characterized in that, In S1, all external load forces are combined into a single external load concentrated force F, and all external load moments are combined into a single external load concentrated moment M0.

3. The method for load distribution of fasteners in an aircraft connection structure according to claim 1, characterized in that, In S3, the minimum allowable load is the smaller of the allowable load of the fastener itself and the allowable compressive load of the connected parts.

4. The method for load distribution of fasteners in an aircraft connection structure according to claim 1, characterized in that, In S4, after determining the common centroid coordinates of all fasteners, the x, y, and z values ​​of each fastener in the coordinate system are the center coordinates of the intersection surface between the fastener's cross-section and the neutral plane of the structure subjected to the external load. Based on the distance between the common centroid and the concentrated external load force F, the moment M that moves F to the common centroid is calculated. F Then, the concentrated torques M0 and M of the external load are... F By superimposing these forces, we obtain the total torque M experienced by all fasteners.

5. The method for load distribution of fasteners in an aircraft connection structure according to claim 1, characterized in that, In S5, the load F(F) of each fastener under the action of the external load concentrated force F is calculated by multiplying the minimum allowable load of the corresponding fastener by the external load concentrated force F and then dividing by the sum of the minimum allowable loads of all fasteners.

6. The method for load distribution of fasteners in an aircraft connection structure according to claim 1, characterized in that, In S6, the fastener load F(M) under the action of the total moment M is calculated by multiplying the minimum allowable load of the corresponding fastener by the total moment M, and then dividing by the distance between the center of the corresponding fastener and the common centroid and the sum of the minimum allowable loads of all fasteners.

7. The method for load distribution of fasteners in an aircraft connection structure according to claim 1, characterized in that, The F(F) and F(M) vectors of all fasteners are superimposed, and then the vectors in different directions are merged to obtain the total load of the fasteners.

8. The method for load distribution of fasteners in an aircraft connection structure according to claim 1, characterized in that, The load type in S2 includes shear load.

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