A Stress Analysis Method for the Structures of Each Jacking Point under the Aircraft Jacked-up State

Abstract

A stress analysis method for the structure of each jacking point under the aircraft jacking state. In view of the actual scenario that when the aircraft is jacked up, due to the shaking of the aircraft, a horizontal acceleration is generated. Therefore, in addition to the vertical load, the structure in the jacking area also bears a horizontal load. A reasonable stress analysis method for the structure of each jacking point under the aircraft jacking state is proposed to make the stress analysis result of the structure in the jacking area more accurate.

Description

Technical Field

[0001] The present invention belongs to, but is not limited to, the field of aerospace engineering applications, and relates to a method for stress analysis of the jacking point structure during aircraft jacking, which is of great significance for reducing structural weight and improving the rationality and safety of structural design. Technical Background

[0002] The airworthiness standards stipulate that when an aircraft is jacked up, the structure is designed to withstand the vertical and horizontal loads "acting separately on each jacking point", and do not clearly specify the source of the jacking load and its balancing method. Generally, only the maximum vertical and horizontal loads at the jacking points and the structure in the constrained jacking area are considered for local stress analysis. According to the experience of actual models, the results of local stress analysis of the jacking point structure are inaccurate. Summary of the Invention

[0003] In order to solve the problem of the accuracy of local structural stress analysis during aircraft jacking, in view of the actual scenario that when an aircraft is jacked up, due to the shaking of the aircraft, a horizontal acceleration is generated, so in addition to the vertical load, the structure in the jacking area also bears a horizontal load, the present invention proposes a reasonable and accurate method for stress analysis of the structure of each jacking point during aircraft jacking.

[0004] A method for stress analysis of the structure of each jacking point during aircraft jacking, given the overall structural digital model of the aircraft, the total mass of the aircraft and the mass distribution, the positions of three jacking points of the aircraft, and the maximum vertical and horizontal loads at each jacking point, is characterized by the following:

[0005] 1) Establish a finite element model of the whole aircraft structure according to the overall structural digital model of the aircraft;

[0006] 2) Apply the distributed load generated by the aircraft mass distribution on the finite element model;

[0007] 3) On the finite element model, apply the maximum vertical load at one of the jacking points and the concentrated horizontal load in the most unfavorable direction for the load-bearing of this jacking point;

[0008] 4) Apply the constraint conditions at the center of gravity of the aircraft on the finite element model;

[0009] 5) Conduct a stress analysis on the whole aircraft on the finite element model, and the result of this stress analysis is the structural stress of this jacking point;

[0010] 6) On the finite element model, apply the maximum vertical load at another jacking point and the concentrated horizontal load in the most unfavorable direction for the load-bearing of this jacking point, and repeat steps 4) and 5) to obtain the structural stress of this jacking point;

[0011] 7) According to step 6), apply the maximum vertical load of this jacking point and the concentrated horizontal load in the most unfavorable direction for the bearing of this jacking point to the remaining jacking points, and repeat steps 4) and 5) to obtain the structural stress of the remaining jacking points.

[0012] The beneficial effects of this application are as follows: The method of this application can accurately simulate the horizontal acceleration generated by the shaking of the aircraft during the jacking of the aircraft, so as to create the actual use scenarios of horizontal loads generated at the jacking points, as well as similar scenarios, making the structural stress analysis results of the jacking area more accurate.

[0013] The following further describes this application in detail with reference to the accompanying drawings of the embodiments. Description of the Drawings

[0014] Figure 1 It is a schematic diagram of the horizontal load distribution of each jacking point of the aircraft;

[0015] Figure 2 It is a schematic diagram of the vertical load distribution of each jacking point of the aircraft;

[0016] Description of the numbers in the figure: 1 First jacking point, 2 Second jacking point, 3 Third jacking point, 4 Aircraft center of gravity Specific Embodiments

[0017] In the prior art, for the stress analysis of the structure of the aircraft jacking area, a local model of the jacking area is first established, constraints are applied outside the jacking area, and the vertical load and horizontal load specified in the regulations are applied at the jacking points. Both the vertical load and the horizontal load are considered to be balanced by the constraint points. The mass distribution of the aircraft in the jacking state is not considered, and the transfer relationship between the vertical load and horizontal load of the analyzed jacking area structure and the adjacent area structure is not considered, resulting in inaccurate stress distribution in the adjacent area of the analyzed jacking area structure.

[0018] Referring to the accompanying drawings, the task and purpose of the present invention are to propose a reasonable and reliable stress analysis method for the actual jacking scenario where the aircraft will experience horizontal shaking when the aircraft is vertically jacked up (the horizontal loads on each jacking point are in the same direction).

[0019] Given the overall structural digital model of the aircraft, the total mass of the aircraft, the mass distribution, and the position of the aircraft center of gravity 4, the aircraft in the embodiment has three jacking points. The first jacking point 1 is located at the front of the lower side of the aircraft fuselage, the second jacking point is located at the lower side of the right wing of the aircraft, and the third jacking point is located at the lower side of the left wing of the aircraft. The positions of the three jacking points of the aircraft and the maximum vertical load and horizontal load of each jacking point are known. The steps for the structural stress analysis of each jacking point are as follows:

[0020] First, establish a full-aircraft structural finite element model according to the overall structural digital model of the aircraft; apply the distributed load generated by the aircraft mass distribution on the finite element model. The distributed load generated by the aircraft mass distribution includes the distributed vertical load G generated by the aircraft mass Z and the distributed horizontal load G X .

[0021] On the finite element model, apply the maximum vertical load F at the first jacking point 1 AZ and the concentrated horizontal load F in the most unfavorable direction for the load-bearing of this jacking point AX ;

[0022] Apply the maximum vertical load F at the first jacking point 1 AZ and the horizontal load F AX . At the same time, apply the corresponding vertical load and horizontal load to the second jacking point 2 and the third jacking point 3 respectively. The horizontal load directions of the second jacking point 2 and the third jacking point 3 are the same as the horizontal load direction of the first jacking point 1

[0023] The distributed horizontal load G generated by the aircraft mass X is in the opposite direction to the horizontal load F at the first jacking point 1 AX . The ratio of the distributed horizontal load G generated by the aircraft mass X to the distributed vertical load G Z is equal to the ratio of the horizontal load F at the first jacking point 1 AX to the vertical load F AZ .

[0024] Next, apply constraint conditions at the aircraft center of gravity 4 on the finite element model

[0025] The constraint conditions are heading, lateral, and vertical linear displacement constraints and angular displacement constraints. The actual constraint reaction force is 0, and the constraint moment generated by the horizontal load is not 0

[0026] On the finite element model, perform a stress analysis on the entire aircraft. The result of this stress analysis is the structural stress of the first jacking point 1

[0027] Use the same method to perform a structural stress analysis on the second jacking point 2 and the third jacking point 3

[0028] On the finite element model, apply the maximum vertical load F at the second jacking point BZ and the concentrated horizontal load F in the most unfavorable direction for the load-bearing of this jacking point BX, at the same time, corresponding vertical loads and horizontal loads should be applied to the first jacking point 1 and the third jacking point 3 respectively. The directions of the horizontal loads of the first jacking point 1 and the third jacking point 3 are the same as the direction of the horizontal load of the second jacking point 2. The direction of the distributed horizontal load GX generated by the aircraft mass is opposite to the direction of the horizontal load F of the second jacking point 2. The ratio of the distributed horizontal load GX generated by the aircraft mass to the distributed vertical load GZ is equal to the ratio of the horizontal load F of the second jacking point 2 to the vertical load F. Then, on the finite element model, constraint conditions should be applied to the aircraft center of gravity 4. The constraint conditions are heading, lateral, and vertical linear displacement constraints and angular displacement constraints. Finally, a stress analysis is performed on the entire aircraft, and the result of this stress analysis is the structural stress of the second jacking point 2. BX The direction of the distributed horizontal load GX generated by the aircraft mass is opposite to the direction of the horizontal load F of the second jacking point 2. The ratio of the distributed horizontal load GX generated by the aircraft mass to the distributed vertical load GZ is equal to the ratio of the horizontal load F of the second jacking point 2 to the vertical load F. BX and the vertical load F BZ . Then, on the finite element model, constraint conditions should be applied to the aircraft center of gravity 4. The constraint conditions are heading, lateral, and vertical linear displacement constraints and angular displacement constraints. Finally, a stress analysis is performed on the entire aircraft, and the result of this stress analysis is the structural stress of the second jacking point 2.

[0029] Finally, on the finite element model, the maximum vertical load F of this jacking point should be applied to the third jacking point 3 CZ and the concentrated horizontal load F in the direction most unfavorable to the load bearing of this jacking point CX . At the same time, corresponding vertical loads and horizontal loads should be applied to the first jacking point 1 and the second jacking point 2 respectively. The directions of the horizontal loads of the first jacking point 1 and the second jacking point 2 are the same as the direction of the horizontal load of the third jacking point 3. The direction of the distributed horizontal load GX generated by the aircraft mass is opposite to the direction of the horizontal load F of the third jacking point 3. The ratio of the distributed horizontal load GX generated by the aircraft mass to the distributed vertical load GZ is equal to the ratio of the horizontal load F of the third jacking point 3 to the vertical load F. CX Then, on the finite element model, constraint conditions should be applied to the aircraft center of gravity 4. The constraint conditions are heading, lateral, and vertical linear displacement constraints and angular displacement constraints. Finally, a stress analysis is performed on the entire aircraft, and the result of this stress analysis is the structural stress of the third jacking point 3. CX and the vertical load F CZ . Then, on the finite element model, constraint conditions should be applied to the aircraft center of gravity 4. The constraint conditions are heading, lateral, and vertical linear displacement constraints and angular displacement constraints. Finally, a stress analysis is performed on the entire aircraft, and the result of this stress analysis is the structural stress of the third jacking point 3.

[0030] The stress analysis method for the aircraft jacking state considering aircraft horizontal sway provided by this application is more reasonable and reliable than the traditional stress analysis method. It can be used for the detailed design of the aircraft structure, making the structural design safer and more advanced.

[0031] Although the disclosed embodiments of the present invention are as above, the described content is only the embodiments adopted for the convenience of understanding the present invention and is not used to limit the present invention. Any person skilled in the art within the scope of the present invention can make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed by the present invention. However, the scope of patent protection of the present invention shall still be subject to the scope defined by the appended claims.

Claims

1. A stress analysis method for the structures of each jacking point when an aircraft is in a jacked-up state. Given the overall structural digital model of the aircraft, the total mass of the aircraft and its mass distribution, the positions of three jacking points of the aircraft, the first jacking point is located at the front part under the fuselage of the aircraft, the second jacking point is located under the right wing of the aircraft, the third jacking point is located under the left wing of the aircraft, and the maximum vertical load and horizontal load of each jacking point, it is characterized in that It includes the following contents: 1) Establish a full-aircraft structural finite element model based on the overall structural digital model of the aircraft; 2) Apply the distributed load generated by the aircraft mass distribution on the finite element model; 3) On the finite element model, apply the maximum vertical load at one of the jacking points and the concentrated horizontal load in the most unfavorable direction for the load-bearing of this jacking point. At the same time, apply the corresponding vertical load and horizontal load to the other two jacking points respectively. The horizontal load directions of the other two jacking points are the same as the horizontal load direction of the jacking point being analyzed; 4) Apply constraint conditions at the aircraft center of gravity on the finite element model; 5) Conduct a stress analysis on the entire aircraft on the finite element model, and use the stress analysis result as the structural stress of this jacking point; 6) On the finite element model, apply the maximum vertical load at another jacking point and the concentrated horizontal load in the most unfavorable direction for the load-bearing of this jacking point, and repeat steps 4) and 5) to obtain the structural stress of this jacking point; 7) According to step 6), apply the maximum vertical load at the remaining jacking points and the concentrated horizontal load in the most unfavorable direction for the load-bearing of this jacking point, and repeat steps 4) and 5) to obtain the structural stress of the remaining jacking points.

2. The stress analysis method for each jacking point structure in the aircraft jacked-up state according to claim 1, characterized in that In steps 2) and 3), the distributed load generated by the aircraft mass distribution includes the distributed vertical load and distributed horizontal load generated by the aircraft mass. The direction of the distributed horizontal load is opposite to the horizontal load direction of the jacking point being analyzed, and the ratio of the distributed horizontal load to the distributed vertical load is equal to the ratio of the horizontal load to the vertical load of the jacking point being analyzed.

3. The stress analysis method for the structure of each jacking point under the aircraft jacking state according to claim 1, characterized in that, In step 4), apply constraint conditions at the aircraft center of gravity. The constraint conditions are the heading, lateral, and vertical linear displacement constraints and angular displacement constraints. The actual constraint reaction force is 0, and the constraint moment generated by the horizontal load is not 0.

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