A damping design method for aircraft main landing gear buffer
By designing a buffer damping curve that matches the vertical load time history curve of the landing gear ground, a concave and gentle section is formed, and the ground load and fuselage bending mode is decoupled, which solves the problem of dynamic response load and acceleration when the aircraft lands. The problem has achieved improvements in structural economy and riding comfort.
Patent Information
- Application Number
- CN202011106833.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2020-10-16
- Publication Date
- 2024-12-17
- Estimated Expiration
- 2040-10-16
AI Technical Summary
The existing aircraft landing gear buffer design results in a larger dynamic response load and dynamic response acceleration of the fuselage during landing, resulting in increased structural design weight and poor ride comfort.
By designing a buffer damping curve that matches the vertical load time curve of the landing gear ground, a load concave flat and gentle section is formed, decoupling the vertical load on the landing gear ground and the first-order bending mode of the fuselage, adjusting the shape of the buffer damping characteristic curve. Reduce buffer damping at specific strokes to mitigate and suppress the body's dynamic response load.
It effectively reduces the vertical dynamic response load and dynamic response acceleration of the fuselage when the aircraft lands, reduces the weight of the structural design, improves ride comfort, and achieves these effects without increasing the structural weight.
Smart Images
Figure CN114386157B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of aircraft design, in particular to a damping design technology for a main landing gear buffer of an aircraft, and relates to reducing or easing the dynamic response load and dynamic response acceleration of a fuselage during landing impact. Background Art
[0002] In the design of traditional aircraft landing gear buffers, oil needle type variable damping buffers are generally used, and sometimes fixed oil hole type buffers are also used. The buffer design optimization goal is usually to maximize the buffer's power absorption efficiency. At this time, the landing gear buffer damping curve and static compression stiffness curve are generally first formulated based on model design experience, and then the landing gear load drop shock simulation analysis is carried out through the landing gear drop shock simulation software, and the landing gear landing load and the absorption rate of the landing gear buffer power are calculated and analyzed. Then, the landing gear buffer damping curve and static compression stiffness curve are adjusted to make the buffer load curve as full as possible without peak loads, so that the buffer can absorb as much power as possible within a smaller stroke range. Finally, the above design is specifically implemented by reasonably designing parameters such as the initial gas pressure, the volume of the air cavity and the oil cavity, the oil hole area, and the oil needle cross-sectional area. In the existing actual aircraft design, in order to make the absorption rate of the landing gear buffer work as high as possible, when designing the landing gear buffer, the vertical load curve of the landing gear is generally made as full as possible without peaks. At this time, the time history curve of the vertical load on the ground of the landing gear is generally a single-peak pulse curve or a double-peak M-type curve. For fuselage-type or wing-type landing gear, if the main frequency contained in the single-peak pulse curve or the double-peak M-type curve is close to the first-order bending mode frequency of the fuselage, the vertical load on the ground of the landing gear and the first-order bending mode of the fuselage are coupled, which arouses or even amplifies the first-order bending mode dynamic response load of the aircraft fuselage, resulting in a large vertical dynamic response load and dynamic response acceleration of the fuselage during landing impact, increasing the design weight of the fuselage structure and poor riding comfort at both ends of the cabin. In order to reduce the design weight of the fuselage structure and increase the riding comfort at both ends of the fuselage, it is necessary to reduce the dynamic response load and dynamic response acceleration generated on the fuselage during the landing impact of the aircraft.
[0003] The time history curve of the ground vertical load of the landing gear is related to parameters such as the aircraft equivalent mass, sinking speed, aircraft state angle, aircraft landing speed, landing gear buffer damping curve, static compression curve, aircraft tire stiffness and damping. Among them, the parameters such as the aircraft equivalent mass, sinking speed, aircraft state angle, and aircraft landing speed are related to the aircraft landing impact load. The tire stiffness and damping parameters depend on the tire design characteristics. When designing the aircraft landing gear, the buffer damping curve and static compression curve can be reasonably designed to adjust the ground vertical load time history curve of the landing gear by designing the landing gear geometric parameters, air chamber size, initial pressure, oil-gas ratio, oil hole size or oil needle cross-sectional area parameters. Summary of the invention
[0004] The purpose of the invention is to provide a damping design method for a buffer of an aircraft main landing gear.
[0005] A design method for the damping of a main landing gear of an aircraft, wherein the damping of the buffer is designed according to a buffer damping curve, the buffer damping curve matches a time history curve of a ground vertical load of the landing gear, and the first-order bending frequency F of the aircraft fuselage is known. The method is characterized in that the horizontal axis of the time history curve of the ground vertical load of the landing gear is the time axis of the aircraft tire landing, and the vertical axis represents the ground vertical load after the landing gear touches the ground. Between 0 and T1 after the aircraft tire touches the ground, the time history curve of the ground vertical load of the landing gear rises rapidly, and in the time period from T1 to T2, the time history curve of the ground vertical load of the landing gear forms a concave flat period, and after T2, the time history curve of the ground vertical load of the landing gear continues to rise to a maximum value, and then slowly decreases as the time when the aircraft tire touches the ground increases.
[0006] The horizontal axis of the buffer damping curve represents the compression stroke percentage of the buffer, and the vertical axis of the buffer damping curve represents the damping percentage of the buffer. The maximum stroke of the buffer is set to 100% compression stroke, and the maximum damping of the buffer is set to 100% damping. The buffer damping curve is between 0 and T1 after the aircraft tire touches the ground, and the damping of the buffer gradually increases with the increase of the compression stroke of the buffer. Between T1 and T2 after the aircraft tire touches the ground, the damping of the buffer decreases with the increase of the compression stroke of the buffer. The buffer damping curve forms a concave flat period here. After T2 time after the aircraft tire touches the ground, the damping of the buffer reaches the maximum with the increase of the compression stroke of the buffer.
[0007] The buffer damping curve sets the damping of the buffer at the initial stroke to 5%, the damping at 5% of the buffer stroke to 7%, the damping at 25% of the buffer stroke to 14%, and the damping at 50% of the buffer stroke to about 12%, so that the buffer damping curve forms a concave flat period, and the buffer damping is gradually increased to 100% between 60% and 100% of the landing gear buffer design stroke.
[0008] The relationship between the T1 time after the aircraft tire touches the ground and the first-order bending frequency F of the aircraft fuselage is T1=0.25 / F, and the relationship between the T1 time and the first-order bending frequency F of the aircraft fuselage is T2=0.5 / F.
[0009] The beneficial effects of the present application are as follows: the present application calculates T1 and T2 according to the first-order vertical bending frequency F of the aircraft fuselage, and adjusts the shape of the damping characteristic curve of the aircraft main landing gear buffer through the variable cross-section design of the main landing gear buffer oil needle, and changes the shape characteristics of the time history curve of the ground vertical load of the landing gear during the aircraft landing impact, so that during the aircraft landing impact process, in the rising section of the ground vertical load of the landing gear, in the time period from T1 to T2, a load concave buffer section is formed, so as to achieve the decoupling of the ground vertical load of the aircraft main landing gear and the first-order vertical bending mode of the fuselage, and to reduce and suppress the ground dynamic response load of the first-order vertical bending mode of the fuselage, thereby reducing the vertical dynamic response load and dynamic response acceleration generated by the fuselage during the aircraft landing impact, thereby reducing the design weight of the fuselage structure, and improving the economy of the aircraft structure and the riding comfort of the fuselage cabin.
[0010] The present application is further described in detail below in conjunction with the accompanying drawings of the embodiments. BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Figure 1 This is a curve showing the change of buffer damping with stroke.
[0012] Figure 2 The time history curve of the landing gear ground vertical load DETAILED DESCRIPTION
[0013] Referring to the attached drawings, the damping design method of the aircraft main landing gear buffer of the present application, the buffer damping is designed according to the buffer damping curve, the buffer damping curve matches the time history curve of the ground vertical load of the landing gear, the first-order bending frequency F of the aircraft fuselage is known, the horizontal axis of the time history curve of the ground vertical load of the landing gear is the time axis of the aircraft tire landing, the vertical axis represents the ground vertical load after the landing gear lands, between 0 and T1 after the aircraft tire lands, the time history curve of the ground vertical load of the landing gear rises rapidly, in the time period from T1 to T2, the time history curve of the ground vertical load of the landing gear forms a concave flat period, after T2, the time history curve of the ground vertical load of the landing gear continues to rise to the maximum value, and then slowly decreases with the increase of the time when the aircraft tire lands. The relationship between the T1 time after the aircraft tire lands and the first-order bending frequency F of the aircraft fuselage is T1=0.25 / F, and the relationship between the T1 time and the first-order bending frequency F of the aircraft fuselage is T2=0.5 / F. The horizontal axis of the buffer damping curve represents the compression stroke percentage of the buffer, and the vertical axis of the buffer damping curve represents the damping percentage of the buffer. The maximum stroke of the buffer is set to 100% compression stroke, and the maximum damping of the buffer is set to 100% damping. The buffer damping curve is between 0 and T1 after the aircraft tire touches the ground, and the damping of the buffer gradually increases with the increase of the compression stroke of the buffer. Between T1 and T2 after the aircraft tire touches the ground, the damping of the buffer decreases with the increase of the compression stroke of the buffer. The buffer damping curve forms a concave flat period here. After T2 time after the aircraft tire touches the ground, the damping of the buffer reaches the maximum with the increase of the compression stroke of the buffer.
[0014] According to the first-order vertical bending frequency F of the aircraft fuselage, T1 and T2 are calculated. Through the design of the variable cross-section characteristics of the buffer oil needle, the buffer damping is gradually increased between 0% and 25% of the design stroke of the landing gear buffer, and the buffer damping is gradually reduced between 30% and 50% of the design stroke. A minimum damping point is formed at 40% to 50% of the design stroke of the buffer, and the buffer damping is gradually increased to 100% between 60% and 100% of the design stroke of the landing gear buffer. Therefore, when the aircraft lands, on the landing gear ground load time history curve, a load concave flat section is designed in the time period from T1 to T2. The main landing gear ground vertical load time history curve is as follows: Figure 2 As shown, the ground vertical load excitation of the main landing gear is decoupled from the first-order vertical bending mode of the fuselage to mitigate and suppress the dynamic response load of the first-order vertical bending mode of the fuselage, reduce the dynamic response load and dynamic response acceleration excited by the ground vertical load of the main landing gear on the fuselage during the landing impact of the aircraft, reduce the design weight of the fuselage structure, and increase the riding comfort of the fuselage cabin.
[0015] An example of the design of the damping curve shape of the main landing gear buffer with the function of reducing the ground dynamic response load of the fuselage of the above-mentioned fuselage-type landing gear aircraft is as follows: based on the first-order vertical bending frequency F of the aircraft fuselage, T1 and T2 are calculated, and the cross-sectional area of the oil needle of the ordinary buffer is reduced and the area of the oil hole is increased between 40% and 50% of the design stroke of the ordinary buffer oil needle, thereby forming a buffer damping concave flat zone at 40% to 50% of the design stroke of the buffer, and the cross-sectional area of the oil needle is gradually increased between 60% and 100% of the design stroke of the landing gear buffer, and the area of the oil hole is reduced to improve the buffer damping, so that the time curve of the landing gear ground load force is as full as possible without a peak value, thereby improving the efficiency of the landing gear in absorbing work. Through the shape design of the damping curve of the main landing gear buffer, a concave flat section is designed in the time period from T1 to T2 of the landing gear ground load time history curve, thereby alleviating and suppressing the coupling between the landing gear ground vertical load and the first-order vertical bending mode of the fuselage, and reducing the dynamic response load and dynamic response acceleration excited on the fuselage by the main landing gear ground vertical load during the landing impact of the aircraft, thereby reducing the design weight of the fuselage structure and increasing the riding comfort of the fuselage cabin.
[0016] The buffer damping curve of an optimal embodiment sets the damping of the buffer at the initial stroke to 5%, the damping at 5% of the buffer stroke to 7%, the damping at 25% of the buffer stroke to 14%, and the damping at 50% of the buffer stroke to about 12%, so that the buffer damping curve forms a concave flat period, and the buffer damping is gradually increased to 100% between 60% and 100% of the landing gear buffer design stroke.
[0017] The invention discloses a damping design method for a main landing gear buffer of an aircraft. According to the first-order vertical bending frequency F of an aircraft fuselage, T1=0.25 / F and T2=0.5 / F are calculated. By adjusting the damping curve of the main landing gear buffer, a concave flat zone is formed on the damping curve of the main landing gear buffer, thereby changing the time history curve of the ground vertical load of the main landing gear. On the time history curve of the ground vertical load of the landing gear, a load concave flat zone is formed in the time period from T1 to T2. The start time and the end time of the load flat zone are related to the first-order vertical bending frequency of the fuselage, thereby reducing or slowing down the coupling between the ground vertical load of the landing gear and the first-order vertical bending mode of the fuselage, and reducing the ground dynamic response load of the first-order vertical bending mode of the fuselage. The present invention can adjust the shape of the time history curve of the ground vertical load of the main landing gear by adjusting the shape of the damping curve of the main landing gear buffer, thereby adjusting or slowing down the coupling between the ground vertical load of the main landing gear and the first-order vertical bending mode of the fuselage, greatly reducing the landing impact dynamic response load and dynamic response acceleration of the aircraft fuselage, reducing the weight of the aircraft fuselage structure, reducing the installation acceleration requirements of the mechanical environment of the system equipment, and reducing the weight of the system equipment installation structure. It has a significant technical effect in improving the weight economy of the aircraft fuselage structure and the riding comfort of the aircraft cabin.
Claims
1. A design method for the buffer damping of an aircraft main landing gear, wherein the buffer damping is designed according to a buffer damping curve, wherein the buffer damping curve matches the time history curve of the ground vertical load of the landing gear, and the first-order bending frequency F of the aircraft fuselage is known. It is characterized in that The horizontal axis of the landing gear ground vertical load time history curve is the time axis of the aircraft tire touching the ground, and the vertical axis represents the ground vertical load after the landing gear touches the ground. Between 0 and T1 after the aircraft tire touches the ground, the landing gear ground vertical load time history curve rises rapidly. In the time period from T1 to T2, the landing gear ground vertical load time history curve forms a concave flat period. After T2, the landing gear ground vertical load time history curve continues to rise to a maximum value, and then slowly decreases as the aircraft tire touches the ground time.
2. The aircraft main landing gear buffer damping design method as claimed in claim 1, It is characterized in that The horizontal axis of the buffer damping curve represents the compression stroke percentage of the buffer, and the vertical axis of the buffer damping curve represents the damping percentage of the buffer. The maximum stroke of the buffer is set to 100% compression stroke, and the maximum damping of the buffer is set to 100% damping. The buffer damping curve is between 0 and T1 after the aircraft tire touches the ground, and the damping of the buffer gradually increases with the increase of the compression stroke of the buffer. Between T1 and T2 after the aircraft tire touches the ground, the damping of the buffer decreases with the increase of the compression stroke of the buffer. The buffer damping curve forms a concave flat period here. After T2 time after the aircraft tire touches the ground, the damping of the buffer reaches the maximum with the increase of the compression stroke of the buffer.
3. The aircraft main landing gear buffer damping design method according to claim 1 or 2, It is characterized in that The buffer damping curve sets the damping of the buffer at the initial stroke to 5%, the damping at 5% of the buffer stroke to 7%, the damping at 25% of the buffer stroke to 14%, and the damping at 50% of the buffer stroke to about 12%, so that the buffer damping curve forms a concave flat period, and the buffer damping is gradually increased to 100% between 60% and 100% of the landing gear buffer design stroke.
4. The aircraft main landing gear buffer damping design method according to claim 1 or 2, It is characterized in that The relationship between the T1 time after the aircraft tire touches the ground and the first-order bending frequency F of the aircraft fuselage is T1=0.25 / F, and the relationship between the T1 time and the first-order bending frequency F of the aircraft fuselage is T2=0.5 / F.