Undercarriage dynamic analysis method based on nonlinear spring damping unit

Abstract

The invention provides an undercarriage dynamic analysis method based on a nonlinear spring damping unit. The method comprises the following steps: step 1, carrying out finite element modeling on an undercarriage bearing assembly by adopting a beam unit, connecting connecting parts among parts of the bearing assembly through a rigid kinematic pair, and finally constructing to obtain a structural finite element model; 2, based on the structure parameters and the filling parameters of the undercarriage buffer, modeling is conducted on the buffer through nonlinear connection elements, and a buffer analysis model is obtained; 3, extracting a middle surface of the undercarriage tire structure model, modeling by adopting a shell unit, and assembling an undercarriage tire and a wheel axle through coupling constraint and a kinematic pair to obtain a tire analysis model; step 4, constructing an undercarriage dynamic analysis model based on the steps 1-3; and step 5, based on a display dynamics calculation method in finite element software, solving a dynamic response result of the undercarriage dynamic analysis model under each combination of sinking speed and body inertial parameters. The method can evaluate the buffer performance of the undercarriage, and provides reference for structural safety design.

Description

Technical Field

[0001] The invention belongs to the technical field of aircraft structure strength calculation, and in particular relates to a landing gear dynamic analysis method based on a nonlinear spring damping unit. Background Art

[0002] The landing gear is the support point of the aircraft and is the main support and shock-absorbing device for the aircraft to land and taxi on the ground.

[0003] The landing gear absorbs and disperses the impact energy generated when the aircraft lands and the bump energy generated when taxiing through the compression deformation of the tires and the compression of the gas or the flow of oil in the buffer, thus reducing the damage to the aircraft structure. With the development of the aircraft industry, there are higher requirements for the research on the landing gear buffer performance.

[0004] The research on landing gear cushioning performance mainly focuses on the dynamic characteristics of the landing gear during landing, which involves modeling the complex structure of the landing gear, including factors such as the nonlinear characteristics of the oil-gas buffer and tires, and nonlinear factors such as structural contact.

[0005] In order to reduce risks, improve efficiency and avoid damage to the aircraft structure, it is necessary to establish an accurate and reliable finite element simulation model that can accurately predict the dynamic response of the landing gear, so as to evaluate the reliability of the landing gear design under different landing conditions and provide a reference for flight safety design. Summary of the invention

[0006] The purpose of the present invention is to provide a landing gear dynamic analysis method based on a nonlinear spring damping unit. The present invention can evaluate the buffering performance of the landing gear and provide a reference for structural safety design.

[0007] The technical solution of the present invention is: a landing gear dynamic analysis method based on a nonlinear spring damping unit, comprising the following steps:

[0008] Step 1. Use beam units to perform finite element modeling on the landing gear bearing assembly, and connect the connection parts between the parts of the bearing assembly through rigid kinematic pairs, and finally construct a structural finite element model; the bearing assembly includes the landing gear strut, outer tube and strut, etc.;

[0009] Step 2. Based on the structural parameters and filling parameters of the landing gear buffer, the buffer is modeled using nonlinear connection elements to obtain a buffer analysis model; the filling parameters of the landing gear buffer, such as the air polytropic index, the main oil hole flow coefficient and the return oil hole flow coefficient, are corrected according to the landing gear drop test results;

[0010] Step 3. Extract the mid-surface of the landing gear tire structure model, use shell elements to model it, and assemble the landing gear tire and the axle through coupling constraints and kinematic pairs to obtain a tire analysis model;

[0011] Step 4. Construct a landing gear dynamic analysis model based on steps 1 to 3;

[0012] Step 5. Based on the explicit dynamics calculation method in the finite element software, the dynamic response results of the landing gear dynamic analysis model under various combinations of sinking speeds and body inertia parameters are solved.

[0013] In the aforementioned landing gear dynamic analysis method based on nonlinear spring damping unit, in step 1, the stiffness of the structural finite element model is corrected using the test results of the landing gear stiffness test.

[0014] In the aforementioned landing gear dynamic analysis method based on nonlinear spring damping unit, in step 2, for the buffer of the air spring structure part, the calculation of the nonlinear connection element modeling is as follows:

[0015]

[0016] In the formula, F a Power for air spring, P air0 is the initial inflation pressure of the buffer, V air0 is the initial air cavity volume of the buffer, A air is the buffer compression area, S is the buffer buffer support stroke, ζ is the gas polynomial index, P atm is the atmospheric pressure.

[0017] In the above-mentioned landing gear dynamic analysis method based on nonlinear spring damping unit, in step 2, for the buffer of the main oil chamber and the return oil chamber structure, the nonlinear connection element is modeled and calculated as follows:

[0018]

[0019] In the formula, F h is the damping force of the oil chamber, ρ is the oil density, A oil is the oil pressure area, A pin is the oil needle area, C k A is the contraction coefficient, hole is the oil hole area, is the buffer compression speed.

[0020] The buffer includes an air chamber, a main oil chamber and an oil return chamber. The air chamber is used to store landing energy, and the oil chamber is used to dissipate landing energy so that the aircraft can quickly return to a stable state. The mechanism of action of the air chamber and the oil chamber in the buffer analysis model is consistent with the actual situation.

[0021] In the aforementioned landing gear dynamic analysis method based on nonlinear spring damping unit, in step 2, parameters of the buffer analysis model are modified according to the test results of the landing gear drop test.

[0022] In the aforementioned landing gear dynamic analysis method based on the nonlinear spring damping unit, according to the tire compression curve obtained from the static compression test of the landing gear, the stiffness of the tire analysis model is parameter-corrected based on the tire compression curve.

[0023] The aforementioned landing gear dynamic analysis method based on nonlinear spring damping unit also includes step 6: comparing the dynamic response result in step 5 with the design value to evaluate whether the strength design of the landing gear meets the requirements.

[0024] In the aforementioned landing gear dynamic analysis method based on nonlinear spring damping unit, in step 5, the dynamic response results are batch calculated based on the algorithm developed by the secondary development plug-in in the finite element software.

[0025] In the aforementioned landing gear dynamic analysis method based on nonlinear spring damping unit, in step 5, the dynamic response results include tire load, buffer load, buffer force, tire compression and buffer compression.

[0026] In the aforementioned landing gear dynamic analysis method based on nonlinear spring damping unit, in step 5, the output variables are set according to the requirements, and the output variable area is named in combination with the definition principle of the landing gear dynamic analysis model to quickly identify the output variables of each part. The definition principle of the landing gear dynamic analysis model refers to naming the output variable area according to the calculation output requirements to quickly identify the output variables of each part. For example, tire force, axle force, air cavity / oil cavity force and buffer compression, etc., the output requirements are customized according to different components.

[0027] In the aforementioned landing gear dynamic analysis method based on nonlinear spring damping unit, in step 3, when modeling the tire, the uniformly distributed pressure on the inner side of the tire is used to simulate the tire pressure, and the influence of symmetric / asymmetric tire pressure on the dynamic characteristics of the tire can be considered by changing the inflation pressure.

[0028] The advantages of the present invention are as follows: the present invention provides a landing gear dynamic analysis method based on a spring damping unit. Since the structure of a real oil-gas buffer is complex, it is also difficult to simulate the real landing gear buffering performance through a complex hydraulic software joint simulation method. Therefore, the present invention uses a formula as the basis and uses a nonlinear spring damping connection element to model the landing gear buffer. The present invention uses beam elements to model the landing gear buffer strut, which greatly optimizes the complexity of the model and avoids the use of complex body elements for meshing each part, so that engineers can quickly complete the preliminary modeling, correct the buffer strut stiffness through the stiffness test results, complete the first step of the building block model verification, avoid subsequent repeated modifications, and complete the modeling cycle of several weeks within one week. The present invention establishes a buffer hydraulic model through a simple and efficient formula, avoids the use of complex hydraulic models, reduces the influence of complex parameters, and corrects the filling parameters of the hydraulic model based on the drop shock test, so that the model characteristics are more in line with reality, and improves the reliability and efficiency of the design. Different from traditional nonlinear force tire modeling, the present invention uses hyperelastic ply shell elements to establish tire models, and performs model stiffness correction based on tire stiffness tests. The tire model stiffness can be completely corrected using optimization software within one week, significantly improving the accuracy and efficiency of the model. By combining various components, a landing gear dynamic analysis model is constructed, and engineers can verify and adjust the landing gear dynamic analysis model in a relatively short period of time. The patent greatly improves the design and analysis efficiency of the landing gear by simplifying the modeling process and using efficient model correction methods and optimization techniques, while ensuring the accuracy and reliability of the results. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a schematic structural diagram of the front landing gear in an example of the present invention;

[0030] Figure 2 is a schematic diagram of a finite element analysis model of a front landing gear in an example of the present invention;

[0031] Figure 3 A comparison between the simulation value and the test value of the static compression curve of the front landing gear tire of a type of transport aircraft in the example of the present invention;

[0032] Figure 4 The figure shows the response history of the front landing gear load and the buffer compression of a type of transport aircraft in the examples of the present invention under restricted working conditions, and the comparison with the test results. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0034] The features and illustrative embodiments of various aspects of the present invention will be described in detail below. In the detailed description below, many specific details are proposed to provide a comprehensive understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without the need for some of these specific details. The following description of the embodiments is only to provide a better understanding of the present invention by illustrating examples of the present invention. The present invention is by no means limited to any specific settings and methods proposed below, but covers any improvements, replacements and modifications of structures, methods, devices without departing from the spirit of the present invention. In the accompanying drawings and the following description, known structures and technologies are not shown to avoid unnecessary ambiguity in the present invention.

[0035] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other, and the embodiments can refer to and quote each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0036] Example 1: The dynamic analysis method of aircraft landing gear provided by the present invention takes a certain type of transport aircraft landing gear as an example. Figure 1 As shown in Figure 2, the dynamic response of the landing gear in the landing situation is calculated, and the specific implementation process is as follows:

[0037] Step 1: Based on the structural parameters of the front / main landing gear, the main load-bearing components are modeled using beam units, and the parts are connected through rigid kinematic pairs to establish a structural finite element model. The stiffness of the finite element model is corrected using the test results of the landing gear stiffness test.

[0038] Step 2: Based on the structural parameters and filling parameters of the landing gear buffer, the buffer is modeled using nonlinear connection elements. Different connection elements are used to model the air chamber, main oil chamber and return oil chamber. The air spring and oil chamber damping force calculation formulas are:

[0039]

[0040] In the formula, F a Power for air spring, F h is the damping force of the oil chamber, S is the landing gear buffer strut stroke, P air0is the initial inflation pressure of the buffer, V air0 is the initial air cavity volume of the buffer, A air is the buffer compression area, P atm is the atmospheric pressure, ζ is the gas polynomial index, ρ is the oil density, C k A is the contraction coefficient, oil is the oil pressure area, A hole is the oil hole area, A pin is the oil needle area, is the compression speed of the buffer. According to the test results of the landing gear drop test, the parameters of the buffer analysis model are modified.

[0041] Step 3: Extract the mid-surface of the tire structure model, use shell elements to build the model, and assemble the tire and axle through coupling constraints and kinematic pairs. According to the tire compression curve obtained from the static compression test of the landing gear, perform parameter correction on the stiffness of the tire analysis model.

[0042] Step 4: Define output variables according to requirements and name the output variable area according to the rules to facilitate quick identification of calculation results later.

[0043] Step 5. In the finite element software, the explicit dynamics calculation method is used for solution. The secondary development plug-in in the finite element software can be used to develop algorithms to batch calculate the dynamic responses under different sinking speed and body inertia combinations.

[0044] Step 6: Use secondary development to batch extract calculation results, compare them with design values, evaluate whether the strength design of the landing gear meets the requirements, and use them to improve the design.

[0045] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A landing gear dynamic analysis method based on nonlinear spring damping unit, characterized in that: The following steps are involved: Step 1. Use beam units to perform finite element modeling on the landing gear load-bearing assembly, and connect the connection parts between the parts of the load-bearing assembly through rigid kinematic pairs, and finally construct a structural finite element model; Step 2. Based on the structural parameters and filling parameters of the landing gear buffer, the buffer is modeled using nonlinear connection elements to obtain a buffer analysis model; Step 3. Extract the mid-surface of the landing gear tire structure model, use shell elements to model it, and assemble the landing gear tire and the axle through coupling constraints and kinematic pairs to obtain a tire analysis model; Step 4. Construct a landing gear dynamic analysis model based on steps 1 to 3; Step 5. Based on the explicit dynamics calculation method in the finite element software, the dynamic response results of the landing gear dynamic analysis model under various combinations of sinking speeds and body inertia parameters are solved.

2. The landing gear dynamic analysis method based on nonlinear spring damping unit according to claim 1, characterized in that: In step 1, the stiffness of the structural finite element model is corrected using the test results of the landing gear stiffness test.

3. The landing gear dynamic analysis method based on nonlinear spring damping unit according to claim 1, characterized in that: In step 2, for the buffer of the air spring structure, the calculation of the nonlinear connection element modeling is as follows: In the formula, F a Power for air spring, P air0 is the initial inflation pressure of the buffer, V air0 is the initial air cavity volume of the buffer, A air is the buffer compression area, S is the buffer buffer support stroke, ζ is the gas polynomial index, P atm is the atmospheric pressure.

4. The landing gear dynamic analysis method based on nonlinear spring damping unit according to claim 1, characterized in that: In step 2, for the buffer of the main oil chamber and the oil return chamber structure, the calculation of the nonlinear connection element modeling is as follows: In the formula, F h is the damping force of the oil chamber, ρ is the oil density, A oil is the oil pressure area, A pin is the oil needle area, C k A is the contraction coefficient, hole is the oil hole area, is the buffer compression speed.

5. The landing gear dynamic analysis method based on nonlinear spring damping unit according to claim 1, characterized in that: In step 2, the parameters of the buffer analysis model are modified according to the test results of the landing gear drop test.

6. The landing gear dynamic analysis method based on nonlinear spring damping unit according to claim 1, characterized in that: According to the tire compression curve obtained from the landing gear static compression test, the stiffness of the tire analysis model is parameter-corrected based on the tire compression curve.

7. The landing gear dynamic analysis method based on nonlinear spring damping unit according to claim 1, characterized in that: The method further includes step 6: comparing the dynamic response result in step 5 with the design value to evaluate whether the strength design of the landing gear meets the requirements.

8. The landing gear dynamic analysis method based on nonlinear spring damping unit according to claim 1, characterized in that: In step 5, the dynamic response results are batch calculated based on the algorithm developed by the secondary development plug-in in the finite element software.

9. The landing gear dynamic analysis method based on nonlinear spring damping unit according to claim 1, characterized in that: In step 5, the dynamic response results include tire load, buffer load, buffer force, tire compression and buffer compression.

10. The landing gear dynamic analysis method based on nonlinear spring damping unit according to claim 1, characterized in that: In step 5, the output variables are set according to the requirements, and the output variable areas are named according to the definition principles of the landing gear dynamic analysis model to quickly identify the output variables of each part.

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