Complex aircraft undercarriage overall structure bearing characteristic simulation method

Abstract

The invention discloses a complex aircraft undercarriage integral structure bearing characteristic simulation method, and particularly relates to the technical field of aircraft undercarriage integral structure bearing strength simulation, and the method comprises the steps: simplifying an undercarriage CAD model, applying characteristics to undercarriage parts, defining the material attributes of undercarriage main bearing parts, and simulating the undercarriage integral structure bearing strength. And establishing a connection relation between main force-bearing components of the undercarriage, applying boundary conditions, and applying a load. According to the method for simulating the bearing characteristics of the overall structure of the undercarriage of the complex aircraft, the transmission of the overall structure force of the undercarriage can be well simulated, and key information such as deformation and stress distribution of the undercarriage in the simulation process can be visually displayed; and a more real and effective analysis method is provided for the aspects of overall design of an undercarriage structure, optimization and weight reduction and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of aircraft landing gear integral structure load-bearing strength simulation, and in particular to a method for simulating the load-bearing characteristics of a complex aircraft landing gear integral structure. Background Art

[0002] Among the key structures of aeronautical engineering, the landing gear is responsible for the core load-bearing and buffering tasks during the transition between the ground and the air. Its operating environment is extremely harsh, and it faces severe challenges such as landing impact, taxiing vibration, complex forces, and frequent switching of working conditions. As a result, landing gear failure has become an important cause of aircraft accidents. About two-thirds of aircraft accidents are closely related to it, among which structural strength-related problems are particularly prominent. Although the current research on the load-bearing simulation of landing gear structures has achieved certain results, traditional methods are mostly limited to simple structures or single component analysis, and it is difficult to cope with the urgent need for modern aircraft to accurately simulate the overall load-bearing characteristics of complex and high-performance landing gear. For example, when dealing with landing gear with complex structures and extremely high installation accuracy requirements, existing technologies often cannot fully consider the combined influence of multiple actual factors, resulting in a large deviation between the simulation results and the actual working conditions, which seriously restricts the reliability and innovative development of landing gear design. Therefore, it is particularly important to study the simulation method of landing gear load-bearing characteristics.

[0003] At present, the landing gear simulation technology at home and abroad is relatively mature, but it is mostly limited to the analysis of landing gear with relatively simple structure or a certain component of landing gear. There are few studies on the simulation analysis of the overall structural bearing strength of landing gear with complex structure and strict installation requirements.

[0004] Therefore, it is very necessary to study the simulation analysis of the overall structural bearing strength of the landing gear. Summary of the invention

[0005] To this end, the present invention provides a method for simulating the load-bearing characteristics of the overall structure of a complex aircraft landing gear to solve the problems raised in the background technology.

[0006] In order to achieve the above object, the present invention provides the following technical solution: a method for simulating the load-bearing characteristics of the overall structure of a complex aircraft landing gear, comprising the following steps: S1: Simplify the complex aircraft landing gear CAD model; S2: Find the main load-bearing components of the landing gear from the CAD model; S3: Apply features and additional material properties to the main load-bearing components of the landing gear; S4: Determine the connection relationship between the main load-bearing components of the landing gear; S5: Apply boundary conditions to the connection between the landing gear components and the fuselage; S6: Apply loads at the landing gear axle and tire contact points; By adjusting the loads on the landing gear axle and the tire contact point, the relationship between the parameters related to the load characteristics of the overall landing gear structure and the load application is obtained, and the load is the load required under actual working conditions.

[0007] Preferably, simplifying the complex aircraft landing gear CAD model specifically includes: omitting non-main load-bearing mechanisms, including wheels, turning mechanisms, pins, and locking mechanisms; ignoring geometric details, including small holes, chamfers, and oil nozzles in the model.

[0008] Preferably, the load-bearing components of the landing gear in S2 include: a heading rod, a rocker arm, an outer cylinder, a piston rod, an anti-torsion arm, a rotating cylinder, a lever, a crossbeam, a tension rod, a vertical rod, a locking arm, a universal joint, a bracket, a strut, a locking pin and an axle. The material properties in S3 include 30CrMoSiNi2A, A-100 and TC18, wherein the material properties of the heading rod, the rotating cylinder, the lever, the crossbeam, the tension rod, the vertical rod and the strut are 30CrMoSiNi2A, the material properties of the rocker arm, the outer cylinder, the piston rod, the bracket, the locking pin and the axle are A-100, and the material properties of the anti-torsion arm and the locking arm are TC18.

[0009] Preferably, the features applied to the main load-bearing components of the landing gear specifically include: Create reference points for landing gear components, including: 1 reference point at the connection between the bracket and the fuselage, 1 reference point at the connection between the heading rod and the fuselage, 1 reference point at the connection between the vertical rod and the fuselage, 1 reference point at the connection between the universal joint and the fuselage, 1 reference point on the inner surface of the outer tube, 1 reference point on the outer surface of the piston rod, 2 reference points on the wheel axle, and 2 reference points at the simulated tire contact point under the wheel axle; Create reference planes for landing gear components, including: 2 reference planes at the piston rod and 3 reference planes at the outer cylinder; Create reference coordinate systems for the landing gear components, including: 2 reference coordinate systems at the vertical rod, 2 reference coordinate systems at the heading rod, 5 reference coordinate systems at the torque arm, 3 reference coordinate systems at the lever, 4 reference coordinate systems at the crossbeam, 2 reference coordinate systems at the front strut, 2 reference coordinate systems at the rear strut, 1 reference coordinate system at the piston rod, 2 reference coordinate systems at the tension and compression rods, 2 reference coordinate systems at the lock pin, 2 reference coordinate systems at the lock arm, 3 reference coordinate systems at the outer cylinder, 2 reference coordinate systems at the universal joint, 4 reference coordinate systems at the rocker arm, 4 reference coordinate systems at the bracket, and 3 reference coordinate systems at the rotating drum.

[0010] Preferably, the connection relationship between the landing gear load-bearing components includes a fixed connection, a cylindrical pair connection and a rotating pair connection; Among them, the outer cylinder and the rotating cylinder adopt a fixed connection method; the outer cylinder and the piston rod adopt a cylindrical pair connection method, and the cylindrical pair connection is to select the two reference points on the inner surface of the outer cylinder and the outer surface of the piston rod to couple the inner surface of the outer cylinder and the outer surface of the piston rod respectively. When establishing the coupling constraint, the two reference points on the inner surface of the outer cylinder and the outer surface of the piston rod are selected to couple the two reference points; the outer cylinder and the crossbeam, the outer cylinder and the locking arm, the outer cylinder and the upper anti-torsion arm, the piston rod and the lower anti-torsion arm, the crossbeam and the heading rod, the crossbeam and the vertical rod, the crossbeam and the universal joint, the rotating cylinder and the rocker arm, the rocker arm and the bracket, the rocker arm and the tension and compression rod, the rocker arm and the strut, the lever and the bracket, the lever and the tension and compression rod all adopt a revolute pair connection method, the buffer strut is composed of the outer cylinder and the piston rod, and the vertical load transmission borne by the oil and gas in the inner cavity of the buffer strut is simulated by establishing a SpringA connection.

[0011] Preferably, the boundary conditions imposed on the connection between the landing gear components and the fuselage are specifically: constraining 6 degrees of freedom of 8 nodes at 8 constraint node positions, namely, the connection point between the heading rod and the fuselage, the connection point between the universal joint and the fuselage, the connection point between the bracket and the fuselage, the connection point between the lower support rod and the fuselage, the connection point between the upper support rod and the fuselage, the connection point between the vertical rod and the fuselage, the connection point between the rear locking pin and the fuselage, and the connection point between the front locking pin and the fuselage.

[0012] Preferably, the load is applied at the landing gear wheel axle and tire grounding point by selecting two reference points on the wheel axle and two reference points below the wheel axle that simulate the tire grounding point, respectively coupling the left and right bearings of the wheel axle and the contact part of the wheel axle and the tire grounding point, and applying load at the reference points; the vertical load and the heading load are loaded at the center position of the wheel hub on both sides of the wheel axle, and the lateral load is loaded at the grounding point position of the tires on both sides.

[0013] The present invention has the following advantages: The present invention simplifies a complex aircraft landing gear CAD model, finds the main load-bearing components of the landing gear from the CAD model, applies features and additional material properties to the main load-bearing components of the landing gear, determines the connection relationship between the main load-bearing components of the landing gear, applies boundary conditions to the connection between the landing gear components and the fuselage, applies loads to the landing gear axle and the tire grounding point, and obtains the relationship between the parameters related to the bearing characteristics of the overall structure of the landing gear and the load required by the applied actual working condition by adjusting the loads at the landing gear axle and the tire grounding point. Compared with the prior art, the present invention comprehensively considers the comprehensive influence of multiple actual factors to avoid a large deviation between the simulation results and the actual working condition, and is not limited to the analysis of a landing gear with a relatively simple structure or a certain component of the landing gear, which is conducive to the reliability and innovative development of the landing gear design. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A simplified model of the landing gear provided by the present invention; Figure 2 A schematic diagram of the connection relationship of the landing gear components provided by the present invention; Figure 3 A schematic diagram of the connection of the landing gear SpringA provided by the present invention; Figure 4 A schematic diagram of the landing gear boundary conditions provided by the present invention; Figure 5 A schematic diagram of the landing gear load application provided by the present invention; In the figure: 1. heading rod; 2. crossbeam; 3. universal joint; 4. vertical rod; 5. bracket; 6. tension and compression rod; 7. strut; 8. lever; 9. rocker arm; 10. rotating cylinder; 11. outer cylinder; 12. locking pin; 13. locking arm; 14. anti-twist arm; 15. piston rod; 16. axle. DETAILED DESCRIPTION

[0015] The following is a description of the implementation of the present invention by specific embodiments. People familiar with the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. 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 creative work are within the scope of protection of the present invention.

[0016] Embodiment: In view of the shortcomings of the current structural strength analysis method, this embodiment proposes a method for simulating the overall structural load-bearing characteristics of a complex aircraft landing gear, taking a domestic landing gear with complex retraction and extension conditions and strict installation requirements as an example. The method can not only simulate the transmission of the overall structural force of the landing gear well, but also intuitively display the deformation, stress distribution and other key information of the landing gear during the simulation process. The introduction of large deformation is more in line with the actual situation and has higher safety. It helps designers to better understand the load-bearing characteristics of the landing gear and make more informed design decisions. The method includes the following steps: S1. Simplify the landing gear model used in the present invention in CAD software, i.e., omit non-main load-bearing mechanisms such as wheels, turning mechanisms, pins, and locking mechanisms, and ignore geometric details such as small holes, chamfers, and oil nozzles in the model. The final simplified CAD model of the landing gear is as follows: Figure 1 shown.

[0017] S2. The obtained simplified CAD model is subjected to finite element modeling in ABAQUS software, as follows: S2.1. Establishing a reference coordinate system: This embodiment takes a certain type of aircraft landing gear as an example, and adopts the body coordinate system OXYZ. The origin O is located in the longitudinal symmetry plane of the aircraft, and the foot point of the horizontal reference line is made through the front point of the hull; the X-axis coincides with the horizontal baseline of the aircraft, and the backward direction is positive; the Z-axis is in the symmetry plane of the fuselage, passes through the origin and is perpendicular to the X-axis, and is positive upward; the Y-axis passes through the origin and is perpendicular to the XOZ plane, and is positive to the right along the heading. Establishing a reference coordinate system at the connection of each component of the landing gear is conducive to selecting reference points and coordinate axes during subsequent modeling.

[0018] S2.2. Establish and add material properties: The material properties used for the main load-bearing components of the landing gear include 30CrMoSiNi2A, A-100, and TC18. For each material, define the material behavior as elastic, the type as isotropic, and the elastic modulus and Poisson's ratio; add material properties to the main load-bearing components of the landing gear, among which the material property used for the heading rod, rotating cylinder, lever, beam, tension and compression rod, vertical rod, and strut is 30CrMoSiNi2A, the material property used for the rocker arm, outer cylinder, piston rod, bracket, lock pin, and wheel axle is A-100, and the material property used for the anti-torsion arm and lock arm is TC18.

[0019] S2.3. Edit the section: All section types are solid and homogeneous, and each component is assigned a section.

[0020] S2.4. Edit reference points and reference surfaces: Establish reference points at each component connection, partition the interior of the landing gear and define cutting planes. For example, both the outer tube and the piston rod require cutting planes. This helps to better select reference points and reference surfaces when establishing connection relationships.

[0021] S2.5. Editing and analyzing steps S2.5.1. Edit field output request: Output variables: S (stress components and invariants), E (total strain components), PE (plastic strain components), PEEQ (equivalent plastic strain), PEMAG (plastic strain), EE (elastic strain part), NE (nominal strain components), LE (logarithmic strain components), U (translation and rotation), RF (reaction forces and moments), CF (concentrated forces and moments), NFORC (nodal forces caused by unit stresses), CSTRESS (contact stress), CDISP (contact displacement), CFORCE (contact force) S2.5.2. Edit process output request: ALLEN (total energy) S2.6. Establishing component connection relationships: This embodiment mainly uses the MPC (Multi-point constraints) constraint method to simulate. The components of the landing gear involve connection methods such as fixed, hinged, and cylindrical pairs, such as Figure 2As shown, the outer cylinder and the rotating cylinder are fixedly connected, such as at J; the outer cylinder and the piston rod are connected by a cylindrical pair, such as at L. Specifically, the two reference points are first coupled to the inner surface of the outer cylinder and the outer surface of the piston rod respectively. When establishing the coupling constraint, two reference points are selected and coupled. The Coupling type is motion. The displacement of the node in the Y direction and the Z direction and the rotational displacement of the node around the Y axis and the Z axis are constrained. The outer cylinder and the crossbeam, the outer cylinder and the locking arm, the outer cylinder and the upper anti-torsion arm, the piston rod and the lower anti-torsion arm, the crossbeam and the heading Rods, beams and vertical rods, beams and universal joints, rotating drums and rockers, rockers and brackets, rockers and tension and compression rods, rockers and struts, levers and brackets, levers and tension and compression rods are connected by revolute pairs. For example, at K, a coupling constraint is established. Reference points and reference surfaces are selected, and the reference points and reference surfaces are coupled. The continuous distribution of Coupling is used to constrain the rotational displacement of nodes around the X-axis, Y-axis, and Z-axis. The connection section type is created as hinged, the behavior is elastic, and it is defined as rigid. The rotational displacement of the constraint node around the X-axis is released, such as Figure 3 As shown, the vertical load transfer borne by the oil and gas in the inner cavity of the buffer strut is simulated by establishing a SpringA connection, specifically, connecting a reference point on the outer cylinder and a reference point on the piston rod, the axis follows the action line, and the stiffness of the spring is 100000.

[0022] S2.7, Apply boundary conditions: Boundary conditions are applied to simulate the state of the aircraft landing gear being lowered. The load is applied by reference point coupling. When the landing gear is lowered, it can be regarded as fixed on the aircraft, thus constraining the 6 degrees of freedom (X, Y, Z, RX, RY, RZ) of the 8 nodes. Figure 4 As shown, the eight nodes are: a, the connection point between the heading rod and the fuselage; b, the connection point between the universal joint and the fuselage; c, the connection point between the bracket and the fuselage; d, the connection point between the lower support rod and the fuselage; e, the connection point between the upper support rod and the fuselage; f, the connection point between the vertical rod and the fuselage; g, the connection point between the rear locking pin and the fuselage; h, the connection point between the front locking pin and the fuselage.

[0023] S2.8, Apply load: Figure 5 As shown in the figure, four RPs (reference points) are selected to couple the left and right bearings of the axle with the contact part of the axle and the grounding point of the tire, and loads are applied at the reference points. Specifically, the vertical load and heading load are applied to the center of the wheel hub on both sides of the axle, and the lateral load is applied to the grounding point of the tires on both sides.

[0024] 2. Analyze the results The method described in this embodiment is used to simplify the complex aircraft landing gear CAD model to only retain the main load-bearing components of the landing gear, apply features to the main components of the landing gear, determine the connection relationship of the main load-bearing components of the landing gear, apply boundary conditions to the connection between the landing gear components and the fuselage, and apply loads at the landing gear axle and tire grounding points. It can more accurately simulate the stress distribution of the components under actual working conditions, more clearly understand the interaction between components and the load transfer path, more accurately analyze the strength and stiffness of the connection between the landing gear and the fuselage, and more clearly understand the stress conditions and deformation modes of the axle and tire grounding points. The simulation time can be reduced by about 30%, and the obtained simulation results have an error of less than 5% from the actual test. Failure to use the method of this embodiment may cause stress concentration or distortion at the connection part, resulting in a large deviation in load distribution, and the error between the simulation result and the actual result may reach 10%-15%. The constraint node load comparison is shown in Table 1.

[0025] Table 1

[0026] Although the present invention has been described in detail above by general description and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A method for simulating the load-bearing characteristics of the overall structure of a complex aircraft landing gear, characterized by: The following steps are involved: Simplify complex aircraft landing gear CAD models; Find the main load-bearing components of the landing gear from the CAD model; Apply features and additional material properties to the main load-bearing components of the landing gear; Determine the connection relationship between the main load-bearing components of the landing gear; Apply boundary conditions to the connection between landing gear components and fuselage; Apply loads at the landing gear axle and tire contact points; By adjusting the loads on the landing gear axle and the tire contact point, the relationship between the parameters related to the load characteristics of the overall landing gear structure and the load applied is obtained, and the load is the load required under actual working conditions.

2. The method for simulating the load-bearing characteristics of the overall structure of a complex aircraft landing gear according to claim 1, characterized in that: Simplifying the complex aircraft landing gear CAD model specifically includes: omitting non-main load-bearing mechanisms and geometric details.

3. The method for simulating the load-bearing characteristics of the overall structure of a complex aircraft landing gear according to claim 1, characterized in that: The main load-bearing components of the landing gear found in the CAD model include: a heading rod, a rocker arm, an outer cylinder, a piston rod, an anti-torsion arm, a rotating cylinder, a lever, a crossbeam, a tension rod, a vertical rod, a locking arm, a universal joint, a bracket, a strut, a locking pin and an axle.

4. The method for simulating the load-bearing characteristics of the overall structure of a complex aircraft landing gear according to claim 1, characterized in that: The features applied to the main load-bearing components of the landing gear specifically include: Create reference points for landing gear components, including: 1 reference point at the connection between the bracket and the fuselage, 1 reference point at the connection between the heading rod and the fuselage, 1 reference point at the connection between the vertical rod and the fuselage, 1 reference point at the connection between the universal joint and the fuselage, 1 reference point on the inner surface of the outer tube, 1 reference point on the outer surface of the piston rod, 2 reference points on the wheel axle, and 2 reference points at the simulated tire contact point under the wheel axle; Create reference planes for landing gear components, including: 2 reference planes at the piston rod and 3 reference planes at the outer cylinder; Create reference coordinate systems for the landing gear components, including: 2 reference coordinate systems at the vertical rod, 2 reference coordinate systems at the heading rod, 5 reference coordinate systems at the torque arm, 3 reference coordinate systems at the lever, 4 reference coordinate systems at the crossbeam, 2 reference coordinate systems at the front strut, 2 reference coordinate systems at the rear strut, 1 reference coordinate system at the piston rod, 2 reference coordinate systems at the tension and compression rods, 2 reference coordinate systems at the lock pin, 2 reference coordinate systems at the lock arm, 3 reference coordinate systems at the outer cylinder, 2 reference coordinate systems at the universal joint, 4 reference coordinate systems at the rocker arm, 4 reference coordinate systems at the bracket, and 3 reference coordinate systems at the rotating drum.

5. The method for simulating the load-bearing characteristics of the overall structure of a complex aircraft landing gear according to claim 4, characterized in that: The connection relationship between the main load-bearing components of the landing gear includes fixed connection, cylindrical joint connection and rotating joint connection; Among them, the outer cylinder and the rotating cylinder adopt a fixed connection method; the outer cylinder and the piston rod adopt a cylindrical pair connection method, and the cylindrical pair connection is to select two reference points on the inner surface of the outer cylinder and the outer surface of the piston rod to couple the inner surface of the outer cylinder and the outer surface of the piston rod respectively. When establishing the coupling constraint, the two reference points on the inner surface of the outer cylinder and the outer surface of the piston rod are selected to couple the two reference points; the outer cylinder and the crossbeam, the outer cylinder and the locking arm, the outer cylinder and the upper anti-torsion arm, the piston rod and the lower anti-torsion arm, the crossbeam and the heading rod, the crossbeam and the vertical rod, the crossbeam and the universal joint, the rotating cylinder and the rocker arm, the rocker arm and the bracket, the rocker arm and the tension and compression rod, the rocker arm and the strut, the lever and the bracket, the lever and the tension and compression rod all adopt a revolute pair connection method, the buffer strut is composed of the outer cylinder and the piston rod, and the vertical load transmission borne by the oil and gas in the inner cavity of the buffer strut is simulated by establishing a SpringA connection.

6. The method for simulating the load-bearing characteristics of the overall structure of a complex aircraft landing gear according to claim 1, characterized in that: The boundary conditions imposed on the connection between the landing gear components and the fuselage are specifically: constraining 6 degrees of freedom of 8 nodes at 8 constraint node positions, namely, the connection point between the heading rod and the fuselage, the connection point between the universal joint and the fuselage, the connection point between the bracket and the fuselage, the connection point between the lower support rod and the fuselage, the connection point between the upper support rod and the fuselage, the connection point between the vertical rod and the fuselage, the connection point between the rear locking pin and the fuselage, and the connection point between the front locking pin and the fuselage.

7. The method for simulating the load-bearing characteristics of the overall structure of a complex aircraft landing gear according to claim 4, characterized in that: The specific method of applying loads at the landing gear wheel axle and tire grounding point is as follows: two reference points on the wheel axle and two reference points below the wheel axle that simulate the tire grounding point are selected, the left and right bearings of the wheel axle are coupled to the contact part of the wheel axle and the tire grounding point respectively, and loads are applied at the reference points; vertical loads and heading loads are loaded at the center positions of the wheel hubs on both sides of the wheel axle, and lateral loads are loaded at the grounding point positions of the tires on both sides.

Images