Fault state divergence analysis method for seaplane buoy

Abstract

The invention discloses a seaplane buoy fault state divergence analysis method, which comprises the following steps of: 1, establishing a finite element structure model and an aerodynamic model of wings, buoys and supporting rods in a normal state according to the actual shapes of the wings and the buoys of a seaplane and the movement of the supporting rods; step 2, establishing a buoy fault state model based on a fault state encountered by the stay bar; 3, on the basis of the buoy fault state model, the divergence speed of the buoy in the fault state is solved through a static aeroelasticity method; 4, for the buoy fault state model of which the divergence speed exceeds the aeroelastic stability speed envelope, calculating a buoy divergence motion mode; 5, determining a main supporting rod for supporting the buoy in the divergent motion mode of the buoy; calculating the maximum deformation of the main supporting rod in the pitching direction under the maximum damage bending moment; and judging the interference condition of the stay bar with the wing after the stay bar elastically deforms based on the maximum deformation. According to the invention, the flight safety of the airplane can be evaluated, so that the safety and reliability of the seaplane are improved.

Description

Technical Field

[0001] This invention belongs to the field of static aeroelastic design technology for seaplanes, and relates to a divergent analysis method for the fault state of seaplane floats. Background Technology

[0002] Aircraft are elastic structures. Under aerodynamic forces, the structure undergoes elastic deformation, which in turn generates additional aerodynamic forces. These additional aerodynamic forces, in turn, induce new elastic deformations, generating even more aerodynamic forces. This mutual coupling can cause the elastic body to gradually reach an equilibrium state or diverge and lose stability, leading to structural damage and affecting flight safety. Therefore, it is crucial to conduct divergence characteristic analysis on all morphologies and design conditions within the aircraft's aeroelastic stability envelope during the aircraft design process.

[0003] Seaplanes, as special-purpose aircraft capable of both air flight and takeoff, landing, and parking on water, possess a unique structure beneath their wings—the floats. These floats are connected to the wings by several struts. The float cavities are filled with air, allowing the aircraft to float on the water. During takeoff and landing on water, the floats cushion the impact forces on the aircraft, reducing the effects of wind and waves and ensuring the overall stability and safety of the aircraft. Therefore, the float struts are crucial structural supports for the floats. If the floats suffer single strut failure, or damage from discrete impact sources (such as bird strikes, tire blowouts, and rotor non-containment failures) or structural fatigue, the stiffness of the connection between the floats and the wings will decrease. This may affect the divergent characteristics of the aircraft, causing flight instability, and could even damage the aircraft structure, affecting flight safety.

[0004] Current divergent analysis of aircraft primarily focuses on the entire aircraft, wings, and tail, and is mostly conducted under normal conditions, without specifically considering the scenario of pontoon malfunctions. Seaplanes are currently a crucial and urgently needed piece of aviation equipment, and pontoons, as a unique and vital structure, require divergent analysis under malfunction conditions. Assessing their stability and impact on the airframe structure is therefore essential for seaplane design. Summary of the Invention

[0005] The purpose of this invention is to propose a divergent analysis method for the fault status of seaplane floats. This invention improves the safety and reliability of seaplanes by enabling the assessment of flight safety.

[0006] The technical solution of this invention is: a method for divergent analysis of the fault state of seaplane floats, comprising: Step 1: Based on the actual shape of the seaplane's wings and floats and the movement of the struts, establish the finite element structural model and aerodynamic model of the wings, floats and struts under normal conditions; Step 2: Based on the failure state encountered by the strut, establish a failure state model for the pontoon; Step 3: Based on the pontoon failure state model, use the static aeroelastic method to solve for the divergence velocity of the pontoon under failure state; Step 4: For the float failure state model where the divergence velocity exceeds the aeroelastic stability velocity envelope, calculate the float divergence motion mode; Step 5: Determine the main strut supporting the float in the divergent motion mode of the float; calculate the maximum deformation of the main strut in the pitch direction under the maximum destructive bending moment; and determine the interference between the main strut and the wing after elastic deformation based on the maximum deformation.

[0007] In the aforementioned divergent analysis method for seaplane float failure states, in step 1, the aerodynamic model is modeled using slender body elements and disturbance body elements, and six degrees of freedom constraints are applied to the wing.

[0008] In the aforementioned divergent analysis method for seaplane float failure states, step 2 includes failure states such as discrete source damage and fatigue damage of the strut.

[0009] In the aforementioned divergent analysis method for seaplane float failure states, step 2 includes one or more of the following: bird strikes to the strut, impacts from tire rupture fragments, and fragment impacts during rotor non-containment failure.

[0010] In the aforementioned divergent analysis method for seaplane float failure status, in step 2, fatigue damage is determined based on the damage tolerance analysis and inspection interval of the strut joint lugs.

[0011] In the aforementioned divergent analysis method for seaplane float failure states, step 5 is as follows: The main strut is equivalent to a cantilever beam fixed at the wing side connection. The maximum deformation of the main strut on the float side is calculated based on the maximum slope failure bending moment borne by the main strut. When the maximum deformation is less than one-tenth of the length of the main strut, it is determined that the main strut does not interfere with the wing during the divergent motion.

[0012] In the aforementioned divergent analysis method for seaplane float failure states, the maximum deformation on the strut float side is calculated using the cantilever beam deflection formula: f 0 =Pl 3 / 3 EI (1) In the formula, E The Young's modulus of the main strut. I The moment of inertia of the main strut about its centroid. l The length of the main strut. P The applied force corresponding to the maximum breaking bending moment of the main strut. f0 represents the maximum deformation.

[0013] In the aforementioned divergent analysis method for seaplane float failure states, P=M / l (2) In the formula, M The maximum destructive bending moment of the main strut.

[0014] In the aforementioned divergent analysis method for seaplane float failure states, the maximum failure bending moment of the main strut... M for: M= [ σ ] W (3) In the formula, [ σ The main strut requires bending stress. W This is the section modulus for bending resistance.

[0015] Beneficial Effects: This invention addresses potential fault states that floats may encounter during flight. Based on the actual shape of the float, the movement of the strut, and the fault conditions, divergent analysis is performed on the float model to obtain divergent velocity and dynamic pressure. For float fault states exceeding the aeroelastic stability velocity envelope, the stability of the float during divergence and its impact on the airframe structure are evaluated through divergent motion mode analysis and maximum destructive deformation analysis. Specifically, this invention addresses potential fault states that seaplane floats may encounter during flight, identifying failure modes including strut damage from discrete sources and fatigue damage; establishing finite element structural and aerodynamic models of the seaplane wing and float fault states; calculating the float divergence velocity and dynamic pressure under fault conditions using the static aeroelastic method; and evaluating the stability of the float during divergence and its impact on the airframe structure based on the float divergent motion modes, using the static divergence principle and maximum destructive deformation analysis for float fault states exceeding the aeroelastic stability velocity envelope. This invention provides a reasonable and feasible analysis method for the divergence problem of seaplane floats. It has high modeling quality and can obtain the divergence characteristics of seaplane floats under fault conditions, which can guide the structural strength design, evaluate the flight safety of the aircraft, and improve the safety and reliability of the aircraft.

[0016] The present invention provides a divergent analysis method for seaplane float failure states. The method has a clear process and models the float based on its actual shape, strut movement, and failure conditions, resulting in high-quality modeling. Furthermore, the method summarizes the possible failure states that seaplane floats may encounter and provides a divergent calculation method for modeling these failure states. For float failure states exceeding the aeroelastic stability velocity envelope, the method analyzes stability using the divergent motion modes of the float and the static divergence principle. It also analyzes whether the float interferes with the wing using the maximum destructive deformation generated after divergence. This invention provides a reasonable and feasible evaluation method for the stability and impact on the airframe during divergence under float failure states. This method can guide structural strength design, assess aircraft flight safety, and has guiding significance and practical engineering value for the design and airworthiness of seaplanes. Attached Figure Description

[0017] Figure 1 This refers to the float strut and wing structure in the example of this invention.

[0018] Figure 2 This is the finite element model in the example of this invention.

[0019] Figure 3 This is the divergent motion mode of the float in the example of this invention. Detailed Implementation

[0020] 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.

[0021] 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.

[0022] Example 1. A divergent analysis method for the fault state of a seaplane float, such as... Figures 1-3 As shown, it includes the following steps: Step 1: Based on the closed-cell profile theory and the results of the full-aircraft ground resonance test, the stiffness of the wing, struts and floats is modeled using variable profile beam elements to simulate the distribution of bending stiffness and torsional stiffness. Step 2: Based on the load-bearing capacity and direction of motion of the strut, set the degrees of freedom of the strut. Step 3: Based on the mass distribution results of the aircraft, select beam element nodes as loading nodes for lumped mass according to the principle of proximity of control. Use lumped mass elements to simulate the mass distribution of the wing and floats to improve computational efficiency and simulation accuracy. Step 4: Combine steps 1, 2, and 3 to form a finite element model of the wing, struts, and floats. Apply six degrees of freedom constraints to the entire wing as a model under normal conditions. Figure 2 As shown; Step 5: Using the dipole mesh method, establish an unsteady aerodynamic model of the wing, strut, and floats. Divide the wing into a series of aerodynamic meshes, and use slender body elements and disturbing body elements for the aerodynamic meshes of the strut and floats. Step 6: Based on the possible failure states that the strut may encounter, including the damage caused to the strut by discrete source damage and fatigue damage, identify the failure modes (single or combined) of the strut. Step 7: Based on the failure mode of the strut, delete the corresponding strut elements in the normal state finite element structural model and establish the pontoon failure state model. Step 8: Use the static aeroelasticity method to solve the divergence velocity of the float under fault conditions, and compare whether it meets the aeroelastic stability envelope requirements of the seaplane under fault conditions involved in this invention. Step 9: Perform inherent mode analysis on the float failure state exceeding the aeroelastic stability velocity envelope to obtain the float divergent motion modes, such as... Figure 3 As shown, the static divergence principle is used to determine whether the buoy meets the static divergence design requirements and whether it has stability after the remaining support rods of the buoy undergo elastic deformation. Step 10: For float failure states exceeding the aeroelastic stability velocity envelope, further consider the main strut in the float divergent motion mode as a cantilever beam fixed at the wing-side connection. Calculate the maximum deformation of the main strut on the float side based on the maximum slope failure bending moment borne by the main strut, and compare its length with that of the main strut to determine whether the main strut interferes with the wing during divergent motion. Combine this with Step 9 to assess whether the float divergence affects the airframe structure.

[0023] The maximum deformation of the pontoon side strut is calculated using the cantilever beam deflection formula, as follows: f 0 =Pl 3 / 3 EI (1) In the formula, E The Young's modulus of the main strut. I The moment of inertia of the main strut about its centroid. l The length of the main strut.P The applied force corresponding to the maximum breaking bending moment of the main strut. f 0 represents the maximum deformation.

[0024] The applied force corresponding to the maximum breaking moment of the main strut P for: P=M / l (2) The maximum breaking moment of the main strut is: M= [ σ ] W (3) In the formula, [ σ The main strut requires bending stress. W This is the section modulus for bending resistance.

[0025] The divergence analysis method for seaplane float failure states provided by this invention mainly establishes structural and aerodynamic models of the seaplane wing and floats according to given modeling rules, identifies failure modes of the float struts after encountering failures, and further establishes a float failure state model. The static aeroelastic method is used to solve for the divergence velocity and divergence dynamic pressure of the float under failure states. For float failure states exceeding the aeroelastic stability velocity envelope, the stability and impact on the airframe structure are evaluated based on the float divergence motion modes, using the static divergence principle and maximum destructive deformation. Using this method, the divergence characteristics of seaplane floats under failure states can be obtained, guiding aircraft structural strength design, assessing flight safety, and improving the safety and reliability of aircraft.

[0026] 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 divergent analysis method for the fault state of a seaplane float, characterized in that, include: Step 1: Based on the actual shape of the seaplane's wings and floats and the movement of the struts, establish the finite element structural model and aerodynamic model of the wings, floats and struts under normal conditions; Step 2: Based on the failure state encountered by the strut, establish a failure state model for the pontoon; Step 3: Based on the pontoon failure state model, use the static aeroelastic method to solve for the divergence velocity of the pontoon under failure state; Step 4: For the float failure state model where the divergence velocity exceeds the aeroelastic stability velocity envelope, calculate the float divergence motion mode; Step 5: Determine the main strut supporting the buoy in the divergent motion mode of the buoy; Calculate the maximum deformation of the main strut in the pitch direction under the maximum failure bending moment; The interference between the strut and the wing after elastic deformation is determined based on the maximum deformation.

2. The divergent analysis method for seaplane float failure states according to claim 1, characterized in that, In step 1, the aerodynamic model is modeled using slender body elements and disturbance body elements, and six degrees of freedom constraints are applied to the wing.

3. The divergent analysis method for seaplane float failure states according to claim 1, characterized in that, In step 2, the fault states include: discrete source damage and fatigue damage of the strut.

4. The divergent analysis method for seaplane float failure states according to claim 1, characterized in that, In step 2, discrete source damage includes one or more of the following: bird strikes to the strut, impacts from tire rupture fragments, and fragment impacts from non-containment failure of the rotor.

5. The divergent analysis method for seaplane float failure states according to claim 1, characterized in that, In step 2, fatigue damage is determined based on the damage tolerance analysis of the strut joint lugs and the inspection interval.

6. The divergent analysis method for seaplane float failure states according to claim 1, characterized in that, Step 5 is as follows: The main strut is equivalent to a cantilever beam fixed at the wing side connection. The maximum deformation of the main strut on the float side is calculated based on the maximum slope failure bending moment borne by the main strut. When the maximum deformation is less than one-tenth of the length of the main strut, it is determined that the main strut does not interfere with the wing during the divergent motion.

7. The divergent analysis method for seaplane float failure states according to claim 6, characterized in that, The maximum deformation on the side of the strut pontoon is calculated using the cantilever beam deflection formula: f 0 =Pl 3 / 3 EI （1） In the formula, E The Young's modulus of the main strut. I The moment of inertia of the main strut about its centroid. l The length of the main strut. P The applied force corresponding to the maximum breaking bending moment of the main strut. f 0 represents the maximum deformation.

8. The divergent analysis method for seaplane float failure states according to claim 7, characterized in that, P=M / l （2） In the formula, M The maximum destructive bending moment of the main strut.

9. The divergent analysis method for seaplane float failure states according to claim 8, characterized in that, Maximum breaking moment of the main strut M for: M= [ σ ] W （3） In the formula, [ σ The main strut requires bending stress. W This is the section modulus for bending resistance.

Images