Equivalent method and system for simulating heavy-load throwing impact load of flexible machine body

Abstract

The invention belongs to the field of aircraft structure dynamics analysis, and particularly relates to an equivalent method and system for simulating a flexible airframe heavy-load throwing impact load, and the method comprises the steps: simulating an initial balance state of an airframe structure before a heavy object is thrown, and obtaining a bearing reaction force of a constraint point position; lift force change before and after heavy load release is determined for equivalent calculation, and an equivalent lift force change curve is obtained; a bearing reaction and equivalent lift change curve of a constraint point position is added to the full-aircraft finite element model in the gravity state, heavy load release analysis calculation is conducted on the full-aircraft finite element model in the gravity state according to different working conditions, and an acceleration impact response curve of each part is obtained; and extracting the acceleration impact response curve of each part to obtain the throwing impact load of each part of the airframe.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of aircraft structure dynamics analysis, and particularly relates to an equivalent method and system for simulating heavy-load release impact load of a flexible aircraft body. BACKGROUND

[0002] Heavy-load external store air-drop technology is a technology for launching various aircrafts in the air, and is a research hotspot in the field of aerospace at present, and is of great significance for rapid deployment and deployment, and rescue and disaster relief actions.

[0003] When a flexible aircraft performs heavy-load external store air-drop, the mounting part of the aircraft body will be subjected to a transient reverse impact force, thereby causing a large transient impact response of each component of the flexible aircraft body. If the structure is not reasonably designed, the local dynamic response of the structure may be too large, local plastic deformation may occur at the key connection part of the aircraft body, and even structural damage may occur. At present, the key technologies such as dynamic response of the flexible aircraft body during heavy-load air-drop are still blank in the application of the type, and have not been mastered.

[0004] The heavy-load external store air-drop will cause a series of drastic changes of the flexible aircraft body, such as sudden change of the mass, center of mass and moment of inertia of the aircraft; and a certain reaction impact load is generated on the aircraft. How to obtain the impact load of each part of the whole aircraft after heavy-load release is a difficult problem worthy of attention. SUMMARY

[0005] In order to solve the above problems, the present application provides an equivalent method and system for simulating heavy-load release impact load of a flexible aircraft body, so as to solve the problem that the impact load of each part of the whole aircraft after heavy-load release is difficult to determine in the prior art.

[0006] The technical scheme of the present application is: an equivalent method for simulating heavy-load release impact load of a flexible aircraft body, comprising:

[0007] A shell element and a beam element are used to establish a whole-aircraft finite element model of the flexible aircraft body;

[0008] An acceleration field is set on the whole-aircraft finite element model of the flexible aircraft body, so as to obtain a whole-aircraft finite element model in a gravity state;

[0009] Constraints are added to the whole-aircraft finite element model in the gravity state, so as to simulate an initial equilibrium state before the aircraft body structure releases a heavy object, and a support reaction force of a constraint point is obtained;

[0010] The whole-aircraft finite element model in the gravity state after the heavy object is released is added with constraints, so as to determine a lift change before and after heavy-load release for equivalent calculation, and an equivalent lift change curve is obtained;

[0011] The support reaction force and the equivalent lift change curve of the constraint point position are added to the full machine finite element model under gravity, the full machine finite element model under gravity is calculated under different working conditions, and the acceleration impact response curve of each part is obtained.

[0012] The acceleration impact response curve of each part is extracted, and the drop impact load of each part of the machine body is obtained.

[0013] Preferably, the shell element and the beam element are used to establish the flexible machine body full machine finite element model, the thickness is the same as the actual thickness of each component, the material properties of each component of the full machine, the cross-sectional area of the beam element and the moment of inertia are given, and the heavy object is simulated by a rigid element. The heavy object does not establish a detailed model and is equivalent to a beam element.

[0014] Preferably, the acceleration value of the acceleration field is 9.8 m / s^2.

[0015] Preferably, when simulating the initial equilibrium state of the machine body structure before the heavy object is dropped, it is assumed that the aircraft is only affected by the lift at the wing and tail, the Z-direction translation constraint is first performed on the wing and tail, and the initial equilibrium state is calculated by using the finite element software, that is, when the deformation of the wing tip reaches the maximum value and is stably converged, the initial equilibrium state is obtained, so as to obtain the support reaction force of the constraint point position.

[0016] Preferably, the lift change before and after the heavy object is dropped is determined for equivalent calculation, specifically: the model of the machine body after the heavy object is dropped is equivalent to the model of the machine body without the heavy object, and the Z-direction translation constraint is performed on the wing and tail, and the equivalent lift of the wing and tail of the machine body after the heavy object is dropped is obtained by using implicit calculation, so as to obtain the equivalent lift change curve before and after the heavy object is dropped.

[0017] Preferably, when the full machine finite element model under gravity is analyzed and calculated, the heavy load drop analysis and calculation process is divided into two working conditions, working condition 1: the support reaction force of the constraint point position is loaded on the full machine finite element model under gravity by using explicit static analysis, so that the machine model reaches the equilibrium state; Working condition 2: the rigid element is used to connect the heavy load and the machine body, and the connection is disabled at a certain time to simulate the drop of the heavy object, and the equivalent lift change curve is loaded on the full machine finite element model under gravity.

[0018] Another technical scheme of the application is an equivalent system for simulating the heavy load drop impact load of a flexible machine body, comprising:

[0019] The model establishing module is used to establish a flexible machine body full machine finite element model by using shell elements and beam elements.

[0020] The acceleration field applying module is used to set an acceleration field on the flexible machine body full machine finite element model, and obtain a full machine finite element model under gravity.

[0021] An initial equilibrium state simulation module is configured to add constraints to the full-aircraft finite element model in the gravity state, simulate the initial equilibrium state of the aircraft structure before the heavy object is launched, and obtain the support reaction force of the constraint point position;

[0022] A lift change calculation module is configured to add constraints to the full-aircraft finite element model in the gravity state after the heavy object is launched, determine the lift change before and after the heavy object is launched, perform equivalent calculation, and obtain an equivalent lift change curve.

[0023] A launch analysis module is configured to add the support reaction force of the constraint point position and the equivalent lift change curve to the full-aircraft finite element model in the gravity state, perform heavy launch analysis and calculation on the full-aircraft finite element model in the gravity state according to different working conditions, and obtain an acceleration impact response curve of each part.

[0024] A launch impact load determination module is configured to extract the acceleration impact response curve of each part to obtain the launch impact load of each part of the aircraft body.

[0025] Preferably, a shell element and a beam element are used to establish the full-aircraft finite element model of the flexible aircraft body, the thickness is the same as the actual thickness of each component, the material properties of each component of the full-aircraft, the cross-sectional area of the beam element, and the moment of inertia are assigned, a rigid element is used to simulate the heavy object mounting, and the heavy object does not establish a detailed model and is equivalent to a beam element.

[0026] Preferably, the acceleration value of the acceleration field is 9.8 m / s^2.

[0027] Preferably, when simulating the initial equilibrium state of the aircraft structure before the heavy object is launched, it is assumed that the aircraft is only affected by the lift at the four parts of the wings and the tail, the Z-direction translation constraint is first performed on the wings and the tail, the preliminary equilibrium state of the aircraft body is calculated by using the finite element software, that is, when the deformation of the wing tip reaches the maximum value and is stably converged, it is the initial equilibrium state, so as to obtain the support reaction force of the constraint point position.

[0028] Preferably, the lift change before and after the heavy object is launched is determined for equivalent calculation, specifically: the aircraft model after the heavy object is launched is equivalent to the aircraft model without mounting the heavy object, Z-direction translation constraints are performed on the wings and the tail, the equivalent lift of the wings and the tail of the aircraft body after the heavy object is launched is obtained by using implicit calculation, and an equivalent lift change curve before and after the heavy object is launched is obtained.

[0029] Preferably, when the full aircraft finite element model under gravity is calculated by the heavy load release analysis, the heavy load release analysis process is divided into two working conditions, working condition 1: through explicit static analysis, the constraint point position support reaction is loaded on the full aircraft finite element model under gravity, so that the aircraft model reaches the balanced state; working condition 2: the rigid element is set to connect the heavy load and the aircraft, and the connection is failed at a certain time to simulate the heavy load release, and the equivalent lift curve is loaded on the full aircraft finite element model under gravity.

[0030] The equivalent method and system for simulating the heavy load release impact load of the flexible aircraft body of the application have the following advantages:

[0031] Through the combination strategy of shell element+beam element hybrid modeling, gravity field and constraint reaction equivalent, equivalent lift curve loading, and split working condition explicit / static analysis, the target of high-precision prediction of the heavy load release impact load of the flexible aircraft body under limited computing resources is achieved, the technical gap of existing type application is filled, and reliable numerical basis is provided for structure design and flight safety evaluation.

[0032] The grid size and contact nonlinear calculation amount are greatly reduced, so that the large-scale flexible aircraft full aircraft model can be calculated on a conventional workstation. Avoid high-precision geometric modeling of the heavy load, reduce the pre-processing workload, and improve the engineering implementability.

[0033] The impact load of each part of the full aircraft after heavy load release can be effectively obtained, the efficiency of heavy load release dynamic response calculation is improved, and guidance significance is provided for mechanical environment impact load design of airborne equipment and aircraft body structure design. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The figure is a schematic diagram of the whole process of the application. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the application clearer, the technical scheme in the embodiment of the application will be described in more detail below in combination with the drawings in the embodiment of the application. In the drawings, the same or similar reference signs represent the same or similar elements or elements with the same or similar functions throughout. The described embodiments are part of the embodiments of the application, not all embodiments. The embodiments described below by referring to the drawings are exemplary and are intended to explain the application, and cannot be understood as limiting the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application. The embodiments of the application will be described in detail below in combination with the drawings.

[0036] The first aspect of this application provides an equivalent method for simulating the impact load of a heavy load on a flexible machine, comprising the following steps:

[0037] Step 1: Establish a finite element model of the entire flexible body using shell elements and beam elements.

[0038] Preferably, a finite element model of the flexible body is established using shell elements and beam elements, with the thickness being the same as the actual thickness of each component. Material properties are assigned to each component, the cross-sectional area of ​​the beam elements, and the moments of inertia in three directions. , , The load is simulated using rigid elements, and the load is not modeled in detail but is equivalent to a beam element.

[0039] The moments of inertia in the three directions are:

[0040] ;

[0041] ;

[0042] ;

[0043] in For cross-sectional area, Each refers to a micro element. The perpendicular distance to the corresponding axis.

[0044] Step 2: Set an acceleration field on the full-body finite element model of the flexible body to obtain the full-body finite element model under gravity.

[0045] The acceleration value of the acceleration field is taken as 9.8 m / s^2 to simulate the gravity state of the entire machine structure.

[0046] Step 3: Add constraints to the finite element model of the whole machine under gravity to simulate the initial equilibrium state of the machine structure before the heavy object is placed, and obtain the support reaction forces at the constraint points.

[0047] Preferably, when simulating the initial equilibrium state of the aircraft structure before dropping a heavy object, it is assumed that the aircraft is only affected by lift in four parts: the wings and tail. First, Z-axis translational constraints are applied to the wings and tail. Finite element software is used to calculate the initial equilibrium state of the aircraft. That is, the initial equilibrium state is when the deformation at the wingtip reaches its maximum value and converges stably. According to the moment balance equation... , ,in They are respectively The resultant force and moment in the direction are obtained, thereby obtaining the support reaction force at the constraint point, that is, the equivalent lift force of the initial equilibrium state.

[0048] Step four, add constraints to the full aircraft finite element model in the gravity state after the launch, determine the lift change before and after the heavy load launch for equivalent calculation, and obtain the equivalent lift change curve.

[0049] Preferably, the lift change before and after the heavy load launch is determined for equivalent calculation, specifically: the aircraft model after the launch is equivalent to the aircraft model without the heavy load, while the Z-direction translational constraints are applied to the wings and tail, and the equivalent lift of the wings and tail of the aircraft after the launch is obtained by using implicit calculation, and the equivalent lift change curve before and after the launch of the heavy load is obtained.

[0050] Step five, add the support reaction force of the constraint point position and the equivalent lift change curve to the full aircraft finite element model in the gravity state, and perform heavy load launch analysis and calculation on the full aircraft finite element model in the gravity state according to different working conditions, to obtain the acceleration impact response curve of each part.

[0051] Preferably, when the full aircraft finite element model in the gravity state is analyzed and calculated, the heavy load launch analysis and calculation process is divided into two working conditions, working condition 1: through explicit static analysis, the support reaction force of the constraint point position is loaded on the full aircraft finite element model in the gravity state, so that the aircraft model reaches a balanced state; working condition 2: a rigid element is set to connect the heavy load and the aircraft, and the connection is disabled at a certain time to simulate the launch of the heavy load, and the equivalent lift change curve is loaded on the full aircraft finite element model in the gravity state.

[0052] Step six, extract the acceleration impact response curve of each part to obtain the launch impact load of each part of the aircraft.

[0053] Each part includes a central wing mounting position, a wing tip, a tail, a fuselage, and a nose. Each part of the full aircraft is extracted separately.

[0054] As another specific embodiment, an equivalent system for simulating the heavy load launch impact load of a flexible aircraft includes:

[0055] A model establishment module is configured to establish a full aircraft finite element model of the flexible aircraft using shell elements and beam elements.

[0056] An acceleration field application module is configured to set an acceleration field on the full aircraft finite element model of the flexible aircraft to obtain a full aircraft finite element model in a gravity state.

[0057] An initial balanced state simulation module is configured to add constraints to the full aircraft finite element model in the gravity state to simulate the initial balanced state of the aircraft structure before launching the heavy load, and obtain the support reaction force of the constraint point position.

[0058] The lift change calculation module is configured to add constraints to the full-aircraft finite element model in the gravity state after the payload is mounted, determine the lift change before and after the heavy payload is released, and perform equivalent calculation to obtain an equivalent lift change curve.

[0059] The payload analysis module is configured to add the support reaction force of the constraint point and the equivalent lift change curve to the full-aircraft finite element model in the gravity state, perform heavy payload analysis calculation on the full-aircraft finite element model in the gravity state according to different working conditions, and obtain an acceleration impact response curve of each part.

[0060] The payload impact load determination module is configured to extract the acceleration impact response curve of each part to obtain a payload impact load of each part of the aircraft body.

[0061] Preferably, the shell element and the beam element are used to establish the full-aircraft finite element model of the flexible aircraft body, the thickness is the same as the actual thickness of each component, the material properties of each component of the full-aircraft, the cross-sectional area of the beam element, and the moment of inertia are assigned, and the heavy object is simulated by using the rigid element, and the heavy object is not established in detail. The model is equivalent to a beam element.

[0062] Preferably, the acceleration value of the acceleration field is 9.8 m / s^2.

[0063] Preferably, when simulating the initial equilibrium state of the aircraft body structure before the payload is released, it is assumed that the aircraft is only affected by the lift at the four parts of the wing and the tail. First, the Z-direction translation constraint is performed on the wing and the tail, the preliminary equilibrium state of the aircraft body is calculated by using the finite element software, that is, when the deformation of the wing tip reaches the maximum value and is stably converged, it is the initial equilibrium state, so as to obtain the support reaction force of the constraint point.

[0064] Preferably, the lift change before and after the heavy payload is released is determined for equivalent calculation, specifically: the aircraft model after the payload is mounted is equivalent to the aircraft model without mounting the heavy object, and the Z-direction translation constraint is performed on the wing and the tail. The equivalent lift of the wing and the tail of the aircraft body after the payload is mounted is obtained by using implicit calculation, and the equivalent lift change curve before and after the payload is mounted is obtained.

[0065] Preferably, when the full-aircraft finite element model in the gravity state is subjected to heavy payload analysis calculation, the heavy payload analysis calculation process is divided into two working conditions. Working condition 1: the support reaction force of the constraint point is loaded on the full-aircraft finite element model in the gravity state by using explicit static analysis, so that the aircraft model reaches an equilibrium state. Working condition 2: the rigid element is used to connect the heavy object and the aircraft body, and the connection is disabled at a certain time to simulate the release of the heavy object, and the equivalent lift change curve is loaded on the full-aircraft finite element model in the gravity state.

[0066] In summary, the present application has the following advantages:

[0067] By the combination strategy of shell element + beam element hybrid modeling, gravity field and constraint reaction force equivalence, equivalent lift curve loading and explicit / static analysis of sub-scenarios, the high-precision prediction of flexible body heavy-load release impact load under limited computing resources is realized, which fills the technical gap of existing type application and provides reliable numerical basis for structural design and flight safety evaluation.

[0068] The grid size and contact nonlinear calculation are greatly reduced, so that the large-scale flexible body full machine model can be calculated on a regular workstation. Avoid high-precision geometric modeling of heavy objects, reduce the pre-processing workload, and improve the engineering practicability.

[0069] The impact load of each part of the full machine after heavy-load release can be effectively obtained, and the efficiency of heavy-load release dynamic response calculation is improved, which provides guiding significance for the mechanical environment impact load design of airborne equipment and the structure design of the machine body.

[0070] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited to this. Any skilled person in the art can easily think of changes or replacements within the technical scope disclosed in the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An equivalent method of simulating a heavy load release impact load for a flexible vehicle, characterized by, The application relates to a method for calculating the impact load of a flexible aircraft body. A flexible aircraft body finite element model is established by using shell elements and beam elements, the thickness of the model is the same as the actual thickness of each component, material properties of each component of the aircraft, cross-sectional areas of the beam elements and inertia moments are given, and a rigid element is used to simulate the mounting of the heavy object, the heavy object is not modeled in detail and is equivalent to a beam element. The acceleration value of the acceleration field is 9.8 m / s^2. When the initial equilibrium state of the aircraft body structure before the heavy object is mounted is simulated, it is assumed that the aircraft is only affected by the lift force at the four parts of the wings and the tail, Z-direction translation constraints are first performed on the wings and the tail, the initial equilibrium state of the aircraft body is calculated by using a finite element software, that is, when the deformation of the wing tip reaches the maximum value and is stably converged, the initial equilibrium state is achieved, and the support reaction force of the constraint point position is obtained. The equivalent calculation of the lift force change before and after the heavy object is mounted is determined, specifically: the aircraft model after the heavy object is mounted is equivalent to the aircraft model without the heavy object, Z-direction translation constraints are performed on the wings and the tail, the equivalent lift force of the wings and the tail of the aircraft body after the heavy object is mounted is obtained by using implicit calculation, and the equivalent lift force change curve before and after the heavy object is mounted is obtained. When the heavy object is mounted on the aircraft body, the heavy object mounting analysis and calculation process is divided into two working conditions, working condition 1: by using explicit static analysis, the support reaction force of the constraint point position is loaded on the aircraft body finite element model in the gravity state, so that the aircraft model reaches the equilibrium state; working condition 2: a rigid element is used to connect the heavy object and the aircraft body, and the connection is disabled at a certain moment to simulate the mounting of the heavy object, and the equivalent lift force change curve is loaded on the aircraft body finite element model in the gravity state. The application relates to a method for calculating the impact load of a flexible aircraft body.

2. The method of simulating a flexible vehicle impact load equivalent to a heavy load drop of claim 1, wherein, The model establishment module is used for establishing a flexible aircraft body finite element model by using shell elements and beam elements.

3. The method of simulating a flexible vehicle impact load equivalent to a heavy load drop of claim 1, wherein, The acceleration field application module is used for setting an acceleration field on the flexible aircraft body finite element model to obtain the aircraft body finite element model in the gravity state.

4. The method of simulating a flexible body under a heavy load drop impact load of claim 1, wherein, The initial equilibrium state simulation module is used for adding constraints to the aircraft body finite element model in the gravity state to simulate the initial equilibrium state of the aircraft body structure before the heavy object is mounted, and the support reaction force of the constraint point position is obtained.

5. The method of simulating a flexible body under a heavy load drop impact load of claim 1, wherein, The lift force change calculation module is used for adding constraints to the aircraft body finite element model in the gravity state after the heavy object is mounted, determining the equivalent calculation of the lift force change before and after the heavy object is mounted, and obtaining the equivalent lift force change curve.

6. The method of simulating a flexible body under a heavy load drop impact load of claim 1, wherein, ​ 7. An equivalent system for simulating the heavy load release impact load of a flexible body using the method according to any one of claims 1 to 6, characterized in that, ​ ​ ​ ​ ​ The drop analysis module is configured to add a support reaction force and an equivalent lift change curve of a constraint point of a full machine finite element model in a gravity state, perform a heavy load drop analysis calculation on the full machine finite element model in the gravity state according to different working conditions, and obtain an acceleration impact response curve of each part. The drop impact load determination module is configured to extract the acceleration impact response curve of each part to obtain a drop impact load of each part of the machine body.

8. An equivalent system for simulating a flexible vehicle under a heavy load drop impact load as claimed in claim 7, wherein, A shell element and a beam element are used to establish a flexible machine body full machine finite element model, the thickness is the same as the actual thickness of each component, the material properties of each component of the full machine, the cross-sectional area and the moment of inertia of the beam element are assigned, and a rigid element is used to simulate the heavy load hanging, the heavy load is not established in detail, and is equivalent to a beam element.

9. The equivalent system of analog flexible body under heavy load drop impact load of claim 7, wherein, The acceleration value of the acceleration field is 9.8 m / s^2.

10. The equivalent system of analog flexible body under heavy load drop impact load of claim 7, wherein, When simulating the initial equilibrium state of the machine body structure before the heavy load is dropped, it is assumed that the aircraft is only affected by the lift at four parts of the wing and the tail, the wing and the tail are first constrained in the Z direction, the preliminary equilibrium state of the machine body is calculated by using the finite element software, that is, when the deformation of the wing tip reaches the maximum value and is stably converged, it is the initial equilibrium state, so as to obtain the support reaction force of the constraint point.

11. The equivalent system of simulating a flexible body under a heavy load drop impact load according to claim 7, wherein, The lift change before and after the heavy load is determined to be equivalent to the calculation, specifically: the machine body model after the heavy load is dropped is equivalent to the machine body model without hanging the heavy load, and the wing and the tail are constrained in the Z direction, the equivalent lift of the wing and the tail of the machine body after the heavy load is dropped is obtained by using implicit calculation, and the equivalent lift change curve before and after the heavy load is dropped is obtained.

12. The equivalent system of analog flexible body under heavy load drop impact load of claim 7, wherein, When the full machine finite element model in the gravity state is analyzed and calculated, the heavy load drop analysis calculation process is divided into two working conditions, working condition 1: by using explicit static analysis, the support reaction force of the constraint point is loaded on the full machine finite element model in the gravity state, so that the machine model reaches the equilibrium state; working condition 2: the rigid element is used to connect the heavy load and the machine body, and the connection is disabled at a certain time to simulate the heavy load drop, and the equivalent lift change curve is loaded on the full machine finite element model in the gravity state.

Images