CN114239130A - Analysis method for airbag inflation and deployment after helicopter is watered - Google Patents

Analysis method for airbag inflation and deployment after helicopter is watered Download PDF

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CN114239130A
CN114239130A CN202111391747.0A CN202111391747A CN114239130A CN 114239130 A CN114239130 A CN 114239130A CN 202111391747 A CN202111391747 A CN 202111391747A CN 114239130 A CN114239130 A CN 114239130A
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air bag
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water
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袁李斌
树德军
吕乐丰
徐朝梁
刘文琦
洪蛟
刘海
吴远飞
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China Helicopter Research and Development Institute
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Abstract

The invention provides an analysis method for airbag inflation and deployment after water landing of a helicopter, which comprises the following steps: establishing a full-mechanical elastic-plastic analysis model, and establishing an air bag folding and inflating model; assembling the full-mechanical elastic-plastic analysis model with an air bag folding and inflating model; establishing a water area model, and performing fluid-solid coupling model analysis and airbag deployment analysis; according to the method, the water-landing load of the airbag deployment condition after the helicopter lands water can be predicted during model design, analysis basis is provided for design of the emergency airbag, the connecting structure of the emergency airbag and the structure of the helicopter body, the test times can be reduced, the design research and development cost and the research and development risk can be reduced, and meanwhile, important support can be provided for establishing a water forced landing program and obtaining evidence for seaworthiness of the helicopter through the analysis method.

Description

Analysis method for airbag inflation and deployment after helicopter is watered
Technical Field
The invention belongs to the technical field of structural strength design of helicopters, and particularly relates to an analysis method for airbag inflation and unfolding after a helicopter is watered.
Background
Forced landing on water is an emergency measure for landing on the water surface when the aircraft cannot fly continuously under special conditions. The process of forced landing on water by a helicopter is generally divided into three stages: the flight stage before entering water, the structural response stage in the water entering process and the stabilization stage after entering water. The problem analysis of the helicopter in the water process stage is a nonlinear dynamics problem related to fluid-solid coupling and large structural deformation, the analysis is very complicated, and effective prediction cannot be carried out by an analytical method.
The current research means mainly includes model tests and numerical simulation, and the test method has the advantages of accurate and real and credible results, but the large-scale model tests are long in time consumption and high in manpower and material cost, and response results of all the points cannot be obtained. On the other hand, with the development of finite element technology and computers, a numerical method is developed rapidly, and a relatively efficient analysis method can be provided for the typical fluid-solid coupling problem.
Disclosure of Invention
In order to solve the technical problem, the invention provides an analysis method for the inflation and deployment of an airbag after the helicopter is watered, which comprises the following steps:
establishing a full-mechanical elastic-plastic analysis model, and establishing an air bag folding and inflating model;
assembling the full-mechanical elastic-plastic analysis model with an air bag folding and inflating model;
and establishing a water area model, and performing fluid-solid coupling model analysis and airbag deployment analysis.
Preferably, the establishing of the full-mechanical elastic-plastic analysis model comprises the following steps:
establishing a full-machine simplified model according to a full-machine structure main force transmission path; the metal frame beam structure is simulated by a shell and beam unit, and the composite web and skin structure is simulated by a shell unit;
and respectively determining corresponding material constitutive models for the characteristics and failure modes of metal materials, composite materials and honeycomb materials, and endowing corresponding attributes to all parts of the whole machine.
Preferably, the finite element analysis of the whole machine structure adopts a kinetic equation:
Figure BDA0003364632770000021
wherein, the structural damping C is very small and can be ignored;
verifying and correcting the effectiveness of the analysis of the main force transmission structure path based on the static test result to obtain a relatively real rigidity matrix K;
and verifying and correcting the effectiveness of the main mass distribution based on the dynamic characteristic test result, and further acquiring and verifying a mass stiffness matrix M and a stiffness matrix K.
Preferably, the creating of the balloon fold and inflation model comprises:
establishing an air bag analysis model according to the structure of the air bag; wherein, according to the stress characteristics of the air bag, a membrane unit is adopted for simulation;
according to the air bag folding mode, the air bag is folded by adopting a folding module, and is loaded into a floating barrel cabin structure for unfolding analysis and test;
acquiring the inflating and unfolding time of the air bag according to an air bag inflating test, performing inflation simulation on a single folded air bag, and adjusting an air bag inflating curve to obtain the unfolding time same as the test;
the mass flow curve of the air bag inflation considers a trapezoidal curve, and the total gas quantity can be calculated according to the final pressure, the gas component and the air bag unfolding volume of the air bag and a gas state equation:
Figure BDA0003364632770000022
where P is the gas pressure, V is the gas volume, m is the gas mass, R is the universal gas constant, T is the temperature, and μ is the molar mass of the gas.
Preferably, said assembling said full-mechanical elasto-plastic analysis model with an airbag folding and inflation model comprises:
according to the stress characteristics of the air bag bandage, a shell unit is adopted to simulate the air bag bandage;
and connecting and assembling the full-machine elastic-plastic analysis model and the airbag folding and inflating model by establishing a rotating shaft JOI NT unit to realize load transfer on grid nodes.
Preferably, the establishing a model of a water area includes:
establishing a water area model according to the range of the water-landing area; wherein, the water body adopts the simulation of smooth particle fluid dynamics unit.
Preferably, the establishing a water area model further includes:
based on the numerical wave-making method theory, a push plate wave-making method and a dynamic boundary wave-making method are adopted to generate a corresponding sea condition model;
and according to the result of the water test, performing parameter optimization correction by taking result precision and model calculation amount as optimization targets and taking the particle grid size, the particle smooth length, the artificial viscosity coefficient and the damping coefficient as optimization variables to obtain a parameter model with high precision and high operation efficiency.
Preferably, the fluid-solid coupling model analysis and the airbag deployment analysis include:
analyzing the response of deformation and damage of the machine body structure in the process of water-catching to obtain the structure strain response time course, the machine body motion attitude and the overload time course;
and analyzing the stress of the air bag and the connection load time history of the air bag bandage in the air bag unfolding process.
The invention has the beneficial technical effects that:
according to the method, the water-landing load of the airbag deployment condition after the helicopter lands water can be predicted during model design, analysis basis is provided for design of the emergency airbag, the connecting structure of the emergency airbag and the structure of the helicopter body, the test times can be reduced, the design research and development cost and the research and development risk can be reduced, and meanwhile, important support can be provided for establishing a water forced landing program and obtaining evidence for seaworthiness of the helicopter through the analysis method.
Drawings
FIG. 1 is a flow chart provided by an embodiment of the present invention;
FIG. 2 is a typical mass flow curve for an air bag provided by an embodiment of the present invention;
FIG. 3 is a schematic diagram of sea state wave generation provided by the practice of the present invention;
FIG. 4 is a schematic view of an assembly model of a helicopter provided by the practice of the present invention;
wherein: 1-full-machine elastic-plastic analysis model, 2-air bag folding and inflating model and 3-water area model.
Detailed Description
The invention provides an airbag inflation and deployment analysis method after water immersion of a helicopter based on numerical simulation and tests, which is characterized in that a large and effective numerical simulation model is established by combining a Finite Element Method (FEM), a uniform pressure method (UP) and a smooth particle fluid dynamics method (SPH), and the problem of deployment analysis after water immersion of the airbag of the helicopter is solved by combining test correction and verification, and belongs to the innovation of analysis methods.
The invention relates to a helicopter airbag inflation and deployment analysis method after water landing, which analyzes the dynamic deployment influence of an airbag in the water landing process by establishing a full-machine structure model and an airbag folding model, combining the full-machine structure and the airbag model and finishing the water landing analysis in a combined state, and obtains the load analysis of a machine body and the airbag and the structural damage condition under the condition that the helicopter airbag is deployed after water landing, and the method mainly comprises the following steps:
(1) and (3) establishing a full-mechanical elastic-plastic analysis model, wherein a Finite Element Method (FEM) is adopted as an organism structure analysis method.
a) And establishing a full-machine simplified model according to a full-machine structure main force transmission path, wherein the metal frame beam structure is simulated through a shell unit and a beam unit, and the composite web plate and the skin structure are simulated through the shell unit.
b) And respectively determining corresponding material constitutive models aiming at typical material characteristics and failure modes of metal materials, composite materials and honeycomb materials, and endowing corresponding attributes to all parts of the whole machine.
c) The finite element analysis of the organism structure adopts a kinetic equation:
Figure BDA0003364632770000041
the structural damping is small and can be ignored, and the validity of the path analysis of the main force transmission structure is verified and corrected based on the static test result to obtain a relatively real rigidity matrix K; and verifying and correcting the effectiveness of the main mass distribution based on the dynamic characteristic test result, and further acquiring and verifying a mass rigidity matrix M and a rigidity matrix K.
(2) And (3) establishing an air bag folding and inflating model, wherein an air bag analysis method adopts a uniform pressure method (UP).
a) And establishing an air bag analysis model according to the structure of the air bag, wherein the membrane unit is adopted for simulation according to the stress characteristics of the air bag.
b) And (3) according to the folding mode of the air bag, folding the air bag by adopting a folding module, loading the air bag into a floating barrel cabin structure, and performing unfolding analysis test.
c) And acquiring the inflating and unfolding time of the air bag according to the air bag inflating test, performing inflation simulation on a single folded air bag, and adjusting an air bag inflating curve to obtain the unfolding time same as the test. The air bag inflation mass flow curve considers a trapezoidal curve, and the total gas quantity can be calculated according to the final pressure of the buoy, the gas component and the air bag unfolding volume and a gas state equation:
Figure BDA0003364632770000042
(3) assembly of body and air bag model
a) According to the stress characteristics of the air bag bandage, the shell unit is adopted for simulation.
b) And connecting and assembling the engine body and the air bag model by establishing a rotating shaft JOINT unit to realize load transfer on the grid nodes.
(4) Establishing a water area model, wherein a water body analysis method adopts a Smooth Particle Hydrodynamics (SPH) method.
a) Analyzing the range of the waterlogging area, establishing a water area model, simulating the water body by adopting an SPH unit, and adopting a Monaghan state equation:
p＝p0+B((ρ/ρ0)r-1)
b) based on the numerical wave-making method theory, a push plate wave-making method and a dynamic boundary wave-making method are adopted to generate a corresponding sea condition model, wherein a corresponding wave height wavelength ratio is determined according to the type of the rotorcraft, and a wave surface equation is obtained:
ξ＝Acos(x-wt)
and the particle equation of motion:
Figure BDA0003364632770000051
Figure BDA0003364632770000052
c) and (3) performing parameter optimization correction by using the result precision (overload, pressure and test result error value) R and the model calculated quantity T as optimization targets and using the particle grid size, the particle smooth length, the artificial viscosity coefficient, the damping coefficient and the like as optimization variables according to the model waterlogging test result to obtain a parameter model with higher precision and higher operation efficiency.
(5) Fluid-solid coupling model analysis and airbag deployment analysis.
a) And analyzing the responses of deformation, damage and the like of the machine body structure in the water-catching process to obtain the structural strain response time history, the machine body motion attitude and the overload time history.
b) And analyzing the stress of the air bag and the connection load time history of the air bag bandage in the air bag unfolding process.
An example application of the present invention is illustrated in FIGS. 1-4:
the airbag deployment analysis method is used for carrying out airbag deployment analysis on the helicopter after the helicopter is watered.
(1) Simplifying a full-machine body model, and setting materials and attributes, wherein according to the mechanical characteristics of the adopted materials, the metal adopts an elastic-plastic material model with failure, the composite material adopts a multilayer anisotropic composite material model, and the failure mode adopts the classic Tsai-Wu rule; balancing the mass and the inertia according to the mass and the inertia of the whole machine; and refining the grid size on the basis of a static model and a dynamic model (verified by tests) to establish an impact dynamic model.
(2) Simplifying and characterizing the air bag, and establishing an air bag model; folding the air bag to complete the installation of the air bag in the floating barrel cabin; the air bag is inflated by liquid helium, the pressure is 20KPa, the temperature of the gas in the air bag is basically at the normal temperature level (294K, 21 ℃), and the inflated mass flow curve of the air bag is corrected and adjusted according to the test inflation and deployment time of 5 s.
(3) And assembling the body model and the air bag model according to the method.
(4) Establishing a water area model, and simulating by adopting SPH particles; numerical wave generation is carried out by combining a push plate wave generation method and a dynamic boundary wave generation method, according to the fact that the helicopter type is an A-type rotor craft, the ratio of the wave height to the wave length is 1:12.5, the maximum wave height under 5-level sea conditions is 4-6.4 m, and the wave surface equation is obtained through calculation:
Figure BDA0003364632770000061
obtain the corresponding particle velocity of
Figure BDA0003364632770000062
Figure BDA0003364632770000063
And according to the wave surface equation and the particle velocity, finishing the setting of the relevant boundary conditions and finishing the wave generation.
(5) Establishing a fluid-solid coupling analysis model to realize the coupling of an organism elastic-plastic model, an air bag folding model and a water body model; the body, air bag and other water-absorbing responses are analyzed.
The core point of the invention is as follows:
1. the method has the advantages that the full-helicopter structural analysis model is established, the influence of full-helicopter elastic-plastic deformation is considered, the coupling effect of the structure and the fluid in the water landing process of the helicopter can be truly reflected, and the coupling effect between the water body and the airframe structure under the sea condition is considered.
2. And decomposing an analysis object, and implementing corresponding effective tests for different purposes to correct and verify the model so as to ensure the effectiveness of the model and analysis.
3. The influence analysis of airbag folding, inflation and unfolding is considered in the water landing process of the helicopter, and the application of various numerical analysis methods (FEM, UP and SPH) in large-scale engineering problems is realized.

Claims (8)

1. A method for analyzing the inflation and deployment of an airbag after water attack in a helicopter, the method comprising:
establishing a full-mechanical elastic-plastic analysis model, and establishing an air bag folding and inflating model;
assembling the full-mechanical elastic-plastic analysis model with an air bag folding and inflating model;
and establishing a water area model, and performing fluid-solid coupling model analysis and airbag deployment analysis.
2. The analytical method of claim 1, wherein the establishing a full-mechanical elasto-plastic analytical model comprises:
establishing a full-machine simplified model according to a full-machine structure main force transmission path; the metal frame beam structure is simulated by a shell and beam unit, and the composite web and skin structure is simulated by a shell unit;
and respectively determining corresponding material constitutive models for the characteristics and failure modes of the metal material, the composite material and the honeycomb material, and endowing corresponding attributes to all parts of the whole machine.
3. The method of claim 2, wherein the full-machine structural finite element analysis uses the kinetic equation:
Figure FDA0003364632760000011
wherein, the structural damping C is very small and can be ignored;
verifying and correcting the effectiveness of the analysis of the main force transmission structure path based on the static test result to obtain a relatively real rigidity matrix K;
and verifying and correcting the effectiveness of the main mass distribution based on the dynamic characteristic test result, and further acquiring and verifying a mass stiffness matrix M and a stiffness matrix K.
4. The analytical method of claim 3, wherein the modeling of the balloon fold and inflation comprises:
establishing an air bag analysis model according to the structure of the air bag; wherein, according to the stress characteristics of the air bag, a membrane unit is adopted for simulation;
according to the air bag folding mode, the air bag is folded by adopting a folding module, and is loaded into a floating barrel cabin structure for unfolding analysis and test;
acquiring the air bag inflation unfolding time according to an air bag inflation test, performing inflation simulation on a single folded air bag, and adjusting an air bag inflation curve to obtain the same unfolding time as the test;
the mass flow curve of the air bag inflation considers a trapezoidal curve, and the total gas quantity can be calculated according to the final pressure, the gas component and the air bag unfolding volume of the air bag and a gas state equation:
Figure FDA0003364632760000021
where P is the gas pressure, V is the gas volume, m is the gas mass, R is the universal gas constant, T is the temperature, and μ is the molar mass of the gas.
5. The method of claim 4, wherein said assembling the full mechanical elasto-plastic analysis model with a balloon folding and inflation model comprises:
according to the stress characteristics of the air bag bandage, a shell unit is adopted to simulate the air bag bandage;
and connecting and assembling the full-machine elastic-plastic analysis model and the airbag folding and inflating model through establishing a rotating shaft JOINT unit to realize load transmission on grid nodes.
6. The method of claim 5, wherein the establishing a model of water comprises:
establishing a water area model according to the range of the water-landing area; wherein, the water body is simulated by adopting a smooth particle fluid dynamic unit.
7. The method of claim 6, wherein the establishing a model of a body of water further comprises:
based on the numerical wave-making method theory, a push plate wave-making method and a dynamic boundary wave-making method are adopted to generate a corresponding sea condition model;
and according to the result of the water test, performing parameter optimization correction by taking result precision and model calculation amount as optimization targets and taking the particle grid size, the particle smooth length, the artificial viscosity coefficient and the damping coefficient as optimization variables to obtain a parameter model with high precision and high operation efficiency.
8. The analytical method of claim 7, wherein the fluid-solid coupling model analysis and the airbag deployment analysis comprise:
analyzing the response of deformation and damage of the machine body structure in the process of water-catching to obtain the structure strain response time course, the machine body motion attitude and the overload time course;
and analyzing the stress of the air bag and the connection load time history of the air bag bandage in the air bag unfolding process.
CN202111391747.0A 2021-11-19 2021-11-19 Analysis method for airbag inflation and deployment after helicopter is watered Pending CN114239130A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115795644A (en) * 2022-10-08 2023-03-14 南京航空航天大学 Method for analyzing lateral stability of helicopter with flexible air bag based on equivalent pressure field

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115795644A (en) * 2022-10-08 2023-03-14 南京航空航天大学 Method for analyzing lateral stability of helicopter with flexible air bag based on equivalent pressure field

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