Discussion on the aeroelasticity of the large aspect ratio wing. Huang Liyao Chen Kuilin Hongdu Aviation Industry Group 650 discussed; analyzed the influence of structural nonlinearity on the aeroelasticity and flight load of the large aspect ratio wing; proposed a large aspect ratio The content of the aerodynamics of the wing is discussed, and its technical difficulties are pointed out.
Large aspect ratio wing structure nonlinear aeroelastic flight load 1 Introduction For more than a decade, high-altitude long-haul aircraft have gained worldwide attention. Due to their high altitude and long-haul performance requirements, such aircraft are particularly large. Compared with the aspect ratio, the large aspect ratio wing has an aspect ratio of up to 35, the structure weight is lightly extended to lkgm, and the flexible large static elastic deformation can reach 25 exhibition length.
The structural analysis of the aircraft with large aspect ratio and high compliance is a large displacement problem under the condition of small strain. It is a typical geometric nonlinear condition of the structure. Even with the traditional analysis method, the aerodynamic flight of the wing can be flexibly Dynamic characteristics have significant effects, but these studies do not consider the geometric nonlinear effects caused by large deformation of the structure, so it is necessary to study the aeroelasticity of large aspect ratio wings.
2 Development Status at Home and Abroad In recent years, the article by American Patil.MJ proposed the nonlinear aeroelastic and nonlinear flight dynamics of high-altitude long-time aircraft, and studied the geometric nonlinearity of structure and aerodynamics. The importance of aeroelastic behavior over the wing.
Due to the large flexibility of the large aspect ratio wing, the foreign direct research on the structural design of the aircraft uses composite materials with light weight, high strength, high stiffness and insensitivity to fatigue. According to relevant information, the aircraft currently being produced in foreign countries, in terms of structural weight, an average of about 13 structures are composite materials, the application of composite materials can average the aircraft weight loss 3 in the domestic, high-altitude long-haul aircraft military value and The economic significance has long been recognized by the relevant departments. Some aviation colleges and research institutes such as Beihang Xigong University are exploring and analyzing key technical questions.
Domestic technical research on composite structure has been more than 30 years old, and has been applied in various types of aircraft body structures such as strong front fuselage, integral oil tank, composite material, wing, å¤åˆ10 composite material, Composite material flat tail. In the design of the aircraft of our company, the 90 with the rudder structure in the vertical tail is a carbon fiber composite material, and only the metal material is mainly used as a coupling member. In the design, the finite element mathematical model of the composite material is used to design and analyze the aeroelastic optimization with the critical velocity of the flutter as the objective function. The angle between the direction of the composite laminate and the thickness of the laminate in the local region are changed to reduce the bending stiffness of the airfoil and to improve the torsional stiffness of the airfoil. The flutter value analysis of the aircraft ground resonance test wind tunnel flutter test and flight flutter test eliminates the aeroelastic instability of the 18-tailed directional snake structure with a full composite structure. So far, Hongdu has been able to produce a full-composite material with a rudder with 8 rudders equipped with the Air Force. The key technology of composite materials for lifting surfaces, namely aeroelastic tailoring, has also been applied.
3 The content of the study takes into account the influence of geometric nonlinearity caused by large deformation of the structure. In order to meet the needs of aeroelastic research and development of large flexible aircraft with large aspect ratio, it is necessary to carry out some research.
3.1 Large aspect ratio composite wing dynamic characteristics research Structural dynamic characteristics are the basis for performance analysis of aircraft dynamic stability flight control. For large aspect ratio wings, the wing will produce a large deformation under the action of the flight load, and the conventional small deformation assumption for structural dynamic characteristics analysis of the linear system is no longer applicable. The dynamic characteristics of nonlinear structures are significantly different from those of linear structures. For large aspect ratio wings, the dynamic characteristics of the wing after equilibrium in large deformation must be studied; the influence of geometric stiffness matrix on structural dynamic characteristics; geometric nonlinearity The influence of structure on flight dynamics; the structural mathematical model of composite finite element of structural nonlinearity is established, and the full-machine dynamics of composite structure with large aspect ratio layout is studied.
3.2 Large aspect ratio composite wing aeroelasticity study The aeroelasticity of composite wing is analyzed from the static aeroelastic phenomenon.
Huang Liyao Chen Kuilin's aeroelasticity of the chord ratio wing. Because the flight load and static aeroelastic characteristics of the composite wing of the large aspect ratio are mainly determined by the large deformation of the wing, it is necessary to have a large aspect ratio composite. The aerodynamic elastic divergence of the wing is manipulated. The effect of elastic deformation on the load distribution of the wing is studied.
For flutter analysis of large aspect ratio wings, the solution of unsteady aerodynamic forces is very important. A nonlinear unsteady aerodynamic calculation method is established to solve the unsteady aerodynamics of a large aspect ratio composite wing.
The aeroelastic equation of the wing with structural geometric nonlinearity is established. The critical flutter velocity is solved by frequency domain or time domain, and its vibration characteristics are analyzed.
Study on the influence of nonlinear damping of composite materials on the critical speed of wing flutter, research on the flight load of composite shaft wings with large aspect ratio considering the nonlinear characteristics of the structure of the large aspect ratio wing and the influence of static aeroelasticity It is necessary to carry out a research on the flight load.
3.3.1 Elasticity correction of aerodynamic derivative The static aeroelasticity of a large aspect ratio wing is very serious, which has a great influence on the aerodynamic characteristics of flight performance and load distribution. As an important raw data for load calculation, in order to obtain accurate flight motion parameters and maneuvering loads, the aerodynamic derivative should adopt elastically corrected wind tunnel test data.
3.3.2 Study of nonlinear flight load calculation The conventional flight load calculation is based on the linearized small disturbance equation. In most cases, the change of each main aerodynamic parameter is linear with the disturbance amount, even if there is a fairly strong disturbance in flight. In a limited time, the line speed and angular velocity of the aircraft are often a small amount of disturbance.
Considering the influence of the geometric nonlinearity caused by the large deformation of the large aspect ratio wing structure, it is a case of large disturbance. Therefore, from the dynamic equation around the centroid, the six-degree-of-freedom equation suitable for nonlinear theory is solved. According to the longitudinal and lateral lateral steering laws, the relevant aerodynamic parameters of the typical calculation points in the covered line are obtained with time.
The load distribution is calculated according to the severe load of the longitudinal maneuvering lateral lateral maneuver selected by the flight load. According to the nonlinear aerodynamic theory, the aerodynamic method based on the combination of the Shen 3 equation and the structural finite element is established. Load distribution for each flight attitude.
Considering the influence of aeroelastic deformation on the load distribution, the distributed load should be elastically corrected to obtain the aerodynamic parameters such as the distributed load of the elastic wing, which can be used for structural proofing.
3.4 Aeroelastic tailoring technology for composite wings with large aspect ratio composites The composite has the characteristics of high specific strength, high stiffness and insensitivity to fatigue. Aeroelastic tailoring controls the static and dynamic aerodynamic elasticity of the structure by changing the stiffness of the material. Deformation to achieve a design method that improves the stiffness distribution characteristics of the airfoil and improves the flight performance of the aircraft.
Flutter optimization and divergence optimization are the focus of aeroelastic tailoring research. It is based on the flutter speed divergence speed and the maneuvering inverse speed. Design the layout direction of the laminate thickness direction of the composite material, and carry out the self-touch of the wing stiffness optimization, the flying static and dynamic pneumatic bomb, and the stability.
3.5 Aerodynamic test of a large aspect ratio wing 3.5.1 Aeroelastic verification test of a large aspect ratio composite wing requires several aspects of work to design and manufacture a static ratio of a large aspect ratio composite wing size Wind tunnel model and wind tunnel test; design and manufacture wind tunnel flutter test model with similar power ratio of composite wing ratio and wind tunnel test; ground vibration mode for wind tunnel test model The test measures the inherent dynamic characteristics and compares them with each other, and uses the dynamic characteristics of the prototype to modify the test model. The large-diameter large Reynolds number wind tunnel test is carried out to determine the divergence aileron effect and the critical velocity of the flutter.
3.5.2 Pressure measurement test of large aspect ratio wing The purpose of load pressure measurement test is to provide direct and reliable raw data for the determination of aircraft load. At the same time, the load pressure test can also check the result of numerical calculation.
According to the ability of the domestic wind tunnel, the high and low speed pressure measurement model of the large display wing is designed according to the fixed ratio. When designing the pressure measurement profile, the influence of aeroelastic deformation should be considered, and the pressure measurement profile should be reasonably arranged in each pressure measurement section. Above, the position of the pressure measuring point is arranged according to the severe situation of the pressure change.
Through the high and low speed manometric test, the pressure distribution of the airflow around the model on the model surface is measured, and the lift and differential pressure resistance acting on the airfoil or the wing can be obtained; the pressure center position of each component is calculated; and the model surface is determined. The state of the layer.
4 Technical difficulties to be solved For the above research content, the following technical difficulties exist.
The mathematical model of the structure of the composite wing with a large aspect ratio is established. The structural mathematical model of the composite wing with large aspect ratio based on geometric nonlinearity is established to analyze the dynamic characteristics of the wing structure. Solve the vibration mode and natural frequency of the wing in the state of large deformation, because the mode and frequency are the basis for the aeroelastic analysis of the composite wing with large aspect ratio.
4.2 Unsteady aerodynamic calculation method under non-coplanar conditions The unsteady aerodynamics is the original data of flutter analysis. Due to the large deformation of the aircraft wing, the non-coplanar unsteady aerodynamic calculation is performed due to the airfoil network. The grids are no longer in a plane, and it is necessary to study the nonlinear non-coplanar unsteady aerodynamic calculation method.
4.3 Aeroelastic tailoring of large aspect ratio composite wing The conventional metal material can not meet the aeroelastic design requirements of large aspect ratio wings. The composite material is used for aeroelastic tailoring to realize the static aeroelastic optimization design. .
Model test study of composite wing with 44 large aspect ratios. Due to the characteristics of the large aspect ratio composite wing, the static and dynamic characteristics of the wing are simulated when the static aeroelastic test of the model is carried out. When the dynamic characteristics deviate from the dynamic characteristics of the prototype, it is necessary to study the model modification method.
4.5 Nonlinear flight wear and aerodynamic load distribution calculation software research considers the influence of geometric nonlinearity caused by large deformation of the structure. The research uses nonlinear mathematical model to solve the six-degree-of-freedom equation and studies the Eule1.NS equation and structural finite element. Combined with the calculation of the aerodynamic load distribution, the aerodynamic load distribution of each lifting surface is obtained.
5 Prospect Prediction and Analysis Through the study of aeroelasticity of large aspect ratio wings, static and dynamic aeroelastic analysis software and flight load calculation software for geometric nonlinear structures have been developed for large aspect ratio flexible composite wings. Key technologies such as structural dynamic characteristics analysis shorten the gap with advanced technology countries, promote multidisciplinary optimization, actively suppress the development of intelligent structures, improve the aeroelastic design level of aircraft, and lay a technical foundation for the development of new fighter aircraft and other projects. .
Under the premise of satisfying the aeroelastic stability of the aircraft, the composite material is used to reduce the weight of the wing structure compared with the full metal structure 3040, which will greatly improve the flight performance of the aircraft and increase the payload of the aircraft.
Train the team to cultivate the professional and technical backbone.
Promote the development of the aviation industry, enhance national defense strength, and safeguard national security.
The results of the research and development can be promoted in the aviation sector and in other industries to promote the progress and development of social industrial technology.
Received date 2002 laser processing technology laser is the light emitted by the atom during the amplification of the amplified radiation. Laser processing is a processing method in which a high-energy-density laser beam is used to illuminate a workpiece, and the material is heated and melted and gasified without mechanical contact. Since the laser beam can be focused to a power density of 10,710,012, a small spot of light, it can process almost all metal and non-metal materials, including a variety of hard high melting point materials. The application range of laser processing is very broad. At present, it has been widely used in the fields of mechatronics, aerospace, steel, shipbuilding and military industries. For example, in the automotive industry, about half of the parts have been used or laser processing can be used. Turn down page 17
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