Frequency Response Analysis And Optimization Of Cellular Topology

In modern aerospace field, whether the aircraft can keep stable condition has been a widespread concern. The development trend of modern aircraft is to have adaptive wing in order to achieve self-deformation in an manageable environment——tension and compression in the plane range, bending and twist in the space, and so on--to adapt to different air environmental changes. The research about the adaptive wing focuses on the development of the super-elastic skin, which not only tries to make the outer surface of the wing become streamlined form, and can take the local aerodynamic load of the perpendicular to the surface at the same time, but also can achieve a variety of independent deformation described above through the intelligent control. At present, a variety of studies have been made about the super-elastic skin which has a larger load capacity and super-elastic deformation capacity. But they cannot meet the demands of aircrafts in the future in terms of the amount of deformation, stiffness, strength and vibration resistance, etc. Based on the National Nature Fund Project "Research on the optimum design and deformation mechanism of the super-elastic skin"(Project Number:51075380), honeycomb structure, the research hotpot at present, is applied in the research of the super-elastic skin in this paper. Faced with the weakness of the skin structure and the characteristics of various honeycomb structure, the negative poisson’s ratio hexagonal honeycomb core structure is adopted and the supple honeycomb core layout is used in the study, aiming to design the wing skin structure with universality and adaptive control, through taking the lightweight, high strength structure, high deformation ability, strong vibration resistance, and so on, into consideration. The design focus of the airfoil skin is the negative poisson’s ratio hexagonal honeycomb core structure. And the performance of its structure becomes the primary and the most important issue of the development of the super-elastic skin.The paper takes the second order negative poisson’s ratio cellular topology as the research object, and takes the frequency response characteristics as the research target. The response surface method and the second expression are used to construct the approximate function relation between the research object and the target. The weighted coefficient method, as well as the genetic algorithm is adopted to optimize the first two order approximation frequency expressions. The16orthogonal test is designed to do the ANSYS frequency response analysis. The weighted coefficient method is took to set weighting factors for each target, changing the multi-objective optimization of the first two order natural frequency and the weight of the structure into the single-objective optimization. The genetic algorithms is adopted to realize the iteration and solving of the single-objective optimization. The examples turn out that the vibration resistance is greatly improved for the optimized cellular topology, and the weight of it is decreased significantly. This method is efficient and it provides theoretical support for the design of the super-elastic supple honeycomb skin. The paper mainly includes the following parts.1. It summarizes and explains the research status of the intelligent aircrafts, especially the adaptive wing, at home and abroad. And it introduces and analyzes the intelligent material and honeycomb structure which for the super-elastic skin’s development at the same time. Among them, the negative poisson’s ratio hexagonal honeycomb topology structure is the research focus of this paper. The research framework is expanded for the structure, and the research details are implemented, which lays the foundation of the design of super-elastic skin that based on the negative poisson’s ratio hexagonal honeycomb topology structure.2. The response surface method is applied to establish the model for the natural frequency of the cellular topology structure. The theory and advantages are explained for the response surface method. And the centered point is added in the response surface method of classical Mathematical model at the same time. Improvement of the response surface method is made as well. The model parameters are established for the honeycomb topology structure. Faced with the characteristics of the frequency response, the low-order natural frequency Mathematical model is established and the statistical evaluation of the response surface modeling based on the multiple correlation is founded also. Orthogonal test in the response surface method is analyzed and applied, and the basic process of Modeling—Test—Optimization is established.3. The ANSYS finite element simulation test is done and the low level cellular topology natural frequency mathematical model is established. Explanation of the finite element method and the ANSYS software operation are made. APDL language is used for the parametric modeling, data from the16orthogonal test is used to do the simulation test. The first four modal shapes and the natural frequency value are achieved. The low level natural frequency mathematical model based on the size parameter is deduced at last.4. Genetic algorithm is optimized and the former second-order natural frequency of the structure are improved. With the optimal set method, the former second-order natural frequency of multi-objective optimization model is changed into a single-objective optimization. The former second-order natural frequency of the topology structure is greatly improved finally and the combination of parameters in this mode is achieved at the same time.With the theoretical modeling, simulation analysis and optimization algorithm combined together, the research is of high reliability. Thus, it lays a solid foundation for the realization of the super-elastic honeycomb skin, and provides theoretical support for the study about the stability of the adaptive wing.