Key Technology Of Dynamic Modeling Inhigh-Temperature Environment

Supersonic vehicles are always subjected to an extremely high surface temperature and large temperature gradients, which can seriously affect the modal characteristics of the structure. Usually, the finite element(FE) model analysis methods are employed to predict instability. Hence, accurately determining the modal characteristics of these structures at elevated temperatures is vital. This program develop a dynamic modeling method based on structure dynamic simulation, model updating, parameters identification, model validation,etc for structure under high temperature environment to obtain accurate model. The content is listed below:(1) The problem of temperature-dependent parameters identification has been researched firtstly in the steady-state temperature environment, and two methods, the whole domain method and the equivalent piecewise method based on metamodeling, are developed for the parameters identification problem. The former method could improve the search efficiency and circumvent difficulties of ill-posed problem by multi-objective optimization method and metamodels. In the latter method, the residuals between calculated and experimental results were constructed to identify equivalent parameters of each temperature section, and then regression analysis was used to identify the law of parameters varying with temperature. Finally, examples were given to demonstrate the effectiveness of these two methods.(2) The focus of this section is to find the key factors for the typical aerospace structure and connection structure from the aspect of bolt preload, thermal stress, material softening effect and connection part modeling by FE simulation. The results demonstrate that the natural vibration frequencies of the structures will decrease with the reduction of elastic modulus in the thermal environment; Thermal stresses have vital effects both on natural vibration frequencies and natural shapes, and in some cases, it will lead natural vibration frequencies of structure to increase, and decrease in other cases; In addition, researcher should choose reasonable modeling approaches according to the object of study, since the modeling method has a significant impact on the dynamic characteristics of connection structure in thermal environment.(3) The problem of dynamic modeling and model updating in a thermal environment are presented. By employing the hierarchical method, we decompose the problem into temperature field modeling and dynamic structural modeling, then the correctness has been validated by system optimization theory. Then an implementation process of mathematical model for this approach is given.The method is verified in an FE model of the wing with respect to the effect of the contact stiffness in the boundary. The results show that the developed hierarchical method is capable of identifying and updating the input parameters of the temperature field and the structure with high accuracy.(4) Since the connection parameters of complex engineering structure change greatly in thermal environment, the FE model parameters identification and model updating method are proposed based on FRFs for that problem. With this method, the identification method and model updating method based on FRFs are employed to verify the stiffness matrix of connection part as the first stage, and then a new damping model, whose characteristics vary with excitation frequency, is formulated to simulate the viscous damping of connection structures. The simulation results show that the FRFs simulated by updated FE model correlate very well with the test FRFs.(5) The stochastic model updating approach is formulated to deal with the model updating with uncertainty in thermal environment. Similarly, the stochastic model updating problem in thermal environment can be divided into temperature field model updating and dynamic structural model updating with uncertainty, and model uncertainty quantification and propagation method are presented from a theoretical perspective based on perturbation methods and metamodels, and then the specific implementation steps of the stochastic model updating approach are given. At last, the specific implementation steps of the stochastic model updating approach are applied to an experimental exercise. This research provides an efficient solution of Dynamics modeling of the structures in THE based on statistical ideas.