Analysis On The Nonlinear Response Of The Metal Plate Under Thermal-Acoustic Loading Based On Reduced-Order Method

Quantities of thin-walled structures are adopted in high-speed aircrafts in order to reduce the weight of structures and lower computing costs. During service, the high-speed aircrafts will burden complicated loadings such as mechanical loading, acoustic loading and thermal loading. And under this environment, thin-walled structures will generate a complicated stress-strain relationship, which will give rise to nonlinear response resulting from large deformation. The fatigue life of structures will be largely reduced when the responses are nonlinear. When we are designing the structures fatigue life, the nonlinear responses must be obtained firstly. As there are so many limitations and high computing costs of the classic calculation methods, the paper studies the feasibility of reduced-order method in computing the nonlinear responses.Firstly, the paper introduces the theoretical derivation process of reduced-order method systematically. As the nonlinear stiffness force components cannot be obtained directly from the commercial finite element software, the paper puts forward the indirect method to build the reduced-order model by calculating the nonlinear stiffness coefficients. The paper derives the way to determine the nonlinear stiffness coefficients. And finally, the flow chart of the system reduced-order method is formed.Secondly, the paper introduces the specific process of realizing the reduced-order method in detail, which includes the instruments required and the problems that need attention.Thirdly, the paper calculates the nonlinear stiffness coefficients of the certain simply supported thin-walled structure according to the theoretical derivation. And then the reduced-order model is built. In order to verify the coefficients are right and the reduced-order method is effective in calculating the nonlinear responses, the point force, the pressure and the sine concentrated force are applied successively to the model. After calculation, the results are compared with those obtain by NASTRAN. In this way, the conclusion that the reduced-order method is feasible in calculating nonlinear responses is drawn.Finally, the displacements of the thin-walled structure under thermal-acoustic loading are gotten. And the variation along with temperature and SPL(Sound Pressure Level) are discussed.