Influence of Thermal Loading on the Dynamic Response of Thin-Walled Structure under Thermo-Acoustic Loading

Abstract

Abstract. Future flight vehicle structures will encounter severe loading conditions, a combination of aerodynamic, thermal, acoustic and mechanical loads. Although the analysis methods for responses of structures under acoustic loads have been developed to some extent, but with thermal loads considered, the responses show fundamental differences, which complicate the analysis immensely. It was reported that hypersonic flight may give rise to surface temperature as high as o 3000 F and intense noise whose overall sound pressure level (OSPL) may reach 180dB. Thin-walled structures subjected to such loadings will exhibit nonlinear responses. Large temperature increments may cause thermal buckling, large thermal deflections and large thermal stresses superimposed on dynamic stresses, coupled with changes in material properties. Both the geometry change by thermal buckling and stiffness change by thermal stress account for the changes of natural frequencies and mode shapes. When the acoustic loading increases to a high enough level, the post-buckled structures will exhibit snap-through motion, a large amplitude nonlinear vibration between different equilibrium positions, which will introduce extra large mean stress. As a result, thermo-acoustic fatigue may be caused, which will reduce the structure's fatigue life dramatically. Therefore it is an urgent need to estimate the influences of thermal loads on the nonlinear response of structures.A numerical investigation of the influences of thermal loads on the dynamic response of thin-walled structure under thermo-acoustic loadings is implemented. With clamped-clamped thin flat plate selected, the response characteristics related to temperature are investigated by changing thermal loads. The thermal load is considered as constant both on the surface and across the thickness. The acoustic load is simulated using stationary Gaussian white noise. Firstly, a thermal buckling analysis is proceeded to obtain critical buckling temperatures, followed by modal analysis under different thermal loads. The pre-buckled and post-buckled mode frequencies and shapes are obtained. Then three types of snap-though motions are predicted: i) vibration around one post-buckled equilibrium position, ii) intermittent snap-through, and iii) persistent snap-through.The relations between thermal loads and the occurrence of snap-though is obtained together with results about the statistics characteristic of dynamic response and their relations with thermal loads, which include critical thermal buckling loads, natural frequencies and mode shapes, RMS response and snap-through frequency. Good agreements have been achieved with previous analytical solutions, which demonstrate the effectiveness and reliability of the method employed.

Dynamic Analysis of the Titanium Alloy Plate under Thermal-acoustic Loadings

“…Generally, the nonlinear vibration for thermal bucked structure is considered to calculate the thermal-acoustic response [7][8][9][10][11]. The response of the post thermal buckling plate can be seen as a shell problem, as the FEM is used to solve the shell problem.…”

Nonlinear Vibration Response Analysis and Experimental Verification of Thin-walled Structures to Thermal-acoustic Excitations

“…In China, Professor Sha Yun-dong and his coworkers have already done lots of research work about thermal-acoustic response and fatigue life of flight vehicles thin-walled structures, and published numbers of literatures [13][14][15][16][17][18]. For example, in Ref.…”

Dynamic Response of Thin-Walled Structures to Thermal Loadings and Random Acoustic Excitations

“…The experimental work on nonlinear responses of curved panels under acoustic excitations was done by Holehouse [7], Ng and White [8]. Nonlinear random response and fatigue life of thin-wall flat plates subjected to combined thermo-acoustic loads using PDE/Galerkin method and finite element method are investigated by Yundong Sha [9][10][11][12], and it is shown that snap-through motion will appear due to the critical thermal buckled characteristics under high intensity acoustic random loading, and the fatigue life will decrease with the increase of thermal load before the critical thermal buckled temperature. This paper wok on nonlinear response of thin-walled structures subjected to thermal loads with a linear temperature gradient and acoustic loads, the thermal buckled temperature and modal frequencies of thin-walled structures with liner temperature gradient are calculated, and the displacement and dynamic stress responses of thin-walled structures are obtained.…”