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高速飞行器面临着严酷的高温强噪声环境。温度载荷不仅使结构产生热应力,还会改变材料的物性参数,这使得薄壁结构在宽频噪声激励下具有复杂的运动形式,表现出强非线性特性,严重影响了结构的疲劳寿命。针对热声载荷对结构非线性特性的影响,建立了热声载荷下的非线性大挠度偏微分控制方程,对偏微分方程使用Galerkin法得到了模态坐标下的常微分方程组。计算了四边简支矩形钛合金板在不同温度和声压级(SPL)组合下的动态响应,得到了典型的热声响应运动形式,包括屈曲前的线性随机振动、屈曲后的跳变运动和围绕一个平衡位置的随机振动。通过分析方程中的恢复力项和响应的功率谱密度(PSD)随着温度和SPL的变化规律,对热声响应的非线性特性进行了研究。研究结果表明,热载荷和声载荷对响应非线性特性的影响方式不同:热载荷改变结构刚度特性曲线的形状,以临界屈曲状态的刚度为参照,屈曲前降低结构刚度,屈曲后增加结构刚度;噪声载荷使得结构工作在刚度曲线的不同区域,以不受载荷时的结构刚度为对照,强噪声载荷引起的持续跳变使得结构工作在硬化区域,间歇跳变时结构工作在软化区域。
High-speed aircraft are faced with harsh high temperature and strong noise environment. The temperature load not only causes the thermal stress of the structure, but also changes the physical parameters of the material, which makes the thin-walled structure have complex motion forms under wide-band noise excitation, showing strong nonlinear characteristics and seriously affecting the fatigue life of the structure. According to the influence of thermoacoustic load on the nonlinearity of the structure, a nonlinear large deflection partial differential governing equation under thermoacoustic load is established. For the partial differential equation, the differential equations are obtained by using Galerkin method. The dynamic responses of four simply supported rectangular titanium alloy plates under different combinations of temperature and sound pressure level (SPL) were calculated and the typical forms of thermoacoustic response were obtained, including linear random vibration before buckling, transitional buckling after buckling and Random vibration around a balanced position. The nonlinear characteristics of the thermoacoustic response are studied by analyzing the power term and the power spectral density (PSD) of the response as the temperature and SPL change. The results show that the influence of thermal load and acoustic load on the nonlinear response is different: the thermal load changes the shape of the structural stiffness curve, the stiffness of the critical buckling state is taken as a reference, the structural stiffness is reduced before buckling and the structural stiffness is increased after buckling; The noise load makes the structure work in different regions of the stiffness curve, taking the structural stiffness without load as a control, the continuous jump caused by the strong noise load makes the structure work in the hardening region and the structure works in the softening region in the intermittent jump.