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高超声速飞行器在巡航或再入过程中面临着严酷的气动力/热/噪声等复合环境,对热防护系统结构的完整性和耐久性提出了严峻挑战。热环境下的动特性是进行结构动态响应分析和优化设计的基础,本文对四周简支的飞行器热防护系统金属加筋壁板热动特性进行了分析,使用有限元软件NASTRAN建立分析模型,基于理论和有限元方法获得了壁板结构热屈曲临界温度,研究了热环境对固有振动频率和固有振型的影响,对比分析了均匀和非均匀温度场对结构模态的影响。结果表明,壁板结构在热环境下易发生屈曲,热模态分析中需考虑热屈曲、大位移变形等因素。同时证实热环境对壁板结构动特性影响较大,结构的固有振动频率随热环境下弹性模量的降低而减小,热应力对结构的固有振动频率和振型都有影响,当温度场分布改变时,固有振动频率的变化规律基本相同,固有振型则不同。
Hypersonic vehicles face harsh aerodynamic / thermal / noise conditions during cruise or reentry, posing a serious challenge to the integrity and durability of thermal protection systems. The dynamic characteristics under thermal environment are the basis of dynamic response analysis and optimization design. In this paper, the thermal characteristics of metal stiffened siding panels with thermal insulation system for simply supported aircraft are analyzed. The analytical model is established by using finite element software NASTRAN. Theory and finite element method, the critical temperature of thermal buckling of wall structure was obtained. The influence of thermal environment on natural frequency and natural mode was studied. The effect of uniform and inhomogeneous temperature field on structure modal was analyzed. The results show that the wall structure is prone to buckling under the thermal environment. The thermal modal analysis needs to consider such factors as thermal buckling and large displacement deformation. At the same time, it is confirmed that the thermal environment has a great influence on the dynamic characteristics of the wall structure. The natural frequency of the structure decreases with the decrease of the elastic modulus under the thermal environment. The thermal stress affects both the natural vibration frequency and the vibration mode of the structure. When the distribution is changed, the variation regularity of the natural vibration frequency is basically the same, while the natural vibration mode is different.