热环境对飞行器壁板结构动特性的影响

 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。

Effects of Thermal Environment on Dynamic Properties of Aerospace Vehicle Panel Structures

Hypersonic vehicles are exposed to a severe combination of aerodynamic, thermal and acoustic environments during cruise or re-entry flights, which presents a significant challenge for the integrity and the durability of thermal protection systems of aerospace vehicles. Dynamic properties of structures are the basis of dynamic response analysis and optimum design. Thermal dynamic properties of typical stiffened titanium panels with simply supported condition for aerospace vehicles are analyzed in this paper. A finite element model of panels is created using the software NASTRAN. The critical thermal buckling temperature of panels is solved using theoretical and finite element methods. Moreover, natural vibration frequencies and shapes which change with the increase of panel temperature are researched. Modal parameters of panel structures are compared between uniform and nonuniform temperature fileds. Results show that the thermal buckling of panel structures occurs easily in a thermal environment. Therefore, the thermal buckling and large deformation should be considered in thermal modal analysis. It is concluded that the thermal environment has an important effect on the dynamical properties of aerospace vehicle panel structures. The natural vibration frequencies of the panel structures will decrease with the reduction of elastic modulus in the thermal environment. Thermal stresses have many effects both on natural vibration frequencies and on natural vibration shapes. When temperature distribution is changed, the variations of natural vibration frequencies are approximately the same, but the variations of natural vibration shapes are different.