弹体结构热振动特性分析

【作者】 刘芹；

【导师】 任建亭；

【作者基本信息】 西北工业大学 ， 工程力学， 2004， 硕士

【摘要】 本文研究背景是弹体这类典型结构在高速飞行情况下，由于气动加热引起的高温对结构气动热弹性分析，包括热刚度、热振动问题的研究。重点研究弹体结构的热振动特性。 在计算气动加热及热振动方面，本论文提出了一些解决方法。首先，这篇论文介绍温度场和热应力场的有限元方法，建立了三维热传导模型计算有温度场产生的热应力，计算热应力时运用了一种转化思维：将温度处理为“温度载荷”，这样就能用弹性力学问题的处理方法来求解热应力。其次，将热应力作为结构的“面内力”，而面内力产生附加的几何刚度矩阵，改变了结构的刚度，影响了结构的固有频率。这一方法提高了热振动的分析效率；第三，简要的介绍了工程上计算气动熟的估算方法及热流密度计算的简化公式，在不考虑烧蚀以及质量引射等影响下，本文计算了几种飞行条件下驻点和非驻点区的热流密度分布，作为本论文算例的气动加热环境。最后，采用ANSYS程序分析了合金材料、复合材料的板、弹体结构的热振动特性。在不同的热载条件下，取得以下结论：升温导致的材料机械性能下降都会降低结构固有频率，而温度梯度产生的热应力可能降低也可能提高结构的固有频率；金属材料结构的固有频率受温度的影响要比复合材料结构的固有频率受温度的影响要明显。更多还原

【Abstract】 The aerothermoelastic analysis of missile structure includes the thermal stiffness, thermal vibration and thermal flutter analysis. This dissertation emphasizes on thermal vibration analysis of the aerial vehicle under aerodynamic heat condition.In this paper, some methods are developed to solve the relative problems on thermal vibration of the elastic structure. Firstly, the finite element method is used to analyze the temperature filed and thermal stress, and discuss the three-dimension thermal conductivity mode. The temperature effect which has been calculated is taken as ’thermal load’ forced on the body, then such thermal stress is settled as general elasticity mechanics question; Secondly, the thermal stress is taken as ’surface force’ forced on the body, and the new system stiffness is formed which include the extra stiffness matrix, then it changes the nature frequency of the structure. Thirdly, this dissertation briefly introduces the engineering estimation method of the aerodynamic heat and supplies the simplified formulas. Not considering the rejection, the ablation and some other factors, the author calculates the stagnation heat flux and the non-stagnation field heat flux distribution of some fly situation as the example aerodynamic heat environment. Finally, by using the ANSYS program, the thermal vibration characters of the plate and missile body structures with different materials is analyzed. The conclusions obtained as follows: firstly, the structure’s free frequency is decreased by the reduction of the mechanical property of the material with the increasing temperature; secondly the thermal stress produced by the temperature gradient may decrease or enlarge the structures natural frequency; thirdly, the variety of natural frequency of the alloy structures effected by the heat effect apparently higher than that of the composite material structures.更多还原