【作者】 孙为民；

【导师】 童明波；

【作者基本信息】 南京航空航天大学 ， 飞行器设计， 2009， 博士

【摘要】 随着我国大型民用飞机研制项目的启动,开发设计新型机身结构是提高大型客机寿命、可靠性、经济性、安全性和舒适性的有效手段。因此迫切需要开展民用飞机机身结构设计方面的系统研究,其中包括对目前民机机身壁板结构进行剪切,轴压载荷的试验与结构强度分析,以及整机水上迫降计算分析。首先,进行了民机机身十六种构型组装壁板在剪切载荷下试验研究,得出壁板失效形式,破坏载荷以及许用剪流与桁条剖面积、框剖面积和蒙皮板厚的关系曲线。通过国外材料与国产材料的壁板试验结果比较对使用张力场法计算的壁板剪切许用力进行修正,修正后的壁板剪切应力许用值只有4种构型壁板的估算值略高于试验值,且偏差小于5%,满足工程使用要求。通过名义壁板厚度与实测壁板厚度的许用剪流计算对比发现壁板破坏剪流计算值十分相近,说明蒙皮厚度只要控制在合理的公差范围内,则蒙皮厚度的偏差对壁板剪切强度影响很小。其次,进行了民机机身十一种构型组装壁板在轴压载荷下试验研究,得出壁板失效形式和破坏载荷。在试验的基础上对三种工程算法进行对比评估,发现“Johnson抛物线法”对此类构型壁板计算结果与试验最为接近。建立了基于试验验证的壁板非线性有限元模型,进行了组装壁板截面尺寸敏感度分析,发现长桁的剖面积是壁板轴压破坏载荷主要影响因素,敏感度指标为44.2%,同时给出了该构型壁板精确的轴压载荷二次响应面多项式。通过等重量设计的整体壁板有限元计算发现,其破坏形式与组装壁板不同;整体壁板长桁没有明显的弯扭,最终蒙皮达到塑性屈曲应力发生壁板破坏;并且轴压破坏载荷相对组装壁板提高了18.4%。根据有限元计算结果对整体壁板的“Johnson抛物线法”中的蒙皮有效宽度取法进行定义。在试验设计的基础上,采用多岛遗传算法和序列二次规划算法对整体壁板结构尺寸进行了优化设计,优化后的壁板结构强度保持不变,重量减轻了8.8%,对整体壁板结构设计具有很好的参考价值。最后分别建立了某型飞机的刚体与弹性体水上迫降模型,通过对水体用光滑粒子流体动力学(SPH)无网格单元进行模拟,所得结果体现了水体飞溅、晃动对机体结构坠撞的影响。通过飞机水上迫降刚体模型计算,得到飞机在迫降过程中的运动轨迹和飞机各个部位的过载曲线,分析结果表明飞机起落架放下使迫降过程中整个机体产生横向摆动,增加了飞机横向不稳定性,因此最终确定了该型飞机最佳的水上迫降姿态为:起落架全收,襟翼全偏,最佳着水姿态角为7o。进行了民机机身乘客段的局部弹性体水上迫降模型计算,得到机身结构在水上坠撞过程中的冲击响应,校核了飞机在最大下沉速率情况下的机体结构完整性,为民机机身结构设计及适航认证提供了很好的参考依据。更多还原

【Abstract】 As the starting of commercial aircraft project, the development and application of high performance panel is one of effective ways to improve the life, reliability, economics, safety and comfortableness of the airplanes. Thus, the research of civil aircraft fuselage panel is necessary. The thesis includes the analysis and experiments of the present fuselage structures under shear load and axial compression load, and the numerical analysis of ditching.At first, the test results of failure modes, failure loads and the curves of allowable shear flow with area of the stringers, frames and the thickness of the skin were implemented by 16 configurations of build-up panels under the shear loads. In the comparison between the test results using different panels made of imported materials and domestic materials respectively, the calculated stress has been modified. There are only four estimation values of panel configurations are higher than the test results under the corrected allowable shear flows. Moreover, the errors are less than 5% and meet the requirement of engineering. According to the comparison between the calculation of nominal panel thickness and measured thickness, it can be found that the panel failure shear flows are close. This indicates that once the error is controlled within the tolerance range, the deviation of the skin thickness would not affect the panel shear strength.Secondly, the experiments of 11 build-up panels under the axial compression loads have been carried out. And then the results of the failure modes and failure loads have been obtained. On the other hand, the assessments of three approximate computational methods have been implemented. Based on the experiment, it is found that Johnson’s Parabola Method is the closest to test results. Nonlinear finite element models on the test validation have been built up. Through the analysis of the section dimensions sensitivity, it reveals that the main effect of axial compression load is the cross-sectional area of the stringer, whose sensitivity coefficient is 44.2%. And the panel precise response surface polynomial of the axial compression is given. According to the finite element calculation on the equal weight design, the failure mode is different from the build-up panel: the integral panel stringers do not show obviously crankle and reaches the plastic yield stress of the skin till damaged at last; moreover, the maximum of axial compression is improved 18.4% compared with the build-up panel. According to the finite element calculation result, the valid skin width in the Johnson’s Parabola Method for the integral panel has been defined. Then, the integral structure has been optimized by using the Multi-Island Genetic Algorithm and Sequential Quadratic Programming. Compared to the initial design, the weight after optimization is reduced by 8.8% and the strength remains same, which is very valuable for the design of integral panel.At last, the rigid and elastic models of an aircraft ditching have been built respectively. Through the SPH unit simulation in a meshless method, the results both show effects of the splashing and sloshing flow to the airframe structure strike. Base on the simulation of ditching rigid model, it has been obtained the ditching track and deceleration-time curves of each part of the aircraft. The analysis result indicates that the release of the landing gears could cause transverse oscillation and increase the transverse instability, therefore, the best ditching attitude is identified as: landing gears retraction, flap deflection and the attitude angle to dipping water is 7°. On the other hand, the calculation of a partial elastic body in the passenger section is carried out, which obtains that the response of airframe structure under water strike, and also checks the structure integrity under the maximum sinking velocity of the aircraft. All the tests and calculations above provide a valuable reference to the design of fuselage and airworthiness verification.更多还原