【作者】 陈滨琦；

【导师】 曾建江；

【作者基本信息】 南京航空航天大学 ， 飞行器设计， 2010， 硕士

【摘要】 疲劳寿命是飞机结构优化的一个重要目标,飞机质量又直接影响着飞机的各种性能。如何扩展抗疲劳优化的应用范围,提高优化的工作效率和优化质量,使优化设计尽可能不受变量及目标数量的限制,是亟待解决的一个重大问题。因此本文开展了基于DFR法的疲劳可靠性分析和结构细节抗疲劳优化两部分工作。首先,借鉴了前人的研究基础,对有限元分析中名义应力的求解提出了自己的观点:用有限元法进行名义应力求解时将周围节点的载荷转化到以钉传载荷方向为X向的局部坐标系上,以得到真实的名义应力。并且用VC++与Matlab进行混合编程,建立了与Nastran求解器关联的接口,编写了基于DFR法的疲劳可靠性寿命分析软件FEM-DFR。其次,对某型机前起落架舱进行了疲劳寿命分析,选定了载荷谱,建立前机身有限元模型进行总体应力分析,进而选定危险关键细节,进行细节有限元分析,利用FEM-DFR软件进行了疲劳可靠性分析,结果表明某型机前起落架舱满足疲劳设计要求,但是设计偏于保守。第三,建立了抗疲劳优化平台AFOP,对Patran/Nastran、FEM-DFR和iSIGHT三个软件进行了集成,编写了9个数据接口以实现软件之间的数据传递,提高了优化效率,减少不必要的重复操作,达到高效、便捷的目的。最后,对作动筒支座细节进行了结构质量、最大Von Mises应力和疲劳寿命的多目标优化,并做了敏感度分析。优化结果表明:在Von Mises应力基本保持不变的情况下,含加强板的最优解减重20.17%,不含加强板的最优解减重22.2%。更多还原

【Abstract】 The performances of an aircraft are directly involved by its weight, at the same time the fatigue life has also become a significant objective in structural optimization. These are important problems needed to be settled, such as extending its application range, enhancing its efficiency and quality, and making the optimization depending on the variable and target numbers as little as possible. Fatigue reliability analyses based on DFR method and anti-fatigue optimization of detail structures are presented in this paper.Firstly, based on original research a new method to calculate the nominal stress is raised. In order to get the true nominal stress, the loads of the nodes around the pin node are transformed into the local coordinate whose X-direction is the direction of pin-load. Then coupling VC++ with MATLAB, setting an interface with NASTRAN, a fatigue reliability calculating software, which termed FEM-DFR by author, is given. It can automatically search the load distribution around the pin, calculate the nominal stress, and analyze the fatigue reliability.Secondly, the nose undercarriage bay is analyzed, including selecting analysis load spectrum, establishing an FEM model to analyze general stress, though the result selecting critical dangerous detail and analyzing it, at last, solving fatigue reliability at FEM-DFR. According to the result, the anti-fatigue design of undercarriage bay of an aircraft is appropriate, but tending to conservative. Thirdly, a platform named AFOP is settled, integrating PATRAN/NASTRAN, FEM-DFR and iSIGHT. There are 9 data interfaces to transform the data among the software, which improve the optimization efficient, cut down the repeated work, to make the software efficient and convenient.At last, a multi-objective optimization including structural mass, maximum Von Mises stress and fatigue life is presented for the detail bracket of actuator cylinder, including its sensitivity. The optimization result indicates that in the situation that Von Mises stress keeps a constant, the optimum of the bracket reinforced by a plate makes the mass reduce 20.17%, while the one without the plate can reduce the mass 22.2%.更多还原