【作者】 白金泽；

【导师】 孙秦；

【作者基本信息】 西北工业大学 ， 飞行器设计， 2003， 博士

【摘要】 随着航空器低空高速性能的发展，以及生态环境保护工程卓有成效的工作，飞行器结构鸟撞问题越来越引起人们的注意。在国内外鸟撞飞机风挡的研究中，鸟撞实验是最终、也是最有效的检验方法。现有的鸟撞实验数据分散严重，因而对风挡设计的指导作用较低，同时也无形中增加了实验的次数。 本文采用鸟撞实验、有限元数值模拟与神经网络相结合的方法研究鸟撞飞机风挡过程中风挡的响应以及鸟撞实验中撞击力与撞击参数的获得。本文构造了小波动态延时反馈神经网络，并详细分析了该网络的学习理论、学习方法、实现手段、网络结构、网络的推广能力以及提高网络训练效率的改进算法。本文提出的神经网络方法采用被撞击体上选定两位置点的应变-时间历程数据，即可高精度反演出撞击力-时间历程以及撞击点坐标及撞击动能等撞击参数。网络训练过程平稳、训练效率高，同时具有较高的抗干扰能力，完全可以满足鸟撞问题工程与理论研究要求。 在鸟撞正问题的研究中，本文详细推导了大变形粘弹性接触-碰撞有限元分析的基本理论、数值计算方法、求解过程、关键技术以及上述内容在LS-DYNA3D中的具体应用，算例考察了LS-DYNA3D在求解碰撞以及大变形问题上的计算精度，同时推导了线弹性材料、双线性弹塑性材料以及非线性粘弹性材料增量法迭代方程，编制了相应的用户自定义材料子程序，并进行了子程序验证。在此基础之上建立了鸟撞风挡有限元模型，通过考察该模型的单元类型、结构尺寸、材料模型、边界条件以及与实际鸟撞实验实测数据对比分析，认为本文建立的鸟撞风挡有限元模型正确可靠且计算精度较高，完全可以满足神经网络训练过程中正问题求解的要求，同时也完全可以作为工程中风挡设计分析模型使用。 本文系统总结了鸟撞实验的全部过程、主要仪器设备的工作原理与性能参数，分析了鸟撞实验动态数据采集系统中位移、应变与撞击压力传感器测量系统的测量范围、测量精度及其工作特点，提出了一种更适合鸟撞实验的撞击合力计算拟合方法：加权因子法，同时应用软件工程原理编制了“鸟撞实验计算西北工业大学博士论文机数据分析系统”(CAOABIE)，目前该软件己经在320厂鸟撞实验室以及!RAN一Esfahan空军鸟撞实验室中得到重点应用并获得好评。根据已有的研究成果，本文提出了鸟撞实验的改进方案，可以在满足实验测量要求的基础上简化实验过程，提高实验效率。更多还原

【Abstract】 With the development of the aircraft performance at low altitude and high speed, as well as the marked progress of eco-environmental protection, the issue of bird impact to aircraft has been concerned more and more. In the research of bird-impact to aircraft windshield, the experiment is always the ultimate and the most effective method. But the existing data of bird impact are highly disperse, so that they do less help for the design of windshield and also cost more to experimental work.In this thesis, a combined method of finite element numerical simulation with neural network is studied to obtain the dynamic response, the impetus forces and impact parameters of windshield during bird impact. The thesis presents A wavelet-dynamic-delay-feedback (WDDF) type of neural network and makes in-deep studies of the WDDF theoretical framework, learning theory and method, improved training effectiveness, power to extend, and technical implementation. The presented neural network takes strain-time data as input at two locations on the back of struck body, and gives highly precise outputs of the impact force-time data, impact kinetic energy and the coordinates of impact position. Also the network shows many advantages of high training efficiency, robustness and anti-jamming energy, as well as the extensive applicability to the academic study and practical requirement of bird impact issue.In the positive-issue research of bird impact, the thesis carefully explores the basic theories, finite element numerical method and key techniques of the solution process in LS-DYNA3D software system for contact-impact issue of viscoelastic bodies at large deformation. The well-chosen cases examine the accuracy of solutions in LS-DYNA3D for large deformation impact issues. Under the proof work, the incremental constitutive equation of bilinear and nonlinear viscoelastic materials are derived, coded and verified in LS-DYNA3D. On the basis of the above mentioned theoretical and case-computational work, the element types, structural dimensions, materials, boundary conditions and calculative effects of the finite element modeling (FEM) for bird-impact windshield are all carefully studied, and some practical experiments of bird-impact to windshield are made. It follows that the FEM established in this thesis is well agreed with the experimental results and also shows that it is a reliable and highly accurate model with satisfying the requirement of trainings to the WDDF neural network and engineering windshield design.The thesis systematically describes the detailed experiments of bird impact, including the major test principles and properties of the instruments used in the experimental system. The dynamic data of displacement, strain and impetus force acquired from the experimental collection system are also well analyzed formeasuring precision and errors. Based on the underlying work and experimental features, the thesis proposes a simple, practical and well accurate impetus resultant force fitting method, weighted factor fitting method. A line-off data processing software system for bird-impact experiment, named as CADABIE, is well designed under the principle of software engineering, and has been applied, with high praise, in bird-impact laboratory in the factory numbered 320 and Esfahan bird-impact laboratory of IRAN.According to all the research of this thesis, an improved and promising project of bird impact experiment combined with the WDDF neural network can be suggested, which will be high efficiency.更多还原