【作者】 张旭；

【导师】 赵维涛；

【作者基本信息】 沈阳航空工业学院 ， 飞行器设计， 2010， 硕士

【摘要】 随着对军机性能要求的不断提高,特别是对机动性和经济性要求的提高,现有的基于耐久性和损伤容限的可靠性设计体系已不能很好的满足要求。发展一种全新的设计概念,研究相应的分析方法,已经成为当前飞机结构设计迫切的需要。为了解决单独进行耐久性和损伤容限设计可能会造成的结构重量或检修成本增加的问题,本文在前人研究成果的基础上,主要进行了三个方面的研究工作:1.改进了耐久性/损伤容限综合设计的概念、设计目标并给出了综合设计分析流程。针对现有分析模型不能同时对结构进行耐久性和损伤容限综合分析的问题,以耐久性分析的概率断裂力学(PFMA)方法和概率损伤容限方法为基础,建立并改进耐久性/损伤容限综合分析模型。该模型是建立在结构原始疲劳质量(IFQ)的基础之上的,利用随机裂纹扩展公式,得到裂纹随机扩展时间t后的裂纹分布。2.建立基于TTCI服从三参数Weibull分布,双参数Weibull分布和对数正态分布的三种反推法的安全余量表达式,并求解可靠度随时间变化曲线。在求解方法上采用了一次二阶矩法,由该方法算出均值与标准差的比可直接得出可靠性指标,避免了由理论推导求解三重积分的繁琐,可以在初步设计阶段对结构进行估算。在求解出可靠度随时间变化曲线后,在指定的可靠性要求下分别利用耐久性分析方法和概率损伤容限方法预测出结构的经济寿命和裂纹扩展周期,采用改进结构设计等方法使两者接近相等,这可以作为结构优化的依据。3.采用面向对象的程序设计方法,利用Visual Basic语言将耐久性的几种方法,即耐久性分析的概率断裂力学方法、改进的裂纹萌生方法和确定性裂纹增长方法和耐久性/损伤容限综合模型编制成程序,在综合模型解法模块中除采用一次二阶矩法之外,又加入蒙特卡罗法,可以得到较精确的结果。本文改进了飞机结构耐久性和损伤容限设计思想和分析方法,其理论成果不仅为我国先进战斗机的设计研制提供了重要的技术支持,也为现役飞机结构寿命和安全的综合评定提供了新的方法,具有良好的应用前景。更多还原

【Abstract】 Along with the improving of the requirements for aircraft performance, especially the higher maneuverability and economic capability for the advanced fighter plane, the existing aircraft structure design system which based on durability analysis and damage tolerance design can’t meet all expectations very well. Designing with the durability and damage tolerance method independently tends to enhance the structural weight and its maintenance cost. Under this circumstance, the theory of combined design and analysis of durability and damage tolerance for aircraft structure is talent showing itself and provides novel approaches for the solution of above problem. So in this paper, based on the existed achievement of durability and damage tolerance, the investigation can mainly be described in three areas:Firstly, the conception and objectives of combined design and analysis for aircraft structure have been modified. The combined analysis model based on the durability analysis method PFMA and the probability damage tolerance analysis model is established to solve the problem that the existing model could not carry through the durability and damage tolerance analysis synchronously. The model is built on the basis of initial fatigue quality (IFQ) of structure. Using random crack propagation formula gets a crack random propagation distribution after time t.Secondly, building a safe margin expression based on the TTCI to obey the three-parameter Weibull distribution, two-parameter Weibull distribution and lognormal distribution, and solve the curves of reliability versus time. Methods used in solving are the first order second moment, the reliability index can be directly obtained calculated by this method through the mean and standard deviation and solving the complicated triple integral by theoretical derivation is avoided After solving reliability versus time curve, under the specified reliability requirements structure economic life and crack propagation cycles are predicted respectively by durability and damage tolerance. It makes both equal through improving the structure design and that could pave the way for structural optimization in the future. Thirdly, with object-oriented programming method, some durability methods and durability/damage tolerance integrated model, which are probability fracture mechanics of durability analysis、improved crack initiation method and deterministic crack growth approach and durability/damage tolerance integrated model have compiled into software by Visual Basic language. In the integrated model solution module, except of using the Losm method, the Monte Carlo method is joined, which can get more accurate results.This dissertation improves the idea of aircraft structural design and the durability/damage tolerance analysis methods. Its theoretical achievements not only offer technical support for the research and design of advanced aircraft, but also offer a new method to assess aircraft structural life and safety. It must have a good perspective.更多还原