机翼结构耐久性/损伤容限与可靠性综合分析方法及应用软件研究
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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。
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.
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。
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.
引文
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[2] Rackwitz R, Fiessler B. Structural Reliability under Combined Random Load Sequences [J]. Computers and Structures, 1978, 9(5):489-494
[3] Thoft-christensen P, Murotsu Y. Application of Structural Systems Reliability Theory [M]. Springer-Verlag, 1986: 101-126
[4]冯元生,董聪.枚举结构主要失效模式的一种方法[J].航空学报, 1991,12(9): A37-42.
[5] Ditlevsen O. Narrow Reliability Bounds for Structural System [J]. Journal of Structural Mechanics, 1979, 7(4): 453-472
[6] Feng Y S. A Method for Computing Structural System Reliability with High Accuracy [J]. Computers and Structures, 1989, 33(1): 1-5
[7] Song B F. A Numerical Integration Method in Affine Space and A Method with High Accuracy for Computing Structural System Reliability [J]. Computer and Structures, 1992, 42(2): 255-262
[8]蔡荫林,周健生.结构系统失效概率的近似公式[J].航空学报,1992,13(3):A219-223
[9]安伟光,孙克淋,陈卫东等.随机结构系统基于可靠性的优化设计[J].应用数学和力学,2005,26(10):1175-1182
[10]李洪双,吕震宙,岳珠峰.结构可靠性分析的支持向量机方法[J].应用数学和力学,2006,27(10): 1135-1143
[11] Gayton N, Bourinet J M, Lemaire M. CQ2RS: A New Statistical Approach to the Response Surface Method for Reliability Analysis [J]. Structural Safety, 2003, 25(1): 99-121
[12] Hansson M, Ellegaard P. System Reliability of Timber Trusses Based on Non-Linear Structural Modeling [J]. Materials and Structures, 2006, 39(6): 593-600
[13] Michael H S, Filip C F. Response Gradients for Nonlinear Beam-Column Elements under Large Displacements [J]. Journal of Structural Engineering, 2007, 133(2):155-165
[14] Florian A.Potra and Vlastimil Pták.Numerical Mathematic[DB/OL] .SpringerLink,1980:333-346
[15] Fawaz S A.Fatigue & Fracture of Engineering Materials & Structures[DB/OL].EBSCO,2003:280-290
[16] Manning S D, Yang J N.Guidelines for the analysis and design of durable aircraft structures[M].USAF DURABILITY DESIGN HANDBOOK,AD-A142424,1984:345-367
[17] Manning S D, Yang J N, Shinjuku M, Garver W R.Durability methods development, Summary Aircraft Flight Dynamics Lab[J].AFFDL-TR-79-3118, 1984:314-324
[18] Wang D Y.An Investigation of Initial Fatigue Quality[J].ASTMSTP761,1980:191-200
[19] Yang J N.Statistical Estimation of Economic Life for Aircraft Structures.Proc.AIAA /ASME/ASCE/AHS, 79-0761, 1979:240-248
[20] Zhao L G, Busso E P, O'Dowd N P.Computational modeling of crack initiation in a single crystal super alloy under fatigue[J].Materials Science & Technology, 2007:184-187
[21] Chuang T J, Chu J L and Lee S . Diffusive crack growth at a biomaterial in interface[J].Journal of Applied Mechanics, 1996, 63:793-803
[22] Manning S D, Yang J N.USAF Durability Design Hand-Book[R].ADA 206286, 1989:1045-1049
[23] Yang J N, Donath R C.Statistical fatigue crack propagation in fastener holes under spectrum loading[J].Journal of Aircraft, 1983, 20(12):1028-1032
[24]管德,郦正能.飞机结构强度[M].北京航空航天大学出版社,北京:2005
[25]安伟光,赵维涛,安海.随机结构系统综合考虑静强度、刚度和疲劳等多失效模式的可靠性分析[J].中国科学G辑,2007,37(4):516-526
[26]屈玉池,晁祥林,陈琪.飞机结构完整性研究现状及发展方向[J].飞行力学,2005,23(3):9-12.
[27] R C Alderliesten, J J Homan. Fatigue and damage tolerance issues of Glare in aircraft structures [J]. International Journal of Fatigue, 2006, 28:1116- 1123
[28] Yi Tan, Guocai Wu, Sung S. Suh. Damage tolerance and durability of selectively stitched stiffened composite structures [J]. International Journal of Fatigue, 2008, 30:483-492
[29]上海社会科学院部门经济研究所统计理论研究室.统计工作手册[M].沈阳:辽宁人民出版社,1985:74-76
[30]徐灏.概率疲劳[M].沈阳:东北大学出版社,1994:426-431
[31]杨昨裕.含裂纹构件寿命预测的概率断裂力学方法[J].安徽:合肥工业大学学报,1996:45-49
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