Permissible stresses for transport aircraft structures according to fatigue and damage tolerance criteria

Permissible stresses for wing and fuselage structures are given for passenger (transport) aircraft according to fatigue, fail-safe, and damage tolerance criteria. Permissible fatigue stresses are determined for securing the lifetime of modern aircraft. Permissible stresses according to fail-safe criteria are determined for securing the normalized residual strength of the structure with regulated damages. Permissible stresses according to the damage tolerance criterion are determined for securing the economic efficiency of the maintenance checkup periodicity.     

A way to secure operational safety for an aircraft structure according to a strength criterion

Fatigue and survivability requirements for transport aircraft structures formulated in the US Federal Aviation Regulations FAR 25.571, Advisory Circular AC 20-107B and in the Russian Aviation Regulations AR 25.571 are analyzed. Information on the lifetime of foreign and Russian aircraft, those new and those operating for a long time, is presented. Strength, fatigue and crack growth resistances of foreign and Russian improved aluminum alloys are compared. Ways for applying composite materials in the structure of foreign and Russian aircraft are illustrated. It is shown that aluminum and composite materials fail in different ways.     

分层缺陷对复合材料结构疲劳寿命影响研究

介绍一种新研制的含缺陷复合材料压缩试验装置 ,并采用压缩疲劳试验方法研究中央分层和边缘分层缺陷对飞机复合材料结构疲劳寿命的影响。研究结果表明 ,试件疲劳破坏的起始位置与预制缺陷位置一致。含分层缺陷复合材料结构的疲劳寿命不仅与缺陷尺寸 ,而且与缺陷位置有关。该研究结果为制定生产和使用过程中缺陷或损伤的控制标准提供重要依据     

紧固孔原始疲劳质量控制与制孔技术研究

对飞机结构耐久性和安全性有重要影响的紧固孔原始疲劳质量进行了分析,建立了制孔技术与紧固孔原始疲劳质量的内在联系。提出用满足９５％要求的当量初始裂纹尺寸ａｉ值来定量描述紧固孔原始疲劳质量。给出通过紧固孔原始疲劳质量评定和符合性检查来选择或验证制孔技术的方法。     

飞机结构疲劳损伤的工程类比法

重点论述工程类比法在基于飞参数据进行飞机结构疲劳损伤计算中的应用.通过对两种机型、60多架飞机30000多飞行小时数据的计算分析,提出结构疲劳损伤值(取对数后)与材料常数m成线性关系的观点.用工程类比法计算出的多架飞机累计损伤结果,其相对轻重水平,基本不随m值的不同而改变.在比较多架飞机疲劳损伤情况时,可以排除材料常数m的影响.     

老龄飞机MSD结构剩余强度评定技术

讨论了多部位损伤(MSD)对结构安全性的影响和MSD结构安全性评定所赋予的新内容。通过等距等长共线孔孔边裂纹平板和等距等长共线裂纹平板的剩余强度计算,研究分析了MSD结构剩余强度评定中裂纹之间的相互作用、材料塑性、裂纹连通准则和破坏准则等关键技术。     

飞机结构经济寿命可靠性设计与评定

从经济性和维修性的要求出发,保证飞机结构在使用寿命期间内,在规定的工作条件下完成规定的功能后,因疲劳断裂失效的可能性(失效概率)减至最低程度。为了满足经济寿命的要求,科学地确定飞机结构的目标设计寿命,将安全寿命设计与损伤容限设计有机结合,以此建立飞机结构经济寿命耐久性模型,合理地制定检修周期,既能做到充分挖掘飞机结构潜力,又能保障个体飞机结构安全。将飞机结构安全寿命可靠性设计发展为飞机结构经济寿命可靠性设计,为飞机长寿命、高可靠性和低成本的目标研制构建了理论框架。     

长航时飞行器多元件随机失效模型与损伤评估

为评估飞机服役过程中出现的多元件损伤，根据元件疲劳特性建立了随机失效模型，基于元件失效寿命计算广布疲劳损伤平均行为，从而确定飞机检查修理时刻。通过五隔框机身段算例验证所提模型的有效性，研究模拟次数及概率分布模型对多元件损伤结构检修时间的影响。根据七隔框机身段疲劳试验结果进行多元件损伤评估，给出结构检查修理时刻。结果表明，评估结果与算例数据吻合良好，正态回归模型能够更好地模拟结构失效特性。     

考虑环境腐蚀效应影响的飞机结构日历使用寿命修正方法

基于皮劳额定值ＤＦＲ与大气暴露时间Ｔ之间的关系式推导出了环境腐蚀造成的结构波劳寿命与日历使用寿命之间的关系式,从而给出了结合线笥螺积损伤理论的一种考虑环境蚀效应影响的飞机结构日历使用寿命的估算方法。     

用代表中值损伤的"飞行大纲"编排飞机载荷谱的方法

通过对飞机使用情况的统计分析，在“用中值寿命(损伤)代表起落编制飞机载荷谱方法”的基础上，提出用代表中值损伤的飞机实用“飞行大纲”来编排各代表起落的编谱方法。按这种方法编出的载荷谱，能真实地反映整个机群的平均使用情况。     

Fatigue and service lives of airplane structures

The modern state of the fatigue and service life periods of the structures of passenger and cargo aircraft is presented. Information on the ICAF 2009 conference and symposium is provided.     

环境条件下军用飞机使用寿命研究

介绍了环境条件下飞机结构损伤的模式及其描述方法,讨论了飞机结构使用寿命的影响因素,回顾了国内外研究现状。通过引入飞行强度参量,研究了军用飞机使用寿命的评定技术,为合理制订飞行计划、充分发挥军用飞机的使用功效、保障飞行安全提供了理论基础。     

增强飞机损伤容限的设计一体化探讨

为了提高未来军用飞机的作战效率,在设计的早期就要考虑到飞机的损伤容限而对飞机进行一体化设计。本文讨论了飞机生存力的设计要求,以及战斗损伤容限和具有很强生存能力飞机的设计方法。     

飞机结构强度试验中应变量三线测量法的应用

全尺寸飞机结构的静力和疲劳试验中,应变数据作为最主要的试验数据,其精确度直接影响到飞机结构的应力应变分析以及与理论计算的对比分析。给出了应变测量电桥三线测量法的理论依据,并通过计算对比分析了二线测量法与三线测量法的精度差异。     

结构损伤监测的研究现状与展望

为了从设计思想上保证结构具有良好的可监测性,使重要结构的安全运行确实得到保障,将损伤容限耐久性设计思想、现代智能测控技术、分布式数字信号处理技术和先进的在线故障诊断技术相结合,在总结相关学科领域研究进展的基础上,进行了多学科交叉和多方法、多技术的融合研究,提出了未来机械设备结构损伤监测的发展方向。     

The concept of safety of aircraft structures

This article deals with modern approaches to providing endurance strength, safe operating life, and durability of aircraft. The major survival criteria mentioned here are scheduled damages, fatigue fractures, inspection intervals in duplicated strength components, and the prevention of fatigue damages.     

腐蚀对新型高强度铝合金疲劳裂纹萌生机制及扩展行为的作用

根据编制的某机场环境加速试验谱,通过腐蚀试验模拟飞机服役过程中遭受的潮湿空气、盐雾、二氧化硫、酸雨和干/湿交变等严酷条件的侵蚀作用,采用飞机主承力结构新型高强度铝合金7B04-T74,制备单边缺口拉伸(Single edge notch tension, SENT)试样进行预腐蚀和疲劳试验,分析不同程度腐蚀损伤对疲劳裂纹萌生、裂纹扩展行为和疲劳寿命的影响,揭示腐蚀对裂纹萌生及扩展行为的作用机理。结果表明,在腐蚀初期,疲劳裂纹萌生源主要为单个蚀孔,裂纹扩展路径较为平直;随着腐蚀程度的加重,在多个蚀孔处同时萌生多条小疲劳裂纹,萌生疲劳裂纹的蚀孔具有隧道效应,扩展路径不规则,形成“之”字形裂纹;疲劳裂纹萌生机制是材料第二相与腐蚀损伤之间相互竞争的结果;腐蚀导致疲劳寿命显著降低,尤其是裂纹萌生寿命,腐蚀12年试验件裂纹萌生寿命仅为未腐蚀试验件裂纹萌生寿命的2.2%。     

STRUCTURAL HEALTH MONITORING OF AN AIRCRAFT JOINT

A major concern with ageing aircraft is the deterioration of structural components in the form of fatigue cracks at fastener holes, loose rivets and debonding of joints. These faults in conjunction with corrosion can lead to multiple-site damage and pose a hazard to flight. Developing a simple vibration-based method of damage detection for monitoring ageing structures is considered in this paper. The method is intended to detect damage during operation of the vehicle before the damage can propagate and cause catastrophic failure of aircraft components. It is typical that only a limited number of sensors could be used on the structure and damage can occur anywhere on the surface or inside the structure. The research performed was to investigate use of the chirp vibration responses of an aircraft wing tip to detect, locate and approximately quantify damage. The technique uses four piezoelectric patches alternatively as actuators and sensors to send and receive vibration diagnostic signals.Loosening of selected screws simulated damage to the wing tip. The results obtained from the testing led to the concept of a sensor tape to detect damage at joints in an aircraft structure.     

THEORETICAL ANALYSIS AND EXPERIMENTAL VERIFICATION ON TERNARY-WAVES METHOD TO COMPILE ACCELERATED SPECTRA

The equivalent damage calculation formulae of fatigue crack formation and growth are established. In order tocompile the fatigue crack formation and growth accelerated load spectra, the main wave shapes and load sequence of theactual load spectrum are kept constant, and the carrier waves are cut off. And secondary waves are put together into newsecondary waves to shorten the test time according to the equivalent damage calculation formulae respectively. Then bythe fatigue cumulative damage calculation of the fatigue crack formation and growth accelerated load spectra, the onecorresponding to the bigger damage is determined as the fatigue accelerated test load spectrum. Therefore in the test process, the fatigue accelerated test spectrum may be applied till fatigue failure, the engineering fatigue crack length of full-scale structure need not be inspected, and the fatigue crack formation accelerated load spectrum need not be transferredinto the fatigue crack growth accelerated load spectrum. Finally, it     

军用飞机结构疲劳寿命研究

简述飞机结构疲劳问题的重要性,特别结合军用标准规范对飞机结构疲劳设计要求的变化勾画飞机结构疲劳设计思想演变的情况;着重论述工程实际中常用的疲劳寿命分析方法,论述全尺寸结构疲劳试验的作用意义、试验载荷谱、试验实施的有关环节,概要介绍在飞机构件寿命分析与全尺寸结构疲劳试验方面所做的一部分研究工作,并就疲劳研究的发展提出一些粗浅看法。