目录 摘要III Abstract IV 第一章绪论1 1.1研究背景1 1.2MED剩余强度分析国内外现状2 1.3本文主要内容3 第二章MED剩余强度分析理论1 2.1广布疲劳损伤敏感结构1 2.2应力强度因子3 2.2.1裂纹模型4 2.2.2计算应力强度因子的几种基本方法4 2.3相互影响因子7 2.4剩余强度理论8 2.4.1平均应力准则9 2.4.2净截面屈服准则10 2.4.3塑性区连通准则11 2.4.4断裂力学准则13 2.5本章小结13 第三章有限元建模14 3.1ABAQUS软件介绍14 3.2ABAQUS验证14 3.2.1验证模型14 3.2.2输出值比较15 3.3建模过程16 3.3.1模型尺寸以及材料参数17 3.3.2abaqus仿真建模18 3.4有限元计算和结果分析27 3.4.1桁架应力和位移的云图27 3.4.2应力强度因子结果曲线图30 3.4.3相互影响因子分析33 3.4.4剩余强度分析35 3.5本章小节40 第四章结束语41 4.1本文的主要贡献41 4.2需要进一步研究的问题41 参考文献42 致谢44 MED剩余强度分析 摘要 结构疲劳损失形式WFD(广布疲劳损失)是在Aloha事件之后，开始广泛出现在人们的视野中。目前实验已表明飞机在长期的飞行过程中，由于疲劳载荷等内部与外部原因会在结构上产生多部位损伤（MSD）与多元件损伤（MED）,这两种损伤会导致飞机结构的剩余强度迅速降低，严重情况下会在飞行过程中产生严重的事故。本文主要针对飞机结构进行多元件损伤的研究与分析，重点对裂纹尖端应力强度因子，相互影响因子、以及剩余强度等方面进行了研究。 本文给出了获得多元件裂纹尖端应力强度因子的有限元分析计算过程，对典型的飞机蒙皮与桁架连接处铆钉孔的裂纹进行模拟计算，获得了裂纹开裂状态下裂纹尖端处多元件相互影响因子的数值拟合结果。在此基础，通过进一步计算分析，利用净截面屈服准则，塑形区连通准则等判据得出含多元件损伤结构的剩余强度，最终结果表明多元件损伤对结构剩余强度有显着的影响。因此在结构损伤容限评定中，对多裂纹损伤结构应当予以重视，从而为飞机结构的安全提供保障。 关键词：广布疲劳损伤;多元件损伤;多元件相互影响因子;剩余强度;应力强度因子 The a
nalysis of residual stre
ngth of MED Abstract After the Aloha i
ncide
nt, a
new form of structural fatigue damage (WFD) appeared i
n people's field of visio
n. Duri
ng lo
ng-term flight, the aircraft will suffer multiple structural damages due to i
nter
nal a
nd exter
nal causes such as multiple site damage (MSD) a
nd multiple eleme
nt damage (MED), which ca
n lead to a rapid decrease i
n the remai
ni
ng stre
ngth of the aircraft structure,which may also cause serious accide
nts duri
ng the flight. It is very importa
nt to predict a
nd study multiple site damage a
nd multiple eleme
nt damage. This paper mai
nly focuses o
n the research a
nd a
nalysis of multiple eleme
nt damage of aircraft structure, focusi
ng o
n two aspects of the i
nflue
nce factors of crack tip a
nd residual i
nte
nsity. I
n this paper, the fi
nite eleme
nt calculatio
n process for obtai
ni
ng multiple eleme
nt i
nflue
nci
ng factors is prese
nted. The cracks i
n the rivet holes at the ju
nctio
n of a typical aircraft ski
n a
nd truss are simulated a
nd calculated. Through this way, the
numerical simulatio
n of multiple eleme
nt i
nteractio
n factors at the crack tip i
n crack cracki
ng state is obtai
ned. O
n this basis, through further calculatio
ns a
nd a
nalysis, the residual i
nte
nsity of multiple eleme
nt crack structures is obtai
ned, by usi
ng criteria such as the
net sectio
n yield criterio
n a
nd the shapi
ng zo
ne co
n
nectivity criterio
n. The results show that the mutual i
nflue
nce betwee
n multiple eleme
nt damages is sig
nifica
nt for the residual i
nte
nsity of the structure. I
n the evaluatio
n of structural damage tolera
nce, more atte
ntio
n should be paid to the damage of multiple cracks, so as to guara
ntee the safety of the aircraft structure. Key words: widespread fatigue damage; multiple eleme
nt damage; multiple eleme
nt i
nteractio
n factor ; residual stre
ngth ; stress i
nte
nsity facto