飞机机身蒙皮均布增压疲劳裂纹扩展研究  

RESEARCH ON THE FATIGUE CRACK PROPAGATION OF AIRCRAFT FUSELAGE SKIN UNDER UNIFORM PRESSURIZED LOAD

作　　者：刘礼平[1] 韩毫毫 刘佳欢 鲍蕊[2] 蔺越国[1] LIU LiPing;HAN HaoHao;LIU JiaHuan;BAO Rui;LIN YueGuo(College of Aviation Engineering,Civil Aviation University of China,Tianjin 300300,China;School of Aeronautic Science and Engineering,Beihang University,Beijing 100083,China)

机构地区：[1]中国民航大学航空工程学院,天津300300 [2]北京航空航天大学航空科学与工程学院,北京100083

出　　处：《机械强度》2023年第4期985-992,共8页Journal of Mechanical Strength

基　　金：中国民航大学实验技术创新基金(2020CXJJ69)资助。

摘　　要：为研究机身蒙皮在均布增压循环载荷作用下的疲劳裂纹扩展,用自制的飞机机身蒙皮均布增压疲劳装置进行实验。首先通过扩展有限元法计算出应力强度因子,然后基于最大周向应力(Maximum Circumferential Stress,MCS)准则和应变能密度因子(Strain Energy Density Factor,SEDF)准则计算裂纹偏转角,对机身蒙皮疲劳裂纹扩展路径进行预测,最后在扫描电镜下对疲劳断口进行观察与分析。结果表明,两种准则预测的裂纹扩展路径与实验得到的裂纹扩展路径基本一致。机身蒙皮表面裂纹为复合型裂纹,随着裂纹长度增加,KⅠ先增大后减小,KⅡ在数值上先迅速降低至0附近,然后在0附近振荡,最后在接近下孔即将贯穿的时候迅速增大。观察疲劳断口发现,疲劳裂纹呈多疲劳源萌生;裂纹扩展区具有典型的准解理断裂特征,并且疲劳裂纹扩展速率随裂纹长度的增大呈先增大后减小的变化趋势;瞬断区则为典型的大小不等的韧窝特征。In order to study the fatigue crack propagation of the fuselage skin under uniform pressurized cyclic load,experiments were carried out with the self-made aircraft fuselage skin uniform pressurized fatigue device.Firstly,the stress intensity factor was calculated by the extended finite element method.Then,the deflection angle of the crack was calculated based on the maximum circumferential stress criterion and the strain energy density factor criterion,and the fatigue crack propagation path of the fuselage skin was predicted.Finally,the fatigue fracture was analyzed under scanning electron microscope.The results show that the crack propagation paths predicted by the two criteria are basically consistent with the crack propagation path obtained by experiment.The surface cracks of the fuselage skin are mixed mode cracks.With the increase of the crack length,KⅠfirst increases and then decreases,KⅡfirst decreases rapidly to around 0,then oscillates around 0,and finally increases rapidly when the lower hole is about to penetrate.Observing the fatigue fracture shows that the fatigue cracks are initiated by multiple fatigue sources.The crack propagation zone has typical quasi-cleavage fracture characteristics,and the fatigue crack growth rate first increases and then decreases with the increase of crack length.The instantaneous fracture zone is a typical dimple feature with different sizes.

关 键 词：机身蒙皮 均布增压 疲劳裂纹 裂纹扩展 疲劳断口 

分 类 号：V252.2[一般工业技术—材料科学与工程]