飞机结构搭接件腐蚀三维裂纹扩展特性分析

 通过对某型退役飞机分解检查,发现搭接件在腐蚀产物的膨胀作用下产生了裂纹。采用20节点等参奇异元,运用三维有限元法分析含半椭圆裂纹的飞机结构搭接件的应力应变状态,通过计算裂纹前缘典型部位的应力强度因子,预测了裂纹的扩展趋势,分析了其危害性。结果表明,搭接件半椭圆形裂纹以较小的形状比(a/b)扩展,在较长阶段内并不会扩展到外表面。所以裂纹具有隐蔽性,对飞机安全构成潜在的威胁。

Analysis of Growth Characterization of 3-D Cracks in Corroded Lap Joints of Aircraft Structure

A military aircraft, which had serviced for more than twenty years and retired recently is torn down and then inspected. It is found that there are corrosion pillowing cracks in lap joints. By use of three-dimensional finite element method (FEM), stress and strain distributions of lap joints with semi-elliptical cracks of aircraft structure are analyzed, and 20-node singular isoparametric element is used. By calculating the stress intensity factors (SIFs) of typical locations around the crack tip, its growth direction is predicted, and its effect on the structural integrity of aircraft is analyzed. The results show that semi-elliptical crack with small aspect ratio's (a/b) will not break the outside surface. So they are hidden, and there is potential danger to the safety of aircraft.