复合载荷下裂纹体的弹塑性断裂行为的电镜原位观察

AN IN SITU ANALYSIS TO THE BEHAVIOUR OF ELASTIC-PLASTICOF A CRACK BODY UNDER MIXED MODE LOADING

应用电镜原位拉伸的方法观察了铝合金ＬＹ１２在不同（Ⅰ＋Ⅱ）复合型下裂纹尖端的塑性变形和断裂过程。结果表明，复合载荷作用下裂纹尖端的变形是纯一锐化变形模式。裂纹的断裂发生于钝化区，断裂方位与最大应力三轴性水平的分布方位一致。不同复合型下的断裂遵循等轴状孔洞损伤机制，最大周向拉应力是铝合金复合型断裂的力学控制因素。随Ⅱ型分量增加，ＬＹ１２启裂ＣＯＤ值增加。

An in situ tensile experiment in a SEM was carried out to investigate the deformation and fractureat the crack tip in LY12 Al alloy under different mixed(Ⅰ+ Ⅱ)loading.It's shown that the model of crack tip de formation under mixed mode loading is sharpening-blunting.The fracture of a mixed crack occured at blunting sideand crack propagates along the direction of maximum stress triaxiality level of the crack tip. The fracture of differ ent mixed loading obeys the void damage mechanism and is controlled by maximum circle tensile stress for LY12 Alalloy. With an increasing of mode Ⅱ component,the initiation COD value of LY12 Al alloy increases.