晶体取向对单晶体断裂特征影响的模拟分析

结合Ni基单晶合金制三种不同晶体取向的紧凑拉伸试样试验,本文利用考虑有限变形和品格转动效应的晶体滑移有限元程序对单晶体三维断裂特征进行了模拟计算分析,详细考察了裂纹尖端三维应力场特征和断裂特征,结果表明:晶体取向对裂纹尖端应力场有较大影响,但应力沿试样厚度方向明显分成两个部分,在试样心部,应力沿厚度方向变化不大,在试样外表面则明显变化。裂纹尖端张开位移(CTDD)沿厚度方向类似分成两个部分。垂直于滑移面的应力分量致单晶体的准解理断裂,即裂纹的起裂和扩展途径均与该应力分量有关。

The analysis of the effect of crystallographic orientations on the fracture of nickei-base single crystals

Combined with the experiments of compact tensional (CT) specimens made of nickel-base single crystals in three crystallographic orientations, the three dimensional fracture have been analyzed by a crystallographic finite element program, which takes the effects of lattice rotation and finite deformation into consideration. The special attention were paid on the three dimensional stress structure and fracture characteristics. The results show that the stress structure is dependent on the crystallographic orientations of specimens. For the considered three specimens, the stress structures near the crack tips can be devided into two parts along the thickness direction. One part is the central region, where the stress keeps similar along the thickness direction, another is the lateral region, where the stress changes obviously. The crack tip openning displacement (CTOD) has the similar distribution as stresses along the thickness direction. The stress component normal to the slip plane results the quasicleavage fracture, on which the initation and growth of the crack are dependent.