晶体随机取向对单晶切口试样尖端滑移特性的影响

Effect of Randomness Orientation on Crystal Slipping around Notch in Single Crystal Superalloy

利用考虑潜在硬化和晶格转动效应的率相关晶体滑移有限元程序,采用镍基单晶双切口模型,针对不同切口取向,分析了叶片随机取向对切口附近区域应力应变分布特性和滑移系激活规律的影响。结果表明:不同取向单晶切口附近的滑移系开动存在显著差异,开动的滑移系随载荷增大而增多,在切口不同部位,激活的滑移系也不同。切口取向平行于[310]晶向时,在切口10o和170o处,滑移系成对发生开动。在取向偏角β=45o附近,最大分切应力达到极大值,在0o和90o时,为多滑移开动情形。在切口厚度方向上,最大分切应力在中心部位分布均匀,在临近外表面处存在明显的梯度波动,可知滑移(裂纹启裂)事实上在中面开始,然后延伸至表面上。

The three-dimensional elastic-plastic stress fields around the notch have been analyzed by a crystallographic finite element program, which takes the effects of lattice rotation and finite deformation into consideration. The primary orientation is fixed along the [001] direction while the notch directions are parallel to [010] and [310 ]. The special attention is paid on the activating characteristic of slip systems. The numerical results show that the randomness orientations have important consequences on the activation of slip systems and the maximal resolved stress for the notch, The extreme of the maximum resolved stress appears around β=45°. The maximum resolved stress has an obvious fluctuation along the thickness direction, which is nearly constant in the midsection and tends to decrease sharply near the free surface. We can conclude that the slip （crack） is likely initiated at the midplane first. In the experiment, these regions correspond to the smooth region and the shear lip on the fracture face.