Effect of a dislocation pile-up at the neutral axis on trans-crystalline crack growth for micro-bending fatigue
Effect of a dislocation pile-up at the neutral axis on trans-crystalline crack growth for micro-bending fatigue
复制标题
DOI：
10.1016/j.ijfatigue.2016.09.015
复制
发表时间：
2017-01-01
影响因子：
6
通讯作者：
Motz, Christian
中科院分区：
文献类型：
--
作者：
Eisenhut, Lena;Schaefer, Florian;Motz, Christian
FCC的微弯梁。采用聚焦离子束技术(FIB)加工的镍基高温合金CMSX-4，研究了弯曲构型引起的应力梯度对小尺寸疲劳裂纹扩展行为的影响。为了避免位错反应对裂纹扩展行为的影响，在具有最高施密德因子的单滑移几何形状中，在滑移面上的缺口处萌生了跨晶I阶段疲劳裂纹。通过在扫描电子显微镜上对原位疲劳过程中的裂纹扩展进行可视化观察，结合实验柔度测量和有限元模拟，收集了DA/dN曲线数据。位错在中性轴的堆积导致明显的包辛格效应和作用在裂纹尖端的背应力，导致裂纹减速，疲劳裂纹扩展早期从I阶段转变为II阶段。(C)2016爱思唯尔有限公司。保留所有权利。
Micro-bending beams of the f.c.c. nickel based superalloy CMSX-4, machined by the focused ion beam technique (FIB), are used to study the effect of a stress gradient associated with the bending configuration on the fatigue crack growth behavior in small dimensions. To avoid an impact of dislocation reactions on the crack growth behavior, a trans-crystalline stage-I fatigue crack has been initiated at a notch placed on a slip plane in a single-slip geometry with the highest Schmid factor. da/dN-curve data was gathered by visual crack extension observation during in-situ fatigue in the SEM combined with experimental compliance measurements and FEM-simulations. A dislocation pile-up at the neutral axis results in a significant Bauschinger effect and a back stress acting on the crack tip causing a crack deceleration and an early change from stage-I to stage-II fatigue crack growth analyzed by FIB tomography. (C) 2016 Elsevier Ltd. All rights reserved.