Three-Dimensional Visualization of the Interaction between Fatigue Crack and Micropores in an Aluminum Alloy Using Synchrotron X-Ray Microtomography
Three-Dimensional Visualization of the Interaction between Fatigue Crack and Micropores in an Aluminum Alloy Using Synchrotron X-Ray Microtomography
复制标题
DOI：
10.1007/s11661-007-9214-6
复制
发表时间：
2007-07
期刊：
影响因子：
--
通讯作者：
H. Zhang;H. Toda;H. Hara;M. Kobayashi;Toshiro Kobayashi;D. Sugiyama;N. Kuroda;Kentaro Uesugi
中科院分区：
文献类型：
--
作者：
H. Zhang;H. Toda;H. Hara;M. Kobayashi;Toshiro Kobayashi;D. Sugiyama;N. Kuroda;Kentaro Uesugi
采用同步x射线显微断层扫描技术研究了流动成形过程对Al-Si-Mg合金疲劳行为的影响。在各应力幅值下，流动成形t6试样的疲劳寿命均大于铸态t6试样的疲劳寿命。重建了流形t6试样的x射线扫描x线照片，以实现微孔分布和孔-裂纹相互作用的三维可视化。在不同的层析薄片上观察微孔与裂纹之间的相互作用。微孔与裂纹路径的偏转有关。采用细观力学模型计算了疲劳裂纹路径上各位置的ⅰ型和ⅱ型应力强度因子。当疲劳裂纹接近微孔时，SIF迅速增大。结果表明，沿全裂纹路径的SIFs平均值略高于远端施加应力强度，但局部区域存在明显的抗屏蔽作用。晶体织构是流动成形t6材料具有较高抗疲劳性能的重要因素。
The effect of the flow-forming process on the fatigue behavior of an Al-Si-Mg alloy was investigated using synchrotron X-ray microtomography. The fatigue life of the flow-formed-T6 specimen was found to be longer than that of the as-cast-T6 in all the selected stress amplitudes. The X-ray-scanned radiographs of a flow-formed-T6 specimen were reconstructed to allow three-dimensional (3-D) visualization of distribution of micropores and pore-crack interactions. Observations were performed on different tomographic slices to investigate the interaction between the micropores and the crack. Micropores have been associated with deflections of the crack path. Mode I and Mode II stress-intensity factors (SIFs) were calculated at each position along the fatigue-crack path using a micromechanics model. The SIF increased rapidly when the fatigue crack came close to a micropore. It was found that the average value of SIFs along entire crack paths was slightly higher than the remotely applied stress intensity, although the level of antishielding was pronounced in some local regions. Crystallographic texture is proposed to be the important factor for the observed higher fatigue resistance in flow-formed-T6 material.