Observations of Fatigue Slip-Band Growth and Crack Initiation in .ALPHA.-Brass under Cyclic Shear Stresses by Means of Atomic-Force Microscopy
Observations of Fatigue Slip-Band Growth and Crack Initiation in .ALPHA.-Brass under Cyclic Shear Stresses by Means of Atomic-Force Microscopy
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通过原子力显微镜观察循环剪切应力下 .ALPHA.-黄铜中的疲劳滑移带生长和裂纹萌生
DOI：
10.2472/jsms.52.625
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发表时间：
2003
期刊：
影响因子：
--
通讯作者：
K. Maeda
中科院分区：
文献类型：
--
作者：
Y. Nakai;K. Maeda
利用原子力显微镜（AFM）研究了α-黄铜在循环剪切应力作用下的滑移带形成和裂纹萌生过程，并用取向成像显微镜（OIM）确定了滑移方向。原子力显微镜观察发现，滑移带并不总是沿着最大分解剪应力方向形成，滑移体系可以在与表面夹角大于22°的方向上被激活。侵入深度随循环次数的对数线性增加，随着裂缝的扩展，侵入深度的增加速率急剧增加。结合AFM和OIM分别测量的侵入深度和滑动方向，可以评估滑移距离的值，发现所有裂纹起裂点的滑移距离临界值都是恒定的，而侵入深度则不恒定。循环剪应力（扭转）滑移距离临界值与循环法向应力（弯曲）滑移距离临界值相同。在循环扭转和弯曲加载下，得到了滑移方向剪切应力幅值与破坏循环次数之间的独特关系。
Slip-band formation and crack-initiation processes in α-brass under cyclic shear stress were examined by means of atomic force microscopy (AFM), and the slip-direction was identified with orientation imaging microscope (OIM). From AFM observations, it was found that slip-bands were not always formed along the maximum resolved shear stress directions, and slip-systems could be activated in the direction whose angles from the surface were larger than 22°. The depth of an intrusion increased linearly with the logarithm of the number of cycles, and the increasing rate of the intrusion depth drastically increased with its outgrowth to a crack. By combining the intrusion depth and the slip direction, those were measured with AFM and OIM, respectively, the value of slip distance could be evaluated, and the critical values of the slip distance for the initiation of transgranular crack was found to be constant for all crack initiation sites, while the intrusion depth was not constant. The critical value of the slip distance for cyclic shear stress (torsion) was identical for cyclic normal stress (bending). A unique relationship between shear stress amplitude in the slip direction and number of cycles to failure was obtained for cyclic torsion and bending loadings.