微孔洞在材料表面的深度变化对应力集中及疲劳裂纹萌生的影响规律研究

采用线弹性有限元法模拟分析了微孔洞相对材料表面深度的变化对应力集中及疲劳裂纹萌生的影响,研究结果表明：微孔洞直径尺寸大小仅影响相应的应力集中分布区域的大小,而微孔洞相对材料表面深度的位置决定了其最大应力集中系数的大小。当微孔洞处于材料表面下并与表面相切时,应力集中系数达到最大值,当微孔洞相对材料表面深度的位置偏离此位置时,应力集中系数急剧下降。研究结果合理解释了实验中观察到的疲劳裂纹在微孔洞处萌生现象,即疲劳裂纹优先在与样品表面相切上半部的微孔洞上萌生,尤其在样品表面下且与表面相切的微孔洞处。

Effect of pore position in depth on stress concentration around pore on sample surface

Stress field around a pore is analyzed as a function of the pore position in depth in the surface of a linear elastic solid using FEM. It is found that the pore size only affected the size of the stress concentration region and the magnitude of the maximal stress concentration ratio around the pore only depended on the relative depth of the pore. The maximum of the maximal stress concentration ratio appeared when the pore intercepted with the surface at its top and the maximal stress concentration ratio decre- ased sharply when the pore diverges from the tangency position. These results are consistent with experimental observations that the fatigue crack initiation starts at the pore which intercepted with the surface at its top, especially is just buried underneath the surface.