中文摘要：

疲劳裂纹萌生经常发生在材料中气孔、夹杂等各种微观结构不连续区域，是一种高度局部化过程。分别考虑受单调拉伸和循环拉压载荷条件，利用有限元法研究夹杂物周围的局部力学行为，分析夹杂性能、位置、多夹杂、循环迥性对局部应力集中的影响。在模拟中，金属基体定义为弹塑性材料，材料本构采用各向同性．随动硬化混合模型，夹杂模拟为各向同性线弹性材料。结果表明，夹杂与基体弹性模量的差别越大，产生的局部应力集中越大，软夹杂导致的应力集中人于硬夹杂；多夹杂引起的应力场强化作用与夹杂排列方向和加载方向有关；循环硬化导致气孔周围应力集中增大，对硬夹杂周围应力集中几乎没有影响：高应力水平下，近表面气孔的应力应变集中系数托较大，低应力水平下内部气孔处托较火，表明疲劳裂纹易于萌生。

英文摘要：

The formation of fatigue crack is a highly localized process that occurs at various microstructure inhomogeneities like pores, inclusions within materials. Under the monotonic tension and cyclic tensile-compressive loadings, the local mechanical behavior around the inclusions is investigated using the finite element method. The influence of inclusion property, location of inclusion in materials and multiple inclusions interaction on local stress concentration factor is addressed. Results reveal that, the local stress concentration factor increases with the increase of elastic modulus difference between inclusions and matrix. The stress concentration factor due to softer inclusion is greater than that due to harder one. The enhancement of stress field caused by multiple inclusions interaction depends both on the array of inclusions and on the loading direction. The cyclic hardening leads to an increase of stress concentration factor around the pore, while shows an insignificant effect on that around hard inclusions. In addition, a greater stress-strain concentration factor Kg is observed for the subsurface pore under the higher stress levels. Under the lower stress level, the greater Kg shifts to the internal pore and thus indicates a transferred fatigue crack initiation.