Abstract: 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.

Key words: Fatigue crack initiation, Finite element method, Inclusions, Pore, Stress concentration