Quantification of the interaction within defect populations on fatigue behavior in an aluminum alloy Original Research Article

The interaction between fatigue crack evolution and porosity in A356-T6 alloys was characterized using both X-ray microtomography and finite-element analysis. The formation and propagation of fatigue cracks are dominated by the highest local stress–strain concentration (image) caused by the presence of porosity adjacent to the free surface and the crack tip, respectively. The image factor proved to be a suitable parameter to quantify the influence of porosity on fatigue cracking and to predict the fatigue crack growth rate (image). Although microporosity has a complex, tortuous morphology, a simple method for mapping the shape to an idealized sphere was proposed. It was found that using a sphere with equal projected area in the plane normal to the loading direction was a good approximation, allowing an equivalent image to be calculated.