In further steps, finite element models of the close-to-real structural homogeneities were created. Based on the microstructures in aluminium specimens which were reconstructed with the help of computed tomography, the micromechanical stresses were simulated and parameterized. Further, the internal notch effect was correlated with the characteristic geometry parameters of the pores. From these results, we then derived a parameterized service-life model. We then subjected the unnotched specimens to fatigue strength tests, in order to validate the model. The developed service life model enables three-dimensional sample components to be deduced, which show the admissible degrees of porosity.
Basically, this opens up the possibility of quantitatively assessing the fatigue strength of aluminium castings on the basis of non-destructive testing methods without real tests or FEM calculations.
This method was developed in the AiF research project EPOS (Development and integration of assessment criteria for quality assurance and component calculation, taking account of the influence of pores and non-metallic inclusions on the fatigue strength of aluminium casting alloys) of the German Foundry Industry Association (BDG) (project no. 295 ZN, AiF report no. E-376).