Local Porosity Consideration in Fatigue Life Calculation of High Pressure Die Cast Aluminium Components

Aluminium high pressure die casting (HPDC) reduces cost and weight of components, therefore they find a wide application in the car construction. To better capitalize on the potential of the HPDC procedure, inhomogeneities, like gas pores and blowholes, and their influence on the fatigue life must be precisely determined. This assessment is complicated by the fact that the pores are not distributed homogeneously across the component section. The component surface layer is usually free of pores and the porosity is concentrated at the centre of the component. Size, form and location of the single pore as well as the relative location of the pores also influence the fatigue strength. The influence of the pores on the local loading condition is investigated in detail through FEM calculations. In these calculations different kinds of pores are taken into consideration, varying from ideal spherical shape to the real three-dimensional pore geometry extracted from microfocus computer tomography investigations. Furthermore the porosity in the component is statistically evaluated. With this knowledge a method is developed to consider the effect of porosity on fatigue life. The procedure is applied and verified on a series-production HPDC component.