An approach for the fatigue estimation of porous cast iron based on non-destructive testing results

Big cast iron components made of spheroidal cast iron allow constructing big structures such as stone mills, engine blocks or wind mills with acceptable expenses. Thus, in economically optimized cast processes pores cannot be always prevented in thick walled cast iron components and these components are often rejected because of safety reasons. On the one hand the fatigue performance of high loadable spheroidal cast iron components is reduced significantly by the presence of local porosities which has been pointed out in the past. On the other hand concepts for the fatigue estimation based on fracture mechanics which take the size and localization of the defect into account can lead to erroneous estimations because the defect is modelled as a crack. The challenge of an estimation method is to derive a fatigue life without the necessity to perform component tests. In the contribution an estimation method is presented which is able to determine the fatigue strength of a material volume taking the pores into account. The method can be applied based on data from computer tomographic X-ray (CT) or Sampling Phased Array (SPA) ultrasonic analyses. The method is presented for three spheroidal cast iron types: ferritic GJS-400-18, ferritic GJS-450-15 with high silicon content and perlitic GJS-700-3

Fatigue assessment of thick-walled nodular cast iron with regard to highly loaded machine structures using the strainlife approach

For a light-weight design and a safe material and component utilization the cyclic and elastic plastic material behavior of thick-walled structures needs to be included in fatigue analyses. Especially for usage in wind energy applications, thick-walled components such as the hubor the carrier of the nacelle are partially highly loaded by extreme loads due to storms or during grid losses. For this purpose EN-GJS-400-18U-LT has been investigated under constant and variable amplitude loading by means of strain controlled fatigue tests and numerical simulation with special regard to extreme loads and local plastic deformation