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To reduce the weight and to increase the power as well as to enable the utilization of nodular cast iron components, e.g. for wind turbines and heavy industry parts, locally higher stresses need to be withstood by the material. This becomes crucial, when additional overloads influence the structure of thick-walled components causing high local elastic-plastic deformations. In this case, the cyclic, elastic-plastic material behavior and its development under cyclic loading are important points to be considered during component design. To assess the material’s local elastic-plastic material behavior, strain-controlled fatigue tests were performed under alternating loading, Rε = -1, with unnotched specimens removed from cast blocks as well as from a hub and a planet carrier of wind turbines, made of EN-GJS-400-18U-LT, EN-GJS-700-2, ADI-800 and ADI-900.

In vehicle design and engineering, the fatigue of materials is a size-dependent phenomenon, which occurs in every safety-relevant component. An inaccurate fatigue assessment, neglecting relevant influencing factors, may therefore either lead to considerable safety risks or to a significant oversizing of the component. Due to the size dependency of the microstructure and the related deformation and fatigue mechanisms, the fatigue life estimation requires an understanding of the cyclic material behavior as well as the damage mechanisms of materials on different scales. In this respect, local strain-based fatigue design concepts are advantageous for the estimation of the fatigue properties of components with arbitrary size and geometry, because the applicable material models allow an implementation of a realistic cyclic material behavior and a relation to different fatigue damage mechanisms in the elastic and the elastic-plastic load regime.

For the design of thick-walled nodular cast iron components, fatigue assessment, especially in the context of local imperfections in the material, is a challenging task. Not only the cyclic material behavior of the sound baseline material, but also the cyclic behavior of materials with imperfections, such as shrinkages, dross and chunky graphite, needs to be considered during the design process of cast iron components. In addition to this, new materials, such as solid solution strengthened alloys, offer new possibilities in lightweight design, but need to be assessed concerning their fatigue strength and elastic-plastic material behavior. If a safe and reproducible fatigue assessment for any component cannot be performed and a secure usage is therefore not given, the cast components are generally rejected, leading to a loss of additional material, energy and money for recasting the component.