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Technical Paper

Fatigue Behavior of Large Cast Components under Variable Amplitude Loading with Overloads

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.
Journal Article

Fatigue Assessment of Nodular Cast Iron with Material Imperfections

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.
Technical Paper

Deriving Strain Based Local Structural Element Concept for the Fatigue Assessment of Additively Manufactured Structures

Additive manufacturing offers new options for lightweight design for safety parts under cyclic loading conditions. In order to utilize all advantages and exploit the full potential of additive manufactured parts, the main impact factors on the cyclic material behavior not only have to be identified and quantified but also prepared for the numerical fatigue assessment. This means in case of the AlSi10Mg aluminum alloy to consider influences related to the exposure strategy, heat treatment, microstructure, support structures and the surface conditions, as well as the influence of the load history and finally the interaction of these influences in order to perform a high quality fatigue assessment. Due to these reasons, and with respect to the numerical effort, the cyclic material behavior of additively manufactured AlSi10Mg produced by selective laser melting will be discussed.