Deriving Representative Structural Elements for the fatigue approach of Wire Arc Additively Manufactured components

The relevance of the additive manufacturing technology is steadily growing, especially for metallic structures. In order to exploit the lightweight design potential for cyclically loaded safety parts in industrial applications, tools and methods are required to describe the cyclic material behavior in order to simulate the structural behavior with respect to the build conditions. Furthermore, a fatigue approach has to ensure the transfer of the cyclic behavior derived by the use of specimens to arbitrary structures and loading conditions. In order to enable a high-quality design process, Representative Structural Elements will be used to describe the cyclic stress-strain behavior as well as the fatigue life from the Low Cycle Fatigue up to the Very High Cycle Fatigue. Therefore, the Fatigue Life Curve will be implemented to consider the load-time histories at different maximum stress amplitudes. For the transfer of the cyclic properties, determined on the basis of specimens, to arbitrary component geometries and loading scenarios, the importance of the description of the investigated material state is increased. It is also important to ensure that the characteristic values used also describe the intended properties or influences. Therefore, a new method for describing the surface structure is presented, which is based on the idea to consider the notch effect and stress concentrations as influencing variables on the fatigue strength. For this purpose, the surface profile is conceived as a sequence of geometrical notches and the notch sharpness is estimated using the ratio of local profile height and length between the respective peaks and valleys. It should be noted that the aim of this method of describing the surface condition is not to be able to derive a direct influencing factor, but rather to optimize and narrow down the range of validity of the Representative Structural Elements.