Simplified design of cast steel components under fatigue loads

Theoretically, cast steel is ideally suited for use in structures subject to fatigue loads due to its high mechanical strength and virtually free shaping possibilities. However, the component resistance is determined by manufacturing-related imperfections. Due to a lack of knowledge and the absence of easily applicable design approaches, the use of cast steel components is usually rejected or countered by the highest demands on manufacturing quality. This blanket choice is usually uneconomical and not necessary from a technical point of view, since even major casting defects do not necessarily reduce the performance of a component. In this paper, an easy-to-use design approach is presented, which allows the determination of manufacturing quality based on local stresses. The link between fatigue strength and allowable defect sizes is established by newly defined resistance categories. The component design is carried out by limiting maximum stress ranges, is based on established verification concepts, and is thus directly adapted to practical construction applications. Influences such as medium-voltage dependence, shape tolerances, brittle fractures, stress gradients and interaction of neighbouring flaws are considered by reduction factors or additional conditions.