The Application of the Cyclic Void Growth Model to Assess the Ultra-low-cycle Fatigue Life of Steel Castings

Steel castings have been used increasingly to develop new seismic force resisting systems. Although they have primarily been used as elements which are to remain elastic during seismic events, recent developments have proposed and validated systems that rely on the yielding response of steel castings, taking advantage of their freedom of geometry and chemistry to obtain optimum combinations of strength, stiffness, and ductility. To this end, an understanding of their ultra-low-cycle fatigue life is paramount. To further this understanding, in this thesis, fatigue laws are calibrated for multiple cast steel heats using a fatigue model which has recently been proposed in the literature for rolled steel elements. The calibrated models are used to predict the ductile failure in multiple full-scale experiments. A method is proposed to assess the casting's fatigue life at the foundry and to utilize the model in designing prototype steel castings for ductile applications.M.A.S