SHORT CRACK GROWTH BEHAVIOR OF IN718 UNDER HIGH TEMPERATURE CONDITIONS IN CONSIDERATION OF PLASTICITY INDUCED CRACK CLOSURE
Timo BruneGrand Ballroom E
The behavior of short fatigue cracks under high temperature conditions is of significant importance for lifetime predictions and defect assessment of components in aircraft and gas turbine applications. The cyclic R(esistance) curve provides a possibility to describe phenomenologically the crack growth behavior below the long crack threshold. Within this paper experimentally determined cyclic R-curves of the nickel based alloy IN718 for varying load ratios (Rσ = -1, 0 and 0.5) at 650 °C are compared to each other. Furthermore, an approach supporting a mechanism-based understanding of the cyclic R-curves, taking plasticity induced crack closure (PICC) into account, is developed. Finite element analysis is used to estimate the amount of PICC in the short crack regime. For a systematic investigation of the impact of different ductility properties on short crack behavior, results from an additively and two conventionally (cast and wrought) manufactured material variants of IN718 are part of the investigations.