Impact of high cycle fatigue on dwell time crack growth in a Ni-based superalloy
2015 (English)Manuscript (preprint) (Other academic)
Sustained load have been shown to give rise to increased crack growth rate at elevated temperature. Such loads generate a history dependent fatigue problem due to weakening and cracking of grain boundaries during dwell times, later broken apart during subsequent load cycles. So far most studies have focused on sustained load and the interaction of load cycles, overloads, and temperature, but few studies have been carried out for vibrations and how these affect the dwell time crack growth. Vibrations of different kinds are frequently seen in engine components, and present in combination with sustained loads a more realistic loading situation than the latter itself. An investigation of how a vibrational load affects the dwell time cracking and how to incorporate it in a modelling context is therefore of importance. In this paper a study of the most frequently used gas turbine material, Inconel 718, has been carried out. Mechanical testing has been conducted at 550◦C for surface cracks with and without the interaction of engine vibrations on sustained load, here represented by a superimposed high cycle fatigue (HCF) load. Subsequent investigation of the fracture behaviour was performed by Scanning Electron Microscope (SEM) and the modelling work has been conducted by incorporating the HCF load description within a history dependent crack growth law. The obtained results show reasonable accuracy with respect to the mechanical tests.
Place, publisher, year, edition, pages
Hold time effects, Dwell times, Sustained load, Crack growth modelling, Inconel 718, High temperature
Mechanical Engineering Materials Engineering Applied Mechanics
IdentifiersURN: urn:nbn:se:liu:diva-121009OAI: oai:DiVA.org:liu-121009DiVA: diva2:850773