On the mechanistic difference between in-phase and out-of-phase thermo-mechanical fatigue crack growth. (June 2020)

• Record Type: Journal Article
• Authors: Norman, V.; Stekovic, S.; Jones, J.; Whittaker, M.; Grant, B.
• Is Part Of: International journal of fatigue. Volume 135(2020)
• Publication Date: 2020-06
• Subjects: Aerospace -- Superalloys -- Thermomechanical fatigue -- Crack growth rate -- Crack opening; Materials -- Fatigue -- Periodicals; Materials -- Fatigue; Periodicals; 620.1122
• DOI: 10.1016/j.ijfatigue.2020.105528
• Languages: English
• ISSNs: 0142-1123

Abstract

Highlights: IP and OP TMF crack growth rates in RR1000 are measured and compared. Crack-tip strain, opening displacement and crack closure are analyzed using DIC. IP and OP growth rates coincide when plotted against crack-tip-opening displacement. Difference in IP and OP is attributed to mechanical conditions at crack-tip region. R-ratio and temperature during pre-cracking affect crack closure during test. Abstract: The crack driving mechanisms in a coarse grained nickel-base superalloy RR1000 when subjected to in- and out of phase thermo mechanical fatigue are investigated. It is found that the difference in fatigue crack growth rate between these two load conditions is accounted for by the different mechanical conditions at the crack tip region, rather than oxidation effects. This is based on digital image correlation and finite element analyses of the mechanical strain field at the crack tip, which demonstrate that in phase leads to larger crack tip deformation and crack opening. Notably, it is demonstrated that in- and out of phase crack growth rates coincide when correlated to the crack tip opening displacement.