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Effects of frequency on fatigue crack growth at elevated temperature
Author(s) -
Tong Tong,
Byrne
Publication year - 1999
Publication title -
fatigue and fracture of engineering materials and structures
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.887
H-Index - 84
eISSN - 1460-2695
pISSN - 8756-758X
DOI - 10.1046/j.1460-2695.1999.00160.x
Subject(s) - superalloy , materials science , paris' law , growth rate , crack closure , alloy , metallurgy , fracture (geology) , constant (computer programming) , waveform , stress intensity factor , composite material , structural engineering , fracture mechanics , engineering , mathematics , geometry , voltage , computer science , electrical engineering , programming language
The effects of frequency on fatigue crack growth behaviour have been studied in a prealloyed powder material, Udimet 720Li, at 650 °C. Fracture mode and fatigue crack growth behaviour were studied at frequencies ranging from 0.001 to 5 Hz using a balanced triangular waveform. Tests were carried out under constant Δ K control, with load ratio and temperature being held constant. A mechanism map was constructed where predominantly time, mixed and cycle‐dependent crack growth behaviour were identified. The results were verified by SEM analyses. Cycle‐dependent crack growth data were obtained at room temperature, while fully time‐dependent crack growth data were generated under sustained loads at 650 °C. It was found that mixed time/cycle‐dependent behaviour is of most significance for this material at the temperature and frequencies studied. Data for other nickel‐based superalloys from various sources in the literature were compiled and compared with those of U720Li alloy at a given stress intensity and temperature in the mixed regime. An analysis was developed to rationalize the observed effect of frequency on fatigue crack growth rate.