Effects of Loading Waveform and Stress Field on High Temperature Fatigue Crack Growth of Alloy 718

✍ Scribed by P. Heuler; E. Affeldt; R.J.H. Wanhill

• Publisher: John Wiley and Sons
• Year: 2003
• Tongue: English
• Weight: 325 KB
• Volume: 34
• Category: Article
• ISSN: 0933-5137
• DOI: 10.1002/mawe.200300663

✦ Synopsis

Abstract

High temperature fatigue in nickel‐base superalloys for aero‐engine applications requires consideration of cycle‐ and time‐dependent phenomena. For waveforms with dwells and/or low frequencies crack growth rates may be significantly accelerated up to the point of fully time‐dependent crack growth. In the paper, the interaction of fatigue (cycle‐dependent) and dwell (time‐dependent) crack growth is addressed using a broad database for IN 718 tested at 600°C. Waveforms with dwells at as well as below maximum load levels are applied to standard CT and CC specimens and blunt notched specimens. It is demonstrated that both the level of dwells with respect to the maximum load level within a cycle as well as the specific conditions at the notch root considerably affect the significance of dwells for fatigue crack growth.