A new approach to estimate fatigue crack delay due to a single cycle overload

✍ Scribed by A.E. Gemma; D.E. Allison; S.W. Hopkins

• Publisher: Elsevier Science
• Year: 1977
• Tongue: English
• Weight: 397 KB
• Volume: 9
• Category: Article
• ISSN: 0013-7944
• DOI: 10.1016/0013-7944(77)90077-7

✦ Synopsis

Fatigue crack growth delay resulting from a single cycle overload is analytically predicted using constant amplitude test data in a fractional calculus form of the Paris crack growth law. The crack growth rate of the Paris law is written as a fractional derivative whose order is given by the overload ratio. An explicit relationship which includes R-ratio is obtained for crack growth delay, Nr> No is defined as the number of cycles required for the crack to propagate a distance ao through the overload-damaged region in front of the crack tip. The delay crack length increment, ao, is expressed in terms of the monotonic and cyclic plastic zones. Good correlation is found between predicted delay and published data for Ti-6AI-4V at room temperature. The application of the analysis to estimate delay for complex cyclic load spectra is discussed. A concise description of fractional calculus is included for convenience in the Appendix.