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THE PREDICTION OF CRACK GROWTH RATES FROM TOTAL ENDURANCES IN HIGH STRAIN FATIGUE
Author(s) -
SKELTON R. P.
Publication year - 1979
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 - 10.1111/j.1460-2695.1979.tb01089.x
Subject(s) - crack closure , materials science , strain (injury) , crack growth resistance curve , paris' law , limiting , strain hardening exponent , fracture mechanics , growth rate , structural engineering , plasticity , hardening (computing) , composite material , mathematics , geometry , engineering , mechanical engineering , medicine , layer (electronics)
— A method of calculating crack growth rates in high strain fatigue from total endurance data is presented. Endurances are known to be affected by dwell periods and environment and the expression derived takes these into account. The basic argument is that crack propagation may be regarded as increments of successive reinitiation and so the deeper a crack grows, with an accompanying increase in strain concentration at the tip, the fewer fatigue cycles are required for the next step. Previously derived expressions for strain concentration are employed which require a knowledge of the cyclic strain hardening properties of the material. These are produced in detail for a cast 1/2 Cr‐Mo‐V steel at 550°C. Two constants in the resulting propagation expression are semi‐empirical, but if the surface (plastic or total) strain range is known then cyclic crack growth rates may be calculated for any crack depth. It is also shown that in the limiting case of zero surface plastic strain, the expression reduces to that observed for crack growth under linear elastic conditions.