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MEAN STRESS EFFECTS ON LOW CYCLE FATIGUE FOR A HIGH STRENGTH STEEL
Author(s) -
Koh S. K.,
Stephens R. I.
Publication year - 1991
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.1460-2695.1991.tb00672.x
Subject(s) - materials science , plasticity , ultimate tensile strength , strain (injury) , stress (linguistics) , composite material , stress relaxation , amplitude , hysteresis , low cycle fatigue , fatigue limit , structural engineering , creep , medicine , physics , linguistics , philosophy , quantum mechanics , engineering
— ASTM A723 Q & T steel with a yield strength and ultimate strength of 1170 and 1262 MPa respectively was evaluated for mean stress‐strain effects under smooth specimen axial strain controlled low cycle fatigue conditions with strain ratios R of −2, −1, 0, 0.5 and 0.75. Cycles to failure ranged from 15 to 10 5 . Cyclic stress‐strain response based upon half‐life hysteresis loop peaks were similar for all R ratios. Mean stress relaxation occurred for R ≠−1 only when plastic strain amplitudes were present and this occurred above total strain amplitudes of 0.005. Thus, mean stress relaxation was completely dependent upon cyclic plasticity. Mean strains did not affect low cycle fatigue life unless accompanied by half‐life mean stress. Tensile mean stress was detrimental and compressive mean stress was beneficial and these effects only occurred at strain ampltidues below 0.005. Three different mean stress models were used to evaluate the low cycle fatigue data and the SWT log‐log linear model best represented the data. These results can be used with the local notch strain fatigue life prediction methodology.