A two-parameter analysis of S-N fatigue life using Δσ and σmax

Abstract The effect of the load ratio, R, or the mean-stress on fatigue life has been recognized for more than a hundred years. In considering the mean-stress effects in the stress-life (S–N) approach, research efforts have been mostly concentrated in establishing correlating functions in terms of the flow stress or yield stress or the ultimate tensile stress, etc., by taking, say, R = −1 test results as a reference. Very little effort has been made towards understanding the role of stress range Δσ and the maximum stress σmax, (or σmean) in the fatigue crack nucleation and propagation and also how to relate this to both the stress-life and the fracture-mechanics descriptions. In this paper we first examine crack nucleation based on the stress-life approach using a two-parameter requirement in terms of Δσ and σmax, and then connect it to crack propagation using the Kitagawa diagram as the incipient crack grows to become a long crack. Since stress-life data include both nucleation and propagation, the connection of the safe-life approach to the fracture-mechanics analysis is pertinent. Comparison of the present analysis with experimental data taken from the literature demonstrates that a two-parameter approach in terms of Δσ and σmax forms a basis for the S–N analysis.

[1]  Cemil Bagci,et al.  Fatique design of machine elements using the “Bagci line” defining the fatigue failure surface line (mean stress diagram) , 1981 .

[2]  W.J.D. Jones,et al.  Effect of stress ratio on the cyclic tension corrosion fatigue life of notched steel BS970:976M33 in sea water with cathodic protection , 1989 .

[3]  A. K. Vasudevan,et al.  Fatigue crack growth mechanisms in steels , 2003 .

[4]  I. R. Kramer.  A mechanism of fatigue failure , 1974 .

[5]  Shyh-Jen Wang,et al.  The Clemson Limit Stress Diagram for Ductile Parts Subjected to Positive Mean Fatigue Loading , 2000 .

[6]  G. Glinka,et al.  Determination of weight functions from reference stress intensity factors , 1991 .

[7]  C. Laird,et al.  Changes in strain localization behavior induced by fatigue in inert environments , 1987 .

[8]  A. K. Vasudevan,et al.  Fatigue crack growth behavior of titanium alloys , 2005 .

[9]  A. Argon,et al.  Creep cavitation in 304 stainless steel , 1981 .

[10]  M. E. Haddad,et al.  Prediction of non propagating cracks , 1979 .

[11]  S. Dinda,et al.  Correlation and prediction of fatigue crack growth for different R-ratios using Kmax and ΔK+ parameters , 2004 .

[12]  Brad Lee Boyce,et al.  On the application of the Kitagawa-Takahashi diagram to foreign-object damage and high-cycle fatigue , 2002 .

[13]  C. Laird,et al.  Cyclic stress-strain response of F.C.C. metals and alloys—I Phenomenological experiments , 1967 .

[14]  D. Kujawski.  ΔKeff parameter under re-examination , 2003 .

[15]  N. Dowling.  Mechanical Behavior of Materials: Engineering Methods for Deformation, Fracture, and Fatigue , 1993 .

[16]  Estimations of stress intensity factor for a short crack in an elastic–plastic notch , 2008 .

[17]  R. Ritchie,et al.  Propagation of short fatigue cracks , 1984 .

[18]  L. Nilsson,et al.  Calculation of Stress Intensity Factors for Cracks in Structural and Mechanical Components Subjected to Complex Stress Fields , 2004 .

[19]  John Goodman,et al.  Mechanics applied to engineering , 1904 .