PSI - Issue 46

Przemysław Strzelecki et al. / Procedia Structural Integrity 46 (2023) 99– 104 Przemys ł aw Strzelecki / Structural Integrity Procedia 00 (2021) 000–000

103 5

1.4301

a

b

Samples from fatigue tests S-N curve 50%

Stress amplitude S a [MPa] 10 4

350 400 450 500 550

5  10 4 10 5

5  10 5 10 6

5  10 6

Number of cycles log N

c

d

Fig. 3. S-N curves for 1.4301 steel with the probability distribution for the yield strength test and the fatigue strength for 10 5 cycles

4. Summary and conclusion The standard deviation for logarithm yield strength was bigger than for the fatigue strength tests in the high-cycles region. The difference was twice for S355J2+C steel and 14 % for 1.4301 steel. So, estimated distribution acc. to eq. (4) gives a bigger scatter of fatigue strength. Consequently, the estimated S-N curve proposed has a lower value of fatigue strength than the S-N curve estimated by the standard method presented in ISO-12107, (2012). That fact can be seen in Fig. 2 (d) and 3 (d) where the estimated S-N curves for 5 % probability acc. to the proposed method has lower fatigue strength than curves from test acc. ISO standard. So, the proposed method is conservative and can be used by engineers. References ASTM E-739-91. 2015. Standard Practice for Statistical Analysis of Linear or Linearized Stress-Life (S-N) and Strain-Life (ε-N) Fatigue Data. https://doi.org/10.1520/E0739-10R15 Gope, P. 1999. Determination of sample size for estimation of fatigue life by using Weibull or log-normal distribution. International Journal of Fatigue. 21(8), 745–752. https://doi.org/10.1016/S0142-1123(99)00048-1 Gope, P. C. 2012. Scatter analysis of fatigue life and prediction of S-N curve. Journal of Failure Analysis and Prevention. 12(5), 507–517. https://doi.org/10.1007/s11668-012-9590-0 Hobbacher, A. F. 2008. IIW document IIW-1823-07 recommendations for fatigue design of welded joints and components. International Institute of Welding. ISO-12107. 2012. Metallic materials - fatigue testing - statistical planning and analysis of data. Lewis, G., & Sadhasivini, A. 2004. Estimation of the minimum number of test specimens for fatigue testing of acrylic bone cement. Biomaterials. 25(18), 4425–4432. https://doi.org/10.1016/j.biomaterials.2003.11.014