PSI - Issue 5

Amal ben Ahmed et al. / Procedia Structural Integrity 5 (2017) 524–530 Amal ben Ahmed et al. / Structural Integrity Procedia 00 (2017) 000 – 000 5 log-normally distributed for defect size under than 500 m and above this value it returns normally distributed. Based on these observations, it clear that the alternate torsion is more sensitive to the SDAS scattering especially in the case of small defects. (iii) Figs 4-5 show the evolution of the reliability as a function of the applied load for √ equals to 500 m (alternate tension) and for √ equals to 600 m (alternate torsion). In fig.5, a deterministic endurance limit, taken from experimental data [IbenHouriya et al. (2015)], is compared to the reliability results. It is noticed that the loading point corresponds to a 25 % of reliability.

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95% reliability 50% reliability 5% reliability Experimental data [18]

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Fig. 2. Iso-probabilistic Kitagawa-Tkahashi diagrams under fully reserved tension fatigue loading

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95% reliability 50% reliability 5% reliability Experimental data [18]

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Fatigue limit (MPa)

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Defect size (um)

Fig. 3. Iso-probabilistic Kitagawa – Tkahashi diagrams under torsion fatigue loading