Metal Fatigue 2021

Dear Colleagues,

The S–N curve of the vast majority of ferritic steels and titanium alloys (BCC: body-centered cubic structure) exhibits a nearly horizontal line ranging from 10⁶ to 5 × 10⁶ cycles. In classic fatigue modeling, the strength value of the horizontal asymptote is usually regarded as a fatigue limit for this type of materials. Assuming that this curve corresponds to a probability of failure, for a given R-value (S_min/S_max ratio), the conventional fatigue limit would provide a stress value to use as a reference value for mechanical design purposes in the high cycle fatigue region (N < 10⁷ cycles).

Other materials, however, such as austenitic steels and aluminum alloys (FCC: face centered cubic structure), do not show this horizontal zone, and the fatigue design is performed using fatigue strength for a given number of cycles.  

On the other hand, it is also known that for a higher number of cycles exceeding 10⁷ (VHCF, UHCF), FCC and most of the BCC materials exhibit a decrease in fatigue strength with the number of cycles. This fatigue region is characterized by a modification of the place of the crack initiation process, changing from surface (HCF) to subsurface initiation (VHCF). Other studies suggest that internal initiation can be provoked by internal defects even within the HCF region for high mean tensile stresses, so that the stress ratio R plays a key role in the shape of the S–N curve.

In this Special Issue, we aim to gather studies that focus on aspects that influence fatigue strength (both conventional fatigue limit and gigacycle fatigue strength) and the S–N curve and its shape. Studies on the influence of the processes of obtaining the material (composition, grain size, and subsequent thermal or surface treatments), manufacturing processes and later treatments (such as SP, LSP, LPB, and welding), additive manufacturing, residual stresses, and tribological parameters in the fatigue limit value are welcome. Studies on the use of time-varying stress values in fatigue design (cumulative damage) and the influence of mean tensile and compressive stresses (behavior models in the Haigh diagram for infinite life), as well as uniaxial and multi-axial fatigue methods, are also welcome.

Prof. Dr. Joseba Albizuri
Dr. Luis Pallarés-Santasmartas
Guest Editors

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• S–N curve
• conventional fatigue limit
• very high cycle fatigue (VHCF)
• multistage fatigue life diagram
• microstructure-based fatigue model
• residual stresses
• haigh diagram
• mean stress effect
• manufacturing processes