As it can be appreciated after the description of the method for fatigue characterisation, that this is quite an expensive procedure (regarding time and facilities). For this reason, there are alternative quicker and cheaper methods that allow us to determine the fatigue parameters in an approximate way.
Starting with the simplest one, we could use the specialised bibliography. For this method there are two main limitations: (a) due to the high cost, there are few available characterisations and (b) small changes in the composition or manufacturing process generate great changes in the fatigue behaviour.
The alternative is to use mathematical approximations from a static characterisation. The accuracy of this technique is higher, but might be not good enough. There are many methods that work in this way, the most important ones are shown in the slide.