Fatigue of ferrous alloys - Calculation examples

To calculate the fatigue life of a part, the engineer needs to be able to compare, on a very general level, the working stress of the part with a limit permissible stress.

As far as fatigue is concerned, the previous articles on definitions and diagrams and on the factors that influence the best estimate of this permissible limit stress, a function of all the parameters previously taken into account (stress, geometry, material, surface condition, temperature, various treatments, etc.).

If a safety factor is set a priori, and the comparison reveals a significant deviation (plus or minus) from it, then one or more of the above parameters must be modified, either by increasing the admissible limit stress (safety aspect), or by decreasing it (economic aspect).