1. Choosing a diagram

Choosing a diagram for a fatigue calculation is an important task. This choice must be made on the basis of the experimental data available, the nature of the external stresses and the residual stress states.

In the case of uniaxial residual stresses and simple loading, Haigh or Goodman diagrams can be used. If the stresses are multiaxial, or if the multiaxial state of the residual stresses is known, it is preferable to use a diagram derived from a multiaxial fatigue criterion presented in the previous article. . In the event that we do not have all the material data required to construct a multiaxial fatigue diagram, it is also possible to use a uniaxial fatigue diagram using equivalent stresses ( σ _{M eq} , σ _{a eq} ).