10 Tips for Designing Against Fatigue

Roof of AZ stadium collapsed due to fatigue.

Do you want to be responsible for accidents like this? I guess not. To avoid such misery it is always good to keep some elementary things in mind.

Things to keep in mind when designing against fatigue

  • Always remember: fatigue is caused by cyclic stresses.
  • Do recognize that cracks initiate at locations with high stresses, i.e. stress concentrations. The sharper the discontinuity, the higher the stress concentration factor.
  • Provide a smooth flow of stresses.
  • Improve surface finish, cracks almost always initiate at the surface.
  • Consider surface hardening by¬†carburization or nitriding, this improves the fatigue properties at the surface.
  • Increase the fatigue performance by means of residual¬†compression stresses on the surface. Note that residual tensile stresses are unfavorable for fatigue.
  • Know that fatigue life analyses are inherently inaccurate. Simplifications in your analysis increase the inaccuracy.
  • Fatigue testing helps to validate your analysis and to optimize your design.
  • Be aware of disturbance loads; not only operational loads contribute to fatigue.
  • “If you think safety is expensive, try accident”, i.e. ignore your manager.

More about mistakes in fatigue analysis

We have compiled an overview of common mistakes made in fatigue analysis. This overview is available in a free ebook. Use the form below to get this ebook.