Is notch sensitivity a stress analysis problem?

Jaime Tupiassú Pinho de Castro, Marco Antonio Meggiolaro


Semi–empirical notch sensitivity factors q have been widely used to properly account for notch
effects in fatigue design for a long time. However, the intrinsically empirical nature of this old concept can be
avoided by modeling it using sound mechanical concepts that properly consider the influence of notch tip stress
gradients on the growth behavior of mechanically short cracks. Moreover, this model requires only wellestablished
mechanical properties, as it has no need for data-fitting or similar ill-defined empirical parameters.
In this way, the q value can now be calculated considering the characteristics of the notch geometry and of the
loading, as well as the basic mechanical properties of the material, such as its fatigue limit and crack propagation
threshold, if the problem is fatigue, or its equivalent resistances to crack initiation and to crack propagation
under corrosion conditions, if the problem is environmentally assisted or stress corrosion cracking. Predictions
based on this purely mechanical model have been validated by proper tests both in the fatigue and in the SCC
cases, indicating that notch sensitivity can indeed be treated as a stress analysis problem.

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