A unifying approach to fatigue design in presence of defects and notches subject to uniaxial loading

In the recent past, Atzori and Lazzarin proposed a diagram able to include the geometrical effects on the fatigue limit of defects, short cracks, long cracks and U-shaped notches of whatever severity. The diagram shows that defect sensitivity and notch sensitivity can be considered as two sides of the same medal, thus creating a bridging between Linear Elastic Fracture Mechanics and Notch Mechanics. The fundamental material parameter, dependent on the load ratio, necessary to define the diagram is the El Haddad-Smith-Topper length parameter a0 defined by the plain material fatigue limit and the threshold value of the mode I stress intensity factor for long cracks. It is worth noting that a0 does not contain any geometry-related parameter. The diagram has been validated in the past against a number of experimental results and has been subsequently extended to sharp and blunt V-shaped notches, dependent on their absolute dimensions. After summarising the theory supporting the approach, some application examples relevant to both defect and notch sensitivity will be given.