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

Abstract

Abstract. 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 a 0 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 a 0 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.

Notch Stress Intensity Factor (NSIF)-Based Fatigue Design to Assess Cast Steel Porosity and Related Artificially Generated Imperfections

“…In case of a V-notch with an opening-angle equal to 0 • , the Williams eigenvalue results in a value of 0.5 and therefore leads to the fracture mechanical base equation [30,31].…”