Stress intensification factors are fatigue correlation factors that compare the fatigue life of piping components to that of girth butt welds in straight pipe subjected to bending moments. You can read more about Stress intensification factors in this paper.
The stress intensification factor should not be confused with stress intensity factor used in fracture mechanics studies.
Also read Stress concentration factor vs Stress Intensity Factor
This page is part of The Encyclopedia of Stresses in Solids