Stress Elevation
A geometric effect increases the intensity of an internal load at the base of a sharp indentation or change in cross-section. The presence of notch root stress concentration identifies the most likely site for a crack to form in a structural member. It is a function of the radius of the notch relative to the width of the part.
Stress Factor
Numerical calculation of the theoretical stress concentration factor represents the ratio of the maximum stress at the root to the nominal stress in the bulk material. When the radius is very small, notch root stress concentration can reach values many times higher than the average load. Finite element analysis provides the primary method for calculating these values in complex geometries.
Engineers refine the mesh density at the root to ensure the numerical model converges on a stable result. If the mesh is too coarse, the peak load will be underestimated.
Material Ductility
Blunting of the tip occurs in ductile metals which reduces the effective peak load.
Design Rule
Radius specifications in manufacturing drawings define the minimum curvature allowed at a corner. Strict control of the machining process prevents the formation of burrs or accidental gouges that would increase the notch root stress concentration.
