Notch (engineering)

In structural components, a notch causes a stress concentration which can result in the initiation and growth of fatigue cracks.

The most common is the Charpy impact test, which uses a pendulum hammer (striker) to strike a horizontal notched specimen.

The Izod impact strength test uses a circular notched vertical specimen in a cantilever configuration.

[1] Sharp tipped V-shaped notches are often used in standard fracture toughness testing for ductile materials, polymers and for the characterization of weld strength.

The application of such notches for hard-steels is problematic due to sensitivity to grain alignment, which is why torsional testing may be applied for such materials instead.