Classification of Discontinuities

Surface discontinuity: Open to surface discontinuity.

Subsurface discontinuity – a discontinuity that is not open onto the surface of an product or test job.
Non relevant indication – indications that are not due to discontinuities.
May be due to abrupt changes in article shape, surface roughness, etc.
Classification of Defects by Origin
Typically grouped into 3 stages:
1. Inherent
2. Processing
3. Service-Induced (also call In-service discontinuity)