Among all of the industrial applications of nondestructive testing, flaw detection is the oldest and the most common.
Since the 1940s, the propagation of sound waves through solid materials has been used to detect hidden cracks, voids,
porosity, and other internal discontinuities in metals, composites, plastics, and ceramics. High frequency sound waves
reflect from flaws in predictable ways, producing distinctive echo patterns that can be displayed and recorded by portable
instruments. Phased array technology adds color graphics presentations that simplify interpretation of results by drawing
cross-sectional images of internal structures. As well, phased arrays offer beam-steering and dynamic focusing capability
that enhances resolution in challenging applications like turbine rotor and blade root inspection, full data storage and
rapid scanning. Similarly, the physics of electricity and magnetism is the theoretical basis used by eddy current instruments
to find internal flaws in metal sheets, tubes, machined parts, and critical assemblies like aircraft fasteners. Eddy current
is especially well suited for finding surface breaking cracks in almost any metal part.