Ultrasonic testing is the process of applying ultrasonic sound to a specimen and determining its soundness, thickness or some physical property.

Sound is a vibration that transmits energy by a series of small material displacements. Vibrations above human hearing range are called ultrasonics vibrations.

The energy is originated in a piezoelectric transducer which causes material displacement within the specimen. The transducer can also convert mechanical energy coming back from the specimen into electrical energy. Therefore, a transducer can both send and receive energy. The returning energy can be transformed in an electrical impulse which can be displayed on a monitor in form of echoes, thus allowing the identification of flaws within the specimen or directly showing the thickness in mm.

Basic Applications of Ultrasonics

Ultrasonics is a versatile inspection technique, which is used to test a variety of both metallic and non metallic products such as welds, forgings, sheet, tubing, plastics and ceramics.

Ultrasonics has an advantage of detecting subsurface discontinuities with access to only one side of the specimen.

The objective of ultrasonics testing is to ensure product reliability by means of:

1. obtaining information related to discontinuities

2. disclosing the nature of the discontinuity without empairing the uselfuness of the part

3. Separating acceptable and unacceptable materials in according with predetermined standards

Ultrasonics units are portable, radiation free and has major advantages compared to other NDT: can inspect deeper that Penetrants and Magnetic Particles and may reveal flaws that cannot be seen with radiography (such as planar defects).

Major disadvange of ultrasonic is to be too much inspector depending, as no trace is left.

However, in the last few years, new technologies (TOFD) are making UT recordable and replacement of radiography by UT is now possible under circumstances stated in the ASME Code Case 2235- 6.