Radiography involves the use of penetrating X or gamma radiation to examine parts and products for imperfections. An x-ray machine or radioactive isotope is used as a source of radiation. Radiation is directed through a part and onto film. When the film is developed, a shadowgraph is obtained that shows internal soundness of a part. Possible imperfections show up as density changes in the film, in much the same manner as an x-ray can show broken bones.

Magnetic particle testing is done by inducing a magnetic field in a ferro-magentic material and dusting the surface with iron particles (either dry or suspended in a liquid). Surface imperfections will distort the magnetic field and concentrate the iron particles near imperfections, thus indicating their presence.

Ultrasonic testing uses the transmission of high frequency sound waves, into a material to detect imperfections within the material or changes in material propeties. The most commonly used ultrasonic testing technique is pulse echo wherein sound is introduced into the test object and reflections (echoes) are returned to a receiver from internal imperfections or from geometrical surfaces of the part.

Liquid penetrant testing is probably the most widely used NDT method. The test object or material is coated with a visible or fluorescent dye solution. The excess dye is removed from the surface, and then a developer is applied. The developer acts like a blotter and draws penetrant out of imperfections which are open to the surface. With visible dyes, the vivid color contrast between the penetrant and the developer makes the “bleedout” easy to see. With flourescent dyes, an ultraviolet lamp is used to make the imperfections easier to see.

In eddy current testing, one of several electromagnetic testing methods, electrical currents are generated in a conductive material by a magnetic field interruptions in the flow of the electric currents (eddy currents), which are caused by imperferctions or changes in a material’s conductive properties, will cause changes in the magnetic field. These changes when detected, indicate the presence of a change in the test object.

Probably the oldest and most common method of NDT is visual examination, which has numerous industrial and commercial applications. Examiners follow procedures ranging from simple to very complex, some of which involve comparison of workmanship samples with production parts. Visual techniques are used with all other NDT methods.

Phased Array Courses

Test NDT, LLC. is an approved Olympus NDT training partner and will be offering a selection of Phased Array training courses using the OmniScan® equipment. In addition to the 2 day introduction to phased array we also offer Intensive Aerospace UT phased array and Aerospace Eddy Current array courses of 40 hour duration and a 40 Weld Inspection course leading to employer based certification per employer certification programs.