Wednesday, January 20, 2010

NDT methods

First of all let's have a brief look at some of the most common NDT/NDE methods,

•Visual inspection: Visual examiners follow procedures that range from simply looking at a part to see if surface imperfections are visible. He can use the help of a magnifying glass or computer controlled camera. It is the most basic method of all.

•Liquid penetrant Testing: Engineer evaluates defects on the material surface with help of liquids or sprays.

•Eddy Current Testing: Engineer uses equipment with electromagnetic induction to detect flaws in or on conductive materials.
•Acoustics methods (mainly ultrasonic, Acoustic emission, Impedance etc…): Engineer uses different forms of acoustic waves (such as sound, ultrasound and infrasound) in order to evaluate defects. You probably have heard of the Ultrasonic sonogram they use in medicine to see the gender of a baby before birth. It certainly is another use of NDT.
Figure: Ultrasonic Scanning of a T beam

•Magnetic particle crack detection: Engineer evaluates defects of ferromagnetic materials by applying a magnetic field and magnetic particles which are usually mixed with a liquid.

•X-Ray: Use electromagnetic radiation to detect defects as same as in Medicine. Every one of us has seen an X-Ray image. This is one of the most trusted ways of controlling an object.

•Thermography: Engineer uses a camera containing large numbers of sensors sensitive to infrared radiation.