Technical Diagnostics and NDT

Sometimes, smallest of the defects can be hardly visible for human eyes. That is when engineers use the Liquid Penetrant (PT) or Dye Penetrant test. Liquid Penetrant Examination is a Non-Destructive Testing method used to detect surface breaking defects, such as cracks, laps, porosity etc., which are unperceivable with the bare eye. The method is rest upon the ability of a fluid to be drawn into a "clean" surface-breaking flaw by smooth action. After a certain time period, unnecessary surface penetrant is displaced and a developer is applied that functions as a "blotter". Color contrast penetrants demand adequate white light whereas fluorescent penetrants are suggested to be used in dark environment and require ultraviolet "black light" where penetrant glows with a luminous color which can be easily seen from our eyes.

Gas turbine engines are widely used in different fields for generate energy. They are commonly used in aircrafts. If you watch a huge passenger aircraft, you can see the gas turbine engines are either hanging on the wing section or tail section. Those power plants gives enough energy to generate thrust which finally result the aircraft fly. Figure: An Airbus A340's 4 engines are situated on the wing, 2 in each side. Figure: A Tupolev 154 Aircraft where engines situated on the empennage  How does a gas turbine engine work? There are several sections inside of an engine. First one is the air intake and fan which direct the air to inside of the engine, then the compressor, which compress the air to a very high pressure while reducing its speed. Then air meets the combustion chamber, where kerosene (fuel) is spread as small particles and burned in a high temperature.  

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: ...

Diagnostics! Well, yes, we all heard this word very many times in the medicine. There, diagnostics means, identification of the nature of an illness or other problem by examination of the symptoms. As same as Buddha tried to find reason for sadness before cure, doctors try to find reason for illness before cure, Engineers do test and evaluate before thinking a cure for those mechanical objects. It is one of the most important parts of engineering which is closely linked to aerospace engineering, civil engineering, electrical engineering, material science and engineering, mechanical engineering, nuclear engineering, petroleum engineering, physics etc… It’s often used in both constructional and service sides.