29 Jul 2013

Non-Destructive Testing: Doctors of the Engineering World

When human body parts malfunction, it’s time to see a doctor. When mechanical parts malfunction, it’s time to visit a non-destructive testing technician. Non-destructive testing (NDT) is the process of analysing and testing materials, machinery, and components without affecting their functionality. NDT is used across most types of manufacturing and engineering, including the transportation industry. Some NDT methods are even used in the restoration of works of art, or to establish authenticity. NDT is especially important to the aviation industry, where parts and machinery need regular inspection for safety. NDT is a potentially interesting career path for mathematically-minded people who enjoy investigating problems and solving puzzles. This article, presented by Spartan College of Aeronautics and Technology, describes some common NDT methods.

Radiology NDT technicians use x-ray photography to look for damage, just like a doctor looking for broken bones. Radiological methods involve bombarding items with gamma radiation to penetrate through the surface and generate internal images. This can identify weak points or breaks caused by corrosion and damage. Radiological methods of testing can be used on metal, ceramics, or nearly any solid, flat surface. In aviation, x-ray imaging is often used to inspect welds between metal to ensure they are strong enough to handle the forces involved in aircraft operation. Because radioactive materials are involved in x-ray imaging, NDT technicians must follow strict safety procedures.

Eddy Current Testing NDT technicians can detect flaws in materials that conduct electricity using electromagnetism. One method of electromagnetic inspection is eddy current testing. In eddy current testing, the NDT tech places an active electric current next to the item. This causes the item to generate magnetic fields which are known as “eddy currents” due to their similarity with patterns of turbulence seen in water. Analysis of these currents can identify cracks, fatigue, and other problems in the item being tested. Eddy current testing is useful because it is very portable. A drawback is that it can only be used on a limited number of materials. Also, certain types of surface finishes used on items may limit its effectiveness.

Liquid Dye Penetration Liquid dye penetration is a quick, low-cost method of finding surface flaws in a variety of non-porous materials, including metals, plastics, and ceramics. The object to be examined is carefully cleaned. Then, a solution containing a dye is applied to the material’s surface. After the excess material is removed, the penetrant will have sunk into any cracks or other flaws Testers can use dyes visible to the naked eye or fluorescents that show up when exposed to UV light (so-called “black light”).

Magnetic Particle Testing Magnetic particle testing is similar to liquid dye penetration methods in that it uses a solution applied to an object to detect surface flaws such as cracks. However, it is used with conductive materials, such as metals. The part being inspected is cleaned, and then subject to an electric current which magnetizes it. The tester then applies a wet or dry solution containing iron oxide particles to the object. If there are any flaws in the item, the particles will swarm towards it. The tester can then perform further evaluation of the damage.

Ultrasonic Testing You may be surprised to know that ultrasound, which is often used to examine unborn babies, was originally developed for industrial testing purposes. Ultrasound testing uses pulses of short-frequency soundwaves to create sub-surface images of materials, allowing for the discovery of cracks, fatigue, and other flaws. To conduct ultrasonic testing, an oil or gel is first placed on the surface of the object (certain parts may also be immersed in water, which is called immersion testing). The ultrasound probe is run over the surface, and the reflected sound waves create an image on a monitor. Ultrasound is a very portable, quick testing method.

Becoming an NDT Specialist If you’re interested in pursuing a career as an NDT specialist, you can pursue a diploma or associate’s degree and potentially be ready to enter the job market in 12-30 months. Once you have graduated, there are many types of professional certification you can pursue to enhance your resume. This includes certification from the Federal Aviation Administration (for NDT and quality control specialists in the aviation industry), the American Society for Testing and Materials, the American Society for Non-Destructive Testing, and more. With NDT qualifications, you can potentially find work in many different economic sectors, including aviation, transportation, manufacturing , and construction. Look for a training program that offers plenty of hands-on testing opportunities paired with mathematics, physics, and safety practices.