In the manufacturing industry the structural integrity of any material is of prime importance. The overall stability of any product depends on the strength of each of its parts. This is why we have a series of test methods to test their integrity. Of these non-destructive testing is the most popular because it leaves the tested object intact.
In this method non-destructive testing equipment is used to evaluate the properties of a material, substance or component without causing it any damage. The biggest advantage that NDT has and why it is preferred over other methods to test components is that the object tested is not damaged and can be used again.
NDT uses means like sound, electromagnetic radiation and other signals to gauge the object. The properties that are tested include its composition and integrity. Some of the most common methods used are:
Visual and Optical Testing
This method is usually used in data acquisition, data analysis, and quality control. The tests are carried out by using our sense organs like vision, hearing and smell. Non-specialised equipment can also be used. This can include tools like computer cameras and certain precise measuring tools, but not equipment like X-ray machines. The method is very handy in recognising the obvious visual flaws in an object.
Magnetic Particle Testing
This method is effective in testing surface imperfections in ferromagnetic substances like nickel, cobalt,iron, and their alloys. The non-destructive testing equipment here passes a magnetic field through the object. This results in the magnetisation of the object. The magnetisation could be direct or indirect. However, in either case, any surface damage or irregularity will cause leak in the magnetic flux. Ferrous particles are introduced to the part and attach themselves to the leakage point, helping the tester to evaluate the area.
This method is effective in examining the internal structure of a finished product, thereby showing us a complete picture. This is performed through electromagnetic radiations, particularly gamma rays or X-rays. These are preferred because of their short wavelength. This allows them to penetrate through most materials. The method is pretty similar to how we’ll do a human X-ray, giving us a detailed skeleton of a product.
Ultrasonic Testing (UT)
This NDT methodology utilises sound waves. Most ultrasonic non-destructive testing equipments transmit short ultrasonic pulse-waves (0.1 to 15 MHz) through the material. On occasion the frequency may go up to 50 MHz. Common materials to be tested here are metals, alloys, wood, concrete and alloys, though it’s most effective in case of steel. It is common in metallurgy, automotive, manufacturing, steel and aluminium construction, and transportation industry like aerospace.
This method is very effective in detecting deteriorations or imperfections in a material. By using ultrasonic waves we are able to determine the different properties of a material, such as its thickness. This can be used in testing the corrosion of components.
With much lower costs, penetrant testing is quite popular. This is used for non-porous materials like plastics, metals and ceramics. The test is useful in detecting surface defects like fractures, cracks or leaks. A liquid penetrant, usually a dye is applied to the surface. The dye would penetrate any cracks. The excess dye is washed off. A developer is then used to detect the dye which may have penetrated inside. Ultraviolet light is used in case of fluorescent dyes.
NDT is has significant scientific and industrial applications. It is widely used in many engineering and forensic applications. It has also emerged as a major source of quality testing in industrial manufacturing. In fact, you’ll be surprised to know how many things around you had to go through NDT before they were allowed to be used.
Although there are other means of assessing various properties and integrity of a material, NDT is obviously preferred because it causes no damage to the finished product. It means we can test final product and if the tests come out negative, we can carry out repairs. Non-destructive testing equipments also help us to pinpoint the location of the defect.
These methods are, hence, important in ascertaining the quality of a product. By allowing us to repair in time, these are also cost saving.