Magnetic Particle Testing is an Conventional Testing Method which involves the component under testing being magnetized. This magnetization process is supplemented by the application of ferromagnetic particles to the already magnetized surface. The magnetic particles are attracted to areas of flux leakage (escaping magnetism) and form an indication at that point. This NDT method is used to test welds, castings, and forgings for surface or slightly subsurface defects. However Magnetic Particle Testing can only be used to inspect materials that can be magnetized, i.e. ferromagnetic materials.
This Non-Destructive Testing Method involves applying a liquid to the surface of a material and leaving it to rest for a pre-determined period of time. The liquid can be either a colour that is easily visible under normal lighting conditions or a yellow/green fluorescent colour that requires special lighting conditions to be effective. During the Liquid Penetrant Testing the liquid dye enters into discontinuities that are open to the surface of the material through a phenomenon known as 'capillary action'. This capillary action takes place through the resting time and the discontinuity retains this dye when the excess is cleaned from the surface. A certain type of developer is then applied to the surface of the material and the dye that is trapped inside the surface discontinuities is blotted back out on to the surface and forms an indication. This indication is then interpreted by a qualified interpreter. The Liquid Penetrant Testing method, also know as Dye Penetrant Examination is suitable on most non-absorbent materials.
Ultrasonic Testing as a Non-Destructive Testing (NDT) employs high-frequency sound pulses that are emitted from a transducer. The sound wave is induced in to the material through a probe which is usually in contact with the material. These sound waves propagate through the material, and are reflected back to the probe when they reach an interface. The reflected waves are transmitted back through the probe and connecting leads to a detector which can be either analogue or digital. The sound waves are then displayed as a series of signals on a monitor and the qualified inspector can measure and interpret these signals to allow accurate evaluation of the internal structure of the material. Ultrasonic Testing can be used not only to indicate a surface or subsurface flaw but also to determine the depth, size and type of flaw. Another advantage of using Ultrasonic Testing is the accurate measurement of the thickness of the material. The method can be applied to most materials provided those materials can transmit sound waves. Ultrasonic Testing is considered to be a fast and effective way of inspection, ensuring high-sensitivity results.
Radiographic Testing as a Non-Destructive Testing (NDT) is based on the same principle as medical radiography in a hospital. A piece of radiographic film is placed on the remote side of the material under inspection and radiation is then transmitted through from one side of the material to the remote side where the radiographic film is placed. The radiographic film detects the radiation and measures the various quantities of received over the entire surface of the film This film is then processed under dark room conditions and the various degrees of radiation received by the film are imaged by the display of different degrees of black and white, this is termed the film density and is viewed on a special light emitting device. Discontinuities in the material affect the amount of radiation being received by the film through that particular plain of the material. Qualified inspectors can interpret the resultant images and record the location and type of defect present in the material. The Conventional Radiography can be used on most materials and product forms, e.g. welds, castings, composites etc. Radiographic testing provides a permanent record in the form of a radiograph and provides a high sensitivity of the internal structure of the material