Ultrasonic Testing (UT) uses high frequency sound energy to conduct examinations and make measurements. Ultrasonic inspection can be used for flaw detection/evaluation, dimensional measurements, material characterization, and more.
Ultrasonic testing is carried out using an ultrasonic flaw detector and an ultrasonic probe. In the inspection, ultrasound is sent into the area of interest. The ultrasound can be reflected from an interface like discontinuity and received by the probe. The reflected ultrasound is displayed on a cathode ray tube screen in the flaw detector and the signal can be analyzed. This method of inspection is normally carried out on butt welds and is usually limited to section thickness of 10mm and above. It is technically difficult to perform the inspection on thin materials less than 10mm and coarse grain materials like stainless steel using conventional ultrasonic equipment. This method is good for detecting internal discontinuities. Surface or near surface discontinuities may not be easily detected.
Magnetic Particle Testing is an inspection method for finding out discontinuity on the surface or close to the surface (to a depth of approx. 2 mm) in a Ferro-magnetic material.
It uses the principle that a discontinuity on the surface causes a magnetic leakage when apply a magnetic field to the object. A crack will be made visible by an interruption of this field. The indications are judged by their nature, size and location with the aid of an inspection standard. The shape or dimensions of the object do not generally limit it.
Dye Penetrant Testing is a technique by which a specially designed colored dye is used in conjunction with specially formulated developers to detect surface breaking indications on any ferromagnetic or non-ferromagnetic material to assist in determining the material integrity.
Applications include determining weld surface integrity and detection of defects of all types of surface breaking discontinuities resulting from many different reasons. Dye penetrant testing can be used on practically all materials. However, there is a practical difficulty to perform penetrant testing on materials having porus in nature.