What Is a Flaw Detector?
Flaw detectors are non-destructive inspection devices used to detect the position, size, and shape of minute flaws in processed metals and materials that cannot be seen by the human eye.
Flaws in metals can accelerate the deterioration of products made of those metals and sometimes cause them to become defective, which is very dangerous.
The Flaw detector itself is about the size of a palm.
There are various types of Flaw detectors based on the principle of detection, with ultrasonic Flaw detectors being the most common.
Uses of Flaw Detectors
Flaw detectors are used in all kinds of manufacturing industries and workplaces where metal and concrete are used.
Cast iron (iron containing a few percent of carbon or silicon) is the most commonly inspected material, and is used in many heavy industrial products such as automobile parts.
Flaw detectors are also used to measure the length of anchor bolts that secure structures to concrete foundations, to detect the adhesion and delamination of metal and resin such as in the lining of pipes, and to check the water level of liquids inside containers that are difficult to open or close.
Principle of Flaw Detectors
Ultrasonic Flaw detectors can be broadly classified into three types: Pulse Reflection, Transmission, and Resonance.
In the pulse reflection method, a probe or transducer transmitting ultrasonic pulse waves, and when a part of the waves is reflected from a flaw or crack inside a metal, the echoes are displayed on the receiving screen to detect internal defects.
In the transmission method, an ultrasonic wave is emitted from one side of the inspection target by a transmitting probe and received by a receiving probe on the other side.
In the resonance method, ultrasonic waves are continuously emitted from the transmitting probe, and the presence of defects is detected by resonating the emitted and reflected waves.
Among these methods, the pulse reflection method is the most commonly used due to its high detection accuracy, and there are several types of pulse wave modes, such as perpendicular, oblique, surface wave, and plate wave.