Microwave nondestructive testing

Page 1 : Microwave NDT

Page 2 : Experimental set-up

Background of this research

Detection of defect in complex piping systems in early stage of degradation with a high-speed and high-accuracy inspection method is serious concerns in the operation of nuclear power plants. The typical methods for detecting defects such as eddy current testing (ECT) and ultrasonic testing (UT) are time/cost consuming because they need point-by-point inspection for the long pipes. Therefore it is desirable to develop another high-speed technique for crack detection. One of the most promising techniques which might reduce the time/cost of the long range inspection is the nondestructive testing (NDT) method using microwave. We are investigating the microwave NDT to achieve high-speed inspection.

Microwave NDT

Microwave can be propagated through pipes rapidly. We can use TE-modes for detection of defect having longitudinal component, a longitudinal crack for example. The TE-modes are characterized by fields with E_z = 0 and H_z ≠ 0, where z indicates the direction of the axial direction. When microwave wave of TE-modes is propagated in the pipe, the electric surface current with a circumferential component is produced in the inner surface of the pipe. Once this surface current flows in the pipe with a longitudinal crack, the crack prevents the surface current from flowing. Consequently some parts of the incident wave are reflected, which have information about the crack. We can also use TM-modes for detection of defect having circumferential component, a circumferential crack for example. The TM-modes are characterized by fields with E_z ≠ 0 and H_z = 0. When microwave wave of TM-modes is propagated in the pipe, the electric surface current with a axial component is produced in the inner surface of the pipe. Then we can obtain information about a circumferential crack.

TE mode

TM mode