Question

Which of the following terms changes in the eddy current testing method for the detection of defects in the castings?

(a) Resistance

(b) Impedance

(c) Conductivity

(d) Capacitance

I had been asked this question by my college professor while I was bunking the class.

My question comes from Non Destructive Testing in section Inspection Testing in Foundries of Casting-Forming-Welding I

Answer 1

The correct answer is:

(b) Impedance

Explanation: In eddy current testing (ECT), the detection of defects in castings is primarily based on the changes in the impedance of the coil used in the testing. Eddy currents are induced in the material being tested, and any discontinuity, such as a crack or void, will disturb the flow of these currents. This disturbance leads to a change in the impedance (which is a combination of resistance and reactance) of the coil, and the change is measured to detect the presence of defects.