Transient Eddy Current NDE System Based on Fluxgate Sensor for the Detection of Defects in Multilayered Conducting Material
This paper describes a novel transient eddy current non destructive evaluation (NDE) system for the detection of defects in a multilayered conducting material by using fluxgate magnetometer as a sensor. In conventional eddy current NDE, the depth of defect detection is restricted due to the excitation frequency and its associated skin depth. Similarly, in conventional pulsed eddy current testing the time derivative of the secondary magnetic field, which decays much faster than the magnetic field itself, is measured by the induction coil. However, in this work we use fluxgate magnetometer which measures magnetic field directly and double “D” differential excitation coil in order to enhance the depth of investigation. In addition to this, the other instruments such as transmitter, transmitter controller and data acquisition system used for this work are the same one used for TEM based geophysical applications. The system has been used for the detection of an artificially engineered defect in an aluminum plate at a depth of 2 mm as well as 20 mm below the surface.
KeywordsTransient eddy current NDE Fluxgate magnetometer Defect detection Double “D” excitation coil
The authors would like to thank Dr. N.V. Chandra Shekar and Dr. G. Amarendra for their continuous support and encouragement for this work.
- 1.Bray, E., Stanley, R.K.: Nondestructive Evaluation—a Tool in Design, Manufacturing and Service. CRC Press Inc, Boca Raton (1997)Google Scholar
- 2.Rao, B.P.C.: Practical Eddy Current Testing. Indian Society for Non-destructive Testing, Guindy (2007)Google Scholar
- 4.Smith, R.A., Hugo, G.R.: Transient eddy-current NDE for ageing aircraft. Insight 43, 14–20 (2001)Google Scholar
- 7.Sophian, A., Tian, G.Y., Taylor, D., Rudlin, J.: Electromagnetic and eddy current NDT: a review. Insight 43, 302–306 (2001)Google Scholar
- 16.Bartington Instruments Ltd., UK. http://www.bartington.co.uk/