Lock-in Amplifier Based Eddy Current Instrument for Detection of Sub-surface Defect in Stainless Steel Plates
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For detection of sub-surface defects using eddy current (EC) method, increasing the depth of penetration of ECs is essential. This can be achieved through strengthening of the primary magnetic field from the EC probe. This can be accomplished by using low-frequency high amplitude excitation current, precise phase lag measurement and high throughput probes. Working on these lines, the paper presents development of lock-in amplifier based EC instrument and cup-core send-receive type probe. Experiment results indicate that the proposed instrument and probe is able to detect sub-surface defects located at 8.0 mm below surface and classify sub-surface as well as surface defects in stainless steel plate.
KeywordsEC probe EC instruments Sub-surface defects Stainless steel Non-destructive testing
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