How does frequency selection impact defect detection in Eddy Current Testing?

The impact of frequency selection on defect detection in Eddy Current Testing is critical because different frequencies interact with materials and defects in distinct ways. Lower frequencies are generally associated with higher penetration depths within the material, but they may not provide sufficient sensitivity to detect smaller surface defects. This is due to the nature of electromagnetic induction: lower frequencies induce currents that flow deeper into the material, but these currents may not be influenced significantly by very small surface defects or fine features, which require higher frequency signals to create a more concentrated and sensitive eddy current response.

By using higher frequencies, the electromagnetic fields generated are more sensitive to small surface anomalies because these frequencies result in eddy currents that are more confined to the surface of the material. This makes it more likely to detect small cracks, pits, or other surface-related defects. Consequently, the relationship between frequency and defect size is essential for optimizing detection capabilities in Eddy Current Testing.

In summary, the choice of frequency plays a vital role in the effectiveness of detecting surface defects, highlighting why lower frequencies may miss small surface defects.