ACPD stands for Alternating Current Potential Drop.

What is ACPD?

ACPD is a well-established electromagnetic technique for sizing surface-breaking defects in metals. It is particularly suited to obtaining detailed crack profiles and to monitoring crack growth or initiation. It is a contacting method which requires a high level of surface cleaning (at least Swedish Standard SA 2 1/2) to achieve best results.

How does ACPD Work?

ACPD works by inputting an alternating current into the sample so it flows across the defect. The current is normally directly injected, but can be induced. A voltage probe then measures surface potential differences.

By comparing potential differences across the crack with a reference value, the extra path length caused by the defect can be estimated, giving a value for the crack depth.

Further Information

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