What is the most effective current to be used with dry magnetic particles?

The most effective current to be used with dry magnetic particles is half-wave rectified alternating current. In magnetic particle testing, the primary objective is to create a reliable magnetic field that can effectively gather magnetic particles at discontinuities. Half-wave rectified current provides a pulsed magnetic field that enhances the magnetization of the material and improves the attraction of dry magnetic particles to any surface flaws present. This pulsed effect allows for a more concentrated magnetic field, which helps in lifting and holding the magnetic particles on the surface where cracks or defects may exist.

Using half-wave rectified alternating current combines the benefits of both direct and alternating current. While direct current creates a steady magnetic field, it may not provide the same level of effectiveness in mobilizing dry particles as the half-wave rectified current. Alternating current, on the other hand, can result in a fluctuating magnetic field that may not attract the particles as effectively. Full-wave rectified current, while also effective, does not offer the same beneficial pulsing effect as half-wave rectified current specifically for dry magnetic particle application. By leveraging the characteristics of half-wave rectified alternating current, more precise indications of defects can be observed during testing.