## Magnetic Hysteresis in Line Pipe Steels

When a ferromagnetic material is magnetized, some of the domains are driven beyond the point at which the changes are reversible. Then, when the imposed field intensity is decreased to zero, the material retains some degree of magnetization. If the coil current that produces the imposed field is slowly cycled between maximum values in either direction, the corresponding values trace out a closed curve which is called a "hysteresis loop". The phenomena of magnetic hysteresis is very complex, and it is not yet fully understood, despite the many attempts which have been made to develop mathematical models of it for ferromagnetic and ferrimagnetic materials.

Stoner & Wohlfarth postulated a theory based on the rotation of the magnetic moments of single-domain particles with respect to their easy axes. Jiles and Atherton developed a theory in which pinning sites (i.e. inclusions, voids, crystal boundaries and lattice defects, etc.) inhibit domain wall motion. Another competing mathematical description is the Preisach model which assumes a ferromagnet to consist of many small magnetic domains, each with its own characteristic hysteresis loop. WE work on all these models and also the interactions between stress and magnetic properties.

* Papers detailing Magnetic Hysteresis in Line Pipe Steels
* Papers detailing Stress/Magnetic Interactions in Line Pipe Steels

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Last revised August 10 1998
Created by Inba Kehoe (KEHOEI@QUCDN.QUEENSU.CA)
Updated by Kristine Spekkens (6ks@qlink.queensu.ca)

URL:http://physics.queensu.ca/atherton/linepipe.html