Magnetostrictionon 24/2/2012 & Updated on Wednesday 27th of June 2018 at 06:01:20 PM
Then the ratio of δL to L is Joule’s magnetostriction coefficient (λ). λ = δL / L. There is a loss in energy due to friction in magnetic material cores. This effect is the reason of humming sound that we hear in transformer. Next, we can go through some of the effects used in magnetostriction. They are
- Joules Effect: When a ferromagnetic substance is subjected to magnetic field, it will alter in shape.
- Villari Effect: When a substance is subjected to a mechanical stress, the susceptibility of that substance changes (magneto elastic effect i.e. inverse of magnetostriction)
- Matteucci Effect: When a magnetostrictive material is subjected to a torque, a helical anisotropy of the susceptibility of that material will be created.
- Wiedemann Effect: When a helical magnetic field is applied to a material, it results in twisting of that material (reverse of Matteucci effect). It is shown in figure below.
This is because dissimilar crystal directions are related with dissimilar length. Matteucci effect and Wiedemann effect are linked with magnetostriction. They are explained above. Villari effect is contrary of magnetostriction effect.
Magnetostriction MaterialsThis effect is mostly seen in the magnetic materials such as iron, nickel, cobalt, iron-aluminium alloy and some other alloys like Terfenol-D, Galfenol, Metgla etc. They are mainly used in actuators and some motors.
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