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Magnetostriction is a property of magnetic materials that causes them to change their shape or dimensions during the process of magnetization.The variation of materials' magnetization due to the applied magnetic field changes the magnetostrictive strain until reaching its saturation value, λ.
where is the magnetostrictive expansion at saturation, and is the angle between the saturation magnetization and the stress's direction. When λ s {\displaystyle \lambda _{s}} and σ {\displaystyle \sigma } are both positive (like in iron under tension), the energy is minimum for θ {\displaystyle \theta } = 0, i.e. when tension is aligned with ...
Terfenol-D, an alloy of the formula Tb x Dy 1−x Fe 2 (x ≈ 0.3), is a magnetostrictive material. It was initially developed in the 1970s by the Naval Ordnance Laboratory in the United States. The technology for manufacturing the material efficiently was developed in the 1980s at Ames Laboratory under a U.S. Navy-funded program. [1]
The magnetocrystalline anisotropy energy is generally represented as an expansion in powers of the direction cosines of the magnetization. The magnetization vector can be written M = M s (α,β,γ), where M s is the saturation magnetization. Because of time reversal symmetry, only even powers of the cosines are allowed. [2]
Inverse magnetostrictive effect; Wiedemann effect; Matteucci effect; Guillemin effect; Magnetostriction is thermodynamically opposite to inverse magnetostriction effect. The same situation occurs for Wiedemann and Matteuci effects. For magnetic, mechanical and electric phenomena in fluids see Magnetohydrodynamics and Electrohydrodynamics.
Magnetostrictive position sensors use the Wiedemann effect to excite an ultrasonic pulse. Typically a small magnet is used to mark a position along a magnetostrictive wire. The magnetic field from a short current pulse in the wire combined with that from the position magnet excites the ultrasonic pulse.
Continuous charge distribution. The volume charge density ρ is the amount of charge per unit volume (cube), surface charge density σ is amount per unit surface area (circle) with outward unit normal nĚ‚, d is the dipole moment between two point charges, the volume density of these is the polarization density P.
The name was first given to iron-gallium alloys by United States Navy researchers in 1998 when they discovered that adding gallium to iron could amplify iron's magnetostrictive effect up to tenfold. Galfenol is of interest to sonar researchers because magnetostrictor materials are used to detect sound, and amplifying the magnetostrictive effect ...