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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 ...
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 ...
However, all methods have similar magnetostrictive properties. [10] Due to size restriction, MB is the best process to produce Terfenol-D. However it is a labor-intensive method. A newer process like MB is Etrema crystal grower (ECG) that results in larger diameter Terfenol-D crystals and increased magnetostrictive performance. The reliability ...
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.
Magnetostrictive materials exhibit a change in shape under the influence of magnetic field and also exhibit a change in their magnetization under the influence of mechanical stress. Magnetic shape memory alloys are materials that change their shape in response to a significant change in the magnetic field.
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.
EMATs are suitable to generate all kinds of waves in metallic and/or magnetostrictive materials. Depending on the design and orientation of coils and magnets, shear horizontal (SH) bulk wave mode (norm-beam or angle-beam), surface wave, plate waves such as SH and Lamb waves , and all sorts of other bulk and guided-wave modes can be excited.