Electromagnetic acoustic transducers (EMATs) are ideal for on-line inspection of hot metal sheets, because they provide a noncontacting means for generating and detecting ultrasound in metals. EMATs are especially attractive for probing steels and magnetic alloys, because their transduction efficiency is larger than in nonferromagnetic materials. The source of the enhanced efficiency is magnetostriction, the change of length of a ferromagetic material that accompanies magnetization.
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