Patent ID: 7024935
Filing Date: 2006-04-11
Classification: B06B,G01N

Abstract:
1. An electromagnetic acoustic transducer for exciting ultrasound in a ferromagnetic material under test, the transducer comprising magnetic means comprising a linear array of magnets with alternating magnetic poles, arranged to be moved relative to the material under test to magnetize a surface layer of the material, and an electrical winding supplied by an alternating current source; characterized in that: the centers of said alternating magnetic poles are spaced apart by a distance equal to or shorter than half the wavelength of said ultrasound, and the electrical winding is spaced from the array of magnets so that the magnetic means and the electric winding are arranged to be applied in sequence to the material under test whereby the electrical winding is for positioning adjacent the material subsequent to magnetization thereof by the magnetic means, the alternating magnetic flux created by the winding being arranged to interact with the remanent magnetization of the material to create ultrasonic vibration of the material.