Patent ID: 6294912
Filing Date: 2001-09-25
Classification: G01N

Abstract:
A method for nondestructive inspection of a plate type ferromagnetic structure, whether flat or curved, for anomalies therein, which anomalies can indicate defects such as notches, cuts, cracks, wear or corrosion, using magnetostrictive techniques, said method comprising the following steps:first locating a transmitter adjacent to said plate type ferromagnetic structure;providing a first DC bias magnetic field in said plate type ferromagnetic structure near said transmitter;second locating a receiver adjacent to said plate type ferromagnetic structure;providing a second DC bias magnetic field in said plate type ferromagnetic structure near said receiver;generating a pulse signal in a transmitter control circuit and delivering said pulse signal to said transmitter, said pulse signal causing a fluctuation in said first DC bias magnetic field sufficient to generate guided waves through said plate type ferromagnetic structure as a result of the magnetostrictive effect;detecting fluctuations in said second DC bias magnetic field as a result of the passage of said guided waves and reflected waves through said plate type ferromagnetic structure, said fluctuations in said second DC bias magnetic field caused by an inversed magnetostrictive effect resulting from said passage of said guided waves or said reflected waves from anomalies within said plate type ferromagnetic structure; anddetermining if said reflected waves were due to anomalies that should not exist in said plate type ferromagnetic structure;said transmitter and said receiver having a core with an elongated axis and a coil wound lengthwise therearound so that said guided wave front is parallel to said elongated axis and moves perpendicular thereto.