Patent ID: 6396262
Filing Date: 2002-05-28
Classification: G01N

Abstract:
A method of nondestructive, short term inspection or long term monitoring of a structure to determine if said structure (a) has a defect such as a crack, corrosion or erosion or (b) has a transient stress signal due to vibrations, cracking or mechanical impacts, said method comprising the following steps:preparing a plurality of thin strips of ferromagnetic material of appropriate width and length; inducing residual magnetization along said length of said thin strips by applying an external magnetic field and thereafter removing said external magnetic field; coupling said thin strips in parallel to said structure; installing a magnetostrictive probe on each of said thin strips; generating a pulse signal in a transmitter control circuit and delivering said pulse signal to a first of said magnetostrictive probes to create guided waves in a first of said thin strips, which guided waves are coupled to said structure for propagation therein; magnetostrictively detecting any reflected waves by a second of said magnetostrictive probes in combination with a second of said thin strips, said reflected waves being coupled from said structure to said second of said thin strips; and determining if said reflected waves are due to said defect or said transient stress signal.