US 6,396,262 B2Granted

Method and apparatus for short term inspection or long term structural health monitoring

AssigneeSouthwest Research Institute

InventorsGlenn M. Light, Hegeon Kwun, Sang-Young Kim, Robert L. Spinks, Jr.

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Abstract

A method and apparatus is shown for implementing magnetostrictive sensor techniques for the nondestructive short term inspection or long term monitoring of a structure. A plurality of magnetostrictive sensors are arranged in parallel on the structure and includes (a) a thin ferromagnetic strip that has residual magnetization, (b) that is coupled to the structure with a couplant, and (c) a coil located adjacent the thin ferromagnetic strip. By a transmitting coil, guided waves are generated in a transmitting strip and coupled to the structure and propagate along the length of the structure. For detection, the reflected guided waves in the structure are coupled to a receiving strip and are detected by a receiving magnetostrictive coil. Reflected guided waves may represent defects in the structure.

Claims19

Dependent claims

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.

5 more elements

An apparatus for 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 impact, said apparatus comprising:

a plurality of thin ferromagnetic strips that have residual magnetization therein, said thin ferromagnetic strips being coupled in parallel to said structure;
a transmitter coil being located adjacent to a first of said thin ferromagnetic strips;
a receiver coil being located adjacent to a second of said thin ferromagnetic strips;
a transmitter control circuit connected to said transmitter coil for generating a pulse signal and delivering said pulse signal to said transmitter coil, said transmitter coil creating magnetostrictively a guided wave that is coupled from said first thin ferromagnetic strip to said structure to propagate along said structure;
said receiver coil magnetostrictively detecting said guided wave and any reflected signals, including any caused by defect or transient stress signals in said structure;
said transmitter coil and said receiver coil being wound adjacent said first and second thin ferromagnetic strips, respectively, said guided waves moving perpendicular to said first and second thin ferromagnetic strips.

3 more elements

Dependencies are inferred from the claim text.

Facts

Application: 09/855,460Filed 15 May 2001 · continuation in part
Priority: 17 Mar 1999
Published: US 2001/0022514 A120 Sep 2001
Granted: 28 May 2002
Term ends: Not estimatedThe source records don’t support an estimate.

Classification10 codes

G01N 29/11
Analysing solids: by measuring attenuation of acoustic waves
G01N 17/006
Investigating resistance of materials to the weather, to corrosion, or to light: of metals
G01N 29/2412
Probes: using the magnetostrictive properties of the material to be examined, e.g. electromagnetic acoustic transducers [EMAT]
G01N 2291/0421
Wave modes: longitudinal waves

Family

Application60/124,763Us provisional application · filed 17 Mar 1999
Application09/519,530Parent of this continuation-in-part · filed 25 Feb 2000
Application09/815,219Parent of this continuation-in-part · filed 22 Mar 2001
US 6,294,912 B1Parent of this continuation-in-part
US 2001/0022514 A1Published application
US 2002/0105324 A1Published application
US 6,429,650 B1Related patent
US 6,396,262 B2This patent

From the US filing history. Foreign family members aren’t listed.