Crack detection system

• US 5,638,165 A
• Filed: 04/28/1995
• Issued: 06/10/1997
• Est. Priority Date: 04/28/1994
• Status: Expired due to Fees

• Current Assignee: BAE Systems Plc
• Original Assignee: British Aerospace, Inc.
• Inventors: Duke, Philip A., Ball, Andrew
• Primary Examiner(s): Rosenberger, Richard A.
• Application Number:
  US08/430,593
• Time in Patent Office: 774 Days
• Field of Search: 356/32, 356/73.1, 250/227.16, 250/227.14
• US Class Current: 356/32
• CPC Class Codes: G01M 11/086 Details about the embedment of the optical fiber within the DUT

Abstract

An apparatus and method for utilizing the deformation characteristics of optical fiber transmission paths to enable the detection of deformations in materials, in which the fibers are disposed in relation to the material such that each separate deformation in the material lying in the path of the fiber results in a corresponding independently measurable deformation along the length of the fiber.

Claims

1. Apparatus for the detection of deformations in a material comprising:

at least one optical fibre defining an optical transmission path within said material,

said at least one optical fiber being adapted for connection to an optical time domain reflectometry system, and being so disposed within said material that deformation of said material results in a corresponding longitudinal strain deformation in the form of necking of said optical fibre, the location and magnitude of which may be determined by said optical time domain reflectometry system.

2. The apparatus of claim 1, wherein said optical fiber extends within said material in a substantially straight direction.

3. A method of utilizing longitudinal strain deformation characteristics in the form of necking of optical fibres defining optical transmission paths to enable the detection of deformations in a material, said method comprising the steps of:

disposing said optical fibres within said material such that deformations in the material result in a corresponding independently measurable longitudinal strain deformations in the form of necking of said optical fibres; and

measuring said deformations.

4. The method of claim 3, wherein said optical fiber extends within said material in a substantially straight direction.

5. Apparatus for detecting deformation in a material, comprising:

a composite material including at least one optical fibre extending substantially straight within said composite material in a given direction and defining an optical transmission path inside said composite material;

said optical fibre being so disposed within said composite material that a mechanical failure or crack in the composite material at a particular location due to deformation of said composite material in opposite directions substantially perpendicular to said given direction causes longitudinal strain in the form of necking of said at least one optical fibre at a location corresponding to said particular location; and

an optical time domain reflectometer connected to said at least one optical fibre for determining the location and magnitude of said necking of said optical fibre and hence of the mechanical failure or crack in said composite material.

6. A method of detecting deformations in a material, comprising the steps of:

disposing at least one optical fiber in said material such that said optical fibre extends substantially straight within said material in a given direction and defines an optical transmission path inside said composite material;

said optical fibre being so disposed within said composite material that a mechanical failure or crack in the composite material at a particular location due to deformation of said composite material in opposite directions substantially perpendicular to said given direction causes longitudinal strain in the form of necking of said at least one optical fibre at a location corresponding to said particular location; and

connecting an optical time domain reflectometer to said at least one optical fiber to determine a location and magnitude of said necking of said optical fibre and hence the mechanical failure or crack in said material.