Method for analyzing a separation in a deformable structure

• US 5,948,976 A
• Filed: 06/02/1998
• Issued: 09/07/1999
• Est. Priority Date: 04/17/1996
• Status: Expired due to Fees

• Current Assignee: Michelin Recherche et Technique SA (Compagnie Generale DES Etablissements Michelin SCA)
• Original Assignee: Michelin North America Incorporated (Compagnie Generale DES Etablissements Michelin SCA)
• Inventors: Newman, John W.
• Primary Examiner(s): RAEVIS, ROBERT R
• Application Number:
  US09/088,906
• Time in Patent Office: 462 Days
• Field of Search: 73/13, 73/37, 73/146, 73/760, 73/826, 73/837
• US Class Current: 73/146
• CPC Class Codes: G01B 11/162 by speckle- or shearing interferometry
• CPC Class Codes: G01B 9/025 Double exposure technique
• CPC Class Codes: G01M 17/027 using light, e.g. infrared, ultraviolet or holographic techniques

Abstract

A deformable structure is subjected to a plurality of reduced pressures, causing a bulge in the surface of the deformable structure above a separation in the deformable structure. The cross sectional area of the bulge is measured for each reduced pressure in a plane parallel to the surface of the deformable structure. When the cross sectional area of the bulge does not increase with a reduction in the pressure, the cross sectional area of the bulge approximates the area of the separation. The depth of the separation is calculated using the change in cross sectional area of the bulge per change in pressure.

Claims

1. Method for determining the depth of a separation in the material of a test deformable structure comprising the steps of:

subjecting the test deformable structure to a plurality of test pressures, thereby causing a test bulge in a test surface of the test deformable structure at each test pressure due to the separation in the test deformable structure;

measuring the cross sectional area in a predetermined test plane of the test bulge formed in the test surface of the test deformable structure at each test pressure;

subjecting a reference deformable structure having at least one reference separation of known size and depth to a plurality of reference pressures, thereby causing a reference bulge in a reference surface of the reference deformable structure at each of the reference pressures due to the reference separation;

measuring the cross sectional area in a predetermined reference plane of the reference bulge formed in the reference surface of the reference deformable structure at each reference pressure; and

comparing the cross sectional area of the test bulge formed in the surface of the test deformable structure at each of the test pressures with the cross sectional area of the reference bulge formed in the surface of the reference deformable structure at each of the test pressures to determine the location of the separation in the test deformable structure.

2. The method according to claim 1, wherein said step of measuring the cross sectional area of the test bulge in the test deformable structure includes the predetermined test plane being substantially parallel to the test surface of the test deformable structure, and wherein said step of measuring the cross sectional area of the reference bulge in the reference deformable structure includes the predetermined reference plane being substantially parallel to the reference surface of the reference deformable structure.

3. The method according to claim 2, wherein the distance between the predetermined test plane and the test surface is substantially the same distance as the distance between the predetermined reference plane and the reference surface.

4. Method for determining the depth of a separation in the material of a test deformable structure comprising the steps of:

subjecting the test deformable structure to a plurality of test pressures, thereby causing a test bulge in a test surface of the test deformable structure at each test pressure due to the separation in the test deformable structure;

measuring the diameter in a predetermined test plane of the test bulge formed in the test surface of the test deformable structure at each test pressure;

subjecting a reference deformable structure having at least one reference separation of known size and depth to a plurality of reference pressures, thereby causing a reference bulge in a reference surface of the reference deformable structure at each of the reference pressures due to the reference separation;

measuring the diameter in a predetermined reference plane of the reference bulge formed in the reference surface of the reference deformable structure at each reference pressure; and

comparing the diameter of the test bulge formed in the surface of the test deformable structure at each of the test pressures with the diameter of the reference bulge formed in the surface of the reference deformable structure at each of the test pressures to determine the location of the separation in the test deformable structure.

5. The method according to claim 4, wherein said step of measuring the diameter of the test bulge in the test deformable structure includes the predetermined test plane being substantially parallel to the test surface of the test deformable structure, and wherein said step of measuring the diameter of the reference bulge in the reference deformable structure includes the predetermined reference plane being substantially parallel to the reference surface of the reference deformable structure.

6. The method according to claim 5, wherein the distance between the predetermined test plane and the test surface is substantially the same distance as the distance between the predetermined reference plane and the reference surface.