Method for analyzing a separation in a deformable structure

• US 6,089,085 A
• Filed: 06/30/1999
• Issued: 07/18/2000
• 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:
  US09/345,160
• Time in Patent Office: 384 Days
• Field of Search: 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. A method for determining the depth of a separation in the material of a test deformable structure, comprising the steps of:

reducing the pressure in the vicinity of the separation in the test deformable structure and thereby forming a bulge in a surface of the test deformable structure due to the separation in the material of the test deformable structure, until the bulge crosses a predetermined plane;

determining the size of the separation in the test deformable structure;

providing a reference deformable structure having at least one reference separation in the material of the reference deformable structure at a predetermined depth;

reducing the pressure in the vicinity of the reference separation in the reference deformable structure and thereby forming a reference bulge in a surface of the reference deformable structure, until the bulge crosses a predetermined plane;

comparing the pressure at which the bulge formed in the surface of the test deformable structure crossed the predetermined plane with the pressure at which the reference bulge formed in the surface of the reference deformable structure crossed the predetermined plane; and

determining the depth of the separation in the test deformable structure.

2. The method as claimed in claim 1, wherein the predetermined plane for the test deformable structure and the predetermined plane for the reference deformable structure are substantially parallel to the respective surfaces of the test deformable structure and reference deformable structure.

3. The method as claimed in claim 1, wherein the step of determining the size of the separation includes continuing to reduce the pressure at least until the bulge reaches a maximum area measured in the predetermined plane.

4. The method as claimed in claim 1, wherein the test deformable structure is a tire having an outer surface and an inner surface, and wherein the step of reducing the pressure in the vicinity of the separation is performed on the inner surface.

5. A method for determining the depth of a separation in the material of a test deformable structure, comprising the steps of:

reducing the pressure in the vicinity of the separation in the test deformable structure and thereby forming a bulge in a surface of the test deformable structure due to the separation in the material of the test deformable structure, until the bulge attains a predetermined size parameter;

providing a reference deformable structure having at least one reference separation in the material of the reference deformable structure and at a predetermined depth;

reducing the pressure in the vicinity of the reference separation in the reference deformable structure and thereby forming a reference bulge in a surface of the reference deformable structure, until the bulge attains a predetermined size parameter;

comparing the pressure at which the bulge formed in the surface of the test deformable structure attained the predetermined size parameter with the pressure at which the reference bulge formed in the surface of the reference deformable structure attained the predetermined size parameter to determine the depth of the separation in the test deformable structure.

6. The method as claimed in claim 5, wherein the predetermined size parameters comprise the bulge in the test deformable structure crossing a predetermined plane and the bulge in the reference deformable structure crossing a predetermined plane.

7. The method as claimed in claim 5, wherein the predetermined plane for the test deformable structure and the predetermined plane for the reference deformable structure are substantially parallel to and spaced from the respective surfaces of the test deformable structure and reference deformable structure.

8. The method as claimed in claim 5, wherein the predetermined size parameter comprises an area of the bulge in the test deformable structure surface reaching a maximum.

9. The method as claimed in claim 5, further comprising the step of determining the size of the separation in the test deformable structure.

10. The method as claimed in claim 5, further comprising the steps of

measuring an area of the bulge in the test deformable structure and an area of the bulge in the reference deformable structure at a plurality of pressure values as the pressure is reduced, and

comparing the area of the bulge in the test deformable structure at each pressure value with the area of the bulge in the reference deformable structure at the same pressure value to determine the depth of the separation in the test deformable structure.

11. The method as claimed in claim 5, wherein the test deformable structure is a tire having a generally hollow, annular shape with an outer surface and an inner surface, and wherein the step of reducing the pressure in the vicinity of the separation is performed on the inner surface.