Method and apparatus for inspecting a structural part having surface irregularities

• US 5,567,881 A
• Filed: 05/05/1995
• Issued: 10/22/1996
• Est. Priority Date: 05/05/1995
• Status: Expired due to Term

• Current Assignee: Mcdonnell Douglas Corporation (The Boeing Co.)
• Original Assignee: Mcdonnell Douglas Corporation (The Boeing Co.)
• Inventors: Myers, Eugene A.
• Primary Examiner(s): Williams, Hezron E.
• Assistant Examiner(s): MOLLER, RICHARD ALAN
• Application Number:
  US08/435,580
• Time in Patent Office: 536 Days
• Field of Search: 73/618, 73/619, 73/621, 73/627, 73/629, 73/632, 73/633, 73/634, 73/640, 73/644, 73/866.5, 73/582, 73/584, 73/587, 73/588, 73/596, 73/620, 73/643, 324/262, 324/226, 33/501, 356/376, 356/379, 356/380
• US Class Current: 73/629
• CPC Class Codes: G01N 2291/0231 Composite or layered materials
• CPC Class Codes: G01N 2291/101 one transducer
• CPC Class Codes: G01N 2291/2691 Bolts, screws, heads
• CPC Class Codes: G01N 29/225 Supports, positioning or alignment in moving situation
• CPC Class Codes: G01N 29/265 by moving the sensor relative to a stationary material
• CPC Class Codes: G01N 29/28 providing acoustic coupling , e.g. water impedance matching G10K11/02

Abstract

An inspection apparatus and associated method includes a sensor housing defining an internal cavity in which a sensor is at least partially disposed for inspecting the surface of a structural part and for detecting defects in the surface and the substructure of the part. The inspection apparatus includes a plurality of compliant fibers extending outwardly from a first end of the sensor housing and circumferentially about an opening defined by the first end of the sensor housing. The compliant fibers support the sensor housing above the surface of the part and maintain the sensor in a predetermined position relative to the surface of the part. The plurality of compliant fibers are adapted to flex laterally to accommodate obstructions on the surface of the part, such as raised fasteners, doublers or lap joints while maintaining the sensor in the predetermined position relative to the surface of the part. Consequently, the sensor can continue to acquire accurate signals which indicate the presence of structural defects in the surface and the substructure of the part as the inspection apparatus moves over the obstructions which protrude upwardly from the surface of the part.

Claims

1. An inspection apparatus comprising:

a sensor housing defining an internal cavity opening through a first end of said sensor housing;

a sensor disposed at least partially within the internal cavity of said sensor housing for inspecting the surface of a structural part and for acquiring signals that indicate the presence of defects in the part;

a plurality of compliant fibers extending outwardly from the first end of said sensor housing and circumferentially about the opening defined by the first end of said sensor housing such that said sensor can transmit signals to and receive signals from the surface of the structural part independent of said plurality of compliant fibers, wherein each compliant fiber extends from a first end to an opposed second end, and wherein said plurality of compliant fibers have a predetermined compressive stiffness and a predetermined bending stiffness;

a sensor housing support assembly, operably connected to said sensor housing, for independently positioning said sensor housing in at least two mutually perpendicular directions such that parts having a compound curvature may be inspected, wherein said sensor housing support assembly comprises biasing means for urging said sensor housing in the direction of the surface of the part such that the respective second ends of said plurality of compliant fibers contact the surface of the part, wherein the predetermined compressive stiffness of said plurality of compliant fibers is sufficient to support said sensor housing above the surface of the part such that said sensor remains in a predetermined position relative to the surface of the part, and wherein the predetermined bending stiffness of said plurality of compliant fibers is sufficient to permit said compliant fibers to flex laterally to accommodate obstructions on the surface of the part while maintaining said sensor in the predetermined position relative to the surface of the part such that accurate signals which indicate the presence of defects in the part are acquired by said sensor.

2. An inspection apparatus according to claim 1 wherein said plurality of compliant fibers are secured to the first end of said sensor housing such that the respective second ends of said plurality of compliant fibers extend a first predetermined distance beyond the first end of said sensor housing so that said plurality of compliant fibers thereby support said sensor at a second predetermined distance above the surface of the part.

3. An inspection apparatus according to claim 1 wherein said plurality of compliant fibers are disposed in a plurality of circumferentially extending layers about the opening defined by the first end of said sensor housing.

4. An inspection apparatus according to claim 3 wherein said plurality of compliant fibers and the cavity defined by said sensor housing define a fluid reservoir, and wherein the inspection apparatus further comprises a fluid disposed within the fluid reservoir for coupling signals transmitted between said sensor and the surface of the part.

5. An inspection apparatus according to claim 1 further comprising a controller for moving said sensor over the surface of the part according to a predetermined inspection pattern such that the part is automatically inspected.

6. An inspection apparatus according to claim 1 wherein said sensor housing is cylindrical, and wherein said plurality of compliant fibers extending circumferentially about the opening defined by the first end of said sensor housing define a compliant fiber ring.

7. An apparatus for supporting a sensor in a predetermined position relative to the surface of a part, the apparatus comprising:

a plurality of compliant fibers extending longitudinally from a first end to an opposed second end, wherein the respective second ends of said plurality of compliant fibers are adapted to contact the surface of the part, and wherein said plurality of compliant fibers have a predetermined compressive stiffness and a predetermined bending stiffness; and

compliant fiber support means for fixing the position of said plurality of compliant fibers relative to the sensor, wherein said compliant fiber support means comprises a sensor housing defining an internal cavity which opens through a first end of said sensor housing and within which the sensor is at least partially disposed, wherein said plurality of compliant fibers extend outwardly from the first end of said sensor housing and circumferentially about the opening defined by the first end of the sensor housing such that the sensor can transmit signals to and receive signals from the surface of the part independent of said plurality of compliant fibers, wherein the predetermined compressive stiffness of said plurality of compliant fibers is sufficient to support the sensor above the surface of the part such that the sensor remains in a predetermined position relative to the surface of the part, wherein the predetermined bending stiffness of said plurality of compliant fibers is sufficient to permit said compliant fibers to flex laterally to accommodate obstructions on the surface of the part while maintaining the sensor in the predetermined position relative to the surface of the part such that the sensor can accurately inspect the surface and the substructure of the part, and wherein said plurality of compliant fibers and the cavity defined by said sensor housing define a fluid reservoir which is adapted to receive and maintain a fluid in direct contact with the surface of the part for coupling signals transmitted between the sensor and the surface of the part.

8. An apparatus according to claim 7 wherein said plurality of compliant fibers are secured to said compliant fiber support means such that the respective second ends of said plurality of compliant fibers extend a first predetermined distance outwardly therefrom so that said plurality of compliant fibers support the sensor at a second predetermined distance above the surface of the part.

9. An apparatus according to claim 7 wherein said compliant fiber support means fixes the relative positions of said plurality of compliant fibers according to a predetermined pattern.

10. An apparatus according to claim 7 wherein said sensor housing is cylindrical, and wherein said plurality of compliant fibers extending circumferentially about the opening defined by the first end of said sensor housing define a compliant fiber ring.

11. A method of inspecting the surface of a structural part with an inspection apparatus comprising a sensor housing defining an internal cavity opening through a first end of said sensor housing, a sensor disposed at least partially within the internal cavity of said sensor housing, and a plurality of compliant fibers extending outwardly from the first end of said sensor housing and circumferentially about the opening defined by the first end of said sensor housing, the method comprising the steps of:

interrogating the surface of the part with the sensor;

obtaining signals indicative of the presence of structural defects in the part based upon the interrogation of the part;

moving the inspection apparatus along the surface of the part while continuing to interrogate the surface of the part;

independently positioning the sensor housing in at least two perpendicular directions to thereby enable a structural part having a compound curvature to be inspected, wherein said independently positioning step comprises the step of maintaining the sensor in a predetermined position relative to the surface of the part as the inspection apparatus moves over an obstruction on the surface of the part, said maintaining step comprising the steps of;

urging the sensor housing in the direction of the surface of the part such that the plurality of compliant fibers contact the surface of the part;

supporting the sensor housing above the surface of the part with the plurality of compliant fibers which have a predetermined compressive stiffness sufficient to support the sensor in a predetermined position relative to the surface of the part; and

bending a portion of the compliant fibers which have a predetermined bending stiffness sufficient to permit the compliant fibers to be bent laterally to accommodate the obstruction on the surface of the part without altering the predetermined position of the sensor relative to the surface of the part such that accurate signals which indicate the presence of defects in the part are obtained.

12. A method according to claim 11 wherein the inspection apparatus further comprises a fluid reservoir defined at least partially by the internal cavity of the sensor housing and the plurality of composite fibers, and wherein the method further comprises the steps of:

maintaining fluid within the fluid reservoir and in direct contact with the surface of the part; and

coupling signals transmitted between the sensor and the surface of the part with the fluid disposed within the fluid reservoir.

13. A method according to claim 11 wherein said moving step comprises the step of moving the sensor over the surface of the part according to a predetermined inspection pattern such that the part is automatically inspected.