Location
Howard Johnson Plaza-Hotel, Columbia/Enterprise Rooms
Start Date
21-4-1992 2:00 PM
Description
This abstract describes the nondestructive evaluation (NDE) of Orbiter Vehicle (OV)-102 tile bonds, performed in August 1991 by Rockwell International's Space Systems Division and its subcontractors, NAVCON Engineering Network/Ometron Inc. and Laser Technology Inc. The purpose was to help NASA develop fast, reliable methods to diagnose problems in tile bonding other than the present "pull" and "wiggle" tests. Forty-one tiles were evaluated by laser vibrometry in conjunction with modal testing and vibration imaging techniques, and/or by laser shearography, at Rockwell's Palmdale Facility. Both evaluation methods involve the acoustic excitation of tiles and the identification of the consequent tile vibration by laser techniques. After evaluation, tiles were removed from the Shuttle. The condition of the tile bond (strain isolation pad [SIP]/structure bond) was documented by experts. In addition, photographs were taken of all tiles before removal and of their SIP after removal. The results of the NDE of the bond agreed with the expert evaluation of the bond. The NDE did not find any indication of bond problems, and all bonds were classified as "nominal" by the experts. The work shows the feasibility of using NDE techniques in a dynamic, real-world environment without interfering with Shuttle rework schedules. Some of the data will be useful in verifying analytical models of tile behavior, developed at the University of Central Florida. Finally, the work suggests the need for a tile test bed containing known tile misbonds. The test bed could be subject to NDE techniques to provide NASA with a data base of the vibration characteristics of tiles with known bond problems.
Paper Session I-B - Non-Destructive Evaluation of Shuttle Columbia Tiles
Howard Johnson Plaza-Hotel, Columbia/Enterprise Rooms
This abstract describes the nondestructive evaluation (NDE) of Orbiter Vehicle (OV)-102 tile bonds, performed in August 1991 by Rockwell International's Space Systems Division and its subcontractors, NAVCON Engineering Network/Ometron Inc. and Laser Technology Inc. The purpose was to help NASA develop fast, reliable methods to diagnose problems in tile bonding other than the present "pull" and "wiggle" tests. Forty-one tiles were evaluated by laser vibrometry in conjunction with modal testing and vibration imaging techniques, and/or by laser shearography, at Rockwell's Palmdale Facility. Both evaluation methods involve the acoustic excitation of tiles and the identification of the consequent tile vibration by laser techniques. After evaluation, tiles were removed from the Shuttle. The condition of the tile bond (strain isolation pad [SIP]/structure bond) was documented by experts. In addition, photographs were taken of all tiles before removal and of their SIP after removal. The results of the NDE of the bond agreed with the expert evaluation of the bond. The NDE did not find any indication of bond problems, and all bonds were classified as "nominal" by the experts. The work shows the feasibility of using NDE techniques in a dynamic, real-world environment without interfering with Shuttle rework schedules. Some of the data will be useful in verifying analytical models of tile behavior, developed at the University of Central Florida. Finally, the work suggests the need for a tile test bed containing known tile misbonds. The test bed could be subject to NDE techniques to provide NASA with a data base of the vibration characteristics of tiles with known bond problems.
