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  • 1
    Publication Date: 2019-06-28
    Description: This report describes Government Work Package Task 29 (GWP29), whose purpose was to develop advanced strain gage technology in support of the National Aerospace Plane (NASP) Program. The focus was on advanced resistance strain gages with a temperature range from room temperature to 2000 F (1095 C) and on methods for reliably attaching these gages to the various materials anticipated for use in the NASP program. Because the NASP program required first-cycle data, the installed gages were not prestabilized or heat treated on the test coupons before first-cycle data were recorded. NASA Lewis Research Center, the lead center for GWP29, continued its development of the palladium-chromium gage; NASA Langley Research Center investigated a new concept gage using Kanthal A1; and the NASA Dryden Flight Research Center chose the well-known BCL-3 iron-chromium-aluminum gage. Each center then tested all three gages. The parameters investigated were apparent strain, drift strain, and gage factor as a function of temperature, plus gage size and survival rate over the test period. Although a significant effort was made to minimize the differences in test equipment between the three test sites (e.g., the same hardware and software were used for final data processing), the center employed different data acquisition systems and furnace configurations so that some inherent differences may be evident in the final results.
    Keywords: Instrumentation and Photography
    Type: NASA-TP-3540 , NAS 1.60:3540 , NASP-TM-1186 , E-9513
    Format: application/pdf
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  • 2
    Publication Date: 2019-06-28
    Description: Two flat 12 by 72 inch Rene 41 honeycomb sandwich panels were tested in a manner to produce combined thermal and mechanical longitudinal stresses that simulated those that would occur in a larger, more complex integral tank and fuselage structure of an earth to orbit vehicle. Elastic strains measured at temperatures below 400 F are compared with calculated values obtained from a linear elastic finite element analysis to verify the analytical model and to establish confidence in the calculated strains. Elastic strain measurement at higher temperatures (between 600 F and 1400 F), where strain measurement is more difficult and less certain, are also compared with calculated strains. Agreement between measured and calculated strains for the lower temperatures is good, but agreement for the higher temperatures is poor because of unreliable strain measurements. Test results indicate that an ascent and entry life cycle of 500 is attainable under high combined thermal and mechanical elastic strains.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TP-3145 , L-16752 , NAS 1.60:3145
    Format: application/pdf
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  • 3
    Publication Date: 2019-06-28
    Description: The environmental aspect of elevated temperature and its relationship to the science of strain gage calibrations of aircraft structures are addressed. A section of a wing designed for a high-speed aircraft structure was used to study this problem. This structure was instrumented with strain gages calibrated at both elevated and room temperatures. Load equations derived from a high-temperature load calibration were compared with equations derived from an identical load calibration at room temperature. The implications of the high temperature load calibration were studied from the viewpoint of applicability and necessity. Load equations derived from the room temperature load calibration resulted in generally lower equation standard errors than equations derived from the elevated temperature load calibration. A distributed load was applied to the structure at elevated temperature and strain gage outputs were measured. This applied load was then calculated using equations derived from both the room temperature and elevated temperature calibration data. It was found that no significant differences between the two equation systems existed in terms of computing this applied distributed load, as long as the thermal shifts resulting from thermal stresses could be identified. This identification requires a heating of the structure. Therefore, it is concluded that for this structure, a high temperature load calibration is not required. However, a heating of the structure is required to determine thermal shifts.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TP-2921 , H-1331 , NAS 1.60:2921
    Format: application/pdf
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