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Proceedings Paper

Estimation of accuracy in ultrasonic preload measurements
Author(s): Ajay M. Koshti
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Paper Abstract

An ultrasonic extensometer is used to measure tensile preload in fasteners such as bolts and studs. Raymond Boltgage and StressTel Boltmike are two of the most commonly used extensometers. It is necessary to know the accuracy of extensometer measurements. Many factors affect the accuracy of extensometers. Characteristics of the fasteners affect the accuracy. Moreover, the variability in transducer coupling also affects the accuracy. Variation in the grip length of fastener also affects the accuracy. Therefore, the extensometer doesn't have a fixed amount or percentage of measurement accuracy. A detailed procedure to estimate the accuracy is currently not available in the manufacturer's manuals. The paper discusses all sources of errors and provides a procedure to compute the preload measurement accuracy for the two instruments. The paper also provides relationships between the corresponding parameters of the two instruments. Moreover, it provides equations to program the two instruments so that the difference between preload measurements by the two instruments is minimized.

Paper Details

Date Published: 24 July 2001
PDF: 12 pages
Proc. SPIE 4335, Advanced Nondestructive Evaluation for Structural and Biological Health Monitoring, (24 July 2001); doi: 10.1117/12.434186
Show Author Affiliations
Ajay M. Koshti, Boeing Reusable Space Systems (United States)


Published in SPIE Proceedings Vol. 4335:
Advanced Nondestructive Evaluation for Structural and Biological Health Monitoring
Tribikram Kundu, Editor(s)

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