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Proceedings Paper

Ultrasonic measurement of stress in pin and hanger connections
Author(s): Al V. Clark; C. S. Hehman; D. Gallagher; Margarit G. Lozev; P. A. Fuchs
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Paper Abstract

Pin and hanger connections can sometimes lock up due to corrosion. As the stresses in the connection are cycled due to thermal expansion and contraction of the bridge, fatigue cracking and failure may occur. We constructed an apparatus to simulate a locked-up pin and hanger connection. It consists of a 12 tooth spline bolted to the base of a mechanical testing machine. Hangers were mounted on the spline, which constrains their ends against rotation. The free ends of the hangers were loaded by the test machine's piston. We performed proof of concept tests of a method to detect stresses in pin and hanger connections prior to cracking. The method uses the fact that stress causes change in sound velocity. We propagated shear waves polarized parallel and perpendicular to the hanger axis. The normalized difference in shear wave velocities is called the birefringence. We measured the birefringence near the outer fibers of the hangers, at midsection. We simulated 3 scenarios: continuous monitoring of hanger status; intermittent monitoring from a known initial state; measurement with no a priori knowledge of hanger status. Good agreement with strain gauge data was obtained for all three scenarios.

Paper Details

Date Published: 31 March 1998
PDF: 12 pages
Proc. SPIE 3400, Structural Materials Technology III: An NDT Conference, (31 March 1998); doi: 10.1117/12.300089
Show Author Affiliations
Al V. Clark, National Institute of Standards and Technology (United States)
C. S. Hehman, National Institute of Standards and Technology (United States)
D. Gallagher, National Institute of Standards and Technology (United States)
Margarit G. Lozev, Virginia Transportation Research Council (United States)
P. A. Fuchs, Federal Highway Administration (United States)

Published in SPIE Proceedings Vol. 3400:
Structural Materials Technology III: An NDT Conference
Ronald D. Medlock; David C. Laffrey, Editor(s)

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