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Proceedings Paper

Safety assessment of railroad wheels through roll-by detection of tread cracks
Author(s): Al V. Clark; Raymond E. Schramm; Stephen R. Schaps; B. J. Filla
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Paper Abstract

A prototype system has been developed for roll-by inspection of cracks in the treads of freight car wheels. The system uses noncontacting electromagnetic-acoustic transducers (EMATs) which generate and receive surface waves propagating along the tread surface. If a defect is present it reflects an echo back to the EMAT. The EMAT itself consists of a coil and permanent magnet which are embedded in a 'rocking shoe'. This device is a piece of impact- absorbing polymeric material having a curvature to match the radius of a 910 mm (36 in) diameter wheel. The rocking shoe is suspended by a spring system in a recess, machined into the outer surface of a rail plug. When the wheel is centered over the shoe, it activates a trigger circuit which energizes the EMAT and causes propagation of the surface wave. The detected echoes are analyzed by a microprocessor which characterizes the wheel as being safe or unsafe. The crack detector system has been subjected to field testing using actual locomotive and rolling stock. It has been able to detect both artificial and real defects at roll-by speeds of 25 km/h (15mph).

Paper Details

Date Published: 30 June 1995
PDF: 11 pages
Proc. SPIE 2458, Nondestructive Evaluation of Aging Railroads, (30 June 1995); doi: 10.1117/12.212694
Show Author Affiliations
Al V. Clark, National Institute of Standards and Technology (United States)
Raymond E. Schramm, National Institute of Standards and Technology (United States)
Stephen R. Schaps, National Institute of Standards and Technology (United States)
B. J. Filla, National Institute of Standards and Technology (United States)


Published in SPIE Proceedings Vol. 2458:
Nondestructive Evaluation of Aging Railroads
Donald E. Gray; Daniel H. Stone, Editor(s)

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