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).
Safety assessment of railroad wheels through roll-by detection of tread cracks
Nondestructive Evaluation of Aging Railroads ; 1995 ; Oakland,CA,United States
Proc. SPIE ; 2458
1995-06-30
Conference paper
Electronic Resource
English
Safety assessment of railroad wheels through roll-by detection of tread cracks [2458-09]
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