Nondestructive Residual Stress Measurements in Railroad Wheels Using the Low-Field Magnetoacoustic Test Method

Residual tensile stresses in the rims of railroad wheels created by repeated applications of brakes have been known to contribute to catastrophic wheel failures. About 235,000 potentially dangerous railroad wheels are being removed anually in the US to prevent the wheel-related accidents [1]. The current industrial standard determining the removal of a particular wheel from service is the federal regulation of a visual inspection method. In this method one determines the width of a discolored band in the rim of a wheel radially, and if the width exceeds 10 cm (4 in.) the wheel is considered potentially dangerous. Destructive test methods, e.g., hole-drilling and saw-cutting techniques, however, have shown that the visual inspection method is unreliable. Some wheels considered dangerous had no appreciable residual tensile stresses, while some considered safe (not discolored) had dangerous level of residual tensile stresses in the rim when saw-cut or hole-drilled. To improve the level of safety in railroad transportation and reduce waste, reliable NDE methods have been in great demand.