Inspections of 163 wheelsets conducted by the Wheel Defect Prevention Research Consortium (WDPRC) have produced critical information in identifying the high-level root causes of tread damage. While the overall wheel tread damage problem appears to be split fairly evenly between shelling and spalling, the type of tread damage on a wheelset is strongly linked to the type of car from which it was removed. Coal car wheels, which generally run in heavy axle load, high-mileage service with minimal yard handling, are almost exclusively subject to shelling damage with little spalling damage. On the other hand, mixed freight cars, such as tank cars and covered hopper cars, tend to run in lower mileage service with more yard handling, resulting in fewer loading cycles under lighter stress and more frequent use of hand brakes. Not surprisingly then, wheels from these types of cars were observed to have a mix of spalling and shelling damage, with spalling being the predominant damage mechanism. Nearly every high impact wheel (HIW) inspected showed either spalling, shelling, or some combination of the two. As expected, wheel impact load detector (WILD) readings and radial tread run out data were found to be related. Rim thickness deviations and rim lateral face deviations were not found to be important contributors to shelling. The lateral tread location of radial run-out deviations and crack bands could be an important clue in discovering the root cause of shelling. Radial run-out data and crack band location data shows that shelling damage is most prevalent outboard of the tapeline. This is the expected wheel/rail contact position of a wheel in the lead wheelset position of a truck, while riding on the low (inside) rail of a curve. Many of the wheels that were removed for wear causes were found to have noncondemnable shelling and spalling, indicating that tread damage is more prevalent than repair records would indicate.

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