The journal roller bearing was introduced into the North American freight car fleet prior to 1950, and its population has risen so that today well over 90 % of the fleet is so equipped. The change from the bronze friction bearing dramatically reduced hot bearings and derailments. However, the nearly constant bearing-related derailment rate over the past several years, and the escalating costs of false set-outs and derailments, has prompted the railroad industry to take a closer look at the journal roller bearing and the hot bearing detector systems now in place. The AAR Research and Test Department has been involved in the laboratory testing of railroad journal roller bearings since 1988. The current test program is concerned with the quantification of the mechanisms of final bearing failure and rationalization of reconditioning standards. This is intended to lead to better detection systems and improved bearing designs, while improving the reconditioned bearings that re-enter service. It is estimated that 80 % of all bearings now entering service are reconditioned. As part of its bearing research, the AAR has designed and constructed three bearing test machines, which allow simulated field testing of bearing failure mechanisms and bearing defect growth. These test machines allow variation of several parameters to see their influence on bearing operation and defect progression. The bearing test machines use a standard railroad axle with two journal roller bearings. The wheels have been removed and are replaced by oil-cooled pillow blocks to react the bearing vertical loads. Total axle torque, speed, and bearing temperatures are the main data collected, in addition to the acoustic and vibration signatures emitted by the bearings. Testing of bearing components with repaired spalls was initiated in 1989, with completion expected by the end of 1991. Tests are scheduled to last 200000 miles, approximately a wheel life. Test results have indicated the propensity of a repaired spall to continue to grow or for that component to initiate new spalls within that raceway.
AAR railroad bearing research: laboratory testing of defect progression
Schienenfahrzeuglagerforschung bei der AAR: Laboratoriumsuntersuchung der Schadensentwicklung
1991
6 Seiten, 10 Bilder, 1 Tabelle, 3 Quellen
Conference paper
English
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