Development of a predictive life tool for tapered roller bearings using measured residual stress and retained austenite data

摘要

The development of a tool called the Service Load Factor (SLF) for railway tapered roller bearings using residual stress and retained austenite data is presented. Case-carburized tapered roller bearings used in the railroad industry are manufactured with a dual-phase microstructure that consists primarily of tempered martensite and retained austenite. The retained austenite phase is metastable, and will transform to martensite with sufficient thermal or mechanical energy during service. The increase in surface volume because of transformation, and the subsequent increase in compressive residual stress could indicate the onset of certain failure modes, including fatigue spalling. In addition, retained austenite transformation can lead to an increase in bore diameter, which could result in a loss of fit on the axle journal. Several bearing inner races with various service histories were measured with a Siemens X-ray diffractometer using chromium radiation. Results indicated that the transformation of retained austenite and resultant increase in compressive residual stress are interrelated with load and rolling cycles. Results indicate that the SLF is a useful tool that correlates well with current Association of American Railroads failure criteria.