Wheelclimb Derailment Processes and Derailment Criteria

PDFTech ReportDOT-FRA-ORD-84-05DOT-TSC-FRA-83-6Accident risk forecastingCar wheels (Railroads)DerailmentsForceL/V ratioRail (Railroads)Risk assessmentRolling contactSafetyWheelsUnited StatesJapanUnited States. Federal Railroad AdministrationSweet, Larry M.Karmel, AmirPrinceton UniversityJohn A. Volpe National Transportation Systems Center, (U.S.)United States. Federal Railroad AdministrationNTL-RAIL TRANSPORTATION-Rail SafetyNTL-RAIL TRANSPORTATION-RAIL TRANSPORTATIONNTL-SAFETY AND SECURITY-AccidentsNTL-SAFETY AND SECURITY-Rail SafetyNTL-SAFETY AND SECURITY-SAFETY AND SECURITYNTL-SAFETY AND SECURITY-Vehicle DesignVolpe National Transportation Systems Center, Technical Reference CenterThe most widely accepted criterion for wheelclimb derailment defines an upper limit for safe operation on wheel/rail contact forces on the climbing wheel, with the limit varying with time duration of the forces. For dynamic wheelclimb processes with significant lateral velocities, lateral forces may be measured for short time durations that are larger than those that may be sustained without derailment in steady state. To study wheelclimb derailment processes and evaluate derailment criteria, a series of derailment experiments was conducted using a one-fifth scale model of a single wheelset on tangent track subjected to static and dynamic loading conditions. The results of these experiments were compared to simulations based on a nonlinear theory developed to represent the important phenomena associated with dynamic wheelclimb. The study shows that the Japanese National Railways (JNR) and other time-duration dependent criteria based on wheel load measurements alone are unsuccessful in predicting derailment safety for dymanic wheelclimb. For wheelclimb processes involving negligible lateral velocities, the derailment limit can be estimated from quasi-steady analysis of wheel/rail forces. Evidence has been found that derailment criteria employing variables measured in addition to wheel loads may be successful in predicting derailment safety, and that diagnostic criteria may be developed for warning of impending derailment