A Comparison of Railroad Axle Stress Results Using Different Design Sizes, Loading Criteria and Analysis Methods

Although railroad axles do not often fail in North American freight service, they remain a critical component. This paper presents the results of stress analysis calculations that were performed for various different North American freight railroad axle designs. Loading criteria appropriate for the various axle designs were used, and different methods of axle stress analysis are compared and contrasted. Results are reviewed and discussed. Also, the authors propose that a standard axle stress analysis method be adopted by the North American freight railway industry for new axle designs, particularly for those axles to be used at increased gross rail loads (GRL).

Effects of Cone/Axle Rubbing Due to Roller Bearing Seizure on the Thermomechanical Behavior of a Railroad Axle

A thermomechanical analysis of a railroad axle with a 6 1/2 × 12 tapered roller bearing assembly is conducted to determine the effects of a loose cone rubbing on the axle. For this analysis, it is assumed that the bearing elements have seized or jammed and the smallest resistance torque is due to the friction at the loose cone-axle interface. Temperature-dependent material properties are used as well as a coefficient of friction obtained by means of a pin-on-disk apparatus over a range of temperatures up to 1000° C. For initial radial clearances between cone and axle varying from 0.05 to 5.0 mm and an initial ambient temperature of 25°C, the thermomechanical degradation of the axle is examined as a function of time. The times required for plastic collapse of the axle to occur are determined for the various clearances. For the conditions considered, this collapse takes place in less than three minutes.

Railroad Axle Design Factors

Railroad axle designs have been developed from an application of theoretical principles of Reuleaux combined with extensive laboratory fatigue studies supplemented to some extent by road service tests. The designer is presented with data on the effects of the complex forces acting on axles operating in railroad service. Criteria for wheel seat and axle body stresses established from fatigue tests and modified by practical considerations are discussed. The paper gives elaborate reference material for use by future investigators of axle properties and designs.