FCP Report No. 17

A Fatigue Model for Thermite Rail Welds

by

G. T. Fry
F. V. Lawrence

Abstract

The objective of this project is to examine the fatigue behavior of thermite-welded railroad rail and in particular the occurrence of fatigue defects in the rail head. A rail-head local stress fatigue model (RAHELS) is developed to predict the type of rail-head defect that forms under a given set of operating conditions and to predict the nucleation life of the defect.

Thermite rail welds usually contain pores and alumina inclusions. Using the RAHELS model, the effects of these discontinuities are examined for different discontinuity locations, shapes and orientations. In addition, the effects of residual stresses in the rail head, seasonal temperature variations, vertical wheel loads, tangential wheel loads, and track-foundation stiffness are explored. Predictions are compared with experimental observations to examine the validity of the RAHELS model. Suggestions for improving the fatigue performance of thermite rail welds are presented.

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