Measurement of residual stresses in rails by neutron diffraction

Rolling contact fatigue damage is accumulated in rails during the repeated passage of trains over the rails, and an incipient crack may initiate due to the rolling contact fatigue. Rail failures can occur due to crack growth in the rails. In order to prevent such rail failures, the estimation of the behavior of internal rail cracks is required on the basis of an exact engineering analysis model as well as a method to detect rail defects before the crack grows to critical size. It is expected that the residual stress distribution in a rail has a significant influence on the growth rate of the crack. The purposes of this study are to measure the residual stress distribution in rails utilizing the neutron strain measurement. The test samples were taken from rails used in a service line in Japan for about six years (222 million gross tons). The neutron measurement was conducted using the Residual Stress Analyzer (RESA) at the Japan Atomic Energy Agency (JAEA). This report presents the results of the neutron strain measurements on a longitudinal-cut slice of a rail.