Study on safety assessment of flange climb derailment at low speed based on the relationship between the derailment quotient and wheel rise

Abstract

In railways, on-track running tests are implemented to assess running safety against flange climb derailment. Results of tests depend on the frequency component of measured data. In this paper, the relationship between the measured data of the derailment quotient, which is the assessment quantity of derailment, and wheel rise are investigated. The data for the investigation are obtained in a flange climb running test at low speed on a test track, which includes two sharp curves with cants. Several types of track irregularities, such as track twist, rail misalignment and angular bent at joints, are added to the test track, which are some of factors causing flange climb derailment. Some static wheel unloading is also set at the test vehicle's leading wheelset to induce flange climbing. We show that the derailment quotient data obtained through filter processing with some cutoff frequencies and the amount of wheel rise of the leading outer wheel have a similar tendency in time sequence, which indicates the usability of the filtered derailment quotient data for the assessment of flange climb derailment at low speed. Further, the cumulative value of the derailment quotient which is larger than the target maximum value is examined in order to evaluate the safety margin for derailment more precisely compared to the ordinary assessment by the derailment quotient only. As a result, we propose a new assessment quantity considering the cumulative value, and its target maximum value derived from the wheel rise and running distance.