Formation of Internal Stress Fields on a Rail Surface during Operation

• Published in: Technical physics letters Vol. 49; no. 10; pp. 117 - 122
• Main Authors: Popova, N. A., Gromov, V. E., Ivanov, Yu. F., Porfiriev, M. A., Nikonenko, E. L., Kryukov, R. E., Gostevskaya, A. N.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.10.2023; Springer Nature B.V
• Subjects: Bending; Carbon content; Classical and Continuum Physics; Contours; Dislocation density; Electrons; Extinction; Fillets; Magnetic methods; Measurement methods; Parameters; Physics; Physics and Astronomy; Rail steels; Rails; Residual stress; Stress distribution; Transmission electron diffraction; Wear resistance; excess dislocation density; electron microscopy; internal stress fields; surface; rails
• ISSN: 1063-7850; 1090-6533
• DOI: 10.1134/S1063785023700116

The level of microscopic internal long-range stress fields σ lr on the tread surface and working fillet has been determined for two rails with a carbon content of 0.74 and 0.91 wt % of categories DT350 (of general purpose) and DT400IK (with increased wear resistance and contact endurance) after a passed tonnage of 1770 million t (for DT350), and 187 million t (for DT400IK) (1) and 234 million t (for DT400IK) (2). For this purpose, the bending extinction contours are analyzed by means of transmission electron diffraction microscopy, the parameters of which are used in calculating σ i . The presence of excess extinction contours indicates the bending–torsion of the lattice, which is characterized by an excess density of dislocations. A comparison is made with other methods for measuring internal stress fields at the meso and macro levels (optical and magnetic methods, X-ray diffraction analysis), which are integral. It is shown that the parameters of the bending extinction contours are the most informative and allow one to control locality of the σ lr measurement. Sources of internal stress fields in rail steels are noted. An increase in the level of σ lr in D400IK rails in comparison with rails of the DT350 category has been revealed. The growth in the passed tonnage for rails of the DT400IK category leads to an increase in σ lr , while the values of internal stresses on the fillet surface exceed the corresponding values on the tread surface. The physical reasons for the observed changes are discussed.