Neutron Residual Stress Measurements on Rail Sections for Different Production Conditions

Abstract

Rail sectioning with subsequent neutron diffraction experiments has been used to assess residual stresses in the rails. In this study we present the results of neutron stress measurements performed at the NIST Center for Neutron Research (NCNR) on rail sections from rails that were produced under various conditions. Specifically, these are air-cooled, air-cooled and roller-straightened, head-hardened and head-hardened and roller-straightened. More significantly, a head-hardened and roller-straightened rail was also studied after service to elucidate evolution of the service-induced residual stresses. In the latter case both a transverse-cut slice and the central region of a 0.53 m long piece were studied. Measurements on this piece are the first in which triaxial stresses have been determined for an intact rail. Neutron strain measurements with 3×3×3 mm3 spatial resolution were successfully employed for transversally cut slices to verify the difference in the stress state depending on the production process. Although examination of slices allows determination of only two-dimensional stresses in the plane of the slice, additional measurements on obliquely-cut slices, which were also carried out, and utilization of FEM gives the possibility of reconstructing the full triaxial stress distribution. Together, these approaches provide a better understanding of rail fabrication and the possibility of improving the durability and safety of rails in the future.

Experimental characterization and modelling of triaxial residual stresses in straightened railway rails

“…Similarly, Jun et al 11 performed neutron diffraction measurements on a 16-mm-thick transverse slice through the entire profile of a rail which has been in service. In order to eliminate the effect of the sectioning, Luzin et al 12,22 characterized residual stresses in a 10-mm-thick rail section and in a 0.5-m-long rail. The results documented that the sectioning results in the significant modification of the original residual stresses in the rail where especially longitudinal stress components were affected.…”

“…Residual stresses in railway rails have been characterized primarily in used rail sections in order to evaluate the influence of the service on the stress development. 7,8,11,12,15,16 The experimental stress characterization in ‘as-produced’ rails with preserved longitudinal components, that is, in an unsectioned rail, has not been performed yet. There have been however a few approaches to determine the stress state in straightened rails using FEM.…”

Research with Neutron and Synchrotron Radiation on Aerospace and Automotive Materials and Components

“…A prominent example is the stress and the degradation of railway tracks. Residual stresses and texture of rails have frequently been measured 275–282. The increase of axle loads of the freight trains and the increase of speed of passenger trains within recent years – leading to integrated loads beyond 10 Mtons y −1 – have led to an increase of wear of the rails that appeared, for example, in an increase of frequency of structure modifications and defects in their surface layers 275.…”

Residual Stresses in Rail-Ends from the in-Service Insulated Rail Joints Using Neutron Diffraction

“…Detailed 2-D and 3-D maps enable railway engineers to model and to better understand how residual stress fields are generated and to determine the most appropriate rail maintenance and replacement schedules for safe and economic operation. There are a handful of examples in the literature of use of neutron diffraction to investigate residual stresses in rail, including [5][6][7][8]. These investigations usually involve measurements of slices out of rails, like in the study on comparison of rails (slices) produced under different production conditions and investigations of residual stresses in wheel damaged track [8].…”

“…There are a handful of examples in the literature of use of neutron diffraction to investigate residual stresses in rail, including [5][6][7][8]. These investigations usually involve measurements of slices out of rails, like in the study on comparison of rails (slices) produced under different production conditions and investigations of residual stresses in wheel damaged track [8]. In this work, residual stresses in rail heads were analysed using the dedicated neutron residual stress diffractometer Kowari at the Australian Nuclear Science and Technology Organisation (ANSTO).…”