College Park, Maryland June 6 - 10 , 2004 |
WP55: Neutron Residual Stress Measurements on Rail Sections for Different Production Conditions
V. Luzin (National Institute of Standards and Technology; State University of New York, Stony Brook, NY 11794-2275), J. Gordon (Volpe National Transportation Systems Center, Cambridge, MA 02142), T. Gnaupel-Herold (National Institute of Standards and Technology; University of Maryland, College Park), H.J. Prask (National Institute of Standards and Technology)
Rail sectioning with subsequent neutron or synchrotron x-ray diffraction experiments is the most effective technique for assessment of the residual stresses in the rails. In this study we present the results of stress measurements performed on the BT8 diffractometer at the NIST Center for Neutron Research (NCNR) on 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. In addition, a head-hardened and roller-straightened rail was also studied after service to elucidate evolution of the service-induced residual stresses. Neutron strain measurements with 3x3x3 mm3 spatial resolution were successfully employed for transversally-cut sections 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.
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