The high resolution neutron diffraction technique has been applied to determine, non-destructively, the residual stress distribution developed in the head of a railway rail after normal service.
Measurements were made, using the neutron strain scanner at the Institut Laue Langevin, Grenoble, on a transverse slice of rail 12mm thick taken from a section of straight track. The rail head was scanned in the three principal orientations in a series of parallel traverses sufficiently close to enable a two- dimensional matrix of data to be accumulated and vertical, transverse and longitudinal residual stress contours to be drawn.
Substantial residual compressive and tensile stresses and steep stress gradients were observed related to the depth below the top surface, distance from the running line and shape of the rail head. The highest stresses and stress gradients were observed in transverse and vertical directions but significant stresses were also retained in the longitudinal (12mm thick) direction of the rail.
The results demonstrate the effectiveness and unique characteristics of the neutron technique to determine non- destructively and continuously the residual stresses inside engineering components.