【正文】 a finite element model of rail length only for similar study, in order to save puter time and storage space largely. Keywords: straightness, residual stresses, sweep, camber, elasticplastic bending 1. IntroductionThe rails are, manufacture from bloom by hot rolling. They are initially cooled on cooling bed and then inside a closed pit. During cooling, temperatures at different regions of rails differ and the rails bend. The magnitude of bending is generally termed as camber and is measured by the rail. Subsequently, the rails are straightened in the rollerstraightening machine.In the straightening machine, the rails undergo alternate bending, and are subjected to elasticplastic deformations under high magnitude of loads. The straightness of the finished rail and the residual stress developed during straightening, depend on the loads applied in the straightening machine. The study has been made to examine straightness values along the straightening machine. The study has been made to examine straightness values along the plete length of the rail. It is observed that the front and rear ends of the rail are subjected to different patterns of loading while passing through the straightening machine pared to the middle portion of the rail. Therefore the straightness near the ends differs considerably pared to the uniform straightness pattern observed in the middle portion of the rail. The present study also provides guidance for the minimum length of the rail at the ends, which need to be cut to achieve the straightness within the acceptable limit. The generation of residual stresses in new rails during the process of rail straightening has attracted the attention of many researchers. Both theoretical and experimental studies have been carried out to determine the residual stresses in the rollerstraightened finished rail. Finstermann have simulated the elasticplastic bending process of the straightening operation on a nineroller machine. A threedimensional finite element model has been used for the purpose. The study has been made to examine residual stress in rail for a particular camber. Brunig have represented the rail as a bar with crosssection of variable width. The calculated stress values after straightening are interpreted as average variable width. The calculated stress values after straightening are interpreted as average value over the width. The simulated model used by Varney and Farris shows encouraging result. However, they used twodimension model and the method is unable to predict the variation in residual stress in the transverse direction. They have suggested closer spacing of rollers in order to reduce residual stress but expressed doubt in achieving straightness of the rails. While carrying out finite element simulation of a twoplane roller straightening machine, Schleinzer experimentally investigated the plastic behaviour of the rail material. They observed typical Bauschinger effect for different grade of rail steels. Experimental investigations have also been carried out to determine residual stress in new rail by different investigators have also been carried out to determine residual stress in new rail by different investigators. Ringsberg and Lindback have studied mainly the fatigue damage of rails induced by cyclic loading during service life, on an initially introduced residual stressstate affected rails. The present authors have simulated the cooling process to estimate the magnitude of bending and residual stress developed in the rail after cooling. It has been noted that residual stress in the rail after cooling is of very small magnitude in parison with the yield stress of the material. They have used threedimensional finite element model to simulate the straightening operation. A method for assessment of residual stress and straightness of the finished rails has been reported by the authors for a straight rail under stress free conditions. They have calculated straightness of the finished rail and residual stress for different setting parameters of the machine. Both the magnitudes of residual stress and the degree of straightness near the front end of the rail have been considered in the article to remend the machine setting parameters for efficient straightening operation. However, as per the knowledge of the authors, no study for examining the degree of straightness of “as manufactured” rails throughout the plete length of rail have been yet reported. In order to meet this gap, an effort is given by the authors in the present endeavour to investigate the straightness, achieved after straightening operation of a bent rail.2. Simulated model of straightening process The schematic arrangement of the straightening machine, that is considered here, is shown in Fig. 1. The machine consists of three top rollers (T1T3) and three bottom rollers (B1B3) of same diameter. The distance between each two consecutive rollers is 600mm. The bottom rollers are fixed with their axes on a horizontal plane. The top rollers can be moved up and down independently in order to apply loads of different magnitudes in rail during straightening operation. The present investigation has been carried out for a rail of 156mm height and 13m length. The crosssection of the rail lies in XYplane and half of the rail section along with node numbers is shown in . The section z=0 is chosen at the middle of the rail length as shown in .. Schematic arrangement of rollers in straightening machine In order to set the positions of the top rollers, a straight bar of the same height as that of the rail is placed into the machine and the positions of the top rollers are adjusted so that they just touch the bar. The straight bar is then removed and the positions of the top rollers are set as per the desired magnitudes. The distances by which the first, second and third top rollers are lowered are defined as deformation setting parameters, d1d3 of the straightening operatio