The Theoretical and Experimental Research on the Forward Slip Coefficient in Rail Universal Rolling

Abstract

In rail universal rolling, the forward slip coefficient is one of the most important parameters. For simplifying the analytic model, the vertical roll with box pass has been simplified as an equivalent flat roll firstly. Then the equation of neutral line and the area of forward slip zone on the flank of horizontal roll have been derived. Furthermore, the horizontal resultant force acting on the rolled workpiece has been obtained and the forward slip coefficient of rail universal rolling has been proposed. For verifying the theoretical model, the universal rolling process of 60 kg /m heavy rail and 18 kg /m light rail have been simulated by the RigidPlastic FEM software DEFORM-3D V5.0, and the universal rolling experiments of 18 kg/m light rail has been accomplished in the Yanshan University Rolling Laboratory. Moreover, the theoretical results and numerical simulation results of forward slip coefficient are in agreement with the experimental data basically. So, this theoretical model can be applied in rail universal rolling. (3) where H f is the height of box pass, W t0 is the width of incoming workpiece, W t1 is the width of outgoing workpiece, B 0 is the minimum width of box pass, B f is the maximum width of the box pass. it can be shown as (11) where b t is the spread coefficient of the top of rail, c m is the influence factor of the material on the spread (Table 1), c wt is the deformation conformity factor between the web of rail and the top of rail, w f is the proportion between the volume of metal flowing to the cross section and the total volume of metal flow, G vt is the roll gap, R vt is the maximum radius of vertical roll rolling the top of rail, j is the friction factor of box pass.The width of the top of rail at the exit section W b1 can be calculated by the modified S. Ekelund spread equation (15) where c wb is the deformation conformity factor between the web of rail and the top of rail, l b is the length of contact zone of the base of rail.In this paper, the critical point is defined as the point on the contact boundary at the exit section. It affects the contact status and the shape of the outgoing workpiece directly, so it is indispensable for determining the mean roll radius.At the exit cross-section, the critical point (C y , C z ) can be determined by the intersecting point between the stress free surface and the side wall of box pass. So the critical point (C y , C z ) can be obtained from the following equations: As can be seen in Fig. 2, the little round angle is neglected. Since the small amount of area is neglected, the area of available contact section (hatching zone) A h at the exit section can be determined by.