Abstract: For studying the elongation law of the rail in rail universal rolling, the head, base and web of rail are considered individually, and the deformation concordant coefficient and material influence coefficient are applied in this spread formula to correct the Smirnov spread formula and Gubujin spread formula. Based on the corrected spread formula, the theoretical elongation coefficients of the base and head of rail are obtained, and the mean elongation coefficient is derived by the law of constant volume. For analyzing the law of spread and elongation more deeply, the universal rolling process of 18 kg/m light rail is simulated by using rigid-plastic finite element method (FEM). Moreover, the universal rolling experiment is accomplished in the Rolling Laboratory of Yanshan University, and the spread values and elongation coefficients of the rail subject to different rolling technology are measured. Through comparison, it can be seen that the corrected spread formula is accurate enough and its calculation results are more close to the measuring results, and the mean elongation coefficients can be used to show the elongation law of the rail. So it is reliable and feasible to predict the spread and the elongation of the rail in rail universal rolling and preset the rolling technology rationally according to this corrected spread formula and mean elongation coefficient.

Key words: Deformation concordant coefficient, Experiments, Mean elongation coefficient, Rail universal mill, Rigid-plastic finite element method, Spread, multi-object optimization, autonomous emergency braking, Kriging model, reversible pretension seatbelt, restraint systems