APPLICATION OF THE UPPER-BOUND PRINCIPLE FOR SOLVING THE ROLL FORCE IN HEAVY RAIL ROLLING BY UNIVERSAL MILL

For heavy rail rolling by universal mill, a simplified 3-dimentiontheoretical model is built firstly. The kinematically admissiblevelocity fields of the web, head and base of rail are determined,respectively, and the corresponding strain rate fields and the intensityof shear strain rate are also obtained. Then the plastic deformationpower, the friction powers and the powers consumed on the velocitydiscontinuity surface are obtained. According to the upper-boundprinciple, the roll force of horizontal roll and two vertical rolls can beobtained. Moreover, the roll force can also be calculated by the formulaof slab rolling under the same deformation condition.The roll force from the formula of slab rolling differs greatly from thefield data, and the roll force from upper-bound method is somewhatgreater than the field data but in general the difference is less than 13 percent. So, it is more reliable to preset and optimize the parameters of rolling technology according to the upper-bound method.