Assessment of the position and dimension of no slip zone during longitudinal hot rolling of strip based on computer simulation

Finite Element Method (FEM) computer simulation of the hot strip rolling process was carried out according to different schemes: the first one is symmetrical, the second one is a scheme with rolls diameters asymmetry and the third one is a scheme with rolling speed asymmetry. The simulation was carried out using QForm software. Based on the results of the simulation, a method has been developed to determine the position and length of the no slip zone during rolling. This method is based on the analysis of changes in the parameters of the stress-strain state of the strip along to the length of the geometric deformation zone. The method is based on the search of the area within the geometrical deformation zone, in which the derivatives from the selected parameters of the stress-strain state along the geometric deformation zone length are as close to zero as possible. The following parameters were chosen as criteria for evaluation: accumulated strain, strain effective, strain rate effective and Oyane damage criterion. Using the developed methodology, it was possible to identify a number of differences and similarities in the shape and length of the no slip zone for the simulated schemes. In a symmetrical rolling scheme, the length of no slip zone occupies up to 74 % of the length of the geometrical deformation zone and has a shape that is symmetric with respect to the rolling axis. When rolling with rolls diameters asymmetry, the shape and position of the no slip zone change. In particular, the shape becomes asymmetrical and tilts forward in the rolling direction, forming an angle that reaches 2 degrees (rolls diameters asymmetry) and 30 degrees (rolling speed asymmetry). The greatest length of the no slip zone in both cases is almost the same as with symmetrical rolling. Based on the results of studies, it was found that the greatest length of the no slip zone is obtained when using the Oyane damage criterion, and the smallest one - when using the strain rate effective.