Model of Residual Stresses in Hot-rolled Sheets with Taking into Account Relaxation Process and Phase Transformation

The problem of calculations the residual stresses in hot-rolled sheets is considered in the paper. Residual stresses become of practical importance when the laser cutting of sheets is applied. The main factors influencing the residual stresses are the non uniform distribution of elastic-plastic deformations in the volume and unloading of the sheet material during cooling, phase transformation occurring during cooling and relaxation of the stresses. The goal of this paper is development of a model of residual stresses in hot-rolled sheets based on the elastic-plastic material model, taking into account the above factors. In this work the individual models for cooling of hot rolled sheets in the laminar cooling line and in the coil were developed. Elastic-plastic properties of the material were determined experimentally using tests on GLEEBLE 3800. Model of the thermal deformation during cooling was obtained on the basis of the dilatometric test. Thermal model was based on the solution for two dimensional cross-section of the sheet and the roll longitudinal section. Experimental verification of the thermal model was performed in industrial conditions.