Influence of microstructure on inhomogeneity of stress and strain in the deformation zone during asymmetric cold rolling of ferritic-pearlitic steels

Abstract

Asymmetric cold rolling with different speeds of work rolls is a process which can be used as severe plastic deformation method for improvement of microstructure and mechanical properties of different metals and alloys. The main objective of the asymmetric rolling process optimization from a favourable stress-strain state point of view is to increase the level of shear stresses and strain in the deformation zone. Conventional macro level FE models do not take into account the complicated behavior of the material microstructure in the micro scale. So, the simulation of a homogeneous material does not provide a reliable prediction of the distribution of stress and strain in the processed metals and alloys. The main objective of this paper was development of the multiscale FE model for calculating the shear stresses and shear strain in the deformation zone with taking into account the behaviour of microstructure of the ferritic-pearlitic steel during asymmetric cold rolling. A standard solver of software package Abaqus 6.14-1 was used for the calculations. The modelling of the process was performed at room temperature without taking into account the increment of the metal’s temperature due to the thermal effect of deformation and friction. To save computing time, statistical representation of the microstructure was applied. Statistically similar representative volume element (SSRVE) was developed for representing the microstructure of ferritic-pearlitic steel at FEM simulation. Square with the size of 0.5×0.4 mm was used to create the SSRVE picture of the microstructure. Typical image segmentation and reconstruction algorithms like contrast aligning, adaptive binarization, connected-component labelling, dilation and erosion were used to obtain final image. Influence of microstructure on inhomogeneity of stress and strain in the deformation zone during asymmetric cold rolling of ferritic-pearlitic steel was simulated and analysed. Selected results, as well as discussion of the effect of microstructure on obtained stress and strain distributions, are presented in the paper. Results of multiscale simulation analysis of the stresses and strain characteristics, presented in this study, can be used for optimization of the asymmetric cold rolling process as severe plastic deformation method.