Analysis of micro flexible rolling with consideration of material heterogeneity

• A 3D finite element model for varying thickness rolling of thin strip is built.
• Voronoi tessellation is employed in the workpiece to model the grain morphology.
• The scatter of springback decreases with the number of grains in thickness direction.
• Front and back tensions reduce the average springback in thickness direction.
• A regression model for thickness springback prediction is deduced and verified.

This paper establishes a finite element model to numerically study the springback in thickness direction during micro flexible rolling process, in which 3D Voronoi tessellation has been applied to describe grain boundary and generation process of grain in the workpiece. To reflect material heterogeneity, nine kinds of mechanical properties defined by nine types of heterogeneity coefficients are selected and assigned to Voronoi polyhedrons as per the statistical distribution of hardness of grains identified by micro hardness testing. Initial workpiece thicknesses of 100, 250 and 500 μm with reduction changing from 20% to 50% are respectively considered in the numerical simulation of micro flexible rolling process, and the effects of front and back tensions on the average springback have been discussed. With average grain sizes of 1, 10, 50, 100 and 250 μm respectively employed in the workpieces with the aforesaid initial thicknesses, the scatter of springback in thickness direction has been determined, and a model for springback has also been developed based on the simulation results.