Analysis of micro flexible rolling with consideration of material heterogeneity

Abstract

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. Analysis of micro flexible rolling with consideration of material heterogeneityAbstract: 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 blankworkpiece. 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 blank thicknesses of 100, 250 and 500 m with reductions changingof from 20 toand 50% respectively are respectively considered in the numerical simulation of micro flexible rolling process. With grain sizes of 1, 10, 50, 100 and 250 m respectively employed in the workpieceblank, the scatter of springback in thickness direction has been determined, and a model for springback has also been developed based on the simulation results.

Study on micro hydro-mechanical deep drawing using finite element method

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Size effects in micro rolling of metals

“…It is found that the average springback shows a decreasing trend with the increase of front and back tensions in case of micro flexible rolling of ultrathin aluminium alloy strips. For strips with thickness values of 100, 250 and 500 μm, more front and back tensions play a more crucial role in eliminating the springback despite the change of reduction [4].…”

“…In micro ultrathin strip rolling, the width and thickness of the strip being rolled are normally in the domains of lower millimetre and submillimetre, respectively. With the development of rolling and microforming technology, other micro rolling methods, including micro flexible rolling [3,4] and micro cross wedge rolling [5], have also been successfully developed.…”

Influences of temperature and grain size on the material deformability in microforming process

“…grain size and temperature), a discrete distribution instead of a superposition of flow stress curves was observed due to the grain heterogeneity in micro scale. The scatter of flow stresses obtained from experiments reflects the inhomogeneous material behaviour in microforming [33,37]. Therefore, the scatter of flow stress was used to represent grain heterogeneity in this study.…”