Study of micro flexible rolling based on grained inhomogeneity

Abstract

This paper shows an analytical, numerical and experimental investigation to comprehend the role of grained inhomogeneity which plays in micro flexible rolling in terms of the average rolling force and the thickness directional springback of the workpiece after it exits the roll bite zone. Miniature tensile tests and micro hardness tests are accomplished to identify the scattered stress-strain curves for 500 ¿m thick aluminium alloy 1060 samples with grain size of approximately 23-71 µm and to determine the weighted heterogeneity coefficient for each sample separately, according to which the theoretical calculations and numerical simulations based upon 3D Voronoi tessellation technique have been performed under actual experimental conditions where reductions of 25 to 50 % are selected. The scattering effect associated with the anisotropic nature of single grains has been perceived in the micro flexible rolling process and both the analytical and finite element models developed have been validated via experimental data to hold promise for predicting the rolling force and the thickness directional springback of the workpiece, as well as boosting the thickness profile control performance of the micro flexible rolling mill.

Finite Element Analysis of Forward Slip in Micro Flexible Rolling of Thin Aluminium Strips

“…Figure 1. Forces acting on the unit width of the workpiece within thickness transition zones: (a) Rolling phase to form transition zone with thicker thickness; and (b) rolling phase to form transition zone with a thinner thickness (for the deformation area below arc AC) [32].…”

“…Suppose (1) stress is uniformly distributed along the arc of contact between the rolls and the rolled workpiece, namely is regarded as a constant, and (2) friction coefficient µ remains invariable along the arc of contact and friction between the rolls and the workpiece obeys the Figure 1. Forces acting on the unit width of the workpiece within thickness transition zones: (a) Rolling phase to form transition zone with thicker thickness; and (b) rolling phase to form transition zone with a thinner thickness (for the deformation area below arc AC) [32].…”

“…Suppose (1) stress is uniformly distributed along the arc of contact between the rolls and the rolled workpiece, namely p x is regarded as a constant, and (2) friction coefficient µ remains invariable along the arc of contact and friction between the rolls and the workpiece obeys the Coulomb's law given by τ x = µp x [32]. Then upon integration and rearrangement, Equation (1) yields the following,…”

Size effects in micro rolling of metals

“…For achieving periodical changes in the roll gap, the top and bottom work rolls can move simultaneously in opposite directions, or only the top work roll moves, along the normal direction of the rolled strip. Adjustment of roll gap by vertical movement of the top work roll is commonly found in micro flexible rolling of metals [3]. Micro flexible rolling differs from conventional flexible rolling because size effects that characterise the micro world are involved in the micro flexible rolling process.…”

“…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.…”