Theoretical and experimental analysis of the deformation zone and minimum thickness in single-roll-driven asymmetric ultrathin strip rolling

Abstract

Although asymmetric rolling is employed extensively to produce ultrathin strips in micromanufacturing, microelectronics, and other high precision engineering fields, very limited attention has been given to the deformation zone, which is a direct result of the material thickness reduction behavior during asymmetric rolling. In this study, theoretical analysis of the minimum thickness of single-roll-driven asymmetric rolling is performed by combining FE (finite element) and theoretical analytical models to complete a comprehensive investigation. Based on the FE model calculation results, the deformation zone contour varies with reduction ratio, strip thickness, and yield strength; the Fleck model can be used to describe single-roll-driven asymmetric ultrathin strip rolling when the thickness is small enough. Different from symmetric rolling, a cross-shear zone is inevitably formed during asymmetric rolling, but the cross-shear force resulting from asymmetric rolls decreases and approaches 0 with smaller strip thickness, smaller reduction ratio, and higher yield strength, which means the rolling status of single-roll-driven asymmetric ultrathin strip rolling is very similar to symmetric rolling when the strip reaches its limiting minimum thickness. Therefore, a minimum thickness model is developed for single-roll-driven asymmetric ultrathin strip rolling with different roll diameters, mean tensions and strip yield strengths, and the elastic modulus and Poisson ratio of the two rolls are considered. Eventually, the minimum thickness for single-roll-driven asymmetric rolling of ultrathin strips is estimated using the new minimum thickness model, with further experimental verification by the single-roll-driven asymmetric rolling of various materials, including aluminum, 304 stainless steel, and both non-annealed and annealed copper. Compared with experimental results, the model is shown to be a possible alternative for more accurate minimum thickness prediction in single-roll-driven asymmetric rolling.