<p>Aerospace and automobile industries demand bend sheets with different radii of curvature and in some cases, even the sheets of continuously varying radius of curvature are also required by them. Forming of such parts requires a flexible manufacturing process to closely control the radius of the curvature being formed. Asymmetric rolling is a process to produce sheets with enhanced material properties like improved ductility and strength, with front end curvature (FEC). This work proposes a hybrid process that combines asymmetric rolling with the incremental bending process to form bend sheets with improved mechanical properties. The process would turn the undesirable front end curvature phenomena of asymmetric rolling into a desirable one and uses it to create the curve profile. The proposed hybrid process is based on the theory of sequential bending, and each sequence is supposed to be completed in three steps viz. (a) formation of front end curvature in asymmetric rolling, (b) hammer impact on the rolled sheet, and (c) a new location of hammer impact due to continuous rolling of the sheet. In the proposed hybrid process, thin metal sheets are asymmetrically cold rolled and then bend by a punch placed after the rolling mill, in the direction of sheet flow. The front end curvature produced by asymmetric rolling is further bent by the incremental bending process by utilizing repeated hammering on the sheet to obtain the desired curvature.</p><p>The work presents the numerical simulation of the hybrid process with the help of finite element analysis and attempts to establish a relation between the hammering amplitude and its frequency on the radius of curvature. Besides, the effect of different asymmetric rolling and hammering parameters on the bend sheet being formed is also investigated using analysis of variance (ANOVA). The variation is investigated using five different process parameters namely hammering amplitude, hammering frequency, velocity ratio, the initial thickness of the sheet, and reduction ratio. The work explores the effect of the initial sheet thickness, the velocity ratio between the two working rolls, and the thickness reduction ratio on the curvature of the bent sheet. The radius of curvature is measured up to 300 mm from the rolling axis in the direction of sheet flow by selecting three points on the axis of the rolled sheet. The explicit 3-dimensional (3D) finite element analysis is employed to simulate the proposed hybrid process. The simulation results show that the velocity ratio and amplitude of the hammering are the two most important factors in the proposed hybrid process, and these parameters greatly influence the bend radius. Furthermore, the work also explores the typical bending behavior of the sheet during the hybrid process and sequential bending steps. Simulation results indicate that the radius of curvature can be augmented by decreasing velocity ratio, hammering frequency, and effective amplitude while it could be reduced by reducing the horizontal distance of the hammer from the rolling axis. Simulation results also revealed that the radius of curvature varies along the leading edge of the rolled sheet and it is observed that the radius of curvature increases when moving towards the rolling axis from the leading edge.</p>

Numerical Modeling of a Hybrid Asymmetric Rolling and Bending Process

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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