An analytical model for designing defect-free sheet metal profiles with height-variable cross sections manufactured by Flexible Roller Beading

Abstract

Following the industrial change from mass production towards serial customization flexible technologies are becoming increasingly important. Therefore, the novel forming process “flexible roller beading” (FRB) is developed, which enables the continuous production of sheet metal profiles with customizable variable cross-sectional height and exploits the lightweight potential of profile-based constructions. To guarantee the quality and further processability of the profiles, component defects—primarily sheet wrinkling in the profile flange—must be avoided. The occurrence of wrinkling is affected by various geometric parameters of the targeted profile. This makes an empirical determination of the material-dependent process limits inefficient due to the expensive computational times of numerical simulations and effort of experimental test executions. Therefore, a mathematical model is developed which allows the analytical prediction of the process instabilities causing sheet wrinkling. The presented paper includes the description of the mechanical characteristics of FRB based on numerical and experimental investigations. The predictive analytical model derived from these findings determines the maximum longitudinal compressive stress in the profile flange, which is responsible for the wrinkling formation, based on the relevant geometric characteristics. By the comparison of the calculated occurring longitudinal compressive stress with the material-specific critical stress, sheet wrinkling can be predicted and failure-free profile geometries can be efficiently designed. The generality of the analytical model, independent of the profile geometry, is validated by experimental tests.