03-12-2019 | Original Research | Issue 6/2020

Analytical modelling of buckling in stringer sheet forming
Important notes
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Abstract
Stringer sheet forming enables an efficient production of branched sheet metal structures. Compared to conventional sheet metal components, stringer sheets show a significant increase in stiffness and therefore offer new possibilities for lightweight design. A challenge in stringer sheet forming is the failure due to instability, which appears in the buckling of the stringer in concave curvatures. The prediction of this failure mode is so far only possible by complex numerical simulations. This work introduces an analytical model for the prediction of the buckling failure during forming of concave stringer sheet curvatures under different process boundary conditions. It is derived from Kirchhoff’s plate theory. A detailed sensitivity analysis of all influencing parameters is shown and extends the process understanding. The model is validated by means of a 4-point bending test and a stamping process. It can be used for a conservative estimation of the buckling failure limit in stringer sheet forming.