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.

纵梁板成形能够有效地生产分支的钣金结构。与传统的钣金件相比，纵梁的刚度显着提高，因此为轻量化设计提供了新的可能性。纵梁板成形中的挑战是由于不稳定性造成的故障，这种不稳定性出现在纵梁以凹曲率弯曲的情况下。迄今为止，只有通过复杂的数值模拟才能对这种失效模式进行预测。这项工作引入了一个分析模型，用于预测在不同工艺边界条件下凹形纵梁板曲率形成过程中的屈曲破坏。它源自基尔霍夫的板块理论。显示了所有影响参数的详细灵敏度分析，并扩展了对过程的理解。该模型通过4点弯曲测试和冲压过程进行了验证。它可用于纵梁板成形中屈曲破坏极限的保守估计。