A stabilized underintegrated enhanced assumed strain solid-shell element for geometrically nonlinear plate/shell analysis

In this paper, an underintegrated solid-shell element is developed in the framework of explicit finite element based on the Hu-Washizu variational principle. The reduced in-plane integration with a physical stabilization procedure scheme is adopted to improve computational efficiency. For the underintegrated element, volumetric locking is avoided with the B-bar approach, while thickness locking is eliminated by adopting only one enhancing parameter. In the previous literatures, the assumed natural strain method or artificial stabilization parameters are usually employed to remedy transverse shell locking for the underintegrated element, here a six-parameter enhanced assumed strain method is used, leading to a more straightforward formulation. Several standard benchmark examples including linear and nonlinear problems are calculated. The solid-shell element is proved to be accurate in resolving plate/shell problems. At the end, an in-house program that incorporates the solid-shell element into the explicit finite element method is developed. An S-rail forming process from the NUMISHEET conference is analyzed. The final results are in good accordance with the experiment.