An improved solid-shell element based on ANS and EAS concepts

This paper presents an eight-node nonlinear solid-shell element for static problems. The main goal of this work is to develop a solid-shell formulation with improved membrane response compared with the previous solid-shell element (MOS2013), presented in [1]. Assumed natural strain concept is implemented to account for the transverse shear and thickness strains to circumvent the curvature thickness and transverse shear locking problems. The enhanced assumed strain approach based on the Hu-Washizu variational principle with six enhanced assumed strain degrees of freedom is applied. Five extra degrees of freedom are applied on the in-plane strains to improve the membrane response and one on the thickness strain to alleviate the volumetric and Poisson's thickness locking problems. The ensuing element performs well in both in-plane and out-of-plane responses, besides the simplicity of implementation. The element formulation yields exact solutions for both the membrane and bending patch tests. The formulation is extended to the geometrically nonlinear regime using the corotational approach, explained in [2]. Numerical results from benchmarks show the robustness of the formulation in geometrically linear and nonlinear problems. Copyright (C) 2016 John Wiley & Sons, Ltd.