Shell finite elements are widely used in explicit dynamics codes—such as LS-DYNA and EUROPLEXUS—for simulating impact and crash events. Quadrilaterals are preferred over triangulars. Among quadrilaterals, one-point quadrature elements with hourglass control are favoured for their computational efficiency. However, they can become unreliable in regions undergoing large deformations. To balance accuracy and computational cost, mixed meshes are commonly employed: fully integrated shell elements are placed in zones expected to experience severe deformations, while one-point quadrature elements are used in regions with milder deformations. In LS-DYNA, ELFORM 16 is a highly accurate fully integrated quadrilateral shell element. It employs a Hu-Washizu-based hybrid-mixed formulation with carefully chosen interpolations for the in-plane strains and stresses. As an alternative to this, we propose a simpler membrane-improved standard quadrilateral shell element. Numerical tests demonstrate that our element achieves performance comparable to ELFORM 16—and in several benchmark examples, even superior. The new formulation has been implemented in EUROPLEXUS. The core idea is to apply the assumed natural strain concept to the membrane strains in a way that satisfies the membrane patch test. This enhancement modifies only the membrane part of the strain field, leaving all other code infrastructure unchanged. We evaluated the enhancement in the context of Updated Lagrangian framework for explicit dynamics impact simulations. It softens the membrane response (reducing the highest natural frequency by roughly an order of magnitude), improves the representation of nearinextensional bending modes, effectively suppresses parasitic membrane strains, slightly enhances the conditional stability of the explicit time integration scheme in the nonlinear regime (thus permitting marginally larger stable time steps), and does not increase the computational cost.

BRANK Bostjan;  MARKOVIC Damijan; 

2026-09-23

Budapest University of Technology and Economics

JRC147674

978-615-112-036-1 (online),   

https://repozitorium.omikk.bme.hu/items/eb3b2053-9c68-4323-ab20-9f87163b649a,    https://publications.jrc.ec.europa.eu/repository/handle/JRC147674,   

10.3311/CEACMMSF2026-214 (online),