One point quadrature shell element with through-thickness stretch

A general purpose one point quadrature shell element accounting for through-thickness deformation is developed. In the shell, a complete 3-D constitutive law is introduced, leading to a 7-parameter theory which explicitly accounts for thickness change and also for a linear variation of thickness stretch. An interpolation scheme for the shell director is developed to avoid thickness locking. The developed shell element covers flexible warping behavior by using a local nodal coordinate system at each node, which is updated with second order accuracy. A physical stabilization scheme for zero energy modes is employed based on the decomposition of the strain field into constant and linear terms with respect to the natural coordinates. The rigid body projection is applied to treat rigid body rotations effectively. Linear and nonlinear patch tests including elasto-plasticity and contact are performed and the results are compared with analytical or previously reported results. The results are also compared with those of 5-parameter shell elements, in order to show that there is no significant deterioration in accuracy, especially for thin shell applications.