Defect-free 4-node flat shell element: NMS-4F element

A versatile 4-node shell element which is useful for the analysis of arbitr ary shell structures is presented. The element is developed by flat shell a pproach, i.e., by combining a membrane element with a Mindlin plate element . The proposed element has six degrees of freedom per node and permits an e asy connection to other types of finite elements. Tn the plate bending part , an improved Mindlin plate has been established by the combined use of the addition of non-conforming displacement modes (N) and the substitute shear strain fields (S). Tn the membrane part, the nonconforming displacement mo des are also added to the displacement fields to improve the behavior of me mbrane element with drilling degrees of freedom and the modified numerical integration (M) is used to overcome the membrane locking problem. Thus the element is designated as NMS-4F. The rigid link correction technique is ado pted to consider the effect of out-of-plane warping. The shell element prop osed herein passes the patch tests, does not show any spurious mechanism an d does not produce shear and membrane locking phenomena. It is shown that t he element produces reliable solutions even for the distorted meshes throug h the analysis of benchmark problems.