3-DIMENSIONAL NON-CONFORMING 8-NODE SOLID ELEMENTS WITH ROTATIONAL DEGREES OF FREEDOM

A new three-dimensional 8-node solid element with rotational degrees o f freedom is presented. The proposed element is established by adding rotational degrees of freedom to the basic X-node solid element. Thus the element has three translations and three rotational degrees of fre edom per node. The corner rotations are introduced by transforming the hierarchical mid-edge displacements which are parabolic shape along a n edge. The derivation of the element is based on the mixed variationa l principles in which the rotations are introduced as independent vari ables. Several types of non-conforming modes are selectively added to the displacement fields to obtain a series of improved elements. The r esulting elements do not have the spurious-zero energy modes and Poiss on's ratio locking and pass patch test. Numerical examples show that p resented non-conforming solid elements with rotational degrees of free dom show good performance even in the highly distorted meshes.