Isoparametric hybrid hexahedral elements for three dimensional stress analysis

Abstract

Based on a new functional in which displacements, strains and stresses are taken as independent variables, a set of three 8-node hexahedral hybrid elements is developed. The adoption of separated stress and displacement variables proves to be effective in improving the accuracy of the elements. The new elements are all capable of yielding converging results, and they all possess the properties of having no zero energy deformation modes and of being coordinate invariant. From the numerical example of a beam under bending it is concluded that exact solutions can be obtained for right prism elements, while good results are still attainable for severely distorted elements. The relationship between the new hybrid elements and the conventional displacement elements is also explored in this paper.