A UNIFORM DEFORMATION GRADIENT HEXAHEDRON ELEMENT WITH ARTIFICIAL HOURGLASS CONTROL

An 8-noded linear hexahedron element for large strain hyperelastic ana lysis is presented in this paper. The element is based on a constant d eformation gradient interpolation and is formulated using a mixed vari ational principle of the Hu-Washizu type. Volumetric and isochoric com ponents of the deformation are treated independently to ensure the cor rect evaluation of the element volume. A simple procedure to control t he propagation of spurious hourglass deformation modes is also discuss ed. This is based on the addition of artificial hourglass forces which vanish under constant deformation gradient conditions, thereby ensuri ng that the element passes a non-linear version of the patch test. App lications in the field of neo-Hookean materials and superplastic formi ng processes are also considered.