CONSISTENT GRADIENT FORMULATION FOR A STABLE ENHANCED STRAIN METHOD FOR LARGE DEFORMATIONS

Considers the problem of stability of the enhanced strain elements in the presence of large deformations. The standard orthogonality conditi on between the enhanced strains and constant stresses ensures satisfac tion of the patch test and convergence of the method in case of linear elasticity. However, this does not hold in the case of large deformat ions. By analytic derivation of the element eigenvalues in large strai n states additional orthogonality conditions can be derived, leading t o a stable formulation, regardless of the magnitude of deformations. P roposes a new element based on a consistent formulation of the enhance d gradient with respect to new orthogonality conditions which it retai ns with four enhanced modes volumetric and shear locking free behaviou r of the original formulation and does not exhibit hour-glassing for l arge deformations.