Using assumed enhanced strain elements for large compressive deformation

The formulation of the assumed enhanced strain element proposed by Simo and Armero [(1992). Geometrically non-linear enhanced strain mixed methods and the method of incompatible modes. Inc. J. Num. Methods Engng 33, 1413-14491 encountered difficulties for large compressive deformation with hyperelastic or elastic/plastic materials. The improved formulation presented by Simo et al. [(1993). Improved versions of assumed enhanced strain tri-linear elements for finite deformation problems. Comp. Methods Appl. Mech. Engng 110,3 59-386p1r oposes to alleviate this deficiency with a modified quadrature rule and shape function derivative calculation. In this work, we show an alternative approach which attempts to avoid this limitation by treating the orthogonality constraint on the enhanced field in rate form. Copyright 0 1996 Elsevier Science Ltd.