Enhanced rotation-free basic shell triangle. Applications to sheet metal forming

An enhanced rotation-free three node triangular shell element (termed
EBST) is presented. The element formulation is based on a quadratic interpolation
of the geometry in terms of the six nodes of a patch of four triangles associated
to each triangular element. This allows to compute an assumed constant curvature
field and an assumed linear membrane strain field which improves the in-plane behaviour
of the element. A simple and economic version of the element using a single
integration point is presented. The implementation of the element into an explicit
dynamic scheme is described. The efficiency and accuracy of the EBST element and
the explicit dynamic scheme are demonstrated in many examples of application including
the analysis of a cylindrical panel under impulse loading and sheet metal
stamping problems.