IV. Description of the Elements

A. Introduction

This chapter describes the finite elements available in the ATILA code.  For each element, the name, definition, list ofthe degrees-of-freedom associated with the nodes (translations, rotations, electricalpotential, magnetic potential, pressure), and entry parameters (topology,material properties, geometrical properties) are provided.

Most of the elements in the ATILA library are isoparametric.  Thus, complex structures withcurved sides or faces can be modeled using a reduced number of elements. Nevertheless, the best results are obtained when these elements have a reasonable aspect ratio. Wild distortions lead to inaccuracies because the assumptions made within thecode for strains become unrealistic.  Extreme distortion may even cause programfailure (negative Jacobian determinant).  The user should guard againstexcessive distortion by adhering to the following guidelines for sides of 2-D elements or for faces of 3-D elements:

Element node numbering generally follows simple rules:

WARNING

All data (except the angles) must be givenusing MKS units or any coherent unit system deduced from the MKS system. Angles are always in degrees.