GNATS, Nonlinear Stress Analysis of 2-D and Axisymmetric Static Structure by Finite Elements Method

1 - Description of problem or function: GNATS is a finite element computer program designed for nonlinear analysis of axisymmetric and two-dimensional static structures. 2 - Method of solution: The GNATS program is based on a total Lagrangian description of the displaced equilibrium configuration. The complete strain-displacement equations are used to include the effects of large displacements and large strains. Elastic-plastic material behavior, with either isotropic or kinematic hardening, may be selected. All solution options included in GNATS contain an equilibrium check which assures that the structure satisfies equilibrium to a specified tolerance at each stage of loading. 3 - Restrictions on the complexity of the problem: All large arrays in GNATS, MESH2, and GPRINT are dynamically dimensioned to minimize storage requirements