NISA Software - Non-Linear Static & Dynamic Analysis

Material models include von Mises, Tresca, Mohr-Coulomg, and Drucker-Prager yield criterion
Elastic perfectly plastic, elastoplastic with isotropic, kinematic or mixed work hardening
Uniaxial stress-strain curve description includes elastic perfectly plastic, elastic linear hardening, elastic piece-wise linear hardening, and Ramberg-Osgood curve
Hyperelasticity and rubber-like material behavior, material models include generalized Mooney-Rivlin, Blatz-Ko, Alexander, etc.
Creep laws such as Norton, McVetty, Soderberg, Dorn, ORNL, etc. are supported. These laws can be expressed as general functions of time, stress, and temperature
Anisotropic elastoplastic material model with linear of piece-wise linear hardening for composite shell elements
Temperature dependent inelastic properties
User-defined material model

Simple 2D and 3D node-to-node contact elements with friction
General surface-to-surface frictional contact between flexibleflexible and flexible-rigid bodies
A priori knowledge of contact region not required
Contact surfaces may be of arbitrary curved geometry
Formulation accounts for nonlinear kinematics of large deformation analysis and employs consistent tangent stiffness for contact
Master-slave implementation with single-pass or symmetric-pass treatment
Automatic substructuring analysis, within a wavefront environment, when the nonlinearity is due to contact conditions only
General wavefront solution scheme, with dynamic update of wavefront parameters, for general contact problems involving geometric and/or material nonlinearity
Conservative loading (fixed direction force, moment, and pressure)
Non-conservative loading (deformation dependent follower concentrated force and follower pressure)
Body forces (weight and inertia)
Thermal loading (specified temperature vs. time curve)

Incremental-iterative solution procedure
Full or modified Newton-Raphson techniques
Special formulation for pure incremental analysis with no iterations
Equal, user-defined or automatic load steps
Line search for faster convergence
Convergence checks with displacments, rotation, force, moment, and energy criterion
ARC-length method to improve convergence characteristics specially for post-buckling and snap through problems
Time integration schemes for dynamics, creep and viscous effects including Newmark, Wilson-Theta Central difference, and Houbolt methods
Restarts from the last converged load step

Output at each load step or at every 'N' load step
Stress output in second Picola-Kirchoff or Cauchy stress for geometry nonlinearity
Nodal, Gauss point, and centroidal stresses and strains
Multiple displacement history and stress contours