SOLVERS Home: Nonlinearity

Description

Nonlinear Geometry (GNL)

If set, nonlinear geometry effects are considered in the analysis.

If not set, geometry linear analysis is performed.

In geometric nonlinear analysis, the deformed geometry is used to establish the equilibrium equations, and depending on the element, small or large (finite) strain may be considered.

Geometric linear analysis is a special case of geometric nonlinear analysis and when the displacements are small, the difference between linear and nonlinear results is often negligible. Generally, geometric nonlinearity arises when changes in geometry, large or small, have a significant effect on the load deflection characteristics (that is, stiffness) of the structure, which can be quantified in terms of equilibrium between internal and external forces.

For geometric linear analysis, it is assumed that both displacement and deformation (i.e., strain) in the structure are negligibly small. With this assumption the equilibrium equations are formulated based on the undeformed (initial) geometry. Stress and strain are also defined with reference to the initial geometry, and although geometric linear analysis does not exclude material nonlinearity, element strains nevertheless remain small. Consequently, in geometric linear analysis, strain is always a linear function of displacement, although this may not apply to stress when material nonlinearity is considered.

Nonlinear Material (MNL)

If set, material nonlinearity is considered in the analysis.

If not set, linear material parameters are used if specified.

Nonlinear material includes cutoff bars and elements that reference nonlinear material tables (e.g., Stress vs Strain, Moment vs Curvature, Force vs Displacement).

Creep (CNL)

If set, creep is considered in the analysis.

This is only relevant if one or more element properties reference a creep property set.

Nonlinear Analysis

In heat transfer analysis, only this one option for nonlinearity is given.

if Nonlinear Analysis is set, the variation of material properties with temperature (including conductivity, specific heat, convection coefficient and heat source) is considered.

Nonlinear Analysis must also be set to consider radiation heat transfer.