Nonlinear - Solution

The Solution tab in the Nonlinear dialog box sets solution related options. The following are the options you can set on this tab.

• Stepping Options. Time information is associated with the definition of time curves for loads and boundary conditions. Time is a pseudo variable for static problems without creep, visco-elasticity, or thermal loading using time-dependent results from a transient thermal study.

• Start time. Starting solution time. Not used by the Arc-Length method.

• Restart. Click this checkbox to restart from the last successful solution step. Available only if restart data exist. You can modify your solution parameters before rerunning the study.

• End time. Ending solution time. Not used by the Arc-Length method.

• Save data for restarting the analysis. Check this flag before running the study for possible restart. The software takes some time and disk space to save the data required for a proper restart. If you clear this checkbox, you have to start from the beginning.

Remeshing the study deletes all restart information.

• Time increment. Sets the procedure for incrementing time at each solution step for the Force and Displacement control methods. For the Arc-Length control method, the program uses this value to estimate an arc-length increment.

• Automatic (autostepping). When checked, the program determines an increment internally for each solution step to improve chances of convergence. This option supports all control techniques. If the flag is checked, the following entries are used:

• Initial time increment. The program uses this increment as the initial guess for the time increment.

• Min. Minimum time step. The default is 1e-8 seconds.

For nonlinear dynamic studies only, if the specified minimum increment is equal or greater than the initial time increment, the program resets the minimum time step to 10% of the initial time increment.

• Max. Maximum time step. Default is the End time for the Force and Displacement control methods.

For nonlinear dynamic studies only, the specified maximum time step is not used. The program resets the maximum value to the initial time increment.

• No. of Adjustments. Maximum number of time step adjustments for each solution step.

• Fixed. Fixed time step increment. Default is to run 10 steps.

• Geometry nonlinearity options.

• Use large displacement formulation. Uses the large displacement formulation.

• Update load direction with deflection. If checked, the direction of the applied load (uniform pressure, normal force, torque) is updated for every solution step with deflection.

• Use large strain option (for plasticity material models only). Uses the large strain formulation.

• Solver.

• Direct Sparse. Use the direct sparse solver. This solver have more chances of convergence for highly nonlinear problems.

• FFEPlus. Use the FFEPlus iterative solver. This solver is less demanding on memory. It maybe faster for large problems.

NOTES:

The program stops the analysis if:

• The number of step-size adjustments in any step exceeds the maximum number of step adjustments.

• The step increment required for convergence becomes smaller than the minimum step increment.

Related Topics

Nonlinear - Advanced Options

Flow/Thermal Effects

Remark

What is Nonlinear Static Analysis...