Nonlinear - Advanced Options

The Advanced tab in the Nonlinear dialog box sets options for controlling the solution method. This tab appears when clicking Advanced Options from the Solution tab.

Method

Sets the control technique and the iterative method that is used by the solver.

Control Choose a control technique. Only Force control is available for dynamic studies.

Force

Use force control.

Displacement

Use Displacement control.

Arc length

Use Arc-length control.

Surface-to-surface formulation is used for no-penetration contacts when you select the Arc length Control method.
Iterative Sets the numerical technique that controls the solver iterations.

Newton-Raphson (NR)

Use the Newton-Raphson (NR) iterations.

Modified Newton-Raphson (MNR)

Use the Modified Newton-Raphson (MNR) iteration scheme.

Integration Sets the integration method.

Displacement Control Options

You can use the Displacement Control method to solve nonlinear contact analysis with the Direct Sparse and Intel Direct Sparse solvers only. The Displacement Control method can handle post buckling behavior in nonlinear analysis. Only the surface-to-surface contact formulation is supported when activating the Displacement Control.
Select a vertex or reference point to control the analysis Select a vertex or a reference point to drive the solution. If you select a reference point, the program uses the closest node to the specified point.
Displacement component for the selected location Displacement component. Sets the displacement component to be used in the displacement control method. The valid components are:
UX: X Translation displacement in the Global X-direction
UY: Y Translation displacement in the Global Y-direction
UZ: Z Translation displacement in the Global Z-direction
RX: X Rotation rotation about the Global X-direction for shell studies only
RY: Y Rotation rotation about the Global Y-direction for shell studies only
RZ: Z Rotation rotation about the Global Z-direction for shell studies only
Displacement variation with time Click Edit to define a time variation of the displacement using the Time Curve dialog box. After defining the time variation of the selected displacement component, click Graph to view the displacement as a function of time.
You can use the Displacement Control method to solve nonlinear contact analysis with the Direct Sparse and Intel Direct Sparse solvers only. The Displacement control method can handle post buckling behavior in nonlinear analysis. Only the surface-to-surface contact formulation is supported when activating the Displacement Control.

Arc-Length Completion Options

Maximum load pattern multiplier The maximum load-pattern multiplier at which the solution is to be terminated (approximate value). Default is 1.0E8.
Maximum displacement (for translational DOF) The analysis terminates if any displacement DOF exceeds this value.
Maximum number of arc steps The analysis terminates if the number of arc length steps reaches this limit. Default is 50.
Initial arc length multiplier

To start the arc length solution, an initial arc length is calculated by a user-defined arc length multiplier multiplied by a representative displacement. Default is 1.0.

Intermediate Results

Show intermediate results up to current iteration Select to visualize intermediate result plots while running a nonlinear study. When the first iteration step completes, the results for the active plot are shown on the graphics area. As the solution progresses to the next iteration step, the active plot gets dynamically updated. If you have not selected a result plot, the first default plot under the Results folder is dynamically updated in the graphics area.
By getting visual feedback of the results as the solution progresses, you can make decisions to either stop the simulation and make adjustments to the nonlinear study settings, or let the solution proceed with the current settings.

Step/Tolerance Options

Sets convergence and equilibrium parameters.

Do equilibrium iteration every Sets the frequency of performing equilibrium in number of solution steps.
Maximum equilibrium iterations Sets the maximum number of equilibrium iterations for any solution step.
Convergence tolerance Relative displacement tolerance used for equilibrium convergence.
Maximum increment strain Sets tolerance for strain increment for models with creep or plasticity.
Singularity elimination factor (0-1) Sets stiffness singularity elimination factor (normal solution is set to 1; if less than 1.0, the program modifies stiffness terms causing singularity to help convergence.) If the normal solution fails, trying a different value; for example, 0 might help convergence.
Neither the Arc Length nor the Displacement Control method can resolve rigid body motions that can occur during a nonlinear solution. If you encounter a rigid body motion during a nonlinear analysis, use the Force Control method with a Prescribed displacement to improve the chances of reaching convergence.