Controlling the iteration strategy in Nastran nonlinear analyses

In Pre/Post, you can use different types of modeling objects to control the iteration strategy of Simcenter Nastran and MSC Nastran nonlinear analyses. The type of modeling object you use depends upon which Nastran nonlinear solution sequence you are running.

Controlling the iteration strategy in SOL 106 and SOL 153 analyses

Create a Nonlinear Parameters modeling object to define parameters that control the iteration strategy in the following types of Nastran analyses:

• SOL 106 Nonlinear Statics

• SOL 153 Steady State Nonlinear Heat Transfer

These parameters define strategies for the incremental and iterative solution options. The options in the Nonlinear Parameters dialog box correspond to the fields in the NLPARM bulk entry. When you solve or export a model that includes a Nonlinear Parameters modeling object, the software creates an NLPARM bulk entry in your Nastran input file.

With the NLPARM entry, the software uses a line search method to control the iterations. For more information, see:

• Nonlinear Parameters dialog box

• Controlling Iterations with the NLPARM Entry in the Simcenter Nastran Basic Nonlinear Analysis User's Guide for SOL 106 analyses.

• Nonlinear Iteration Scheme in the Simcenter Nastran Thermal Analysis User's Guide for SOL 153 analyses.

Controlling the iteration strategy in SOL 106 analyses with the arc-length method

In a SOL 106 analysis, you can also use the arc-length method to control the iterations. The arc-length method is appropriate in problems that involve snap-through or post-buckling deformation. To use the arc-length method, you must create an Arc-Length Methods Parameters modeling object in addition to the Nonlinear Parameters modeling object and associate them both with the solution.

When you solve or export your model, the options in the Arc-Length Methods Parameters dialog box define an NLPCI bulk entry in your Nastran input file.

Controlling the iteration strategy in SOL 129 and SOL 159 nonlinear transient analyses

Create a Nonlinear Transient Parameters modeling object to define parameters that control the iteration strategy and time steps in Nastran:

• SOL 129 Nonlinear Transient Response analyses

• SOL 159 Transient Nonlinear Heat Transfer analyses

The options in the Nonlinear Transient Parameters dialog box correspond to the fields in the TSTEPNL bulk entry. When you solve or export a model that includes a Nonlinear Transient Parameters modeling object, the software creates an TSTEPNL bulk entry in your Nastran input file.

For more information, see:

• Nonlinear Transient Parameters dialog box

• Implicit Integration Control: TSTEPNL Data Entry in the Simcenter Nastran Basic Nonlinear Analysis User's Guide

Controlling the iteration strategy in SOL 601 and SOL 701 advanced nonlinear analyses

In Simcenter Nastran SOL 601 and SOL 701 advanced nonlinear solutions, you use the NXSTRAT bulk entry to specify most solution options. These options include controlling automatic time stepping, equilibrium iteration, and convergence criteria.

In Pre/Post, you create a Strategy Parameters modeling object to define fields for the NXSTRAT entry.

For more information, see:

• Strategy Parameters dialog box

• The Simcenter Nastran Advanced Nonlinear Solution–Theory and Modeling Guide

Controlling the iteration strategy in SOL 401 and Multiphysics Multi-Step Nonlinear analyses

For Multi-Step Nonlinear solutions (SOL 401), create a Nonlinear Control Parameters modeling object to control options such as convergence criteria, maximum iterations per time step, and material nonlinear effects (creep and plasticity) at the solution level and at the step level.

The options on the Nonlinear Control Parameters dialog box correspond to the fields in the NLCNTL bulk entry.

Controlling the iteration strategy in SOL 402 advanced nonlinear analyses

In Simcenter Nastran SOL 402 Multi-step Nonlinear Kinematic solutions, you can create Nonlinear Control Parameters modeling objects at the solution and subcase level.

• At the global level, the nonlinear control parameters control solver type, matrix symmetry, stress-strain measure, and initial computation state.The options on the Nonlinear Control Parameters - Global dialog box correspond to the fields in the NLCNTLG bulk entry.

• At the subcase level, the nonlinear control parameters control analysis options (maximum displacement, rotation, and deformation; time-unassigned ramping; stabilization factors, and so on), disabling material nonlinear effects (creep and plasticity), time integration schemes, automatic time stepping, equilibrium iteration, convergence criteria, and contact options.The options on the Nonlinear Control Parameters - Subcase dialog box correspond to the fields in the NLCNTL2 bulk entry.

Where do I find it?

Application	Pre/Post
Prerequisite	A Simulation file as the work part and displayed partSimcenter Nastran or MSC Nastran as the specified solver
Command Finder	Modeling Objects
Location in dialog box	Type list

Learn more

Nastran nonlinear analysis in Pre/Post

Defining time step intervals for transient or nonlinear analyses

Controlling the birth and death times of elements in advanced nonlinear analyses

Post buckling with SOL 601,106 workflow

Quick links

Command reference

Pre/Post video examples

Bulk Entry Descriptions

Simcenter 3D tutorials

Browse Simcenter 3D help by product area

Controlling the iteration strategy in Nastran nonlinear analyses, Simcenter 3D 2021.1 Series

© 2020 Siemens

window.mainLanguage="en_US"

window.delivId=""

window.projectId=""

MathJax.Hub.Config({ TeX: { extensions: ["autoload-all.js"] }, tex2jax: { displayMath: [ ] }, "SVG": { scale: 125 } });