Run Options: SimSolid vs OptiStruct


Run SimSolid Analysis	Run OptiStruct Analysis

Name

When you run an analysis, the name of the run defaults to the name of the model. However, you can assign your own name to the run in the Run Analysis window.

Element Size (OptiStruct)

The element size dictates the quality of your optimization results. In general, the smaller the element size, the more accurate the result, but the slower it will run.

Note: To improve overall performance, when a CAD file is imported the mesh sizes are not calculated and are shown as Auto. Click the

icon to display the Element Size.

The element size is calculated from the smallest features in the CAD. Cleaning up the CAD so there are fewer features will help jobs to run faster.

Normal Modes

You can choose whether or not to include normal modes, and how many, in your analysis. The results show the shape of the vibration at that frequency. You may also select whether to include supports from a particular load case in the drop-down menu.

Buckling Modes (Linear Buckling or Eingenvalue Buckling)

Buckling modes are used to predict when a part will bend or collapse under load. You may select the number of modes and which buckling load cases to include. The resulting buckling load factors help you determine the load required to cause your part to buckle. If the value is in-between -1 and 1 buckling is expected for the given load.

Modal Prestress

Prestressed loadcases are linear.

Depending on preloading conditions, the resulting effect could be a weakened or stiffened structure.

If the preloading is compressive, it typically has a weakening effect on the structure (for example, column or pillar under compressive preloading).
If the preloading is tensile, it typically has a stiffening effect (for example, rotorcraft blade under centrifugal preloading).

Solution Settings (SimSolid)

Solution Settings are available to refine SimSolid solutions.

SimSolid employs a proprietary adaptive technology to automatically refine the solution in the areas where it is necessary to achieve the highest accuracy. Multiple solution passes are performed and with each pass, accuracy measures are created, and equations are enriched locally as required. The only settings specified manually are the maximum number of solution passes along with a small set of optional settings.

Settings can be applied globally to the entire assembly or locally to individual groups of parts. This allows you to first determine the overall system response, then quickly drill-in to specific areas of interest.

The settings are specified independently for each analysis. This provides a convenient method to do analysis comparison and solution convergence studies.

To adjust settings for all load cases, click the Open button.


Adaption	Procedure
Global	Select the Global option. Best for general load path prediction, modes and/or thermal analysis. Uses 3 adaptive passes, Adapt to Thin Solids and global adaption. Refinement Level is set to Standard. Typically the fastest solution method.
Global + Local	Select the Global + Local option. Best for stress calculation with more precision. Uses 4 adaptive passes, Adapt to Features, and Adapt to Thin Solids. Automatically creates local group for the parts and groups based on its relative volume. Part volume grouping is automatically done based on the total volume of the assembly. The parts that account for the 10 percent of the total volume are grouped together. For example, the top 10 percent go into group 1, 10-20 percent in group 2 and so on. Refinement Level is set to Standard.
Custom	Select the Global + Local option and adjust settings as needed. Define the max number of adaptive solution passes. This rarely needs to be more than 6. Click Create to create a new parts group. Select the Parts collector and click the parts you want to include in the group. Optional: Select the Adapt to Features check box for each group to adapt for local features for structural and nonlinear statistics. Optional: Select the Adapt to Thin Solids check box for each group to adapt for thin, curved solid sections. Apply locally on a part-by-part basis. Optional: Refinement Level can be set manually among three options for each group: Standard, Increased, and High. To discard custom settings and use the default Global + Local settings, click Restore Defaults.

Speed/Accuracy (OptiStruct)

Select Faster when stresses are not a major concern and testing your model to ensure that the kinematics of your loads and supports are correct. If you need more accurate results, select More accurate and rerun the analysis to achieve more precise stress and displacement results. This will also increase the run time. More accurate generates second-order elements.

Gravity

If the weight of a structure is a significant portion of the load it is bearing, then you should include gravity when running an analysis. Gravity pulls toward the negative z direction by default, but you can change the direction using the pull-down menu.

Load Cases

A load case is a set of loads and supports that act on a model at one time. You can assign loads and supports to specific load cases using the Model Browser or context menu. Then when you run an analysis, you choose which load cases to include in the Run Analysis window.

Inertia Relief

Inertia relief allows the simulation of unsupported structures. Typical applications are an airplane in flight, suspension parts of a car, or a satellite in space. With inertia relief, the applied loads are balanced by a set of translational and rotational accelerations. These accelerations provide body forces, distributed over the structure in such a way that the sum total of the applied forces on the structure is zero