16.1.16.3. Recommended Settings for Modal and Linked Analysis Systems

The following table provides a summary of the recommended settings for the Store Modal Results and Expand Results From properties based on the analysis type.

Analysis TypeRecommended Store Modal Results SettingsRecommended Expand Results From Settings
Modal with no downstream analysis

No

Stress and strain results not needed to be saved to file.mode because there is no downstream analysis.

Not available.
MSUP Harmonic Response analyses (Linked and Standalone)

No[a]

Stress and strain results from modal analysis are overwritten by stresses and strains which are expanded again in the linked Harmonic Response analysis due to any loads added in the downstream analysis.

Note:  This setting is available for a linked MSUP Harmonic Response analysis only.

Harmonic Solution

Use when number of frequency steps are far less than the number of modes. This option is not available when the Modal has a nonlinear Pre-Stress environment.

Modal Solution

Use when number of frequency steps are far more than the number of modes. This is the only option available when the Modal analysis has a nonlinear Pre-Stress environment.

Modal linked to downstream Random Vibration analysis

For Future Analysis

Stress and strain results from modal analysis are expanded and used in the linked random vibration analysis. No stress or strain expansion is needed again because there is no load.

Not available.
Modal linked to downstream Response Spectrum analysis

No

Stress and strain results are always combined in response spectrum analysis using file.rst and file.mcom.

Note:  To evaluate summation of element nodal forces using FSUM in Command Snippet, it is required to save element nodal forces in modal to file.mode.

Not available.
Modal linked to downstream Structural Optimization analysis

For Future Analysis

The Nodal Forces and the General Miscellaneous properties are set to Yes.

Program Controlled.
Static Structural linked to downstream Structural Optimization analysis

For Future Analysis

The Nodal Forces property is set to Yes.

Program Controlled.
Modal linked to downstream Transient analysis

No[a]

Stress and strain results from modal analysis are overwritten by stresses and strains which are expanded again in the linked transient analysis due to any loads added in the downstream analysis.

Transient Solution

Use when number of time steps accumulated over all the load steps is far less than the number of modes.

This option is not available when the Modal Analysis has a nonlinear Pre-Stress environment.

Modal Solution

Use when number of time steps accumulated over all the load steps is far more than the number of modes.

This is the only option available when the Modal Analysis has a nonlinear Pre-Stress environment.

[a] Review the Requirements and Limitations for Modal and Linked MSUP Analysis Systems shown below.

Requirements and Limitations for Modal and Linked MSUP Analysis Systems

If you have an MSUP analysis, either Harmonic Response or Transient, linked to an upstream Modal system, the Modal analysis does not respect the Expand Results From property setting when:

  • Only Direct FE loads, Remote Force, or Moment are scoped to global remote points.

  • The analysis includes a Commands (APDL) object.

  • No Damping Ratio is specified.

  • If the material damping is specified using the Eqv. Damping Ratio From Modal property (set to Yes) and at least one of the elemental-based Output Controls (Stress, Strain, etc.) is also set to Yes in the linked Modal analysis.

Instead, it will be driven by the Store Modal Results property (of the Modal system):

  • Setting this property to No, the Expand Results From property of the MSUP Harmonic Response or Transient analysis is ignored, even if set to Modal Solution. The results would be as if the Harmonic Solution or Transient Solution option had been set. Given this internal specification, you do not receive the results you expected.

  • Setting the property to For Future Analysis, the Expand Results From property of the MSUP Harmonic Response or Transient analysis is ignored. The results would be as if the Modal Solution option had been set. In this case, be sure that you request the same results from the Output Controls settings for both the Modal and downstream MSUP analyses. Given this internal specification, you do not receive the results you expected.

The scenarios are summarized in the following table.

Store Modal Results Property SettingExpand Result From Property SettingActual Expanded Results
NoExpand from ModalExpanded from Harmonic/Transient
NoExpand from Harmonic/TransientExpanded from Harmonic/Transient
For Future AnalysisExpand from ModalExpanded from Modal
For Future AnalysisExpand from Harmonic/TransientExpanded from Modal
Limitations When Using the Mechanical APDL Solver

The Mechanical application cannot post process split result files produced by the Mechanical APDL solver. Try either of the following workarounds should this be an issue:

  • Use Output Controls to limit the result file size. Also, the size can more fully be controlled (if needed) by inserting a Commands object for the OUTRES command.

  • Increase the threshold for the files to be split by inserting a Commands object for the /CONFIG,FSPLIT command.