Correlation metrics

Use the Correlate Modes command to visualize the following correlation metrics results:

• MAC is a scalar measure that indicates the degree of agreement between reference and work mode shapes. For more information, see Modal Assurance Criteria (MAC).

• COMAC is a vector that helps you to identify those parts of the structure and the degrees of freedom which are responsible for low degrees of MAC correlation. For more information, see Coordinate MAC (COMAC).

• MSF relates two mode shape vectors in terms of the magnitude of their components. For more information, see Modal Scale Factor (MSF).

• X-Ortho quantitatively compares the work mode shapes to the reference mode shapes involving the reduced mass matrix. Available only for a structural shape correlation solution process. For more information, see Cross-orthogonality (X-Ortho).

MAC matrix	COMAC matrix	MSF matrix	X-Ortho matrix

You can also display the correlation metric results in the Information window or export to an Excel spreadsheet or a CSV file.

Cross-orthogonality requirement

To obtain the correlation cross-orthogonality results, the work solution must contain a reduced mass matrix.

Note:

Only work solutions solved with Nastran can contain a reduced mass matrix.

Before the software displays the cross-orthogonality metric results, it performs cross-orthogonality related checks. If it encounters problem in computing the metric, it displays detailed information in an Information window.

Correlation heat map display size

You can control the size of the heat map using the UGII_CORRELATION_HEATMAP_SCALE environment variable.

Example:

If you want to reduce the heat map size to 50% of the original size, set the following:

UGII_CORRELATION_HEATMAP_SCALE = 50

The value that you set represents a percentage. A value of 100 leaves the size unchanged, while 200% makes the heat map twice as big.

Origin of the matrix plot

The origin of the matrix plot corresponds to the cell with the lowest reference and work mode IDs. You set the origin using the Matrix Plot Origin customer default. The Virtual.Lab convention for the location of the origin is the bottom left of the matrix plot.

Tip:

To find a customer default, choose File tab→Utilities→Customer Defaults, and click Find Default .

Where do I find it?

Application	Pre/Post
Prerequisite	Paired reference and work normal modes
Command Finder	Plot MAC or Plot X-Ortho
Simulation Navigator	Right-click the Mode Correlation Metrics node→Correlate ModesRight-click the Mode Correlation Metrics node→Plot MACRight-click the Mode Correlation Metrics node→Plot X-Ortho

Quick links

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Correlation metrics, Simcenter 3D 2021.1 Series

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