FRF pairing

The FRF Pairing node in the Simulation Navigator stores all the reference and work model FRF pairs.

The FRF pairs are created by mapping each active reference FRF to one or more work FRFs when you create an FRF correlation solution process based on a matching tolerance value.

You can modify FRF pairs by:

• Activating or deactivating FRFs in the work and reference FRF sets.

• Increasing the matching tolerance value to map additional work and reference nodes.

• Editing the node map.

Response/excitation measure type

A consistent measure type, such as acceleration over force, velocity over force, or displacement over force is required when you pair the work and reference FRFs. You can set the preferred measure type when you create an FRF correlation solution process.

The analysis (work) FRFs must have been computed at each DOF (X, Y, Z) of the input nodes to transform them to the test coordinate system for FRF pairing, even if you are only interested in one input DOF.

FRF pair details

For each FRF pair, you can view the following detailed information in the Correlation Details View subpanel:

• Input (excitation) and output (response) nodes and DOFs of the reference solution. The reference function string combines this information.

• Input and output nodes of the work solution.

• FRF measure type.

Pair	[Ref] In. Node	[Ref] In. DOF	[Ref] Out. Node	[Ref] Out. DOF	[Ref] Function	[Work] In. Node	[Work] Out. Node	Out./In. Measure
1	10	Z	27	X	(10Z+, 27X+)	38122	27	Acceleration/Force
2	10	X	1	X	(10X+, 1X+)	38122	44149	Acceleration/Force
3	10	X	1	Y	(10X+, 1Y+)	38122	44149	Acceleration/Force

The node IDs are replaced by node names when the names are available from the test model or the selection recipes.

Note:

The sign of the FRF DOF is always displayed as positive in the FRF Set and in the Correlation Details View subpanel. The software internally multiplies the real and imaginary components of the imported FRF having DOFs with negative signs by -1 for correlation computations.

For one or more FRF pairs, you can generate:

• Graphs of the work FRFs, reference FRFs, or both to visually assess their degree of correlation.

• Graphs of Frequency Response Assurance Criterion (FRAC) to identify the correlation between the reference and work frequency response functions.

Filtering FRF pairs

You can create one or more FRF filters that limit the FRF pairs displayed in the Correlation Details View subpanel. You can filter the list of FRF pairs by combinations of the following filter types:

• Reference FRF input DOFs.

• Reference FRF output DOFs.

• Reference FRF input node IDs or names.

• Reference FRF output node IDs or names.

• Work FRF input node IDs or names.

• Work FRF output node IDs or names.

When you create multiple filters, the results that are displayed in the Correlation Details View subpanel depend on whether they contain one or more of the filter types in the following list:

• When active filters contain a single filter type, the result is the union of the FRF pairs from each filter. For example, if the first filter points to work input node IDs in five FRF pairs and the second filter points to work input node IDs in five FRF pairs, but only one FRF pair is different, then the union of the results is six FRF pairs.

• When active filters contain different filter types, the result is the intersection of the FRF pairs. For example, if the first filter points to work input node IDs in seven pairs, the second filter points to work output node IDs in eight pairs, and these filters have five common pairs, then the filter result is five FRF pairs.

• When several active filters contain input nodes and several filters contain different filter types, the result is the intersection of the union of all FRF pairs containing each filter type.

Where do I find it?

Application	Pre/Post
Prerequisite	An FRF correlation solution process
Simulation Navigator	FRF Pairing node

Look up more details

Correlation Details View subpanel (correlation solution process)

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FRF pairing, Simcenter 3D 2021.1 Series

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