Mechanical APDL Basic Analysis Guide

10 20

11 23

12 25

13 28

14 30

15 33

16 35

17 38

Only the mapped nodes will contribute to the MAC calculations.

Important notes:

• Nodes that are coincident may lead to erroneous interpolation. For example, this can occur in the case
  of spring/mass systems attached to solid elements.


• If nodes and/or elements are selected (using the NSEL and/or ESEL commands), the results of the mapping
  and/or the interpolation will show differences. If you want to perform the MAC calculation on a part of
  the model, you can use the ESEL command. For a cyclic analysis, ensure you select the elements of the
  basic sector as well as those of the duplicat e sector. All the selected element nodes must also be selected
  (NSLE).


• If the OUTRES command is used to reduce the solution data written on the first results file (File1), the
  interpolation may be incorrect. For example, this can occur when an element does not have all its nodes
  in the results file. It is recommended that you use the OUTRES command only when generating the
  second results file (File2). This option is not supported when comparing cyclic symmetric structure
  results.

7.3.8.3. Evaluate MAC Between Solutions at Matched/Mapped Nodes

The Modal Assurance Criterion printout for interpolated solutions (mapped nodes) is as follows:

****** Modal Assurance Criterion (MAC) VALUES ******

Solutions are real

Rows: 10 substeps in load step 1 interpolated from file tsolid.rst

Columns: 10 substeps in load step 1 from file tbeam.rst

1 2 3 4 5 6 7 8 9 10

1 1.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

2 0.000 1.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

3 0.000 0.000 1.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

4 0.000 0.000 0.000 1.000 0.000 0.000 0.000 0.000 0.000 0.000

5 0.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 0.000 0.000

6 0.000 0.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000 0.000

7 0.000 0.000 0.000 0.000 0.000 0.000 1.000 0.000 0.000 0.000

8 0.000 0.000 0.000 0.000 0.000 0.000 0.000 1.000 0.000 0.000

9 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 1.000 0.000

10 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 1.000

The modal assurance criterion values can be retrieved as parameters using the *GET command (Entity
= RSTMAC).

Note

The modes obtained after a modal analysis of a cyclic symmetric structure are repeated when

the harmonic index is greater than zero. In this case, the MAC values table is compressed to

allow the solutions matching. This compression consists of summing and averaging the MAC

values of the repeated frequencies.

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