Mechanical APDL Basic Analysis Guide

7.3.8. Comparing Nodal Solutions From Two Models or From One Model and

Experimental Data (RSTMAC)

In a typical design procedure, you may want to make small changes to your model and compare the
solutions you obtain from the new model to solutions from the original model. You may also want to
compare numerical solutions with experimental ones.

The RSTMAC command compares the nodal solutions from two results files (.rst or .rstp) or from
one results file and one Universal Format file (.unv). The details about the Universal Format file sup-
ported records can be found in Universal Format File Records (p. 199).

Only structural degrees of freedom are considered, and nodal solutions (real or complex) from any
analysis type are supported. The procedure is based on the Modal Assurance Criterion (MAC) calculations
(see POST1 - Modal Assurance Criterion (MAC) for more details).

Because the two files may correspond to different models and/or meshes, the first step consists of
either:

• Matching the nodes of model 1 and model 2. This is the default procedure. It is recommended when
  meshes are identical or very similar.

Or

• Mapping the nodes of model 2 into elements of model 1. This procedure is activated with TolerN = -1
  on the RSTMAC command. In this case, the solutions of model 1 are interpolated. It is the most general
  procedure but it is generally more time consuming.

Note

If you want to compare the nodal solutions of cyclic symmetric sectors, use the mapping

and interpolation method (TolerN = -1). Because the nodes of the basic sector and the

nodes of the duplicat e sector are coincident, the node mapping is done separat ely for each

sector. Model 1 and model 2 must have the same number of sectors.

The next two steps consist of:

• Performing the MAC calculations


• Identifying the best solution matches

All three of these steps are detailed below using two models of a simply supported beam. Model 1,
tsolid, is a solid element mesh. Model 2,tbeam, is a beam element mesh.

All of the first ten eigensolutions are compared, and a full printout is requested (KeyPrint=2 on the
RSTMAC command).

7.3.8.1. Mat ching the Nodes

The Mechanical APDL input is:

rstmac, tsolid,1,all, tbeam,1,all,,,, 2

The output is:

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