Exchanging Abaqus data with ZAERO

The universal file is the means of data exchange between Abaqus and ZAERO. It consists of four data sets: 2411, which describes node and coordinate data; 2414, which describes mass-normalized mode shapes; 2420, which describes the global coordinate system; and 2453, which describes the mass matrix in text format, or 2453b, which describes the mass matrix in binary format.

You can specify the universal file's output format by using the mode parameter. Choosing text format enables you to modify the universal file in a text editor but increases the file size to over twice that of similar files in binary format. Text is the default format and the only format supported by ZAERO. Table 1 and Table 2 describe the mass matrix data set text format and binary format, respectively.

Before the interface can create the universal file, you must make the following additions to your Abaqus input (.inp) file, then run Abaqus:

• Normalize the eigenvectors in the eigenfrequency extraction analysis with respect to the structure’s mass matrix. This normalization is necessary because the translator assumes the mode shapes are mass normalized; if you skip this step before the Abaqus run, the modes translated will be incorrect and will give incorrect results with no warnings or errors. For more information, see Natural frequency extraction.

• Include the following line in the analysis step:

  ELEMENT MATRIX OUTPUT, ELSET=allelements, MASS=YES, 
  OUTPUT FILE=USER DEFINED, FILE NAME=mtx-file-name

  where allelements is a defined element set containing all the elements that should be included in the global mass matrix. The matrix output will be placed into the file mtx-file-name.mtx; you should not specify the .mtx extension since Abaqus adds it automatically.

This section describes the input and output of the three main steps in the workflow between Abaqus and ZAERO.