4.2.1.1. Overview

The Abaqus output database file (*.odb) is a neutral binary file used to store model information and analysis results in terms of an assembly of part instances. The results can be postprocessed in Abaqus by using the Visualization module of Abaqus/CAE, and can be postprocessed in Matlab using the Odb2Matlab postprocessor.

Output to the odb file can be requested by specifying suitable output variable identifiers, which can be chosen from docs in "Abaqus/Standard output variable identifiers", "Abaqus/Explicit output variable identifiers" and "Abaqus/CFD output variable identifiers" in the Abaqus documentation. However, only specific output variable identifiers can be postprocessed by Odb2Matlab, as seen in the next sections. The following types of output are available for postprocessing: node output and element output. Apart from the above, the odb file contains diagnostic information that currently cannot be postprocessed by Odb2Matlab.

The results of an Abaqus analysis that can be stored in an odb file can be of two types: "field" output and "history" output. Field output refers to a relatively large portion of the model with infrequent output, whereas history output refers to a relatively small region of the model at a fairly high frequency. Field output is used to plot contours, deformed geometry, X-Y plots, animations, etc of a model. Only complete sets of basic variables (for example, all the stress or strain components) can be requested as field output. History output is used to generate X-Y data plots. Individual variables (such as a particular stress component) can be requested as history output.

The output database is a neutral binary, platform-independent file, i.e. it can be copied from one computing platform to another without the need for translation. This does not happen with the binary results file (fil). Floating point data are written in the odb in single precision by default. The user can change this option so that the data are written in double precision.

You can open an odb file using an older version of Abaqus in Abaqus/CAE or Abaqus/Viewer, with the exception that Abaqus 5.8 odb files cannot be opened in version 6. Odb files that are opened by newer releases of Abaqus have to be updated before they are opened. If the odb file is coming from an older version of Abaqus, this process is done automatically by Abaqus2Matlab for all odb files, before it extracts their data. An odb file created by a newer release of Abaqus cannot be opened by a previous version of Abaqus/CAE.

Model information and analysis results are stored in terms of an assembly of part instances. Output variables that can be postprocessed by Odb2Matlab are printed in the odb file for:

nodes

element integration points, element section points, whole elements, and element sets

the whole model

Field output that can be postprocessed by Odb2Matlab is requested to the odb file by specifying in the input file the first of the following options in conjunction with one or more of the subsequent options:

*OUTPUT, FIELD

*NODE OUTPUT

*ELEMENT OUTPUT

Field output that can be postprocessed by Odb2Matlab is requested to the odb file by specifying in the input file the first of the following options in conjunction with one or more of the subsequent options:

*OUTPUT, HISTORY

*ELEMENT OUTPUT

*ENERGY OUTPUT

*NODE OUTPUT

It is recommended to select individual history output components when output of vector or tensor valued variables is requested, for reasons of reducing the computational effort of Odb2Matlab. For example, selecting S as an output variable identifier in the input file for one C3D8 element will create a total of 64 different history outputs (i.e (6 stress components + 10 stress invariants) x 4 integration points per element). Therefore, care should be taken so that only useful output requests are extracted from the odb file using Odb2Matlab, to minimize computational effort and the associated running time.

The Odb2Matlab postprocessor is comprised of 10 main functions which are presented in the next sections:

exploreFieldOdb.m, exploreFieldOdbPyScript.m

exploreHistoryOdb.m, exploreHistoryOdbPyScript.m

readNodeFieldOdb.m, readNodeFieldOdbPyScript.m

readElementFieldOdb.m, readElementFieldOdbPyScript.m

readHistoryOdb.m, readHistoryOdbPyScript.m

The aforementioned functions are presented in pairs. In each pair, the first function is used for the postprocessing job by the user, and the second function is used by the first function to generate the Python script involved in processing the data contained in the odb file. For more details for the use of these functions, see their documentation (viewed by clicking the above links). In order to use Odb2Matlab, the user has to install the Abaqus2Matlab application first, and select one of the above functions in one's Matlab code to perform the postprocessing. The various input and output arguments of these functions are explained in their documentation; however, the user is advised to study some verification examples before attempting to use any of these functions.

_________________________________________________________________________
Abaqus2Matlab - www.abaqus2matlab.com
Copyright (c) 2017 by George Papazafeiropoulos

If using this application for research or industrial purposes, please cite:
G. Papazafeiropoulos, M. Muniz-Calvente, E. Martinez-Paneda.
Abaqus2Matlab: a suitable tool for finite element post-processing.
Advances in Engineering Software. Vol 105. March 2017. Pages 9-16. (2017)
DOI:10.1016/j.advengsoft.2017.01.006



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