4.2.3.2. Outline of getMatrix.m

In this section the way the function getMatrix.m works is outlined.

Contents

Summary

Detailed outline

Template

Reference

Summary

In summary, the following steps are taken to read a matrix from a mtx file:

[1] Load the contents of the mtx file into a [n x 5] array in Matlab.

[2] Initialize and populate a square matrix with the data contained in the array loaded at step [1]

[3] Delete the rows and columns containing only zero elements.

[4] Format the square matrix appropriately.

Detailed outline

Here the steps summarized in the previous section are explained in detail.

[1] Loading of a comma-delimited text file in Matlab is quite straightforward. The Matlab function "load" is used. For the next steps, assume that the loaded [n x 5] array is named "a".

[2.1] Find n which is the number of rows of "a".

[2.2] Find the degrees of freedom per node of the finite element model.

[2.3] Find the maximum node ID of the model.

[2.4] Initialize a zero matrix (assumed to be named as "K") with dimension equal to the product of the degrees of freedom per node and the maximum node ID of the model.

[2.5] Populate "K" by scanning all the entries at the 5th column of "a" and placing them in the appropriate positions in "K".

[3] This step is relatively straightforward. For more details, the user should see the code of the function getMatrix.m.

[4] Depending on the specifications of the user, the output matrix "K" is formatted according to the following pseudocode:

switch format
    in case of sparse & lower triangular
        ...
    in case of sparse & fully populated
        ...
    in case of full & lower triangular
        ...
    in case of full & fully populated
        ...
    otherwise
        do nothing

Template

An exemplary Matlab script which reads and loads the matrix contained in a mtx file is as follows:

% S is the directory path of the results file. It is assumed that it is
% placed in the folder C:\Abaqus_Temp\
S='C:\Abaqus_Temp';
% AbaqusInputFile.inp is the name of the Abaqus input file
fileID = fopen('AbaqusInputFile.inp','wt');
% Write Abaqus options in the file
fprintf(fileID,' *HEADING\n');
fprintf(fileID,' ...<options in Abaqus input file>...\n');
fprintf(fileID,' *STEP\n');
fprintf(fileID,' ...<options to define the preloading history for the model>...\n');
fprintf(fileID,' *END STEP\n');
fprintf(fileID,' *STEP\n');
fprintf(fileID,' *MATRIX GENERATE, STIFFNESS, MASS, VISCOUS DAMPING,\n');
fprintf(fileID,' STRUCTURAL DAMPING\n');
fprintf(fileID,' *MATRIX OUTPUT, STIFFNESS, MASS, VISCOUS DAMPING,\n');
fprintf(fileID,' STRUCTURAL DAMPING, FORMAT=MATRIX INPUT\n');
fprintf(fileID,' *BOUNDARY\n');
fprintf(fileID,' ...<Options to define the boundary conditions for the matrix generation step>...\n');
fprintf(fileID,' *END STEP\n');
fclose(fileID);
% Run the input file with Abaqus
!abaqus job=AbaqusInputFile
% Give Abaqus enough time to create the lck file
pause(2)
% While the lck file exists then halt Matlab execution
while exist('AbaqusInputFile.lck','file')==2
    pause(0.1)
end
% Obtain the matrix output contained in the various mtx files
format='full'; % other options also possible
Stiffness=getMatrix('AbaqusInputFile_STIF1.mtx',format,S);
Mass=getMatrix('AbaqusInputFile_MASS1.mtx',format,S);
ViscousDamping=getMatrix('AbaqusInputFile_DMPV1.mtx',format,S);
StructuralDamping=getMatrix('AbaqusInputFile_DMPS1.mtx',format,S);
 

Reference

For more details about the functions involved in this section see:

getMatrix.m

_________________________________________________________________________
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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