Examples


IMAT and its related toolboxes provide you with significant functionality. However, it may not seem obvious how to use IMAT's capabilities, even after reading the documentation. Because of this, we have provided several useful examples that demonstrate how to use IMAT. All of the example files can be found in the examples subdirectory of your IMAT installation. We highly recommend that you include this directory in your MATLAB path if you have not already done so.

The following sections describe what you can find in the examples directory.

Example Functions

IMAT provides a number of useful utilities. These utilities are provided as MATLAB m-files, so the source code is readily visible. The following table summarizes the example functions provided.

Function Description
calc_energy_fractions.m Calculate and report kinetic and strain energy fractions for groups
cmif.m Compute Complex Mode Indicator Functions
create_default_fn Create a default imat_fn of a specified type
format_ppt.m Format an imat_fn plot for pasting into Microsoft Powerpoint
frfsyn.m Synthesize Frequency Response Functions from real or complex mode shapes
gmif.m Compute the various mode indicator functions
mmif.m Compute Multivariate Mode Indicator Functions
ortho.m Compute Modal Assurance Criterion or Orthogonality for a set of mode shapes
plot4views.m Create a four-paneled mode shape plot
psmif.m Compute Power Spectrum Mode Indicator Functions
qmif.m Compute Quadrature Mode Indicator Functions (CMIF using the imaginary component of the FRF)
rbmodes.m Generate rigid body modes from FEM geometry
readunv_180.m_example.m Example for using the readunv API to import dataset 180
tdm_xlsread.m Read Test Display Model from Excel worksheets
tdm_xlsread_example_1.xlsx TDM example Excel worksheet
tdm_xlsread_example_2.xlsx TDM example Excel worksheet
tdm_xlsread_template.xlsx TDM Excel worksheet template
tdm_xlswrite.m Write Test Display Model to Excel worksheets
writeblk.m Write to a Nastran BLK file
writedmig.m Write matrix in Nastran DMIG format
writempc.m Write a row- or column-oriented matrix as NASTRAN MPC cards
writerandps.m Write RANDPS and TABRND1 cards to a Nastran bulk data file
writetabled1.m Write imat_fn or fcn as Nastran TABLED1 cards
write_nas_field.m Pack real numbers into 16-character fields in Nastran format
SMAC subdirectory  
smac.m Synthesize Modes and Correlate modal parameter extraction utility
Anapost subdirectory  
aelempost.m Summarize solid element stress results from Nastran Output2/Punch files
max_von_mises.m Compute the highest von Mises stress for a load of unknown direction

 

The examples we provide also happen to be useful. We provide functions to compute Modal Assurance Criteria (MAC) and orthogonality, generate rigid body mode shapes from supplied finite element model geometry, generate a modal substructure from mode shapes, compute normal, complex, and multivariate mode indicator functions, and synthesize frequency response functions (FRF) from real normal modes.

Another very useful set of example functions allows you to easily create and/or modify FEM connectivity using Microsoft Excel. This capability is particularly useful for test engineers who might use a test display model (TDM) for animating mode shapes. The examples directory contains several functions and spreadsheets whose filenames start with tdm_xls*. You can develop FEM connectivity including local coordinate systems, nodes, elements, and tracelines in Excel, and then invoke tdm_xlsread.m to import the TDM into an imat_fem in MATLAB for display. You can export an imat_fem from MATLAB using tdm_xlswrite.m to an Excel spreadsheet for modification and then subsequent import back into MATLAB. Also included are a blank template Excel file called tdm_xlsread_template.xlsx and two example TDM files.

In addition to these useful functions, we provide several readunv extension examples that show you how read Universal file datasets that are not natively handled by readunv. The three examples provided read datasets 2452, 2467, and 2477, which contain group information. If the examples directory is in your MATLAB path, readunv will automatically detect and use these extension functions.

The best way to familiarize yourself with the functions we provide is to browse the examples directory and read the help for these functions.

In addition to the sample functions found in this directory, the main IMAT source directory contains several MATLAB scripts that start with demo_*. These files contain code and comments that show you how to use IMAT by going through some simple examples. You can access these scripts by running them (type demo_ at the MATLAB prompt, followed by a <TAB> to see the available choices).

Demo Data Files

In the Demo_Files subdirectory you will find a number of data files. All of these files are related to a fictional spacecraft (the General Purpose Spacecraft, or GPSC). You can use these data files to exercise the various IMAT import functions, and also to load IMAT datatypes so you can exercise the functionality available to them.

This directory contains function and shape ADFs, Nastran bulk data, Output2, and Punch files, and an Abaqus Input file and ODB.

SMAC

SMAC, or Synthesize Modes and Correlate, is not so much an example as it is a fully functional modal curve-fitting utility. It utilizes a different approach from most modal curve-fitting algorithms. SMAC is based on modal filter theory. You can find an introduction to SMAC along with helpful hints on how best to use it here.

To use SMAC, simply add the examples/SMAC directory to your MATLAB path, and invoke it by typing 'smac' at the MATLAB prompt.

SMAC is generously provided by Sandia National Laboratories through the United States government, and is released under Mozilla Public License version 1.1. The text of this license can be found here.

Analysis Post-Processing Utilities

The anapost directory contains a collection of useful functions for post-processing Nastran results. These include aelempost, a utility that reads solid element stress results from Nastran OP2 or PCH and post-processes them. max_von_mises calculates the worst direction von Mises stress on a per-element basis, given stress inputs in 3 orthogonal directions. For more details on the supplied utilities, please review the contents of this directory in your installation. README.txt, located in this directory, gives more details about the available utilities.

To use any of these utilities, simply add the examples/anapost directory to your MATLAB path.


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