An interface to NASA/FLAGRO has been created within the MSC Fatigue environment. This interface works with NASA/FLAGRO version 2.03 as delivered by COSMIC. The PCL (PATRAN Command Language) within the MSC Fatigue forms allow you to easily set up a NASA/FLAGRO safe life analysis by specifying the crack geometry and parameters, the materials information and the loading schedule. The PCL will write out a NASA/FLAGRO batch file and then execute NASA/FLAGRO interactively in the invoking window using the generated batch file.

Currently, only safe life analysis is supported. Materials defined in the FLAGRO standard or user-defined files may be accessed. Load schedules defined in the FLAGRO schedule file may also be accessed. In certain instances, defined schedules and loading blocks may be saved to this file also.

Most error checking is done by the NASA/FLAGRO program itself. Therefore care should be taken to make sure proper geometry and other input definitions are defined correctly before creating the batch file and executing FLAGRO. If the program fails due to improper input data, then it will be necessary to run FLAGRO interactively to find out where the error occurred.

There are three major inputs to the NASA/FLAGRO program, as there are to any fatigue or fracture program. These are geometric information (crack geometry), materials information and loading information. A familiarity with the use of MSC Fatigue is suggested in that the forms for job set up follow closely to those of other analysis types with in MSC Fatigue.

The NASA/FLAGRO executables themselves can be retrieved form the MSC Fatigue delivery media. It is suggested that you use these files. No guarantee is given if other files are used that may have been modified (this is public domain software). The following files are unloaded:

To load the FLAGRO interface into the MSC Fatigue forms within MSC Fatigue Pre & Post or MSC Patran, type the following command in the command line:

Do this before you open the MSC Fatigue form. You may want to include this line at the end of the init.pcl file so that it always appears automatically.

There are three basic inputs just as for the other analysis types, those being Solution Parameters, Material Information and Loading Information. To run FLAGRO you simply supply the crack geometry information in the Solution Parameters form, the materials information in the Materials Info form and the loading schedule information in the Loading Info form. A description of these are given below. Only the Safe Life option of FLAGRO is supported through these PCL forms. Other limitations are pointed out below.

Select the crack geometry of interest and fill out the dimensions necessary. An icon showing the appropriate parameters that need defining is given for each crack geometry.

Very little error checking is done. So it is possible to create a batch file that will not run through FLAGRO properly if crack dimensions and NDE flaw sizes are not correct. Use Tables 1 & 2 in the FLAGRO user guide to input proper crack geometries. To debug a run that doesn’t seem to be running properly you may, after creating a batch file, type at the system prompt:

 nasfla <jobname.cmd >file

Then inspect the resulting “file” for possible problems in your input.

Data tables and polynomial series not supported. About 95% of all crack geometries and inputs are supported. For crack geometries SC02, SC04, and SC06, you must input stress distributions in the spreadsheet or the problem will not run. If a blank cell is detected starting from the top row, then input is assumed to be at an end. The exception to this is leaving the cells all blank for geometry SC04. This will cause it to use a unit pressure load.

Select a cell from the one row spreadsheet (only one material is supported presently) and then select a material code from the list box that appears. The next cell will be selected and another list box will appear until you have filled in all the materials information. The spreadsheet reads from the NASMFM file if units are SI or from the NASMFC file if units are English. You may select a User Defined Material File (UDMF) using the button called Select User Database. Again the USRMFM or USRMFC file will be read depending on the units.

These files can be located anywhere but there is a hierarchal order in which they are searched. First they will be read if located in the local working directory, next the user’s home directory and finally the <install_dir>/flagro_files directory. In all cases however, the actual file selected will be copied to the local working directory on execution of FLAGRO.

To select the standard database (NASMF*) press the button called Select Standard Database. It again will search for this file in the hierarchal order.

If you select a user database, it must exist in a directory other than the one you are working in. To use an existing database in the current directory use a standard database by pressing the Select Standard Database button. All user databases and standard databases must be called NASMFM, NASMFC, USRMFM, or USRMFC.

At a bare minimum, you must define at least one block. There are three spreadsheets on this form that define the schedule (the order and number of time each block is to be processed), the individual blocks themselves, and the load steps for each block. The last two are three-dimensional spread sheets where the third dimension is the block you are defining.

This is a fairly complicated form and widgets appear and disappear depending on what you are selecting at the moment. For instance, when you are entering information in the block case information spread sheet, the load step information spread sheet will disappear to allow entry of block case info. The same is true for the load step info spreadsheet. To enter data into the spread sheets, simply click on one of the cells. A widget will appear to allow data entry. To get both spreadsheets back on the screen, you only need to deselect the selected spread sheet cell. In some cases, you may need to click twice on a cell.

Stress offset information is only used when a named loading block is selected. Offset information is only used when values are entered. If the offset cells in the spreadsheet are left blank then no offset will be applied to the block.

Scale factor information is not necessary. If these cells are left blank, then unity will be used.

For both scale factor and offset information, you may select a node or element from the graphics screen, indicating that you want the stress result from that node or element to be used as the scale factor or offset value. You must have selected a proper results case from the Select Results Case button. If a tensor value is selected you must select a scalar derivation. Von Mises is the default.

The Load Step Information values that appear when a named block is read from file is purely informational. Changing these values in the spread sheet will have no effect. The values from the file will always be used.

To view the Loading Block Information that corresponds to the proper Load Step Information, make sure both spreadsheets are viewed on the same layer. This can be confusing.

The New Name specified will always be taken from the Block Case Information. It can only ever be eight characters in length and will be truncated. If a name is given, it will be saved to the local SCHDLE file. Existing names will not be overwritten or duplicated. Only a Manually Input block can be saved to file.

To delete a row from the Schedule spreadsheet, a cell from that row must be selected. The maximum number of load steps must be entered in the Max. No. of Load Steps databox to change the number of rows in the Load Step Information spreadsheet. When writing a batch file for NASA/FLAGRO execution, if a blank row in this spreadsheet is encountered, or a blank cell in a row, the load steps will be considered terminated at the previous row regardless of whether any more rows contain data.

The stress values entered into the Load Step spreadsheet must correspond to the proper stresses in the crack geometry as indicated by the icon in the Solution Parameters form. That is if S0 is necessary, then the S0 columns must be filled out. If S0 is not necessary and yet the cells are filled out, they will be ignored.

If you select a user database, it must exist in a directory other than the one you are working in. To use an existing database in the current directory, use a standard database by pressing the Select Standard Database button. All user-defined databases and standard databases must be called SCHDLE.

Reference stresses and setting of Kmax < KIscc check are not supported.

Don’t forget: it is easy to define a lot of blocks then forget to include them in a schedule.

When you wish to run the job, you simply open the Job Control form and press the Apply button with the Action set to Full Analysis. A batch file called jobname.bat is created along with the FLAGRO output file jobname.out.

If the action is set to Save Job Only, then only the batch file will be created with out actual FLAGRO execution. With the batch file you can then run FLAGRO externally and/or edit the file. You may also delete a job and all file associated with that job with the Delete Job action. The other action on this form is Interactive which will simply open an Xterm and allow you to run FLAGRO externally.

On submission of a job, various other files may be created: jobname.bat - this is the FLAGRO batch file, jobname.cmd - this is the command file that drives FLAGRO execution from the MSC Patran interface forms, jobname.sif - this is a compliance function table that is generated for some of the crack geometries.

No results import is supported.