This describes basic usage of a text editor in building, editing and organizing FEA model files. Using text editor allows user to do quick changes to a model setup without the use of a pre-processor.

1. Understanding
Optistruct & LS-
Dyna files Using
Text Editor
AKSHAY MISTRI

2. CONTENTS
S. No. Topic
1 Why text editor?
Optistruct
2 First Look – Optistruct File (.fem)
2A How to read .fem file?
2B Recognizing Control Cards
LS - Dyna
3 First Look – LS-Dyna File (.k/.keyword)
3A How to read .k/.keyword file?
3B Some format exceptions
4 Practical Applications of Text Editor
4A Editing basic model parameters
4B Model File Organization

3. 1. Why text editor?
 Small changes can be done faster when using a text editor.
• Like material assignment change, property change.
 Model file organization can be done using text editor.
• Like creating separate model files for material, contacts, control cards and so on.
 Popular text editors:
• UltraEdit
• Notepad++

4. Optistruct

5. 2. First Look – Optistruct File
21. Contact definition
22. Node definition
26. Property definition
27. Single Point Constraint definition
28. Force definition
Bulk Data Begins
Bulk Data Ends
• This is what you see in a text editor.
• Lines starting with “$” sign are skipped by the
solver
• Hence, comments can be inserted by using
$ sign in a line.
Analysis Step Definition

6. 2A. How to read .fem file?
• “.fem” text file is divided into vertical sections also referred as “fields”.
• Each field is 8 character long as shown below.
• GRID or Node definition is shown above.
• System ID is left blank which assigns nodes to global coordinate system.
• Three global coordinates (x, y and z) are defined in the fields 4, 5 and 6.
• Node ID 1 has coordinates (0, 100, 80).
System
ID
Node ID’s X –
coord.
Y –
coord.
Z –
coord.

7. 2B. Recognizing Control Cards
• Each control card in the file has a field format defined.
• This definition can be understood from “Hyperworks Help Home” as shown.
• This Help menu can be found in Hypermesh menu bar on the top.
• Help menu will
open an internet
explorer session as
shown.
• Search tab can be
used to search for
desired control
cards.
Source: Altair Hyperworks Online Help

8. 2B. Recognizing Control Cards
• Searching for CQUAD control card yields the following results. (complete page shown in previous slide)
Propert
y ID
Element
ID
Grid
point 1
Grid
point 2
Grid
point 3
Grid
point 4
• Hence, from first picture on the top shows field headers for the
control card CQUAD.
• Second picture on top shows what do those headers mean.
• This info can be used to understand CQUAD lines in the model file
as shown in the right image.
• Similarly, other control cards can be understood in the model file.
Source: Altair Hyperworks Online Help
Source: Altair Hyperworks Online Help

9. LS-Dyna

10. 3. First Look – LS-Dyna File
Ending Control card
• Similar to Optistruct, LS-Dyna control cards are
also divided into fields.
• Each field in this “.k/.keyword” file is 10
character long. (generally)
Starting Header Card

11. 3A. How to read .k/.keyword file?
• LS-Dyna control cards can be understood from “LS-Dyna Keyword Manual Vol I” available online.
• This can be downloaded at no cost from LSTC website here: https://www.lstc.com/download/manuals
• The manual contains description of almost all control cards used in LS-Dyna file.
• For example, *CONTROL_TERMINATION in the file can be searched in
the keyword manual under the heading *CONTROL.
• Once found, it would tell you the meaning of all the field headers for the
control card *CONTROL_TERMINATION as shown in pictures on the
right.
Termination
Cycle
Termination
Time
Reduction
factor
Source: LS-DYNA keyword manual

12. 3B. Some format exceptions
• Some LS-Dyna key cards are of 8-character length instead of 10.
• Every card’s character field lengths are described in the LD-Dyna manual as shown in the picture below.
16 -
character
field
8-characters fields
Source: LS-DYNA keyword manual
8 –
char.
16 -
character
field
• Card format describes the field lengths as described
below:
• 5I8: 5 fields with 8-character length.
• E16.0: 16-character length field.
• I8: 8-character length field.
• E16.0: 16-character length field.
7E10: 7 fields with 10-character length.

13. 4. Practical Applications of Text Editor

14. Editing termination time in LS-Dyna file
• Basic parameters in the model file can be changed using the text editor itself.
• Some examples are given below.
• Parameters like thickness value, control parameters, Node IDs can be quickly changed using text editor.
Creating coincident nodes (Optistruct)
• Node ID’s 3 and 4 are coincident.
4A. Editing basic model parameters

15. • Consider a Optistruct model setup as shown in the picture below.
• Grey plate as forces applied on its four corners.
• Bottom green plate is constrained in 1-6 DOF on the four corners.
• Both are assigned steel material with thickness of 3 mm.
4B. Model File Organization
Model Tree
Currently the model file is saved as a
single file.

16. • Now, the single file “plate_setup.fem” can be organized into various files according to the entity type as shown
below.
4B. Model File Organization
Analysis file can be used to call the
other three files using “INCLUDE”
command.
Benefits:
• Quicker individual entity changes
possible without disturbing other files.
• If only model mesh is updated, other
files can be simply copied over for
complete setup.