A graphical interactive procedure operating under TSO and utilizing two CRT display terminals is shown to be an effective means of accomplishing mesh generation, establishing boundary conditions, and reviewing graphic output for finite element analysis activity

Burroughs, S. H.

Lawlor, M. B.

Miller, I. M.

English

NASA Technical Reports Server

PFU AND POST PROCESSING USING THE IBM 3277 
DISPLAY STATION GRAPHICS ATTACHMENT (RPQ7B028 11) 
S .  H. Burroughs, M. 3. Lawlor and Dr. I. M. Millertk 
IBM General Technology Division 
Essex Junction, Vermont 
SUMMARY 
A graphical interactive procedure operating under TSO and 
utilizing two CRT display terminals is shown to be an effective 
means of accomplishing mesh generation, establishing boundary 
conditions and reviewing graphic output for finite element analy- 
sis activity. 
i*bbTGEDIN~ PAGE B L A , l N ~  NOT jqme 0 
INTRODUCTION 
This paper is written to show how a grap5ical interactive 
procedure may be utilized in a time sharing en97ironrnent to create 
input data for the NASTRAN program. In partichuEar the software 
was motivated to assist input to the NASTRAN Thermal Analyzer 
portion of the program. In addition the software was designed to 
run on the IBM 3277 Display Station Graphics Attachment 
shown in figure 1. This hardware takes advantage of the bene- 
fits derived from having two display heads coupled in a work 
station concept, The A/N processing is accosplished on the IBM 
3277 display terminal and the vector graphics information dis- 
played on any o the r  vector graphic display terminal. For this 
work a ~ektronix 619 terminal was connected to the IBM 3277 dis- 
play terminal. However, the graphics attachment RPQ provides a 
standard RS-232 interface f o r  attachment of any user selected 
vector graphics CRT terminal. 
Two display heads axe better than one fox pre and post pro- 
cessing activities since the A/N communication with the program 
does not interfere with the picture being presented. By direct- 
ins all menu related information to the A/N terminal or any 
standard print out information to this terminal, the graphics 
picture is preserved. The graphics attachment offers a per- 
formance improvement over conventional dial up systems. The 
graphics terminal is controlled entirely by the A/N terminal and 
receives data at the same rate data is transferred to the IBM 
3277. Therefore the vector graphics terminal is local to the 
IBM 3277 and unknown to the host system. The work station is 
completed with a suitable hard copy unit. 
* Dr. Miller is at IBM, Poughkeepsie, New York 
https://ntrs.nasa.gov/search.jsp?R=19780024532 2020-03-22T01:55:43+00:00Z
The ~raphics attachment also has a FORTRAN and an APL 
software RPQ support, T h i s  work makes use of t h e  FORTRAN soft- 
ware to generate the graphic orders. 
PHASE 1 MESH GENERATION 
A procedure has been developed which is named QT. This pro- 
cedure is designed to provide an i n t e r a c t i v e  mesh generat ion 
c a p a b i l i t y  fo r  two dimensional models. However a companion pro- 
cedure has been written which uses an imaging technique to create 
three dimensional brick and wedge elements from a two dimensional 
mesh. 
The mesh generation i s  accomplished us ing  the hardware 
described above as shown in t h e  following steps: 
1. Create mesh generation algori thm input data using standard 
TSO editing procedures. Save the file. 
2. Invoke t h e  mesh generation algorithm u s i n g  TSO. 
3. The QT procedure will then display the mesh generated on t h e  
graphics CRT for revie@. 
4 .  Review the mesh for errors. 
5, If the mesh is accepted go on to set boundary conditions. 
6. If t h e  mesh i s  r e j e c t e d  r e t u r n  to Step 4 and modify input 
data for redisplay until model is satisfactorily completed. 
Figure 2-A shows the general flow for i ~ i t e r ac t i ve  processing 
using the QT procedure. 
PHASE BOUNDARY 
Establishing boundary cond i t ions  is a task that requires 
great care. The exact g r i d  p o i n t  number o r  element number, for 
example, must be known in order to establish a constraint or load- 
ing condition. Since this is the case a program was written 
which displayed the results of mesh generation so that the analyst 
could i n t e r a c t  with the design for the purpose of setting bound- 
ary condition information in a manner that did not r e q u i r e  t h e  
key punching of data in the fields required by the NASTRhN pro- 
gram. I n  t h i s  a p p l i c a t i o n  of interactive graphics the use of 
the dual headed work station greatly simplifies the task. 
The procedure is really quite simple in concept; that is, one 
wants to point at a particular grid po in t  or element and (fix 
certain d e g r e e s  of freedom or  establish values of load)  communi- 
c a t e  constraints o r  l o a d s  Co be a p p l i e d  through bulk data cards. 
I n  the interest of speed, it was d e c i d e d  t h a t  a correspond-  
e n c e  t ab l e  shou ld  be e s t a b l i s h e d  between a  g r i d  point o r  e lement  
number and a  t e x t  s t r i n g .  T h i s  co r respondence  t a b l e  would be de- 
coded and t h e  NASTRAN bu lk  d a t a  cards prepared a t  a later t i m e  
t h rough  the execution of a b a t c h  progrzm. ( T h i s  program i s  a 
b a t c h  program and i s  d e s i g n e d  t o  r u n  a t  t h e  same time as 'WASTRAW,) 
The method incorporated for p o i n t i n g  at t h e  display of t h e  
mesh makes use of the cross-hair cursor, A,2:tection i s  made on 
a grid p o i n t  o r  element and control i s  returned to the program 
t h e  A/N keyboard,  The grid p a i n t  o r  element number i s  
the rq i t t e n  on t h e  A/N t e r m i n a l  for c o n f i r m a t i o n  by the d i s p l a y  
opera or, at which time the keyboard is unlocked f o ~  i n p u t .  X f  
Cch i s  correct, a full 80 bytes of informat ion  can be enter- 
the ed, % is procedure  p e r m i t s  several data i t e m s  t o  be entered a t  
one t i m e ,  separated by blanks. Obviously, t h e  first data item 
should  be  t h e  mnemonic a s s o c i a t e d  w i t h  t h e  type of B.C. informa- 
tion r e q u i r e d .  T h e r e f o r e ,  SPC, SPCI, OVOL, e t c . ,  would be the 
f i r s t  data i t e m  fol lowed by a  blank and t h e  r e l a t e d  i n f o r m a t i o n  t o  
he i n c l u d e d  on t h a t  bu lk  data c a r d  when the b u l k  data c a r d  i s  form- 
ed  a t  a later t i m e  i n  batch mode. A n u l l  r e s p o n s e  indicates an i n -  
correct match. A f t e r  e a c h  d e t e c t i o n ,  new d a t a  i s  keyed i n  and t h e  
enter key d e p r e s s e d .  When t h e  p i c t - u r e  must be r e d i s p l a y e d  t o  show 
a d i f f e r e n t  s e c t i o n  of t h e  model or to magnify a s e c t i o n ,  t h e  word 
END i s  e n t e r e d  s o  that a new window may be selected and f u r t h e r  
work done on t h e  constraints, e t c . ,  i n  that s e c t i o n  of t h e  modal, 
A n u l l  r e s p o n s e  on window selection t e r m i n a t e s  t h e  p rocedure .  
When t h e  procedure i s  t e r m i n a t e d ,  t h e  da ta  i s  saved on the f i l e  
i n i t i a l l y  a l l o c a t e d  upon invoking t h e  procedure .  
TRANSLATION OF DATA TO WASTRAN FORMAT 
The mesh and D,C. i n f o r m a t i o n  must be t r a n s l a t e d  from t h e  
graphic structures t o  the rigid forxs-k required for NASTRAN or 
a n o t h e r  f i n i t e  element  a n a l y s i s  program. T h i s  i s  accomplished 
u s i n g  t h e  QTNAST ( Q u a d r i l a t e r a l s  o r  ~ r i a n g l e s / ~ ~ S ~ R A ~ )  program and 
f i l e s  are created a s  shown in fig. 2b. This program can be r u n  as 
a pre-NASTRAN step or as a stand-alone batch job. As a pre-NAS- 
TRAN s t e p ,  the data sets (files) c a n  be t e m p o r a r i l y  a l l o c a t e d  and 
therefore a very compact form of the model data saved in l i e u  of 
the f u l l y  expanded card f o r m a t t e d  d a t a  which c a n  t y p i c a l l y  become 
thousands  of card images. 
The p r e  NASTRAN or pre FEM program s t e p ,  therefore,  has ob- 
vious a d v a n t a g e s  where s p a c e  i s  c o s t l y  o r  d i f f i c u l t  t o  ob ta in  on 
a permanent basis .  
The QTNAST t r a n s l a t i o n  program will n o t  be d e s c r i b e d  i n  detail 
here a s  documentat ion exists on the program. Nevertheless, >his 
program i s  a companion program i n  t h e  procedure d e s c r i b e d  which 
provides a very  necessary  function. The i n p u t  data t o  t h i s  program 
provides substantial flexibility for the a n a l y s t  t o  create, merge 
and modify models.  The creation of three dimensional brick or 
wedge shaped elements from the two dinlensional mesh is just one 
example. 
PHASE 3 POST PROCESSING 
An in terface r o u t i n e  has heen written to read the PET2 p l o t '  
data  which i s  created by selecting to use the NASTRAN general 
purpose plotter i n t e r f a c e .  The Lvl 15 .5  PLT2 data  set  may be 
w r i t t e n  t o  d i s k  instead of tape by making t h e  following declara- 
t i o n  on the NASTRAN card: SYSTEM(45) = 96. Then the PLT2 DD 
card should have a d i r e c t  access da ta  set specified i n  the NASTRiiN 
procedure. This data s e t  may be a p a r t i t i o n e d  da ta  se t  for  saving 
plotting data for more thac one model in each member of the data 
set. 
Once the data has been saved as  described above the post pro- 
cessing (translation) routine can be invoked in the foreground 
using TSO ( t i m e  sha r ing  option) and the various frames can be 
drawn on the display t e r m i n a l  as shown in figure 3, The 
frame can then be manipulated through a windowing technique which 
permits the data to be redisplayed over and over  again u n t i l  t h e  
d e s i r e d  magnification i s  obtained.  (Examples of this f o r  the frame 
shown i n  f i g u r e  3 may be found in eigures 4a E b .  Note t h a t  t h e  
size of the numbers change also which can be of assistance for 
frames with very dense displays. In fact the grid point numbers 
can be suppressed to mere dots on the terminal if required for 
clarity. 
r-- Using this program, framg+,c'hn either be displayed Lndivi- 
dually or over l a i d  i f  desired%.&, 1 
The progi-sm has t h e  a b i l i t y  t o  i r ~ c l . i n s  t he  a lphanumeric  d a t a  
and the c h a r a c t e r  size may be easily varied; hovevex, normally 
s t a n d a r d  u p r i g h t  characters have been used. 
! Fig. 1.  A C~nfiguration of the I3M 3277 Display T e r m i n a l  Graphics Attachment. 
- - -- . - . - 
+TI INPUT 
MODIFY 
I N P U T  
YES 
PROCEDURE r l  
Figure 2a: 
INTERACTIVE PROCESSING 
Figure 2b: 
PRE PROCESSING OF FEM DATA 
Fig. 3 .  NASTRAN P l o t  Output for Sample Problem. 
Window Size: Full Frame 10, 0, 100,  1 0 0 ) .  
Character Size: 1.  
Fig. 4b. 
A G?AWICS TEST Ra;ao.l 
IN FUN? CCGDfN9TES 
lJcmmwSHnFE: 
Fig. 4a. 
Fig. 4a. Window Size: XL=YL=O, XH=28, YH=55. 
Character Size: 0.6. 
Fig. 4b. Window Size: XL=YL=50, XH=YH-90. 
Character Size:  0.07 . 
Fig.  4 .  Examples of Window Cl ipp ing  and Character Scaling for Output Shown in Fig. 3 .  
(Figs. 4a and 4b are formatted so as to be placed on this one page.) 


Pre and post processing using the IBM 3277 display station graphics attachment (RPQ7H0284)

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