CHAPTER 9 Self Documenting Free Format Standard Engineering

Chapter 9
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CHAPTER 9
Self Documenting Free Format
Standard Engineering Command Language for Finite Element Analysis
/Command Driven Input , Basic Finite Element Procedure (Application
GTSTRUDL and NX-NASTRAN)
Menu Driven Solid-Modeling and Finite Element Analysis
(Application NX-6/7 PLM-SIEMENS)
9.1 Introduction
Every 10 to 15 years there is another revolution in engineering. Especially in engineering
design up to date teaching is a challenge . Today a Re-Structuring of the College of
Engineering is obvious . The curriculum must include Solid Modeling . CATIA-3D and
or NX-6/7 PLM-SIEMENS are software programs based on Solid Modeling .
‘Integrated Design and Advanced Manufacturing based on solid modeling is the
core communication cornerstone of concurrent engineering’. Important information
about the design for the Boeing 777 (1990-1994) is listed in the textbook “Engineering
Design”, by George E. Dieter. A statement is copied here, underlining my experience :
“Throughout the undergraduate and graduate curriculum , solid modeling is the core
communication cornerstone of concurrent engineering . Solid modeling provides a
complete geometric and mathematical description of the part geometry . Solid models
can be sectioned to reveal interior details , or they can be readily converted into
conventional two-dimensional engineering drawings . Therefore , solid modeling is
integrating design, advanced manufacturing , analysis , design optimization , simulation ,
rapid prototyping , fluid flow , thermodynamics , animations of mechanical linkages and
numerically controlled tool-path generation for machining operations”.
9.2 GTSTRUDL
Strudl was first developed at MIT ; afterwards , many companies worldwide made
further developments and modifications . The company Messerschmidt-Boelkow-Blohm
(MBB) in Munich Germany , developed under my leadership many new STRUDL
enhancements for internal and external customers . In addition , MBB applied MBBStrudl within a service bureau for external customers .
Today , GTSTRUDL is maintained by Georgia Tech in Atlanta. The research university
has also developed many new features and commands . It is the only software having
build in all building codes following the American , English and German standards . For
steel or concrete structures etc. the design can be performed due to the standard codes .
Chapter 9
9.2.1
562
Standard Engineering Commands Language (SECL) Input-Output
STRUDL Input-Output
STRUDL Language Conventions (COBOL Notation)
The STRUDL language is oriented to normal engineering practice , and is thus quite
flexible in its ordering and usage. Each communication to the computer program is given
through a statement called a command . Each of these commands either supplies some
data to the program or instructs it to perform some calculations on the data already
specified , or both.
1. ELEMENTS OF THE COMMANDS
There are two basic elements that are used to make up the various commands .
They are described below :
a. Integers
These are numbers that do not contain a decimal point .
 Examples:
1 , 38 , -1002 +999999
 Possible errors: (non integers):
6.0
This contains a decimal point .
9,999
This contains a comma .
If a sign is omitted , it is assumed to be a plus (+)
b. Decimals
These must contain a decimal point . There are two basic types of decimal
numbers :
 Normal decimals
These consist of digits with a decimal point , and optionally a sign .
Examples :
6.0 , 3.14159 , -2. , .003
9.2.2 Application GTSTRUDL
Example 9.1
The fixed supported cantilever shown has constant thickness , t , but variable width ,
b  b 
L
and is loaded at the free end by a uniform line load as shown
Lx
(F = (qo bo)/2) .
a) Calculate the exact solution assuming a beam model .
b) Represent one curved edge by six equidistant points in x-direction and generate a 1D ,
and 2D Finite Element Model using GTSTRUDL .
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563
t = 0.4 m; qo = 4000 N/m; bo = 10 m;  = 0.3; E = (2.1)1011 N/m2; L = 9 m
a ) Calculate the exact solution assuming a beam model .
Figure 9.1 Fixed Supported Cantilever with Variable Width
Beam model :
Moment distribution: M ( x )  F  x  c1
M ( L )  0  c1   F  L
M ( x )   F L  x 
E IZ   w  M  x    F L  x 
IZ  b( x ) 
w  

t 3 b t 3
L


or with
12
12 L  x
IZ   b t

3
12

3
 2

F L2  x 2 )
F
 L x  x  c2 
 w  

E IZ   L
E IZ   L 
3

 w
 L2 x 2 x 4

F


 c 2 x  c3 

E IZ   L  2
12

Boundary conditions:
w ( x  0 )  0  c 2  0
w( x  0 )  0  c 3  0
w( L )  wmax  
5
FL3

12 E IZ 
IZ  IZ  
L
Lx
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For b( x )  b  const :
w( L )  
FL3
4
FL3
 
3 E IZ 
12 E IZ 
wmax  
5
FL3
5 12  b  q  L3
5 q  L3

 
  
12 E IZ 
12 2  E  b  t 3
2 E t3
wmax  
4000 N / m  9 3 m 3
5

 0.0005424 m
2 2.1  10 11 N / m 2  0.4 3 m 3
wmax  0.5424 mm
b ) 1D - , and 2D Finite element idealization
b  ( L )  b / 2  5 m
L  L / 6  9 / 6  1.5
b L
90

 8.571
L  1.5 10.5
b( 3 )  90 / 12  7.5
b( 4.5 )  90 / 13.5  6.666
b( 1.5 ) 
b( 6 )  90 / 15  6.0
b( 7.5 )  90 / 16.5  5.455
Figure 9.2 Segmenting Variable Width
STRUDL 1D-Idealization:
Segment 1:  AX 1  t  10  8.571 / 2  t  9.286   3.714 m 2
IZ 1  t
3
12
Segment 2:
Segment 3:
Segment 4:
Segment 5:
Segment 6:
 9.286   0.04953 m 4
 AX 2  t  8.0355  3.214 m 2
IZ 2  0.005333  8.0355  0.04286 m 4
 AX 3  t  7.083  2.833 m 2
IZ 3  0.03777 m 4
 AX 4  t  6.333  2.533 m 2
IZ 4  0.03377 m 4
 AX 5  t  5.728  2.291 m 2
IZ 5  0.03055 m 4
 AX 6  t  5.2275  2.091 m 2
IZ 6  0.02788 m 4
Chapter 9
STRUDL Input for 1D-Idealization:
strudl ‘ beamsec’
Joint coordinates
1 0 0 support
2 9 0
Type plane frame
Member incidences
1 1 2
Member properties variable
1
Segment 1 ax 3.714 ay 3.714 iz
Segment 2 ax 3.214 ay 3.214 iz
Segment 3 ax 2.833 ay 2.833 iz
Segment 4 ax 2.533 ay 2.533 iz
Segment 5 ax 2.291 ay 2.291 iz
Segment 6 ax 2.091 ay 2.091 iz
Constants e 2.1e11 all
Loading 1
Joint loads
2 force y -20000
loading 2
joint loads
2 moment x 50000
stiffness analysis
list displacements
finish
0.04953
0.04286
0.03777
0.03377
0.03055
0.02788
565
ΔL
ΔL
ΔL
ΔL
ΔL
ΔL
STRUDL Output :
Exact
: -0.0005424
1.5
1.5
1.5
1.5
1.5
1.5
Chapter 9
566
2D – Finite Element Idealization –
Figure 9.3 2D-Finite Element Idealization
Output ( Displacements at the free end)
Point (9,0,0) : -0.0005383 mm
Point(9,0,-2.5) : -0.0005296 mm
>
( 1D exact : -0.0005424 mm)
( 1D strudl : -0.0005430 mm)
Again Contour Von Mises Top (load) 1
Step Size 50,000. N/m2
Stress
Stress
Contour Lines
Contour
Lines
The stress- contour lines show that the
supported corner at the top is stress- free .
Figure 9.4 Stress-Contour-Lines of Half
of the Cantilever
Chapter 9
567
9. 3 Application NX - NASTRAN
This concept was first introduced 40 years ago . It must be very good because
NASTRAN is still number one in the world for static and dynamic analysis .
In the PLM/SIEMENS Software System as well as within the CATIA Software ,
NASTRAN is called the ‘WORK-HORSE’.
One example may illustrate this . The standard material card is MAT1 . But to handle
very complex materials , nine other material cards (MAT2-MAT10) exist today . Every
special material feature is specified in a unique MAT-card . Existing MAT-Cards are not
changed or overridden. Another important feature of NASTRAN is that no units are used
Only the statement : “Input-Units are equal to output units” must be followed . On the
following pages some basic cards are listed .
In the last chapters it was demonstrated that the NX-software can be used as a teaching
tool . The Menu driven software is then automatically converted to NX-NASTRAN , but
a conversion to ANSYS , and ABAQUS is also possible . Based on Solid Modeling
an adaptive mesh , with boundary conditions , loadings , and material constants is done
without additional manual work . After the converting to NX-NASTRAN the user can
learn what equivalent NASTRAN cards are used .
9.3.1 NASTRAN (NX-NASTRAN Quick Reference Guide)
GENERAL DESCRIPTION OF DATA DECK
Figure 9.5 NASTRAN DATA DECK
The Executive Control Deck specifies the number of the application . For example, 101
= Static Analysis ; 105 = Buckling etc. There is a DMAP language to change standard
matrix operations in any way the customer wants . But it takes some time to learn the
language . But it is worth mentioning that MATLAB first was created as a copy of
Chapter 9
568
DMAP .
The case control deck specifies the output wanted and some other details .
The bulk data deck specifies the geometry , boundary conditions , loadings , materials ,
etc. . For example , the GRID-Card specifies the location of a node , CBAR specifies a
beam and the connection of two nodes (member incidences) .
Ten basic NASTRAN Cards are listed here and used for small examples and compared
with the equivalent STRUDL Input Commands .
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Chapter 9
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Chapter 9
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Chapter 9
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Chapter 9
573
Chapter 9
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Chapter 9
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9.3.2 NX-NASTRAN Examples , (Equivalent NASTRAN-STRUDL Inputs)
(First the STRUDL Input is listed , and then the equivalent NX-NASTRAN
Input) .
Example 9.2a STRUDL Input, Plane Frame , Constant and Linear Line Loads
N 1 (simply supported)
N 2 ( simply supported)
(X free)
Figure 9.6 Simply Supported Frame , Constant and Linear Line Loads
Chapter 9
579
Example 9.2b NASTRAN –Input , Plane Frame , Constant and Linear Line Loads
101
For the loads the card PLOAD1 is used . SOL 101 solves static problems with options .
The boundary conditions can be specified within the GRID card or the SPC card
1 = u x ; 2 = u y ; 3 = u z (translations) ; 4 = φ x ; 5 = φ y ; 6 = φ z (rotations) .
The standard coordinate system is a Cartesian System , the card CORD2D we may delete .
Grids like GRID , 9999…. can be added , if they are supported and not connected to
elements .
Example 15.6 NASTRAN-Input Plane Truss Structure
Chapter 9
Example 9.3a STRUDL Input , Truss Structure solved in chapter 3
Figure 9.7 Four Member Truss Structure
As shown in chapter 3 , member 25 is stress- free , but if not defined , the
structure is collapsing as a mechanism . The condition number is indicating
Example
Frame
this
, being15.7
verySTRUDL-Input
large . The linearComplex
system ofPlane
equations
canStructure
not be solved ;
( can easily be shown , using FEBEAM ) .
580
Chapter 9
Example 9. 3b NASTRAN Input , Truss Structure Solved in chapter 3
101
The CROD and PROD cards are related to TRUSS Elements .
409 in the CROD cards is referencing the PROD card .
709 in the PROD card is referencing the MAT1 card .
581
Chapter 9
582
Example 9.4a STRUDL Input , Complex Structure with
Plane Frame- , and Shell Elements
UNITS INCHES DEGREES
JOINT COORDINATES
2 X -240. Y 180. SUPPORT
1 X -240. Y
0. S
3 X
0. Y
0. FREE
4 Y
180. X
0.
5 Y
0. X 240.
6 240. 180.
7 480.
0.
S
8 480. 180.
S
TYPE PLANE FRAME
MEMBER INCIDENCES
1 2 1
2 1 3
3 3 5
4 5 7
5 7 8
6 8 6
7 6 4
8 4 2
9 3 4
10 5
6
TYPE PLANE STRESS
ELEMENT INCIDENCES
11 1
3
4
2
12 3
5
6
4
13 5
7
8
6
JOINT RELEASE
7 FORCE X MOMENT Z TH1 30.0
2 MOMENT Z KFY 50000.
1 FORCE X MOMENT Z
8 MOMENT Z
MEMBER RELEASE
7 START MOMENT Z END MOMENT Z
UNITS IN LB FAHRENHEIT
MEMBER PROPERTIES PRISMATIC
1 TO 3 AX 10.
IZ 100.
4
5 AX 10. IZ 100.
6
AX 10. IZ 100.
YD 1.58
8 TO 10 AX 10.
IZ 100.
7
AX 20. IZ 300.
YC
1.58
Chapter 9
583
ELEMENT PROPERTIES
ENDDATA
Figure 9.8 Complex Demonstration Example , Dependent Degrees of Freedom
a
at Node 7 , Hinges at Member 7, Spring at Node 2 ,
Displacements given at Node 1
Chapter 9
Example 9.4b NASTRAN Input Complex Demonstration Example
101
584
Chapter 9
585
The NASTRAN Input for the Complex Demonstration Example is using the CELAS2card for the uncoupled spring at node 2 . The MPC-card (multi-point constraint) is used
for the special boundary condition at node 7. The SPC –card is used for a given displacement at node 1 . The column of the given displacement in the structure stiffness matrix
is moved to the right hand side and the associated row is no longer part of the reduced
matrix ; it is used , to calculate the reaction . In STRUDL the hinges are defined via
MEMBER RELEASE . In NASTRAN the hinges are defined within CBAR (member 7) .
Example 5.5 Two Member Frame
Figure 9.9 Two Member Frame
The structure was solved earlier in Chapter 4 . At this time the STRUDL- and
NASTRAN Inputs are compared .
It is not so well known that for structures , built by 1-D Elements the Finite
Element Method is an exact procedure , including shear deformation . So FEBEAM
, STRUDL , NASTRAN , ANSYS , and ABAQUS , they all lead to exact results
without a fine mesh .
ANSYS –Input :
Chapter 9
NASTRAN Input
586
STRUDL Input
101
On the next page the SOLUTION Options in NX_NASTRAN and MSC NASTRAN
within the Software System CATIA are shown . Please go down the list from 101 to
200 to recognize the Structured Solution Sequences . Beside this via DMAP the Solution Sequences can also be changed using 500,000 or more Degrees of Freedom .
Therefore , NASTRAN is called the WORK - HORSE
Chapter 9
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Chapter 9
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9.4 NX Menu Driven Software
9.4.1 Introduction
The field of Mechanical Computer Aided Engineering (MCAE) is changing rapidly with
advances in computer hardware and software , the Web , 3D computer graphics , VRML ,
and rapid prototyping technologies .
The way the engineering community uses and learns MCAE technology is changing .
What do these changes mean to how we work? In most industries , there is tremendous
pressure to continually shorten the “time to market “, while increasing quality at the same
time . There is a major trend to do more design and analysis early in the design cycle ,
combined with quick prototypes to verify the design . Also, design engineers spend most
of their time modifying existing designs and making iterative changes , rather than
starting from scratch . Because of this , it is important that computer models capture not
just geometry , but the design intent to make modifications easier . As with any tools ,
there are good ways and bad ways to use them . It is important to use good modeling
practices up front , or more time may be spent in the long run as the design changes or is
used as the basis for new products .
The process of design is also changing how we work together . Leveraging the computer
model across multiple disciplines requires sharing of computer-generated information .
New data management tools to manage computer-transmitted information enable people
to work together as teams .
Lastly , technology is changing how we learn . Although we learn in different ways , we
are increasingly more impatient at learning , and don’t like to read a lot of words . We
expect software to be intuitive to learn and use , with visual feedback at every step so we
know what the software is doing . User interface standards also help ; since we can
expect certain types of behavior based on using other software . Although software is
becoming more sophisticated in terms of capabilities , we expect to be able to learn it in
less time . Instructional media must be readily available , and be graphical and concise .
All of the above changes are reflected in the latest version of NX-PLM- SIEMENS Software . This book provides a condensed overview of this family of MCAE tools , and will
guide you to other multimedia and online tutorial materials built into the software to learn
the skills you need .
The following figure demonstrate the unique features of NX .
The Integrated Software System NX- PLM-SIEMENS is available , and is covering
nearly all numerical aspects in Engineering .
Chapter 9
589
Figure 9.10 Integrated Design and Advanced Manufacturing Based on Solid
Modeling as the core communication cornerstone of concurrent engineering .
NX-6/7 , and NX-NASTRAN have unique features to create real life models via solid
modeling . Integrating design , advanced manufacturing , analysis , design optimization
simulation , rapid prototyping , fluid flow analysis, thermodynamic analysis, animation of
mechanical linkages and numerically controlled tool path generation for machining
operations are available , based on the same syntax . NX is much more than a pre-and
post processor for NASTRAN , ANSYS and ABAQUS . These features were discussed
in previous Chapters . Now a real life model or machine part can be generated , then
automatically meshed for Finite Element analysis , with boundary conditions , loadings ,
material properties , element incidences etc.. Before solving the problem directly via NX
, it is possible to convert to the equivalent ANSYS or ABAQUS Input . The not so
experienced user can learn what equivalent NASTRAN cards must be applied . Even if
the problem can not be solved in NX , 99% of the bulk data cards are available as a file ,
and a few NX-NASTRAN cards for very complex and sophisticated applications can be
added .
Many documentations and real life solved problems can be downloaded from the internet
Some vital information is documented here .; the CAST Online Library is the next step
to learn more in other areas of applications .
Chapter 9
9.4.2 Solutions and Solution Processes
in the CAST Online Library
Figure 9.11 Application Areas in the CAST Library
(Example 8.5)
Related References : [ 21 ] , [ 26 ] , [ 31 ] , [ 32 ] , [ 34 ] , [ 35 ] , [ 36 ] , [ 37 ]
590