AE304_ANSYS_truss_tutorial

AE304_ANSYS_truss_tutorial - A E304 - A NSYS Tutorial :...

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Unformatted text preview: A E304 - A NSYS Tutorial : Truss
elements Figure
1
Five‐element
truss
structure
 
 
 
 Simple
truss
as
shown
in
Figure
1
is
subjected
to
a
vertical
load
at
B
and
horizontal
load
at
D.

The
 trusses
are
of
square
cross‐sections
where
the
sides
for
members
AD
and
CD
are
15
mm
and
for
 members
AB,
BC
and
BD
are
12
mm.

The
members
are
made
of
Aluminum
alloy
with
the
Modulus
of
 Elasticity
of
70
GPa
and
Poisson’s
ratio
of
0.3.
The
following
steps
show
the
use
of
ANSYS
to
solve
for
 forces,
stresses,
displacements
and
reactions
at
the
boundary
conditions
in
the
truss
structure.
 
 Start
ANSYS:
 Set
the
working
directory
and
jobname:
 Utility
Menu:

File
>
Change
Directory
 Utility
Menu:

File
>
Change
Jobname
 
 Set
the
type
of
problem
and
method:
 Main
Menu:
Preferences
>
Structural
&
h‐method
>
OK
 
 Develop
the
FEM
model:

 1. Define
the
element
type
 Main
Menu:
Preprocessor
>
Element
Type
>
Add/Edit/Delete
>
Add
>
Structural
 Link
2D
spar
>
OK

>
Close
 2. Define
the
elemet
constant:
for
Link
element,
it
is
the
element
cross‐sectional
area
 Main
Menu:
Preprocessor
>
Real
Constants
>
Add/Edit/Delete
>
Add
>
OK
 Select
proper
Element
Type
Reference
and
create
corresponding
Real
Constant
Set
 For
the
1st
set:
enter
AREA
=
225.e‐6
and
ISTRN
=
0
 For
the
2nd
set:
enter
AREA
=
144.e‐6
and
ISTRN
=
0

 :
You
can’t
directly
define
units
in
ANSYS.
You
need
to
define
them
yourself
and
be
consistent
 with
the
units
(force,
length,
material
properties,
etc.).
 In
this
example,
we
use
SI
units,
i.e.
N,
m,
Pa,
etc.
 3. Define
the
material
properties:
 Main
Menu:
Preprocessor
>
Material
Props
>
Material
Models
 Material
Model
Number
1
 Page
1
of
4

 
 Double
click
Structural
>
Linear
>
Elastic
>
Isotropic
 Enter
EX
=
70e9
and
PRXY
=
0.3

>
OK
 4. Define
the
nodes
 Main
Menu:
Preprocessor
>
Modeling
>
Create
>
Nodes
>
In
Active
CS
 For
node
A:
enter

Node
Number
=1,
X
=
0.0,
Y=0.0


>
Apply
 For
node
B:
enter

Node
Number
=2,
X
=
3.0,
Y=4.0


>
Apply
 For
node
C:
enter

Node
Number
=3,
X
=
6.0,
Y=4.0


>
Apply
 For
node
D:
enter

Node
Number
=4,
X
=
6.0,
Y=0.0


>
OK
 5. Define
the
elements:
 a) Specify
the
material
property
for
members
AD
and
CD
 Main
Menu:
Preprocessor
>
Modeling
>
Create
>
Elements
>
Elem
Attributes
 Select
Material
number
>
1
and
Real
constsnt
set
number
>
1

>
OK
 b) Create
the
elements
for
members
AD
and
CD
 Main
Menu:
Preprocessor
>
Modeling
>
Create
>
Elements
>
Auto
Numbered
>
Thru
Nodes
 Pick
Node
1
then
Node
4

>
Apply
 Pick
Node
3
then
Node
4

>
OK
 c) For
members
AB,
BC
and
BD
 Main
Menu:
Preprocessor
>
Modeling
>
Create
>
Elements
>
Elem
Attributes
 Select
Material
number
>
1
and
Real
constsnt
set
number
>
2

>
OK
 Main
Menu:
Preprocessor
>
Modeling
>
Create
>
Elements
>
Auto
Numbered
>
Thru
Nodes
 Pick
Node
1
then
Node
2

>
Apply
 Pick
Node
2
then
Node
3

>
Apply
 Pick
Node
2
then
Node
4

>
OK
 d) Check
the
element
properties:
 Utility
Menu:
List
>
Elements
>
Node+Attr+RealConst
 This
will
give
a
list
of
elements
with
selected
properties.
 :
ANSYS
doesn’t
have
UNDO
button.
If
you
made
a
mistake,
you
need
to
delete
and
create
 again.
Save
often,
just
in
case
something
bad
may
happen.
 6. Define
the
boundary
conditions
and
loads:
 a) Specify
the
boundary
conditions
at
A
and
C
 Main
Menu:
Preprocessor
>
Loads
>
Define
Loads
>
Apply
>
Structural
>
Displacement
>
On
 Nodes
 Pick
Node
1
>
OK
>
UY

>

Constant
value
>
Enter
0
>
Apply
 Pick
Node
3
>
OK
>
All
DOF

>

Constant
value
>
Enter
0
>
OK
 b) Specify
the
forces
at
B
and
D
 Main
Menu:
Preprocessor
>
Loads
>
Define
Loads
>
Apply
>
Structural
>
Force/Moment
>
On
 Nodes
 Pick
Node
2
>
OK
>
FY

>

Constant
value
>
Enter
‐400
>
Apply
 Pick
Node
4
>
OK
>
FX

>

Constant
value
>
Enter
600
>
OK
 c) Check
the
boundary
conditions
and
loads:
 Utility
Menu:
List
>
Loads
>
DOF
Constraints>
On
All
Nodes
 This
will
give
a
list
of
constraints
for
selected
nodes
 Utility
Menu:
List
>
Loads
>
Force>
On
All
Nodes
 This
will
give
a
list
of
forces
for
selected
nodes
 
 Page
2
of
4

 
 7. Visual
check:
 To
show
the
elemet
and
node
numbers
 Utility
Menu:
PlotCtrls
turn
on
Node
and
Element
Numers
and
All
Applied
BCs
 Utility
Menu:
Plot
>
Elements
 
 **
SAVE
your
job
before
solving**
 
 Other
option:


Use
input
data
file
 Using
text
editor
such
as
notepad,
you
can
prepare
an
input
file.
The
file
can
be
read
using
following
 command:
 Utility
Menu:
File
>
Read
Input
From
 
 Input
data
file:
 /FILNAM, Tutorial-truss /title, Simple truss /prep7 et, 1, link1 mp, ex, 1, 70.e9 mp, prxy, 1, 0.27 r, 1, 225.e-6 r, 2, 144.e-6 n, n, n, n, 1, 2, 3, 4, 0.0, 3.0, 6.0, 6.0, 0.0, 4.0, 4.0, 0.0, 0.0 0.0 0.0 0.0 ! Element type no. 1 is Link 2D spar ! Material properties: elastic modulus for material no.1 ! Material properties: poisson’s ratio for material no.1 ! Real constant no.1 is 225.e-6 (cross sectional area) ! Real constant no.2 is 144.e-6 (cross sectional area) ! Node 1 is located at 0,0,0 ! Set properties before creating elements mat, 1 real, 1 en, 1, 1, 4 ! Element no.1 connects node 1 & 4 en, 2, 3, 4 ! Element no.1 connects node 3 & 4 mat, 1 real, 2 en, 3, 1, 2 en, 4, 2, 3 en, 5, 2, 4 ! Set the boundary conditions d, 1, uy, 0. d, 3, all, 0. ! Set the applied forces f, 2 , fy, -400 f, 4 , fx, 600 ! Element no.1 connects node 1 & 2 ! Element no.1 connects node 2 & 3 ! Element no.1 connects node 2 & 4 ! Vertical displacement at node 1 is zero ! Both Horizontal & Vertical displacements at node 3 are zero ! Force at node 2 in y-direction is -400. ! Force at node 4 in x-direction is 600. Page
3
of
4

 
 Solving
the
FEM
model:

 Main
Menu:
Solution
>
Solve
>
Current
LS
 
 Postprocessing:

 1. Plot
the
results:
 Main
Menu:
General
Postproc
>
Plot
Results
>
Deformed
Shape
>
Def.+Undef.

 2. List
the
displacement
and
stress
results:
 Main
Menu:
General
Postproc
>
List
Results
>
Nodal
Solution
>
DOF
Solution
>
Displacement
vector
 sum
>
OK
 Main
Menu:
General
Postproc
>
List
Results
>
Element
Solution
>
Line
Element
Results
>
Element
 Results
>
OK
 This
file
gives
the
input
parameters
for
each
element
as
well
as
the
computed
results.
MFORX
is
 the
axial
force
and
SAXL
is
the
axial
stress.
 3. For
more
readable
list,
you
may
want
to
use
the
Element
Table
to
access
the
results,
such
as
 forces,
stresses,
and
strains.
It
is
useful
to
look
up
the
ANSYS
help
file
for
your
element
(LINK1)
at
 this
point
to
find
the
terms
for
each
type
of
information
desired,
such
as
SAXL
for
axial
stresses.
 Descriptions
for
all
of
this
information
may
be
found
in
the
documentation
for
the
LINK1
 element.
Each
type
of
element
may
have
different
stresses,
strains,
etc.
in
the
output.
 a. Define
the
element
table
 Main
Menu:
General
Postproc
>
Element
Table
>
Define
Table

 For
a
list
of
axial
force:
 Click
Add

>

Enter
user
label
for
item
=
MFORX
(member
force
in
x‐direction)

>

highlight
By
 sequence
num

>

highlight
SMISC,
for
Comp
Results
data
item,

>

type
1
next
to
SMISC

>

 Apply.
 For
a
list
of
axial
stress:
 Click
Add

>

Enter
user
label
for
item
=
SAXL
(stress
in
x‐direction)

>

highlight
By
sequence
 num

>

highlight
LS,
for
Comp
Results
data
item,

>

type
1
next
to
SMISC

>

OK.
 b. To
view
the
table:

 Main
Menu:
General
Postproc
>
List
Results
>
Elem
Table
Data
 >
 highlight
 MFORX
and
SAXL

>

 OK.

 The
file
will
give
a
list
of
forces
and
stresses
for
all
elements
 
 
 

To
obtain
the
plot
for
insertion
into
a
Word
document
 Utility
Menu:
PlotCtrls

>

Write
Metafile

>


Invert
Black/White
and
save
the
emf

file
to
a
location
 to
be
retrieved
later
 
 Page
4
of
4

 
 ...
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This note was uploaded on 04/12/2011 for the course AE 304 taught by Professor Lestari during the Fall '10 term at Prescott College.

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