MSC Nastran; Patran Tutorial - Normal Modes; Shells and Cylindrical Coordinates

in this video I will be performing a
normal mode analysis using shells in
cylindrical coordinates full details of
this exercise are on page 394 of the PDF
linked in the video description below
first thing I'll do is start a new
patron session create a new file and
I'll call it problem 15 hit OK here and
what I want to do first is to find a new
coordinate system so here on the
coordinates three-point the type is
cylindrical leave the default values
here and hit apply now I'll go ahead and
define two curves the first one using
the line by XYZ method the units for
this example are in inches pounds in psi
here my first curve will be points six
six six six inches in the X traction
from the origin the next point or my
next curve will be three point three
three inches in the x-direction starting
from this point since auto execute is on
once I click this point I'll
automatically create the point you'll
see now I have one and two curves here
next to define or make my surface I'll
revolve these two curves about the third
axis of cornice from zero here the third
axis of coordinate system zero would be
the z-axis here it's what iron goes 90
degrees and now I'll select these two
curves
since auto execute is on once you select
it occurs one and two will create the
two surfaces now I want to mesh this
I'll first set some mesh sheets using
the uniform method type in one here I
want
for this surface here I want one element
or a mesh sheet here along this curve
and this curve next I want five elements
running down this curve and this top
curve lastly I want nine elements down
those curve and this curve and here it's
a curve three of surface one B and the
other one was curved two of surface here
now I can go ahead and mesh this using
the surface measure my element shape is
try so like surface one end to select
apply and now initially by your parents
this looks like it's the entire section
but if I go to display finite elements
and I show the edges and hide the
geometries in this button
I can see that have two separate bodies
here surface one has its own mesh
surface two has its own mesh - we have
to fix this so under meshing hit
equivalence and hit apply you'll see
that duplicate knows I've been deleted
here so now it's one continuous body now
so before we had a line here indicating
the mesh was separated but now after
equivalence seeing the mash is all one
piece so let me switch this back to two
pieces hit apply and the way I got to
this fem attributes of a student display
for the elements now to make the other
three sections I'll go ahead and perform
a mirror operation on these elements so
under mashing click any little thing and
basically you want to get this action
form here set action to transform select
object to element and select method as
mirror so here we'll first to find a
mirror plane normal in here since we're
dealing with
I want to mirror this about the y-axis
I'll select my normal is the extraction
so here select the frame direction one
select this coordinate system here
select these elements and click apply
now I want to marry these about the
x-axis so I'll first have to define the
mirror plane about with a normal in the
y direction after hit frame direction to
and select this coordinate system I'll
change to zero point two here I'll
select all these elements and hit apply
so if we call before I don't want to
display for night elements and hit edges
here now I have
before you saw an entire mesh in reality
you have four separate bodies and the
goal here is to unite all the elements
into one one entire mesh to do this in
the meshing tab hit equivalence and once
you hit equivalence of this will open a
new tab called finite elements you know
you're in equivalence when the action is
equivalence you'll hit apply notice the
pink circles indicate where the
duplicate nodes have been created now
when I back here in FEM attributes
you'll notice that uh those lines over
there before not indicating that this is
all one continuous mesh so here I've
gone back to faces and after I hit apply
I get the mesh back now I can go and
define my materials here under
properties so I'll click isotropic call
this material under input properties we
have a Young's modulus of 10 e 6 psi and
a Poisson ratio 0.3 my density is point
zero zero zero two six hit OK click
apply under 2d properties click shell
type the name s prop under input
properties use material we just created
your thickness for this example is 0.25
inches
click OK for your application region
select shell this will hit this will
allow you to select any try or quad
element I'll simply hit pick all select
all the elements here hit all add ok and
the ply now I can move on to my boundary
conditions over here in this tab I'll
hit displacement constraint well simply
call this constraint under input data I
wish to prevent translation in the one
two and three directions using the
cylindrical coordinate system so make
sure you select the cord line here
before of a scored zero now it's quarter
one hit okay and apply one thing I
forgot to do is ensure that these nodes
are using this score net system for a
bolt of reference and analysis
coordinate system to verify this you can
go to the meshing tab select action to
show node as your object and then plus
location simply click some nodes and
you'll find some details of the node
here I get an indicator that reference
and analysis coordinate system or using
the rectangular ones you have to crack
this by selecting modify object to node
and method to edit check on analysis
coordinate frame and reference
coordinate frame ensure you've selected
cylindrical coordinate system one and
the same for reference pick all the
nodes and click apply you notice every
node is has an indicator on it
indicating I've selected it that's been
cracked at some when I go to analysis I
can analyze the entire model under
solution type select normal modes click
OK
under sub cases all leave that is I'll
leave this for now
I don't just submit this Java analysis
once that is done I'll import the
results and click apply go to my results
tab I can view my initial values here
you see that these values on the line
with what I should be getting and what I
forgot to do is when defining my
boundary condition I forgot to select
wire to apply the condition
so here I've turned out my model tree
I've opened the branches up to
constraint the one boundary condition I
have here your translation is fixed on
one two and three directions and the
cornice is the one which is a
cylindrical coordinate system but I
forgot to add an application region so
what I have to do is select the nodes so
let me orient this I'll use a pickoff
filter here so then all I have to do is
a basically go around the circle and
then close the outer nodes
or just basically do what I'm doing here
and you've noticed that I accidentally
missed some nodes out there or I forgot
to select fam here since we're working
with nodes pick all again and do the
same thing if it if it's sluggish what
you can do is go to preferences and
graphics uncheck hardware rendering hit
apply
click console close that window and then
with that off
I can click faster if my machine happens
to be going slow I've accidentally
double clicked they're too fast
so basically close the loop you double
click and accidentally click too fast
back there and it's selected alternate
the wrong nodes I'm just making an
enclosure for all the outer nodes at it
remember rotate this and you'll see
there's an extra node I'd select there
so I'll pick that one node and remove it
let me rotate this just to make sure I
have an accidentally out of India nodes
that looks fine hit apply and there we
go I have our boundary condition defined
and just give it a quick inspection to
make sure you selected the outer nodes
looks good to me said we analyzed this
solution types of normal modes solution
103 hit apply delete all the ones I
added before I want for my X DB results
hit apply let me hide this boundary
condition here let me turn off the model
tree under results I finally get the
values that should be getting so as she
beginning 7:21
I should be getting 734 mm 370 and so on
but I get approximate values here 721
2030 740 200 get the window back mm and
that is what we do get here now if you
want to see a better visual
representation you can do a fringe plot
here select this result case and select
eigen vectors here translational click
apply you'll notice first set up the
value here is not a it's not one - a
quick plot and here this will give me
the fringe the nice color this will
actually give me a deform result I'm
going to hit that and you'll get this
you're gonna notice that here it's 32.6
ideally what we want is a a 1 here I'll
show you how to do that in a moment so
here they they show a 1 a 1 and so on so
to do that if you go back to the
analysis tab under entire model analyze
you modify your sub cases and this gives
a default sub case under sub case
parameters this normalization method
switch that's a maximum hit okay click
apply I'll ask you if you want to or we
save default and you just click yes
counseling resubmit this job and replace
all your old files once that's done just
import the X DB results again hit apply
and the results click fringe deformation
select this first mode
select this result translational
eigenvectors and here I do the same
thing for defamation result click apply
now you have that one before I was a
thirty two point six or thirty six point
two I forgot but now we get the one here
you can switch between the modes and see
the various shapes here the you can see
that the undeformed matched is
obstructing the view so to turn that off
move over I select this the farm
attributes go down to here and uncheck
show undeformed now it's gone you can
reset graphics return to the original
view make sure to save and that
concludes this example