MSC Nastran; Patran Tutorial - Normal Modes; Point Masses and Linear Springs

in this video I will be performing a
normal modes analysis on this mass and
spring system full details of this
exercise are on page 390 of the PDF
linked in the video description below
my first thing I'll go ahead and do is
switch over to new session of patrin
I'll start where I'll save my file to
this directory and call it problem 14
click OK here and I'll define my spring
and mass system by first defining my
nodes so here under the meshing tab
click node edit and this will allow me
to create my nodes I'll create six nodes
spaced 1 inch apart the units for this
exercise are in inches pounds and for
mass I have pounds second squared per
inch so my first node will be located at
the origin my next one will be located
at one in the X next one will be located
at 2 and X 3 in the X 4 and X 5 and the
X and one last one at 6 and the X to
show your nodes you can go to the Home
tab and turn on your node size or what
you can also do is turn on your label
control for the nodes see we have seven
here I've unfortunately made an
additional notice of what I can go ahead
and do is delete this node now at 7 and
hit apply click refresh graph or reset
graphics you'll notice I here anymore
after you've created your six nodes it's
time to make your elements so here under
element edit we want to make a bar
element from node to node so from 1 to 2
and so
one if I were to AB Auto execute off
when I first select node one or no to
win here in this case I've chosen node
five here and after I select node six
where every other time it's
automatically created the element this
time it didn't because the auto execute
is checked off I can hit apply and
they'll create the element now let me go
ahead and create a separate group for my
masses and this will be current
so then anything else I do after this it
will be added to that group I just
created so here click Edit again in the
same form you'll select the option to
make point elements and then you simply
select the nodes in which you want the
point element to be able to be defined
I'll turn on auto execute so then we'll
have a point mass here here or a point
element
so while point elements from 2 to 5 or
nodes 2 to 5 you can show your group so
I go into the Home tab going to the
model tree and turning them off and on
let me turn off the label control and
the node size and here you'll notice
that point elements are indicated with a
triangle you can turn those off and on
using this point 0 D element marker and
the sub n they're not working
now I can go ahead and move on to my
boundary conditions so here under this
tab I'll define the displacement
constraint and here I'll call this one
fixed and this one is fixed so
translations in all three directions are
fixed and rotations about every axis or
fixed click okay for your application
region or directly working with the mesh
so select fem here you have the option
of selecting nodes if you select one
node hold the shift key Nold the next
node add it okay and now you've defined
this boundary condition then going on to
defining your materials and so on in
this tab select isotropic or anisotropic
we're actually defining properties for
the spring so here under 1d properties
click spring call the spring stiffness
under input properties will give this
spring a value of 100 pounds per inch
and we'll set the degree of freedom at
node 1 and 2 has a X click OK for your
application region simply click beam
elements drag your cursor and select
elements 1 2 3 4 & 5 added ok and apply
now we'll go ahead and high bat I'll go
back to my home tab and click this icon
to turn them on now we have to define
mass properties for these elements so
here ulema close this group tab go back
to the properties tab and select under 0
D properties the mass call this mass
select option to the lumped for input
properties gives us a mass of 2 pounds
second squared per inch
click OK for applique
imogen simply click point element here
and drag and select add okay and apply
now to run this job go to your analysis
tab click entire model under solution
type select normal modes click OK and
hit apply after the analysis is complete
make sure to turn on your default group
let me hide the the masses for now we
minimize this and reset the graphics and
let me import tax DB results close this
group tab hit apply to import the
results here on the results tab will
show vectors will use the vector option
to show the eigen vectors here
so my first frequency is 0.7 Hertz one
point three one point eight and two
point one four and you'll see this
aligns with a what we're expected to get
here point seven one point three two one
point eighty two point one four and so
on
so here I've selected a vector select on
my first mode Oh
select eigen vectors translational show
as component uncheck YY and ZZ s only
have xx check and when I do this and hit
apply
you see vectors where the point masses
would be
so we can view this for let me go back
to the results app you can view this for
the second mode the third mode and
finally the last mode make sure to save
and this concludes this example