MSC Nastran; Patran Tutorial - Modal Frequency Response; Enforced Base Motion Video Lecture | Nastran: Basic Tutorial for Students - Design Softwares

in this example I'll be performing a
normal modes analysis and frequency
response analysis on this given scenario
full details of this exercise are on
page 433 of the PDF length in the video
description below I'll first begin by
opening patrin the units for this
example are in inches pounds in psi I'll
create my new database call it problem
24 hit OK here under geometry o define a
surface that is twelve inches down the X
sin twelve and two inches in the Y so it
would be twelve to and from the origin
next I'll mash this using quad elements
so measure surface select the surface
and check automatic calculation give it
a value of 1 hit apply next I'll define
a node for my tip mass and my base mass
so here under node edit my first node is
located at a 0 1 negative 1 in my second
node located at 14 1 0 and head apply to
get a better view of the nodes go to
home and hit the node size and there you
have the two nodes going back to the
meshing tab go to element edit go to
shape point and pip this node it creates
a point mass and select this node it
creates another point mass let me hide
the node size and then point elements
are represented with triangles now I
have to create a two-bar elements here
so back in meshing element edit we
change this the bar and simply go from
any of the two nodes so from here to
here
from here to here after this I want to
define an rb2 element so I will click
the RB to here on your MPC I will define
my terms I'll first start with the
create independent and I'll uncheck auto
execute I'll select this outer node and
I'll hit apply to drop it in here next
I'll select these three nodes and I'm
holding the shift key to select multiple
nodes I'll select all the degrees of
freedom and had applied to drop it in
here
I'll hit counseling hit apply you'll see
my MPC in sort of a pink color you can
turn them off and on using the NPC
markers on an off icon here after this I
can move on to the properties tab to
define my materials and properties for
everything else I'll click isotropic to
define my first material call it matte
under input properties I'll give it a
young modulus at any 6 psi pesalam value
of 0.3 and the density of point zero to
six pounds second squared per inch to
the fourth and now hit apply next I'll
assign this material to the surface on
your 2d properties click shell under
property name head shell or type in the
name as a shell under input properties
give it a material of user material we
just made for a thickness give it a
thickness of 0.5 inches hit OK or your
application region select the surface
add it ok and apply next we want to give
our bar element some stiffness so under
Wendy properties click spring and I'll
call this K under input properties our
spring constant is 50 pounds per inch
our degree of freedom is a uz now hit OK
for application region they'll select
beam elements and make sure you have
this selected
now select elements 27 and 28 the number
the numbers may be different for you add
it okay and apply next I want to define
our mass for here and here
so hundreds e Rohde properties select
mass here I'll call this first one M for
options make it lump for an input
properties give it a mass of 0.5 pounds
second squared per inch
click OK for application region we want
till when we pick point elements so
select this icon pick this point element
its element 25 in my case added ok and
apply will make a next one base M for
your input properties give it a large
value of 26 pounds second squared per
inch head ok for application we can
select this point element added ok and
apply now I can move on to my load in
boundary conditions for my first
displacement constraint I click this
icon and I'll call it 1 2 4 5 6 and
first I'll select or I'll define that
input data I'm preventing motion in the
one and the two directions the third is
blank on preventing rotation about the 4
the 5 and 6 hit OK for application we're
going to select this one node so switch
this FEM select this node node 41 added
ok and apply next I'll create a new one
called 2 4 6 some preventing translation
in the two I'm preventing rotation them
I'm preventing rotation about the 4 and
the 6 head ok and under application data
select these nodes click Add ok and
apply
now I can go ahead and move on to my
normal modes analysis so under the
analysis tab click analyze entire model
go under solution type and select normal
modes and uh let me review the solution
parameters I don't think I have to
modify anything here hit OK here ok
under your sub cases modify or select
the default sub case make sure it says
default here go to sub case parameters
we want to know the frequencies between
1 and 100 so once you do that hit OK and
click apply make sure it says MC Nastran
sub case create here click cancel you'll
notice we'll be analyzing the default
sub case click OK here Council hit apply
once you do that and pour X DB results
go to the results tab and you'll see
that our one two and three frequencies
are 212 and 71 and we go back here we
add 212 and 71 and you can view the mode
shapes as shown here so that goes on the
McLin the sub here's mode 1 mode 2 and
mode 3 now moving on to our modal
frequency response analysis let me go
back to the boundary conditions tab and
define a new load case called frequency
or freak LC and for type make it
time-dependent and a hit apply and now
let me define an LBC feel that is non
spatial so click this icon call it freak
check frequency for my input data my
first value will be zero my next value
will be 200 this value will be 1 and
this value will be 1 2 hit OK hit apply
at the bottom or just hit enter and make
sure it's ad fuel frequency created a
way to find out if it was created as go
to home trying a model tree and here
under fields you'll find this field
under the boundary conditions tab we'll
define a nodal force call it f under
input data we'll give it a value of 0
and the 1 the 2 and 4 the third
Direction give it a value when you 6
scroll or make sure to close this scroll
to the right and select this frequency
and add it to the adjacent box hit OK
for application regions select this node
added ok and apply so you'll see it
added here to the base before we analyze
this we are working with the frequency
load case and now if I right click and
modify it you'll see that so far there's
only a force in this load case what I
have to do is add the previous
displacement constraints and I simply
click them and the year they are added
to the load case here I hit apply here
to confirm the update and here I get the
feedback load case frequency LC modified
minimize this now I can move on to my
analysis here under analysis analyze
entire model call this problem 20 for
frequency response under solution type
select frequency response and make sure
it says modal here click OK under sub
cases we are no longer working with the
default sub case we are working with the
frequency LC sub case so select that
make sure it's dropped
here under sub case parameters to find
the frequencies here so make sure it
says 100 here enter and 200 here for the
number of increments make sure it says
100 and 200 here hit OK
for modal damping switch is the
structural damping G click define modal
damping for frequency it would be 0 here
and 0.4 here add another row here type
in 2000 and point for here click OK on
all these windows except for this one
you want to change your output requests
so far the analysis will give me
displacements and spz forces I don't
want these so select one delete select
another one and delete I want my
accelerations and velocities hit OK at
the bottom we just had to apply here and
make sure you get this update sub case
create click cancel on your sub key
select if I were to hit apply and
analyze this model it would try to use
the previous default lower case which
only has the displacement constraints
and not the load so half bad this new
one and I'll delete and remove this old
default one so here I have frequency
load case ready to go and be analyzed so
hit OK and hit apply after that and pour
my results so I'll click X DB and hit
apply to import now go to results and
hit graph here I'll click this icon that
expands all the results and here you'll
see your previous frequencies this time
you see an additional set of results
going from 0 to 100 hold the shift key
and select the last result I want to
view my translational accelerations make
sure this is magnitude and I want to
view this for the base so node 41 in my
case the tip of the plate and this tip
mass
so let me head apply and if we compare
this to what they got before that is
approximately what we do get so the max
would be three point six and the
frequency ranges from 0 to 100 now let
me clean up the values so they're easy
to read here let me go to display
attributes for the x-axis format switch
this to fixed and the y-axis for me I do
the same and hit apply and now it's
easier to read goes from 0 to 100 and
from 0 to 3.6 now sometimes you want to
view both the model in the window at the
same time what you can do is drag it or
go to the Home tab and select towel
viewports and I can simultaneously view
the graphs if you want to save this
graph for later where you can do is go
to plot options save grab-ass
accelerations edible hi now I can turn
them off and on so if I were to continue
my review of the results and save you
one of the mode shapes it apply I see my
mode shape if I want to refer back to my
accelerations I can simply check it on I
can check it off off and on I can do the
same for brother friend chair I can turn
it off and on let me expand this I'll
save it and this concludes this example