- [Instructor] In this video we're gonna look at
the frequency response analysis of a simple plate.
We're gonna compare the frequency response results
with underlying resident node shapes.
We're also going to review the influence
the frequency response setup parameters
on the resultant response.
And now we're going to open up the SolidWorks file,
and this is plate one begin.
Now if you don't have access to SolidWorks 2018 or later
then you can use the parasolid file which is shown here.
Now we check on the simulation tab.
We're going to create a new study.
And we're going to change the default type
to be advance simulation,
and the method we're going to use is linear dynamic.
And from within that we're going to choose a harmonic,
or in other words a frequency response analysis.
We can name this as frequency response plate one.
Now we're going to set up the material properties.
We're going to use the alloy steal as usual.
And then we're going to set up the properties
for the harmonic analysis or frequency response analysis.
We can use six modes,
and under harmonic options we're going to
be setting up about 300 hertz
on the frequency response analysis.
And then we're going to stick with
a default of 15 points for each frequency,
bandwidth of .4 and we're going to
stay with a logarithmic spread.
Now these particular settings and the meaning of them
we cover in the accompanying videos.
Now we're going to be doing a 2D shell analysis,
so we select define the shell by selected faces,
pick the top face here.
Now I want to set that thickness .05 of an inch.
We check okay.
Now we define the mesh.
We just create the mesh and check OK.
Now we create the H constraint.
So we go to fixtures.
Go to fixed geometry and we select the top edge here
and then just check OK.
Now the next thing is to define the external loads.
We're going to define a force,
an this force is gonna be at the corner node.
So we select that vertex and we need a direction.
We're going to zoom into the edge and pick that edge
as the direction indicator.
Now I'm going to apply unit force
in that direction along the edge.
I'm going to be putting in a constant line,
and that constant line, if we look at it,
just defines a unit value throughout the run
of the frequency response, which is up to 300 hertz.
Now we just check okay and let's center the mesh,
and then we're going to apply our dampings.
I did define and we've got six modes
and all of them are going to have 2% damping, .02.
And we check OK.
Now we need to run a normal mode analysis
to build up the modal database ready for analysis.
So we just run this frequency
which is running the normal modes.
And again I've sped up the timeline
so now we can check the results.
And we can actually go and look at the resident frequencies.
We see the six resident frequencies have come through.
So from 17 hertz through to 267 hertz,
six modes in there.
So we can close that out.
Now with that complete we can go and check
the mode shape plots
and we can review these mode shapes.
So there's 17 hertz first mode.
Let's change the settings so we're going to look at the mesh
and there's mode shape one.
Now I can come up here and change the definition.
If I pin here so the form stays
I can go to mode two, click to show that.
Go to mode three, click to show that.
And so on, and so there's mode four.
Seeing now.
Mode five we're seeing now.
So just reviewing the mode shapes.
And this is the content we're gonna be having
when we run our frequency response analysis.
So we'll be looking out for these shapes.
Now with that review done we can
go ahead and run this study,
and this is the full frequency response analysis.
Again, I've spread this up
and we go straight to the results.
So let's go and look at response graph.
We're going to look at response graph of some of the nodes.
A node to the corner, a node in the middle,
and the graph is going to be made up of,
on a y axis a displacement,
and we're going to be using the zed displacement.
We need to make sure it's set up in inches.
Check OK.
And we see now our frequency response plot.
Now we need to change the settings here
on the y axis, I want to set that up as a log plot.
Now we can actually see a log
and it separates the frequency response out very nicely.
Again, the style, I want to see solid axes.
I'm going to soften the color a little bit.
I do the same thing on the x axis.
Now the spacing I can adjust and also the scale
are only going up to 300 hertz
so let's clip it to 300 hertz
so we get the maximum on the plot.
Now we go to the chart styles
and we're going to be changing the symbols here.
So the first line is just the node one line
which is on zero.
Style two is on node 46.
I'm going to change that symbol to be a diamond shape.
And that's going to be blue,
so we need to see where the points are
that we've calculated.
Do the same thing for star three.
Let's put a diamond there.
This is the center node.
Click OK.
And now if I expand that we can
really see what's going on here.
We've got our five modes.
Mode one is the bending mode and we can see
this corner and the center both deflect.
Mode two is a torsional mode,
and only the corner node is deflecting.
Mode three, the center node moves the most.
Mode four, the corner node moves the most.
Mode five, the center isn't moving at all.
And mode six, both nodes move together.
So if we compare against the mode shapes
we'll see that they are the same.
But now we can see the relative scaling of the responses.
Now we're going to repeat the exercise,
but I'm going to change some of the
frequency response parameters.
We still stay with six modes,
but in the harmonic options what we're going to do
is go to the advanced options.
I'm going to change the bandwidth to .6
and change the interpolation to linear.
And we just click OK.
Now we want to run the full
frequency response analysis again.
So run this study.
And again, I've accelerated the timeline
so we can go straight to the results.
And we go to response graph.
And again, I've accelerated the timeline
so that we don't go through the setup again.
It's exactly the same process before.
We go straight to the finished response graph.
Now in the second analysis the change in settings
have changed the curve across all of the six modes.
So we just changed two settings.
The first one was the width of the spread
of the points around each natural frequency,
and then secondly we switched to a linear interpolation
which spreads the points out more evenly
around the natural frequencies.
Now you may need to juggle these settings
to capture a good shape of the curve.
Now I want to look at the overall frequency response
to space shape.
So again we set up a defined displacement plot.
And we just set this up
so we're looking at the zed displacement,
and I want to have the plot as discrete,
and we're going to be including the mesh.
And we check OK.
Now I want the mode shape plot to show mode one.
Edit the definition.
Change this now to mode one.
Check OK.
Now click on the frequency response displacement plot
and I want to set this up so I can compare
the frequency response to the mode shapes.
So I'm gonna keep this visible.
I'm going to be changing the position or the steps
with the frequency response.
So I'm aiming for round about 16 hertz the first mode.
I check that, then I see the first mode shape.
And this is a frequency response displacement plot
matching the first mode.
Now I've shown the first mode shape
as an insert bottom left.
It's 180 degrees out of phase but it is still mode one.
Now I'm moving the selection to round about 21 hertz.
If I check OK then I can see the displacement response
is somewhere between the first bending mode
and the first torsional mode.
Now I'm going to move up the frequency response steps.
I'm going to head towards 40 hertz.
When I get there just check OK.
Now if I did mode shape two which is a torsional mode
into the insert lower left.
Now again it is the same mode shape.
What is different about the frequency response, though,
is it's showing the magnitude.
Because of that both of the extreme edge,
the left-hand side, and the right-hand side,
are both positive.
They're both showing a magnitude.
Whereas we have a positive and negative
on the free edge of the plate.
Now I'm going to move the frequency steps up
and I've reached round about 87 hertz.
The frequency response has transitioned out
of the torsional mode and it's heading
towards the next bending mode.
Now we move up the frequency response steps
right to the third natural frequency,
which is the second bending mode.
Now the frequency response displaced shape
takes a bit of interpreting here,
so what I've tried to show is that
we've actually got a nodal line running across,
and whereas the mode shape logically goes up and down,
the frequency response plot is mirrored.
It's all again, it's a positive amplitude,
so both sensors go up, shown with the little arrows.
Now we move up the frequency response curve up to mode four.
I've shown the mode shape in the insert
and again needs a little bit of interpretation to figure out
how to do the mirroring effect between
the frequency response magnitude plot and the mode shape.
Now we've got the frequency response steps to mode five,
which is the second torsional mode.
And again, it's a bit of a challenge
to try and interpret the mode shape with a magnitude plot
in the frequency response.
Now we'll stop our investigations at that point
and we'll save off the file,
and we'll save it as plate one frequency response end.
And we'll also save the results files.