- [Instructor] This video demonstrates the use
of the smeared mass method
and in that method, we replace components
by equivalent mass distributions.
Let's go to File, Open.
Again, if you're using SolidWorks version 2018,
you can use the SolidWorks Part file,
otherwise prior to 2018,
you can open the Parasolid file as before.
So we're going to open up the SolidWorks Part.
Now go to Simulation Tab, New Study,
and select New Study, and select Frequency.
Let's call this tray normal modes.
Check okay.
Now right mouse click on the part name
and select Apply/Edit Material.
Select the default Alloy Steel, click Apply,
and then click Close.
Now we're given the setups and constraints
to simulate the bolts and support region.
So right mouse click on Fixtures.
We're gonna choose Roller/Slider.
Now from this menu we're gonna choose advanced
and we're going to use On Cylindrical Faces.
And here we're going to constrain the radial direction.
Also gonna constrain the axial direction.
The bolts will be free to spin
in a circumferential direction.
Now we need to pick the faces.
Just zoom in
and navigate around.
And then we have the bolt holes at the end here.
That's all complete, so we check okay.
Right mouse click on the Mesh
and select Create Mesh.
We'll accept the default, so just check okay.
And right mouse click on the study name
and go to Properties.
Here we want to update the number of modes to 10.
Check OK.
And now I'm just click on Run This Study.
Let's quickly review the mode shapes.
In version 2018 we can use the double-headed arrows
here in the legend to move up and down.
Prior to version 2018, we need to click the Results set.
So for commonality, let's use the older method.
There's mode two,
mode three,
mode four,
five,
six,
seven,
eight,
nine,
and 10.
And we can see the higher order modes are getting very busy,
they're getting very complicated.
Now we want to compare these modes
with the modes we're gonna get
after we modify the tray.
We're gonna be adding a payload mass
to one of the bays in the tray here.
Now we want to check to see
what the resonant frequencies are,
so right mouse click on Results
and choose List Resonant Frequencies.
The 10 modes run from 212 Hertz
up to around about 1,461 Hertz.
We can save off.
Again we can choose a folder
to save the comma separated variable file into.
And we can close out of that.
Now we want to copy the study
and modify it to add a payload.
So Copy Study and we want to name this
tray-smeared mass.
Check okay.
Now we want to delete the results,
so we just click and drag these
and just delete.
Yes, we want to delete all of the these.
Okay, apply the mass into this position just here.
The way we're going to do it is either distributed
or smeared mass on there.
So we find that under external loads, rather strangely.
Click on here, right mouse click
and then we find distributed mass.
Now we'll need to find a target surface,
and that's our target surface on the top there.
And then we apply the mass that we want to put in there.
Our particular case, we're gonna use two pounds mass,
so we check okay.
And that's now added that mass into the structural solution
as a smeared mass.
No stiffness, what we call the non-structural mass.
Now if we hover over the icon here,
we can see the value is two pounds.
Now as of SolidWorks 2018 service pack one,
there's a bug in the total mass summary
which factors the distributed mass by 2.2.
We can see that if we right mouse click here
and say Mass Properties.
Instead of the value of we we're expecting, we get 4.41.
It's consistently a factor of about 2.2 there.
Now I've checked this bug out extensively,
and the model is correct.
I've checked it against other FEA solutions,
so it's just the reporting here.
So it's just something to bear in mind.
Now we just show the mesh,
which we've inherited from the other study
and now we're ready to run the analysis.
We look at the results and now we've got 159.56
versus 212.6 we had had previously.
So with that added mass, the structure has dropped down
as we would expect from the basic theory
we went through earlier.
So let's go to Window, Viewport, and Two Views - Vertical.
The first view is of the smeared mass.
Let's get an isometric view here
and just scale it.
In the other window here,
we want to have the tray without any mass added to it.
So again, let's choose an isometric view.
Now we want to pick up the first mode here.
So there's a comparison of the two mode results.
What we can do is
just to tidy up these results part a little bit,
let's go into chart options.
We can remove the legend.
We can also change the setting to be discrete contours.
Check okay.
Now we do the same thing for this window here.
So again we change the chart options.
Want to get rid of the legend
and we want discrete.
Check okay.
Let's just scale this side so that it's similar.
So we can see mode one in both cases.
This is the unloaded tray on the right hand side.
It's got a frequency of 212 Hertz, fairly symmetrical.
Now with the mass applied here, our smeared mass,
over this bay here, we've now dropped,
the frequency's dropped down to 160 Hertz.
So it's added no stiffness, it's just added mass.
We know that frequency is equal to the square root
of the stiffness over the mass.
So if we increase the mass,
then the frequency must drop down.
Let's save this file off
and we'll save as tray end.
It wants to know if we want to save the results.
There're gonna be two sets of results
and they're going to be named tray normal modes
and tray-smeared mass with an extension cwr,
so we'd be looking for evidence of those
in our file system.
So click Yes and that will create the file.