- [Instructor] We now have two geometric configurations,
one with fillets and one without fillets.
We can mesh both independently
and check the quality of each mesh.
At the moment, in the Configuration Manager,
we have the original con rod as the active geometry.
We can see the fillets are present here.
Now with that active,
what I can do is go into Simulation and create a New Study.
I'm going to call this with fillets.
We can see the study name appears down in the bottom here.
What I can do is go back to the model,
and I can make the other configuration active.
This is the one we called no_fillets.
If we check, you'll see that the fillets are not present
in the geometry here.
Now, if I go to Simulation,
you can see, I can create another Study here, New Study,
and I'm going to call this no fillets.
What we're doing is building up in parallel two studies,
one with fillets, one with no fillets.
The moment no fillets, I'm linking through
to the Configuration Manager and the geometry,
which is active, which is for the no fillets.
We go to Model, we can see it's the no_fillets option.
If I double-click in the filleted option,
come back to the no fillet study,
you see it's just grayed out.
What that's telling me is that the study
does not tie up with the geometry.
There's a nice clear indication there
to make sure you don't get out of sync.
We go to with fillets, you can see everything's live.
The with fillets analysis feature tree here, the study,
is in sync with the fillet geometry.
I think that's extremely useful
and a very powerful way of working.
We've got, now, our geometry with fillets,
here's our study, which is with fillets.
What we're going to do is Mesh this,
right mouse click, and we're going to Create the Mesh.
What I want to do as a test
is to put a very fine mesh indeed in.
Now, this caused us problems in the introductory course,
when we had to just accept the presence of the fillets here.
Let's see if we can replicate that kind of issue.
Check the box here, it's going to mesh,
and we have a very fine mesh.
Let's zoom into the little end region
so we can see the number of elements, that's high,
that would be great.
Let's check out the quality of that mesh.
Come to Mesh, right mouse click, Create a Mesh Quality Plot.
If you remember, we had a couple of different options,
Aspect ration or Jacobian.
We're going to choose Aspect ratio,
and plot Aspect ratio, distribution.
You can see here we've got an Aspect Ratio of 19.
Let's go into Mesh Quality Plot, choose Chart Options,
and here we can say, Show the maximum annotation.
That's useful just in case it's buried away we can't see it.
Click on that, and there it is.
That's my problem area, spin around,
see what that is looking like.
It's actually a very nasty little element in there.
We zoom really tight in there,
you can see we're getting this sliver type element,
which is always going to cause us a problem.
If I put a finer mesh in,
then that sliver's going to get an even high aspect ratio,
as basically, we approach the vertex down in here.
Now, it's an interesting problem.
It really means that, mathematically,
the finite element analysis is obeying
the strict discipline of the geometry inside the CAD model.
The CAD model itself is an approximation
of the real structure.
There's always going to be rounding,
there's going to be curvature,
if you remember, this is a Ford structure.
We're in this area of really finite element artifacts
is often the phrase that we would use.
We really would like to defeature that.
Let's come back to a standard view.
That's our issue with keeping the fillets in there.
Let's go back to the other study, no fillets.
At the moment, I have the wrong geometry set up,
so I can see the fillets are still there,
and this is all just grayed out,
so let's go back to the model,
make sure we choose a configuration, no fillets,
so double-click on here.
The fillets disappear, come back to the no fillets study,
and that's all nicely live there.
Let's repeat the same meshing operation,
and come in and say, Create the Mesh.
Again, we want to just set this Mesh Parameter down
really tight to really check out these elements,
so .1, check OK, and it's running it.
Quite a lot of elements to mesh,
so it takes quite a while on this machine.
There's our mesh, again,
let's go in and zoom in that local area.
Now, the fillet as such doesn't exist anymore,
we have a simplified view of what's happening.
Let's go and actually look at the quality of the mesh,
so Create Mesh Quality Plot, and we choose Aspect ratio,
check OK, produces the plot.
We're down to 5.34.
Let's see where that is,
so right mouse click, Chart Options,
Show the maximum, check on that.
Now it isn't at the little end anymore,
so we need to come out and do a standard view,
and lo and behold, it's sitting somewhere
in the middle of the con rod body.
Five isn't a bad value, it's just somewhere deep inside here
is a particular tetrahedral element
that's had to form aspect ratio around about five
to do its meshing job.
What we've got is, we don't have that kind of Achilles heel,
that almost impossible road to follow,
which is the issue down at the vertex there.
If we go back to the little end,
the Aspect ratios in what was the problem area
are pretty good and pretty clean.
If I switch off the Quality Plot, Show the Mesh again,
you can see we've got very nice regular mesh in there,
we don't have the transition issues we have with the fillet.
Again, the issue will be, well,
there is actually real material there in practice,
it forms the fill in material, if you like, there.
But in both cases,
the structural representation is really an analogy
of what the real forged process looks like.
It becomes a little bit of an engineering judgment call,
do we accept this and it has a good clean aspect ratio,
or do we try to model that fillet run out,
and in this particular case,
this is a better representation.
We might apply correction factors afterwards
and say, OK, we've got stresses here at a certain level,
I'm going to increase them slightly from experience,
what's called the stress concentration factor.
That's something under our control.
We're not chasing this mathematical kind of rabbit hole
that we could otherwise disappear down into.
Let's switch on the Quality Plot again.
In conclusion,
we've seen how defeaturing the very sharp fillet radius
enables us to have a very fine mesh
without creating local elements
with very high aspect ratios around that fillet vertex.
Let's save this model off, File > Save As,
and we're going to call this con_rod_advanced_6.