- [Instructor] We'll now review the loads
and boundary conditions that are going to be applied
to the model.
There are two sets of loading actions
to be applied to the model, one for the compressive case
and one for the axial case.
In both cases, the loads are applied at the little end.
Let's select the little end view.
Compressive case is going to be spread over
the 120 degrees arc
using the two surfaces highlighted here.
We use the endpoints of the fillet runout
rather than exactly 120 degrees.
This is a reasonable approximation.
The applied force will be correct,
but the area will be slightly less than
the conventional method.
The pressure will be a fraction higher.
The pressure will be a constant pressure distribution
acting normal to these surfaces.
The tensile load will be applied to
the opposite pair of faces, selected here.
The surface distribution is now over 120 degrees,
but it will vary as a sinusoidal distribution
about the horizontal axis.
This is a standard engineering assumption
when applying a tensile load to a lug-type feature.
Now SolidWorks has a specific form of loading
which can handle this type of distribution.
It's called a bearing load, and we'll see that later.
Let's go back to our standard view.
For both load cases, we're going to constrain
the model at the big end.
Now, to be realistic, we should have
a different constraint system for each load case.
The tensile case will react against
the right-hand face of the big end.
The compressive case will react against
the left-hand side of the big end.
We're going to use a fixed constraint
over the complete 360 degrees inside of the inner face
on these surfaces here.
This is effectively super-gluing the big end down
to a rigid crank.
It is not a realistic load path.
This means that we will have to ignore
stresses local to the big end, and our analysis
is really only valid for the little end
and for the shaft to the conrod.
On a full project analysis, I would calculate
and apply the reaction forces at the big end
as equivalent pressure distributions.
That puts the model in the load balance
for the two load cases, but then we would still have to
apply constraints, to stop the model flying around in space.
There are two ways to do that.
We can apply a minimum constraint set
of exactly 60 degrees of freedom,
and that's called the three-two-one method.
Alternatively, we can apply inertia relief.
These methods are outside the scope of this course.
We will stick to fixing the big end constraint fully.
So in conclusion, we've seen how we're going to apply
the loads and boundary condition strategy.
The limitation of the method we've chosen
means that the stresses around the big end
are not going to be realistic.
However, we will be able to predict
stresses at the little end and at the conrod shaft.