- [Instructor] Let's take a look at the background
to the course.
Now why are we doing Dynamic FE Analysis?
And that's a very good question.
Many real-world structures are subjected
to some kind of external dynamic loading environment.
If we think of close to home,
a washing machine can experience severe shaking
if we distribute the wash load badly.
An air-conditioning unit can be very noisy
with annoying hums and rattles.
More specialized cases can include,
a building shaking during an earthquake,
or flying in a helicopter that's top speed
and the vibrations can be very unpleasant in that case.
Now why do Dynamic FEA?
Finite Element Analysis simulations can help design
in all these cases by predicting the structural response.
What are the critical spin speeds for the washing machine?
What is the worse case wash load and its distribution?
What are the peak stresses in the bolts attaching the chasse
What is the bearing fatigue life under random usage?
Things we need to know when we do Dynamic FEA include,
the stiffness distribution throughout the structure,
the mass distribution,
this will often included non-structure components.
What level of damping to use, and we're going to see
on the course this can be quite tricky.
What support conditions are present?
And what form of loading is applied?
The types of Dynamic Analysis we can use are,
a natural frequency assessment,
sometimes called a normal modes analysis.
Response through time, which is a transient analysis.
Response across a frequency range,
which is called a frequency response analysis.
Then we have two advanced types of analysis,
which include shock response
and also random response.
Now, what is Dynamic response?
Dynamic response is the interchange
of two types of internal energies,
kinetic energy, created by the acceleration of the mass,
and potential energy stored by the deflection
of the structure.
We can also have external loading,
which pumps energy into the structure,
and damping will always be present,
and it acts to pump energy out of the structure.
And now we've got some mathematics.
The equation of motion, shown here,
is fundamental to dynamic response.
It balances inertia force, damping force,
stiffness force, and applied force.
And this equation really summarizes dynamics.
And we'll be coming back to this throughout the course.
Course structure is set up as a building block approach,
and it runs through from normal modes analysis
to frequency response analysis.
We're going to be using a set of structural components
and we're going to work these out from initial CAD models,
all the way through into FEA dynamic solutions.