PARTNER SPOTLIGHT
ou hear it all the time – change is
good. Some of that change has to do with
learning what’s new. As the technology of
high performance and racing increases in
complexity, this also introduces new terms that
may not be familiar. But it doesn’t have to be
difficult. Let’s take the case of forged pistons and
a design tool called FEA. This doesn’t stand for
the Futuristic Engineering of Aid or even French
Experimental Aircraft – the acronym stands for
Finite Element Analysis. So right here in our
first paragraph you’ve already learned something
that might lead your car buddies to think you’re
pretty sharp.
What is FEA?
So what is FEA and why should we care? If
you into high performance engines, then you
already know that if your heads offer the airflow
to spin that engine faster – you can make more
horsepower. But this puts a price on piston du-
rability. That’s where FEA can be an important
step toward better pistons.
Finite Element Analysis is essentially a com-
plex computer program that helps the piston
designer create a better part. The program
can pre-determine a weak point in the de-
sign before it ever leaves the confines of the
computer design screen.
In the not-so-distant past, a piston design-
er applied his experience with a sketch on
paper that eventually led to a fully-functional
forged prototype. This one-off part was then
squeezed into an engine and abused on the
dyno or in a race car and then removed and
carefully evaluated. This process demanded
tremendous time and plenty of resources.
Today, that evaluation process still occurs
but only after the program has created sig-
nificant feedback in the design stage as to
where the stresses in the piston will occur.
To get started, let’s first define what we’re talk-
ing about. Finite Element Analysis is a computer
program that evaluates how objects are affected
by stress. The finite element process applies
simulated thermal and mechanical stress to a
complex component like a piston and predicts
where that stress will appear on the piston. By
applying certain techniques, the designer can
reshape the piston to reduce or redistribute the
stress to make the piston more durable.
When a component is designed on a computer
screen, the engineer uses a program called Solid-
Works to create thousands of three-dimensional
cubes that represent a small portion of the com-
ponent. Each of these cubes will react in a predict-
able manner when assigned to represent a given
material such as the 2618 aluminum alloy used in
JE race pistons. The advantage of the computer
program is that it can quickly perform hundreds
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It’s not surprising that all JE pistons begin life on
the computer screen (above). One way to reduce
the cost of race or street pistons is to do as much
development work as possible on the computer,
which leads to a shorter lead time from design to
a piston sitting on the shelf. If you look closely at
the photo on the right, you can see the difference
in the actual piston skirt size between the major
and minor thrust versions. These are pistons for a
stroker LS package. The image below reveals the
results of an FEA test on an JE piston for an LS
engine. In this particular situation, the simulated
stress is a compressive load applied to the top of
the piston to simulate an extremely high cylinder
pressure load equivalent to roughly 150 bar.
of thousands of finite calculations that are used
to predict how the design will react to stress. The
key is to know what stresses to apply and what
to look for as a result of those tests.
In Practice
As an example, an internal combustion en-
gine enthusiast might consider that withstand-
ing combustion pressure would be the ultimate
concern when designing a piston. While that is
certainly important becaus e the loads imposed
are considerable, there are other areas involved
with a piston’s physical operation that are perhaps
of even greater concern. One of the most criti-
cal is the piston’s ability to withstand the high
g-forces imparted into a piston when it changes
direction. A critical point is where the piston
stops momentarily at top dead center (TDC) and
then the crankshaft, through the connecting rod,
yanks downward on the wrist pin.
At high RPM, this simple change in direction
places incredible tensile (stretching) loads on the
piston’s pin boss area, stresses that, in many cases,
are the exact opposite of the compressive loads
placed on the piston during the combustion cycle.
So the piston engineer is faced with creating a
design that is not only lightweight (which reduces
Issue 120
Y
Finite Element Analysis is the
New Shape of Piston Creation