Speaker 1: It's now time to
simulate the performance of this
chassis frame under loading
conditions using SOLIDWORKS
Simulation. Under the SOLIDWORKS
works add-ins tab you can
quickly toggle simulation on or
alternatively navigate to tools,
add-ins and enable Simulation
under the active add-ins column.
Switching to the Simulation tab
in the command manager, we can
now create new studies. Testing
the torsional rigidity is one of
the crucial benchmarks for any
chassis and a number of studies
have been set up in advance with
a partially complete study that
we will review to highlight some
of the best practices. Using the
weldment tools in phase two
means that the body geometry is
automatically imported and
converted to optimized one D
beam elements in simulation,
which are specifically
formulated to handle beam
bending, tension, compression,
and torsion. Cross-sectional two
properties are pulled directly
from the SOLIDWORKS model so we
don't need to worry about
inputting this data. We can
easily right click on the
chassis part in the tree and
apply a material to all bodies.
These bodies are organized into
a cut list, but this can be
deleted to see a full list of
weldment bodies, any smaller
bodies that are not load bearing
have been excluded from the
analysis using the context menu
options. But we can include
these again if required. The
beam joints option allows us to
automatically calculate beam
connection points and add
additional new beams to the
design if updates are made.
Small
gaps between non touching
members can also be considered
as joined by specifying a
tolerance. An important option
to enable is to keep modified
joint on update. So that
individual beam members between
multiple chassis design
iterations can be compared
directly. Beams are assigned a
number that can be referenced
when outputting results turning
this option off low mean that
each beam will be reassigned a
new number. If the joints are
recalculated, meaning beam one
in the first iteration of a
design may not be the same beam
in the secondary iteration Hence
leave this option enabled. The
visibility of all Simulation
symbols can also be toggled from
the heads-up toolbar, which is
useful when reviewing a setup,
this chassis is assumed to be
welded together. So the only
connection between the geometry
is a global bonded contact,
which should be the default
connection in the model. Any
contact sets added to the model
can override the global contact
and would potentially be
required for a chassis that
would fix together or assemble
the using fasteners. We can use
the fixtures advisor to guide us
through adding some constraints,
to simulate torsional test case
where some suspension nodes are
instantaneously fixed in space
and the load is applied on a
pausing suspension nodes,
simulating a speed bump impact
scenario, or cornering loads in
a quasi static analysis. In this
case, we will use a powerful
feature called reference
geometry and independently
control degrees of freedom are
the suspension nodes.
We'll start by picking the floor
as the reference plane, and then
pick four rear suspension
mounting points and stop any
translation in the X, Y and Z
directions, but allow rotational
degrees of freedom. However, we
are analyzing the full chassis
so we can edit the fixture and
also constrain the suspension
nodes on the rear left side of
the chassis. And we can also
increase the symbol size to make
this clearer in the viewport and
for any simulation report
images. The next stage is to
apply the forces on the front
suspension mounting points in
equal, but opposite directions
to simulate a twisting motion
about the chassis center line.
We pick the beam joints option
on the selection heading,
reference plane, and then apply
300 Newtons of loading normal to
the plane to apply a vertical
force on each of the front
mounting points on the right
side of the chassis. We can then
repeat this process, but flip
the loading direction on the
front left mounting points.
We'll add gravity to consider
the self weight of the vehicle.
And we are now ready to mesh.
Beam structures are incredibly
lightweight and quick to solve.
So meshing using this technique,
a number of connected beam
elements can be created in just
a few seconds, which represent
the frame geometry using tubular
members. If the weldment beams
are of different cross-sectional
shape you can right click and
render beam profiles in 3D,
However, this is purely visual
and
does not affect the calculation.
Right clicking at the top level
of the simulation tree and
navigating to properties allows
us to set some simulation
options, including the automatic
solver selection, as well as
manage where the results are
stored. Running this study takes
just a few seconds and we are
presented with stress and
displacement results. We'll
switch to another study to look
at how we can pause process
results to extract the required
information easily. We can edit
the stress plot in this model
and adjust the legend units,
stress type such as axial
bending and sheer and set a
custom defamation scale, other
useful options to toggle are
under the chart options tab
where minimum and maximum values
can be displayed in the viewport
and number formatting can be
adjusted to floating. The
boundary options on the settings
tab, also control outlines and
other useful overlay settings to
superimpose the model on the
original un-deformed shape. We
can animate the motion to view
the distribution of stresses in
the frame members in this case
around 50 megapascals, as well
as displacement plots thoughts
in the global wide direction,
which shows vertical deflection
of the frame notice the
deflection downwards of 1.6
millimeters is actually the
larger of the two displacement
values. We can also manually
probe areas of interest on the
mesh to extract the stress at
the bottom four corners to check
the values are of similar
magnitude or add and remove
additional measurement points if
required.
The summary provides a useful
tabulated data that can be saved
out to a spreadsheet file or
plotted graphically. A similar
setup has been created to test
the torsional rigidity further
by fixing the front suspension
mounting points and applying
force to the rear suspension
nodes we can see the maximum
stress is slightly higher when
considering this case, but still
comparable. And the distribution
of stresses through the engine
support members is more evident
as before we can animate the
displacement in the rear
bulkhead and engine cradle
members extracting forces in
individual beam members is
extremely easy. Right Clicking
on the results folder we can
choose to list beam forces or
stresses. We can then toggle the
range of beam elements to
analyze. There are 168 members
in this model. And the beam
number is related to the keep
modified joint on update setting
mentioned earlier. Once we
accept this, we are presented
with a table of force components
and values for each beam and its
individual mesh elements,
clicking beam one, will
highlight it in the viewport and
working our way down the
columns. We can see the forces
in each beam cell of the first
beam member. This is a lot of
data which might not be required
so we can toggle to only show
extreme, maximum and minimum
values at any cell. Along each
beam, we are interested at joint
forces, so we'll choose to only
show the beam start and end
points indicated by
the red and blue spheres. We can
move through each beam member to
see the values and location of
the beam either by clicking it
in the row or using the
navigation buttons in the
window.