ACA DEMI C

Framing a Lighter,Stronger Race Car
By Paolo Bosetti
Assistant Professor
Department of Industrial Engineering
University of Trento, Italy

Engineering student teams in universities around the world compete
in the Formula SAE (FSAE) competition to build a race car, giving theman opportunity to apply their engineering knowledge in a practicaland fun way. The E-AGLE Trento racing team takes advantage ofANSYS additive manufacturing solutions and topology optimization inANSYS Mechanical to design a car that is lighter, has stronger joints
and is easier to build than a typical FSAE car.

FSAE car frame with increased
torsional stiffness due to3D-printed joints

58 I ANSYS ADVANTAGE

For the E-AGLE Trento racing team at the University of Trento, Italy,
Formula SAE is not just about the race — it is also about implementing
a groundbreaking idea for the design and manufacture of the vehicle
frame. Working closely with the ANSYS technical support team, they
performed simulations using ANSYS Workbench Additive (part of ANSYS
Additive Suite) to produce an innovative frame joint that relies more on themechanical properties of the materials and less on a potentially weaker
weld for its strength. The joint also makes the manufacturing phase easierby minimizing the need for external dies or fixtures to hold components inplace during the welding phase. Workbench Additive enabled the team tomake a traditionally weak part of the frame — the so-called “hard point,”
where the suspension is attached to the car frame — an integral part of the3D-printed joint instead of consisting of a metal tab welded to the outside of

ISSUE 1 | 2019

DEPARTMENTS

the joint. By eliminating this typically weak point, the team made the vehicle
frame more rigid and less susceptible to breakage during a race. Finally,
topology optimization using ANSYS Mechanical helped them to reducethe mass of one component of the car by 55 percent.
ORIGINSThe E-AGLE Trento team was formed in 2016 under the directionof faculty from the University of Trento. Realizing that theywould need to use additive manufacturing for some componentsof the race car they planned to build, the team partnered with
the industrial development company Trentino Sviluppo, which isowned by the local government and funded by the EU, and its facility
for prototyping mechatronics systems, named ProM. The latter is managed
by Trentino Sviluppo SpA, the University of Trento and the Bruno Kessler
Foundation, with some help from Confindustria Trento.
This partnership was a win–win arrangement. The E-AGLE Trento teamneeded to use ProM’s 3D printers, laser cutters and other leading-edge
equipment. ProM needed a first test case to demonstrate their capabilities
to the market. The FSAE car project was an ideal test case.
ENGINEERING THE BASICS
The team started with an open-frame design insteadof the monocoque design used by many teams in
the competition. The open-frame design focused
the engineering challenge on designing the best
configuration of metal tubes and joints. The overall
goal was to determine the high-level geometry of
the frame by optimizing a parameter defined as thetorsional stiffness of the car frame divided by theweight of the frame.
With a wide range of variables possible for thediameters, thicknesses and relative positions ofjoints between three tubes in the car frame, student
engineers performed parametric studies using
ANSYS Mechanical within the ANSYS Workbench
environment to investigate all the options. Finding
the optimal cross sections and thicknesses of tubes at
each point in the frame was critical to strengthening
the frame at points of high stress while minimizing the total weight of theframe. Parametric simulation studies enabled the students to determine theoptimum configuration of each tube and joint in a fraction of the time it would
have taken them had they been limited to traditional manual iterations.
GETTING DOWN TO DETAILSE-AGLE Trento team engineers wanted to go beyond merely designing asatisfactory FSAE car frame — they aspired to introduce a revolutionary
element that would greatly improve the strength and manufacturability of thevehicle. This innovative element would be the frame joint. This is the point
at which three or more frame tubes intersect to form a corner. Traditionally,
the tubes are simply welded end-to-end to form the joint, but welds can be
weak points in a frame. Using ANSYS Mechanical and Workbench Additive,the engineers concentrated on making a frame joint whose strength dependedmore on the mechanical properties of the metal and less on the weld itself.
They also incorporated the hard points of the suspension connections into the3D-printed joint to eliminate another weakness.

© 2019 ANSYS, INC.

3D-printed joint for greater strengthand torsional stiffness

Close-up view of an assembled car
frame section showing a four-way joint
with integral hard point connectors

Original bellcrank

New bellcrank

Bellcrank designed using ANSYS
topology optimization, which reduced
the weight of the part from 345 g to220 g, a decrease of 37 percent

ANSYS ADVANTAGE I 59

Stronger Race Car (continued)

Simulated thermal distortion of FSAE
car component

Using topology“optimization, student
engineers reduced
the bellcrank’s massfrom 345 g to 220 g,
a 37 percent
reduction.

”

Having already determined the optimal frame tube dimensions, theyused Workbench Additive to design the joint with a slightly larger diameterso that the joint ends would fit inside the tails of the frame tubes. The
resulting inner joint has a set of longitudinal crests that are designed tocontact with the outer frame tube. This ensures that the mechanical stresses
between tubes and joints are mainly sustained by the mechanical fit of
the joints in the tube rather than by the subsequent weld. The end of theframe tube has a slight chamfer to accommodate the welding alloy. Small,
tooth-like protrusions spaced at regular intervals along this chamfer ensure
the right distance between the tube and joint. This very precise relative
positioning of tubes and joints has two big advantages:• Only a single die is needed during assembly of the car frame. This single
die helps join the main hoop of the car frame with the rear part of thevehicle during welding. FSAE regulations stipulate that the main hoop
has to be one single tube, so it cannot be joined, only welded. Assemblyof the rear part of the car frame requires no dies because the structure isfixed by precise positioning of tubes relative to joints. This arrangement
enables welding precision and greatly reduces the welding time needed
for the whole car frame.
• The resulting frame is much more robust and rigid when compared witha purely welded open-space frame design.
LIGHTWEIGHTING COMPONENTS
Reducing weight is an obvious way to make a car quicker in acceleration
and able to go faster while consuming the same amount of fuel — criticalto any race car. E-AGLE Trento engineers used topological optimization
with ANSYS Mechanical to redesign three components that were initiallymade of solid metal: the bellcrank, the suspension rockers and the steering
support mechanism. Topology optimization automatically determines wherematerial should exist within a given volume so that loads and stresses canbe efficiently managed when the part is loaded. The resulting frameworkhas open spaces where no material is needed and thicker struts wherestresses are high. Overall, topology optimization reduces the weight of eachcomponent. In this case, the student engineers reduced the bellcrank’s massfrom 345 g to 220 g, a 37 percent reduction. For the steering support, they
reduced the mass by 55 percent, from 450 g to 210 g.
COMPENSATING FOR THERMAL DEFORMATION IN
ADDITIVE MANUFACTURING DESIGNS
Powder-bed metal additive manufacturing involves adding layers ofmaterial and heating them with a laser to fuse the powder. This heating andcooling can result in deformations, which will result in a non-ideal shape.
The E-AGLE Trento team used ANSYS Workbench Additive to simulate theamount of thermal distortion before performing the 3D print run so they
could adjust the geometry of the part to compensate for the distortion.
While distortion still occurred, it happened in a predictable manner thatwas taken into account by the modified geometry. The resulting part met
specifications exactly.

Measured thermal distortion of actual
physical component

60 I ANSYS ADVANTAGECOOPERATION WINS THE RACE
By working closely with the ANSYS technical support team, E-AGLE Trento
student engineers learned how to use Workbench Additive and Mechanicalefficiently and effectively to design a groundbreaking frame design for their
FSAE car. The car is lighter and stronger with increased torsional stiffness,
which should lead to higher speeds, reduced wear and greater safety.

ISSUE 1 | 2019