1. No category

Structural Optimization of the
Rear Swingarm of Ducati
HyperMotard
Stefano Verzelli, Simone Di Piazza
DUCATIMOTOR HOLDING S.p.A.
1st European HyperWorks Technology Conference – Berlin, Germany October 23-24, 2007
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Summary
•Introduction
•Topology optimization problem
•Boundary conditions
•Material properties
•Finite element model
•Topology optimization analysis and results
•Conclusions
1st European HyperWorks Technology Conference – Berlin, Germany October 23-24, 2007
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Introduction
Today the use of structural optimization methods can be very
useful to obtain a proper and efficient solution. These methods
can reduce the development process and improve the quality of
the final product. Solutions that in the past were generated
with several loops by designers and engineers, now can be
found easily using FE optimization tools.
This presentation shows the methodology used to design the
swingarm of Ducati Hypermotard.
Using Altair OptiStruct, Ducati has developed an efficient
structure with a high stiffness to weight ratio, respecting the
constraints given by the stylists.
1st European HyperWorks Technology Conference – Berlin, Germany October 23-24, 2007
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The Topology Optimization Problem
During the Topology Optimization process, the material is
considered to be porous. A relative density 0<ρ<1 is associated
to each element, representing the contribution of this element
to the stiffness of the component.
In order to satisfy the design constraints and the objective of
the optimization, according to the load cases, the elements’
density are variously distributed on the model.
The purpose of the optimization process is to obtain the most
efficient configuration for the component’s structure.
The results of the analysis sometimes need to be interpreted in
order to have a feasible component.
1st European HyperWorks Technology Conference – Berlin, Germany October 23-24, 2007
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Boundary Conditions
Two different load cases were used for this optimization:
• Fatigue test (Leyni test bench)
• Bending and Torsional Stiffness
The Leyni test was simulated using the following scheme:
Rear wheel pin
Rocker
Shock
absorber
Radial runout
Fma
Fa
125.025°
97.787°
Reaction
rod
Swingarm pivot
Rear swingarm
1st European HyperWorks Technology Conference – Berlin, Germany October 23-24, 2007
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Boundary Conditions
(Bending Stiffness)
Bending Stiffness has been
evaluated using the following
formula:
y
x
Vehicle coordinate
system
K Bending =
F
y
|Y |
[N/mm]
Fy
Y
1st European HyperWorks Technology Conference – Berlin, Germany October 23-24, 2007
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Boundary Conditions
(Torsional Stiffness)
Rear wheel hub lenght Lb
Torsional Stiffness has been
evaluated using the following
formula:
e
Δz2
Δz1
α
K Torsion =
Rigid elements
l
F
y
*L
180 Δ Z1 − Δ Z 2
π
LB
[Nm/deg]
z
y
Fy
Vehicle coordinate
system
1st European HyperWorks Technology Conference – Berlin, Germany October 23-24, 2007
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Material properties
The material used for the simulation is an aluminium alloy (EN AC 42100
UNI EN 1706) with the following mechanical properties:
E = 72400 MPa
ν = 0.33
ρ = 2.7 e-6 Kg/mm3
σY = 210 MPa
Accordingly with these values we have used a fatigue limit under
reversed stress of 70 MPa.
1st European HyperWorks Technology Conference – Berlin, Germany October 23-24, 2007
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Finite element model
The model counts 486102 nodes and 1830077 linear tetra elements:
rigid elements were used to simulate hinges and to apply loads.
Bending/torsional beam
1st European HyperWorks Technology Conference – Berlin, Germany October 23-24, 2007
hinges
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Finite element model
(Design Space)
DESIGN
SPACE
NON DESIGN
SPACE
1st European HyperWorks Technology Conference – Berlin, Germany October 23-24, 2007
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Finite element model
1st European HyperWorks Technology Conference – Berlin, Germany October 23-24, 2007
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Topology Optimization
The purpose of the topology optimization was to maximize swingarm
torsional stiffness, minimizing its mass.
It was necessary to try several different analysis setup, changing design
constraints, manufacturing constraints and objective.
Analysis
Manufacturing
Constraints
Design Constraints
Objective
1
Use of MINDIM control
Upper Boundary limits on Bending&Torsion Stiffnesses
Upper Boundary Von Mises Leyni test
minimize mass
2
Use of DISCRETE = 3.0 and
CHECKER 1 controls
Upper Boundary limits on Bending&Torsion Stiffnesses
Upper Boundary Von Mises Leyni test
minimize mass
3
Use of DISCRETE = 3.0 and
CHECKER 1 controls
Upper Boundary limit on MASS
minimize WCOMP
1st European HyperWorks Technology Conference – Berlin, Germany October 23-24, 2007
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Results – Analysis 1
Analysis
Manufacturing
Constraints
1
Use of MINDIM control
Design Constraints
Objective
Upper Boundary limits on Bending&Torsion Stiffnesses
Upper Boundary Von Mises Leyni test
minimize mass
Horizontal distribution
of material
Vertical distribution
of material
1st European HyperWorks Technology Conference – Berlin, Germany October 23-24, 2007
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Results – Analysis 2
Analysis
2
Manufacturing
Constraints
Use of DISCRETE = 3.0 and
CHECKER 1 controls
Design Constraints
Objective
Upper Boundary limits on Bending&Torsion Stiffnesses
Upper Boundary Von Mises Leyni test
minimize mass
Horizontal distribution
of material
Vertical distribution
of material
1st European HyperWorks Technology Conference – Berlin, Germany October 23-24, 2007
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Results – Analysis 3
Analysis
3
Manufacturing
Constraints
Use of DISCRETE = 3.0 and
CHECKER 1 controls
Design Constraints
Objective
Upper Boundary limit on MASS
minimize WCOMP
Horizontal distribution
of material
Vertical distribution
of material
Vertical distribution
of material
1st European HyperWorks Technology Conference – Berlin, Germany October 23-24, 2007
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Feasible Model
The optimization results were combined in order to obtain a more
feasible topology for the rear swingarm.
A new model has been constructed, based on this interpretation.
The following images shown the new F.E.M. model in detail.
vertical wall
horizontal wall
1st European HyperWorks Technology Conference – Berlin, Germany October 23-24, 2007
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Feasible Model
(Leyni test - Von Mises results)
1st European HyperWorks Technology Conference – Berlin, Germany October 23-24, 2007
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Conclusions
•Optistruct allowed us to find the most efficient design, satisfying the
stylistic constraints;
•Stiffness results (bending & torsional) are fully satisfying and
reached the desired targets;
•Resulting part mass was only 4.8kg;
•The component is stressed uniformly below material limits with a
suitable safety factor;
•Topology optimization allowed us to reduce the design time.
1st European HyperWorks Technology Conference – Berlin, Germany October 23-24, 2007
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Thanks for the attention
1st European HyperWorks Technology Conference – Berlin, Germany October 23-24, 2007
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