“From CAD to manufacturing: an

optimization procedure applied in the design

of a motorcycle wheel rim””

Authors:

Sandra Baldini - Daniele Ardiri (Piaggio S.p.A.)

Leonardo Bertini – Francesco Frendo (DMNP Engineering -University of Pisa)

Bonn, Germany 7-9 November 2011

CONTENTS Introduction

Aims of the work

Optimization Problem

Optimization Results

Fem Re-analysis

Radial Impact

Conclusion

Acknowledgements

INTRODUCTION The activity is resulting from the cooperation between

Piaggio&C SpA and Mechanical Engineering Dept. of Pisa

University. It has been carried out within the framework of

the MUSS research project, funded by the Italian Ministry of

Economic Development under the call «Industria 2015 –

Mobilità Sostenibile» (2010-2013).

The MUSS project (Safe and Sustainable Urban Mobility) is

aimed at:

• Making powered-two wheelers vehicle more

environmental-friendly

• Spreading their use as effective alternative to cars

INTRODUCTION

Structural optimisation in order to evaluate the actual

possibilities in reducing the mass of structural parts

The Topics: engines improvement, research on alternative

fuels and new powertrains, improvements of vehicles (weight

reduction, comfort, safety), new prototypes …

This work has been developed by means of the following

commercial software Optistruct and Radioss, included in the

suite Hyperworks v. 11 produced by Altair Engineering

AIMS OF THE WORK

Aim of this work is to develop an optimization procedure in

order to reduce the weight of scooter components. The focus

of this project has been the weight reduction of an

aluminium wheel by means of a topologic analysis

The topologic optimization result has been elaborated by

Piaggio Designers in order to realize the CAD model used

for following structural validation

The CAD model has been tested according to the radial

impact standard in an esplicit FEM simulation ‘URTO

RADIALE’ as well as according to bending and torsion

alternating load

OPTIMIZATION PROBLEM Reference Model

Design Region

NO DESIGN SPACE

DESIGN SPACE

The reference model for the analysis

has been the New Beverly 300 cc

(Front Wheel)

The rim and the hub of the wheel are

interface region that are not included

in the optimization process. The

volume included within the two parts is

design space of the optimization

OPTIMIZATION PROBLEM

Design Constraints:

• Maximum Von Mises Stress < 72 MPa corrisponding

to the fatigue limit (0,3*sR ) of this material for 10^7

cycles

• % of mass reduction: 75 %

Objective:

• Minimum“compliance”

OPTIMIZATION PROBLEM

Manufacturing Constraint:

• Minimum rib thickness: 6 mm

• Structure with polar simmetry (3, 4, 5, 6 spokes)

Geometric Constraints:

• Rotating Bending Fatigue

Test: the wheel must withstand

50000 cycles with an

alternating bending load.

OPTIMIZATION PROBLEM

Geometric Constraints:

• Alternating Torsion Fatigue Test:

the wheel must withstand 10^6

cycles of alternated torsion load

Loads and constraints used in

the analysis

OPTIMIZATION RESULTS Optimization results achieved

with 3,4,5 and 6 spokes

OPTIMIZATION RESULTS

The solution with 6 spokes has

been designed by Piaggio R&D

and a CAD Model has been

realized

OPTIMIZATION RESULTS

Initial Weight= 5,7 Kg

Final Weight = 5,1 Kg

D Weight = 11%

FEM RE-ANALYSIS

The CAD model has been validated according to the

alternated torsion and bending load standard

The maximum stress for the alternated bending is 85 MPa

acceptable for the required fatigue life (172 MPa )

FEM RE-ANALYSIS In the alternated torsion test the maximum Von Mises

Stress achieved has been 67 MPa again acceptable for

the required fatigue life (123 Mpa) .

RADIAL IMPACT

Radial impact test: aim of

this test is to validate the

strength and air thight

capacity of the wheel after an

impact with a given obstacle.

RADIAL IMPACT

BC used in the analysis

m=200 Kg

vel= A m/sec

RADIAL IMPACT

RADIAL IMPACT

In the radial impact test the maximum Von Mises Stress

achieved has been ≈180 MPa again acceptable with

respect to the sy of this material

CONCLUSIONS The activity is resulting from the cooperation between

Piaggio&C SpA and Mechanical Engineering Dept. of Pisa

University.

Aim of this work is to develop an optimization procedure in

order to reduce the weight of scooter components. The focus

of this project has been the weight reduction of an

aluminium wheel by means of a topologic analysis

The CAD model has been tested according to the radial

impact standard in an esplicit FEM simulation ‘URTO

RADIALE’ as well as according to bending and torsion

alternating load

Thank you all

for the attention

ACKNOLEDGEMENTS