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BIKE BRAKE LEVER DESING Continuum Mechanics

Members of the group:

Fargas Cabanillas, Josep Maria Olivé Delgado, Roger Sansalvadó Cabonés, Clara

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BIKE BRAKE LEVER DESING-Continuum Mechanics

1) FIRSTS STEPS-INTRODUCTION

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INTRODUCTION: Basic function and key points

Aim:

Design a brake lever

Use:

The basic function of brake levers is to activate the brake mechanism

They have not only hardness

and stiffness but also

lightness and resistance

Legislation:

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1) FIRSTS STEPS-MATERIAL SELECTION

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MATERIAL SELECTION

Aluminium 6082

Plate thick: 6mm

Laser cutting

Density Modulus of

Elasticity

Poisson

coefficient

Yield

point

Melting

point

Break load

2,7 g/cm3 70 GPa 0.33 260 MPa 555ºC 310 MPa

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1) FIRSTS STEPS-PRELIMINARY DESING

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PRELIMINARY DESING: Data

Pressure P

Force (Fmax)

Thickness (t)

Width (L)

Research Our own experiments

Data values

Real project

Academical project

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PRELIMINARY DESING: Maximum permisible force

This graph comes from joining three ergonomic studies

Real brake lever design: statistical data

Our project: Our own experiments, team members data

Fmax = 535,7 N

Fmax = 392 N

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PRELIMINARY DESING: Hand width

Real brake lever design: statistical data

Our project: Our own experiments, team members data

L = 57,25 mm

L = 70 mm

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PRELIMINARY DESING: Data

Pressure P

Force (Fmax) = 40*9,8 = 392 N

Thickness (t) = 6mm

Width (L) = 70mm

Research Our own experiments

Data values

Real project

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PRELIMINARY DESING

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2) FINITE ELEMENTS MODEL-Boundary conditions

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FINITE ELEMENTS METHOD: Boundary conditions

Equations A: P1-T=0 B: P2-F=0 C : T*X-F*L=0

Hypothesis: 1. Static model 2. Pressure (Pr): Uniform and perpendicular to the surface 3. Punctual contact produces punctual forces at M, N, O.

M

N

O

Pr

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2) FINITE ELEMENTS MODEL-Model characteristics

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FINITE ELEMENTS METHOD: Model characteristics

We choose 183 element type: Quadratic interpolation thus more precision (curved edges).

We are not restricted for computational power

Plane tension analysis

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Material properties: Linear, elastic, isotropic

E= 70 GPa v= 0,33


2) FINITE ELEMENTS MODEL-Results reliability

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FINITE ELEMENTS METHOD: Results reliability

Are numeric singularities affecting our results?

Do we need non-linear study?

Linear: R= 865,95 N Non-linear: R= 860,89 N

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FINITE ELEMENTS METHOD: Results friability

Refining mesh

Biggest element size with stable results

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3) RESULTS ANALYSIS-Current displacements

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RESULTS ANALYSIS: current displacements

Maximum displacement: 1,94mm

Small maximum strain: 3,3·10-3

Displacement Deformed shape

Total strain

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3) RESULTS ANALYSIS-principal strength distribution and directions

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RESULTS ANALYSIS: principal strength distribution

1st principal direction 2nd principal direction 3rd principal direction

Principal stress distribution

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3) RESULTS ANALYSIS-Failure criteria

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RESULTS ANALYSIS: Failure criteria

Posible failure criteria: Tresca-Guest Von Mises

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3) RESULTS ANALYSIS-Security coefficient

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RESULTS ANALYSIS: Security coefficient

3,12,1 eq

e

s

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Our brake lever

σe = 260 MPa σeq= 172,73 Mpa

𝛾 = 1,505

Pe = 1,4 MPa Peq= 0,93 Mpa


4) FINAL DESING- Optimization

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FINAL DESING- Optimization

Problem!

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Prototypes and final design


4) FINAL DESING- Summary

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Boundary conditions

FINAL DESING-Summary

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Pressure: Pn = 0,93 MPa

Force: Fmax = 392N

Thickness: t = 6mm

Width: L = 70mm

3,12,1 eq

e

s

σe = 260 MPa σeq= 214,8 Mpa

𝛾 = 1,21

Pe = 1,13 MPa Peq= 0,93 Mpa

Security coefficient


FINAL DESING-Summary

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Nonlinear deformed shape

Linear deformed shape

Mesh refining


4) FINAL DESING-Environmental impact. Construction and cost.

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FINAL DESING- Environmental impact. Construction and cost

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Environmental impact

A. Our brake lever

Construction and cost

Aluminium: 100% recyclable. Recicled aluminium: 5% of the energy needed to obtain aluminium from the bauxite minerale.

Laser cutting Gluing Aluminium plate

Separated shapes

Brake lever


FINAL DESING- Environmental impact. Construction and cost

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B. Mass production

Economical (for big series) Sustainable

Laser cutting: 14,44€/u x 2u 28,88€ Gluing the shapes: + 5€ Total 33,88€

1. Design extrusion die

3. Cut slices 4. Somoothen the brake lever

2. Extrude profile

Cost


4) FINAL DESING-Test

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FINAL DESING-Test

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Validating the simulation:

Analytically

Test

R

76,37 mm

34,57 mm

20,24 mm 49,63 mm

30 mm

F 1 F 2

R=(34,57F 1+76,37F 2)/30


FINITE ELEMENTS METHOD: Possible improvements

Questions?

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continuum mechanics - docs.gestionaweb.catdocs.gestionaweb.cat/0761/brake-lever-presentation.pdfbike...

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