Caratterizzazione di materiali per

applicazioni innovative in ambito

sciistico

Materials Characterization For The

Innovation Of Ski Equipments

Alex Persico Laurea Magistrale in Ingegneria dei Materiali Relatore: Prof. Nicola Petrone Correlatore: Ing. Giorgio Grandin 10/10/2014

Objective and main steps

Elastic compensation structure

• Prototypes

• Workbenches

• In-field tests

• Results

Foam surrogate for edge load distribution analysis

• Foam characterization

• Laser Scan devices for traces evaluation

• Results

Function of an elastic

compensation structure

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Load distribution from tail to tip [mm]

Load distribution characterization The Arm structure has many effects: •A more uniform load distribution •Increase the ski stiffness •Fill the unloaded ski shovel •Increase ski performances:

Edge switching quickness Edge catching quickness Carving precision Reactiveness at out of a turn Vibration damping

Padua workbench

Angle [°] Load [N]

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30 850

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60 1400

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Load distribution from tail to tip[mm]

Angle: 40°

blizzard SCS

spitfire

Heel

Tip

Force

Slytech bench

Aluminum support developed by

Eng. Federico Signoretto (2013)

ARM Prototypes

WOOD (PD)

ALU (PD)

PU

PU + C

CHB

OAK WOOD Hand-crafted

Aluminum alloy, Ergal 7075 - T6 Al 5,1-6,1%Zn; 2,1-2,9%Mg; 1,2-2%Cu

SG 95 Mix ratio (A:A-LP):(50:50) B:150 Mixing time 45 s to 60 s Resin temperature 40 °C Mould temperature 70 °C Curing temperature 70 °C Curing time in mould 70 min

Vacuum Casting

ARM Prototypes

Nordica

Results

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Load cells: from tail to tip[mm]

Nspitf-PD ICE HL_30°

original

HEEL

LOAD

TIP

Results and Comparisons

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Load cells: from tail to tip[mm]

Nspitf-PD ICE HL_30°

original

ALU

WB300

HEEL

LOAD

TIP

BR300

ALU

WOOD

LARGE

EFFECT

Results and Comparisons

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Load cells: from tail to tip[mm]

Nspitf-PD ICE HL_30°

original

PU

C H B

HEEL

LOAD

TIP

BR300

PU

C H B

SMALL

EFFECT

Chemnitz (DE) workbench

Angle Applied

Load

0° 350 N

20° 500 N

30° 600 N 0

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ski length from tail to tip [mm]

Nspitf-CH MI LL-30°

original

PU (A)

WOOD (B)

CHB (C)

ALU (D)

Limitation

0,00E+00

1,00E+09

2,00E+09

3,00E+09

4,00E+09

5,00E+09

6,00E+09

7,00E+09

8,00E+09

9,00E+09

1,00E+10

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Fle

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od

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s E

J

[Nm

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3/m

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From tail to tip [mm]

Nspitf - Nordica bench

original AA

ALU

PU

C H B

WB 300

portabraccetto

Nordica workbench

The Nordica bench curves show an high influence due to the aluminum support

Even if the benches are showing different parameters, the same configuration trend can be noticed

Arm stiffness

characterization

NORDICA

DII

Arm fixed to the ski Aluminum support

Arm fixed to a rigid support

Ski and Arms stiffness

• Even if CHB is «softer» than PU, CHB has higher influence on total ski+ arm stiffness K

In-field test sessions

METHOD & TESTERS The skiers test all the configuration consequently, filling the evaluation form at the end of each run

Two tests

STUBAI end of July

• Five Nordica testers

• Only one filled evaluation form

• WOOD arm was not tested

HINTERTUX early September

• Three testers: one ex-racer and

two expert amateurs

• Three personal evaluation form

completed

• All arms tested

• Blind testing

In field test results

Summarizing:

The CHB and WOOD during Stubai and Hintertux test respectively had best

scores; the ski behaves like a «longer ski».

The quality percived is the carving precision: all the points of the ski edge

traveling through the same track on the snow surface during a turn.

n=1 n=3

Foam: a new device for edge load profile investigation

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Displacement [mm]

θ=40°

Schiuma_A

Schiuma_RP1

Schiuma_RP2

Schiuma_C

Schiuma_D

Schiuma_G

Schiuma_PEDILEN

Soft snow

Average snow

Hard snow

Federolf’s snow characterization Foam as snow surrogate

Snow indenter

Traces acquisition

FARO SCANARM SMARTSCOPE FLASH

Results

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Load distribution cells 11 12 13 [mm]

40° cells: 11 12 13

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Load distribution cells 11 12 13 [mm]

50° cells 11 12 13

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Load distribution cells 11 12 13 [mm]

60° cells 11 12 13

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Fo

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N]

Displacement [mm]

θ=40°

Schiuma_RP1SoftsnowAveragesnowHardsnow

SLYTECH BENCH

FARO SCANARM

SMARTSCOPE

Conclusions

Elastic compensation structure: • CHB and WOOD arms better influenced the ski •Importance of the subjective evaluation form •More in-field tests are necessary to create statistical results •New prototypes have to be engineered and tested

Foam as snow surrogate: • New foam materials can be tested in order to match the snow

properties • The parameters to be considered are: density, a small spring back,

constant thickness of the keyboard. • Advantage: a “detailed” edge load distribution characterization can be

performed without the array of load cells • Disadvantage: large amount of foam needed.

THANKS FOR THE ATTENTION