Mechanical Traction Testing of 3G Surfaces -...
Transcript of Mechanical Traction Testing of 3G Surfaces -...
Mechanical Traction Testingof 3G Surfaces
James ClarkeMatt Carré
Kathryn SevernPaul Fleming
Sports EngineeringResearch Group
University of Sheffield
Civil and BuildingEngineering
Contents
• Introduction
• Engineering Methods
• Traction Rig
• Key Findings
• Summary
Player Performance - Traction
Performance - Players require sufficient traction to perform.
Traction – Horizontal Resistive force during the shoe-surface interaction.
Player Performance - Traction
Performance - Players require sufficient traction to perform.
•Sprints.
Traction – Horizontal Resistive force during the shoe-surface interaction.
‘High traction characteristics are a necessary feature of shoe outsolesbecause they enhance the athletes ability to successfully run fast.’
Valiant 1990
Player Performance - Traction
Performance - Players require sufficient traction to perform.
•Sprints.
•Changes in Direction.
Traction – Horizontal Resistive force during the shoe-surface interaction.
‘Friction is necesarry for rapid starting, stopping, cutting and pivoting’
Inklaar 1994
Player Performance - Traction
Performance - Players require sufficient traction to perform.
•Sprints.
•Changes in Direction.
•Prevent Slipping.
Traction – Horizontal Resistive force during the shoe-surface interaction.
‘The forefoot pushoff movement is related to performance, where theplayer seeks sufficient traction to avoid slipping.'
Kirk 2007
Traction - Engineering Methods
FIFA Handbook:
•Pendulum test modified from a skid resistancetester.
•Peak deceleration, termed Stud DecelerationValue, is recorded.
•To meet the FIFA two star rating, its mean StudDeceleration Value over 5 tests must lie withinlimits of 3.0 g – 5.5 g
•The relevance of such a test is debatable.
Does it measure the traction a soccer player willexperience?
Traction - Engineering Methods
• Simulate game relevant loadingconditions.
• Portable design to measure on differentplaying surfaces and under variousweather conditions.
• Repeatability.• Adjustability of different load situations.
Mechanical test devices are required to understand the forces likely tobe experienced by stud-surface combinations
Grund et al, Technical UniversityMunich
Apply relevant forces
Apply relevant movements
Force-controlled Traction Rig
Pneumatic ram– forcecontrolleddisplacement
Hydraulic ram– normal force
Studdedplate
LDVT(displacement)
Horizontalandverticalload cells
•SERG Developed a device to measure traction.•Designed to simulate a push off movement.
Parameters –Vertical LoadingPlayers performed a push off into a sprintingmovement – when a player requires high traction.
-500
0
500
1000
1500
2000
2500
0.05 0.1 0.15 0.2 0.25 0.3 0.35
Time (s)
Fo
rce
(N)
Fx
Fy
Fz
Push Off
0
0.05
0.1
0.15
0.2
0.25
0.3
0.222 0.242 0.262 0.282 0.302 0.322
Fy/Fx
Fy/Fz
•Peak Fy/Fz = Player is most at risk of slipping duringpush off – after 0.3 seconds.
•After 0.3 seconds Fz = 350 N. This is an appropriatevertical force for mechanical tests simulating a pushoff movement.
FX
FZ
FY
Fy - High
Fz - Low
Direction of
stud motion
Direction of
player
Parameters - Movement
High Speed Video Analysis:
Small horizontal movement (~ 10 mm) between shoe and surfaceafter initial contact.
0
50
100
150
200
250
300
350
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Horizontal Displacement (mm)
Ho
rizo
nta
lF
orc
e(N
)
Surface B
Surface C
The Horizontal force after 10 mm displacement is measured.
Aim
Understand how stud design and surface properties affect
traction on 3G surfaces.
Surface A B C D
Fibre Material Polypropylene Polyethylene Polyethylene Polyethylene
Fibre Type Monofilament Monotape MonofilamentFibrilated fibre and a curly
fibre (to help hold infill)
Pile Height (mm) 35 40 5065 (fibrillated fibre)
(Also curly stabilising fibre)
No. of Tufts per m2 10600 25200 33600 33600
No. of Fibres per Tuft 12 18 8 2 (which then fibrillate)
Fibre Width (mm) 1.5 1.5 1.3 1 – 3
Fibre Thickness(mm)
0.025 0.025 0.026 0.026
Total Number of Fibres perm2 127200 453600 268800 67200*
Silica Sand0.2 – 0.7 mm
10 kg/m2 10 kg/m2 10 kg/m2 10 kg/m2
SBR Rubber Crumb0.5 – 1.5 mm
4 kg/m2 7 kg/m2 12 kg/m2 20 kg/m2
Aim
Understand how stud design and surface properties affect
traction on 3G surfaces.
The surfaces were tested with 13different bespoke stud designs -resulting in a total of 52 stud-surface combinations.
The 13 stud designs varied inlength, width, and conicity.
The studs were configured in a 5stud formation.
40 mm
30 mm
37 mm
29 mm
30 mm
92 mm
75 mm
Direction of Movement
Translational Traction - Performance
Friction due to the interaction between the outsole and the turf
Ploughing Traction due to the stud and plate clearing a path through the turf
Skin Friction due to the interaction of the stud material with the turf
Ploughing Traction (Fp)
Friction (μp)
Skin Friction (μs)
Normal Reaction Force(N)
The coefficients are dependant on the particular stud andsurface types.
Direction of stud motion
Key FindingsComparing the surfaces – significant differences:
D<A,B,Cp = .012, .005, .032
Traction D<A,B,Cp = 0, 0, .041
VerticalDisplacement
Key Findings
Surface DSurface C
Higher Traction Force Lower Traction ForceResults
Comparing the surfaces – significant differences:
D<A,B,Cp = .012, .005, .032
Traction D<A,B,Cp = 0, 0, .041
VerticalDisplacement
Key Findings
Surface D
Lower Infill
DensityHigher Fibre
Density
Surface Lower Fibre
Density
Higher Infill
DensityStabilisingfibres’
Higher PileHeight
Surface C
High Traction Force Low Traction ForceResults
Comparing the surfaces – significant differences:
D<A,B,Cp = .012, .005, .032
Traction D<A,B,Cp = 0, 0, .041
VerticalDisplacement
Key Findings
Surface D
Lower Infill
Density
Stud and Outsole Penetrates
Surface
Higher Fibre
Density
High Ploughing
Traction Friction
Surface
Hypothesis
Lower Fibre
Density
Higher Infill
DensityStabilisingfibres’
Higher PileHeight
Surface C
High Traction Force Low Traction ForceResults
Comparing the surfaces – significant differences:
D<A,B,Cp = .012, .005, .032
Traction D<A,B,Cp = 0, 0, .041
VerticalDisplacement
Key Findings
Surface D
Lower Infill
Density
Stud and Outsole Penetrates
Surface
Higher Fibre
Density
High Ploughing
Traction Friction
Surface
Hypothesis Stud Compresses
Infill and curlyfibres
Lower Fibre
Density
Lower Ploughing
Traction Friction
Higher Infill
DensityStabilisingfibres’
LowPenetration
Higher PileHeight
Surface C
High Traction Force Low Traction ForceResults
Comparing the surfaces – significant differences:
D<A,B,Cp = .012, .005, .032
Traction D<A,B,Cp = 0, 0, .041
VerticalDisplacement
Key Findings
Surface D
Lower Infill
Density
Stud and Outsole Penetrates
Surface
Higher Fibre
Density
High Ploughing
Traction Friction
Higher Traction
Surface
Hypothesis Stud Compresses
Infill and curlyfibres
Lower Fibre
Density
Lower Ploughing
Traction Friction
Lower Traction
Higher Infill
Density
Result
Stabilisingfibres’
LowPenetration
Higher PileHeight
Surface C
High Traction Force Low Traction ForceResults
Comparing the surfaces – significant differences:
D<A,B,Cp = .012, .005, .032
Traction D<A,B,Cp = 0, 0, .041
VerticalDisplacement
SummaryConclusions:
•Despite differences in make up (fibres, infill, etc) no significant differences intraction were found between surfaces A, B, and C.
•Significantly lower traction and vertical displacement was found with surfaceD.
•The stabilising fibres in surface D prevents stud penetration – this results inhigh skin friction forces but low ploughing traction.
Current / Future work:
•Benchmark Traction – what is considered acceptable traction.
•Effects of stud geometry – investigating the effects of individual stud-surfacecombinations.
Thank you
QUESTIONS??
Acknowledgments:
Bob Kirk
Conclusions
Linear relationships were found between stud penetration with stud length,width, and conicity.
The trend between stud width and traction force differed on different surfacemake ups.
It is possible for the traction performance of a stud to significantly differ fromsurface to surface.
More appropriate test methods and recommendations when assessing thesuitability of third generation artificial surfaces for use in soccer.
The stabilising fibres in surface D prevents stud penetration, resulting in lowertranslational traction.
RECOMMENDATIONS FOR FUTURE WORKtional area of the studs, and the friction between the surface and the stud edges and the general interaction between stud, fibre and infill. A controlled set of experiments could quantify these parameters for different surface and stud combinations.
Key Findings
0
2
4
6
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10
12
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16
18
20
L1 L2 L3 L4 L5
Stud Reference
Vert
ticalD
isp
lacem
en
t(m
m)
Outsole
Stud
Figure 5. Mean vertical displacement (± 95 %confidence limit) of studs and outsole plate at timeof initial movement for surface A with 350 N verticalforce applied.
Linear relationships were found between stud penetration with studlength, width, and conicity. The depth of penetration of a stud intoa third generation artificial surface is dependent on the make up ofthe surface, particularly the density of fibres and infill.
0
2
4
6
8
10
12
14
16
18
W1 W2 W3 W4 W5
Stud Reference
Vert
ticalD
isp
lacem
en
t(m
m)
Outsole
Stud
Figure 5. Mean vertical displacement (± 95 %confidence limit) of studs and outsole plate at timeof initial movement for surface A with 350 N verticalforce applied.
Parameters – Horizontalal Loading
• Force-control perhaps more relevant to manyfootball movements
• Ideal movement: Vhor = 0
– foot pushes against surface
• Surface failure
– performance lost (immediately)