Society of Plastics Engineers Europe - VeMet · Society of Plastics Engineers Europe...
Transcript of Society of Plastics Engineers Europe - VeMet · Society of Plastics Engineers Europe...
Wrijving en slijtage van kunststofproducten
Jan Spoormaker
Spoormaker-Consultancy in
Reliability and Liability of
Plastic Products
Society of Plastics Engineers Europe
Tribologie/polymeren
Friction and wear of plastic products
Spoormaker Consultancy in Reliability & Liability of Plastic Products
Dictaat Hfdst. 3 tekst
Friction
Friction is a force that resist relative movements between two surfaces in contact.
Wear
Wear is a process in which interaction of surface(s) or bounding face(s) of a solid with
the working environment results in the dimensional loss of the solid, with loss of
material.
Friction and wear are system properties
Tribology
Science about friction, lubrication and wear
Tribotechnology
Engineering application of tribology
Tribological System according to Czichos
Spoormaker Consultancy in Reliability & Liability of Plastic Products
Relative movement
Gliding, rolling
Load Fn
Velocity v
Ambient temperature
Friction force Fw
Friction coefficient f, μ
Wear h
Friction temperature
Noise
Loads &
environment
Loads &
environment
Tribological
quantities
Surface parameters
Roughness
Macro geometry
1. Body
2. Body
3. Substance
4. Environment
Dictaat Hfdst. 3 Fig. 3.1
- polymerisatie
- ketenopbouw en ketenlengte
- fysische eigenschappen
- kristallisatie
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Polymeren
Plastics are fantastic, they can fail in many
unexpected ways
Polymeriseren en ketenlengte
additiepolymerisatie
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Polymeriseren van etheen C2H4 PE
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Polymeriseren van etheen C2H4 PE
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onvertakt
vertakt
Ketenlengte
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Dictaat Hfdst. 3 Fig. 3.1
Ketenlengte
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Dictaat Hfdst. 3 Fig. 3.1
Ketenlengte van PE
Paraffine (500 g/mol ) lijmtube (105 g/mol) UHMW-PE (5.106 g/mol)
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Molecuulmassa - sterkte en viscositeit
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Amorf en semi-kristallijn
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tie-molecule
Kristallisatiesnelheid
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wrijving
slijtage
contactoppervlak
vervorming
cohesie en adhesie
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Pwrijving en slijtage bij kunststoffen
Normal force, drag force and friction force
Spoormaker Consultancy in Reliability & Liability of Plastic Products
Material combination μ, f
PA6 - PA6 (no lubrication)
1.20
PA6 – POM (no lubrication)
0.60
PA6 – PTFE (no lubrication)
0.10
POM – POM (no lubrication)
0.55Dictaat Hfdst. 3 Fig. 3.3
Wear
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Material combination wear factor k
POM – steel (Ra = 0.1 μm) 2 10-15 m2/N
POM – steel (Ra = 0.6 μm) 80 10-15 m2/N
h k p v t
Dictaat Hfdst. 3 Fig. 3.4
Micro contact surface
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Dictaat Hfdst. 3 Fig. 3.5
Deformation
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Dictaat Hfdst. 3 Fig. 3.6
Physical processes cohesion and adhesion
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Bonding forces
Cohesion
Adhesion ----------
Dictaat Hfdst. 3 Fig. 3.9
ruwheid
snelheid
stick-slip effect
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Wrijving bij kunststoffen
Friction coeeficient as a function of roughness
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High yield strength Low yield strength
Surface roughness Surface roughness
Dictaat Hfdst. 3 Fig. 3.10
Friction coefficient as a function of roughness for
POM and HDPE
Spoormaker Consultancy in Reliability & Liability of Plastic Products
Roughness Ra (μm) Roughness Ra (μm)
Dictaat Hfdst. 3 Fig. 3.11
Friction coefficient as a function of speed
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Speed
Dictaat Hfdst. 3 Fig. 3.12
Mass-spring model
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Dictaat Hfdst. 3 Fig. 3.13
Stick-slip effect
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time
Dictaat Hfdst. 3 Fig. 3.14
deformatie
adhesieve slijtage
abrasieve slijtage
pitting
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slijtage bij kunststoffen
Boundary and deformation zone
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• Boundary zone
• Deformation zone
Hard roughness
asperity top
Dictaat Hfdst. 3 Fig. 3.15
Adhesive wear
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Dictaat Hfdst. 3 Fig. 3.16
Abrasive wear
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Dictaat Hfdst. 3 Fig. 3.17
Shear stress for rolling contact
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Dictaat Hfdst. 3 Fig. 3.18
Pitching as a result of fatigue
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Fatigue cracks Pitting
Dictaat Hfdst. 3 Fig. 3.19
Knieprothese
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Knieprothese
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Putvorming in UHMPE
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slijtage – ruwheid
meten van slijtage
vlaktedruk – pv waarde
warmte-ontwikkeling
PTFE
Hardheid
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Lagers
Wear as a function of roughness for POM and HDPE
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Dictaat Hfdst. 3 Fig. 3.20
Wear as a function of roughness and pressure for PA6.6
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Dictaat Hfdst. 3 Fig. 3.21
Wear as a function of pressure
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Dictaat Hfdst. 3 Fig. 3.22
Different wear tests
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Dictaat Hfdst. 3 Fig. 3.23
Pin on disk
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Dictaat Hfdst. 3 Fig. 3.24
Calculation of average bearing pressure and wear
Spoormaker Consultancy in Reliability & Liability of Plastic Products
p 43MPa
h k p v t
FT D
p
Extra
Heat flux and Average Bearing Pressure
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2(W/m )h f p v
- heat flux
f – friction coeficient
p – average bearing presure
v - velocity
Dictaat Hfdst. 3 tekst
Critical pv-values
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Dictaat Hfdst. 3 Fig. 3.25
Prediction of wear
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h k p v t
k – wear factor
p – average bearing presure
v – velocity
t - time
Dictaat Hfdst. 3 tekst
Coefficients of friction and wear rates
Spoormaker Consultancy in Reliability & Liability of Plastic Products
1 1h k p v t 2 2h k p v t
Extra
Effect of PTFE content on wear
Spoormaker Consultancy in Reliability & Liability of Plastic Products
Extra
PTFE & silicone to reduce friction and wear
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Extra LNP Lubricomp
Effect of hardness on wear
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Extra LNP Lubricomp
Effect of shaft finish on wear (micro-inches!)
Spoormaker Consultancy in Reliability & Liability of Plastic Products
Extra LNP Lubricomp
warmte-ontwikkeling
vermoeiing
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Tandwielen
Failure analysis
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Extra
Failure analysis
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Extra
Guidelines for plastic bearings
Spoormaker Consultancy in Reliability & Liability of Plastic Products
• Metal bearing surfaces must be smooth (< 1 μm), hard and corrosion
resistant.
• Wear particles must be collected in grooves.
• Bearing clearance must account for high thermal expansion and absorption
of water (PA)
• The average bearing pressure should preferably be not higher than 1 N/mm2
and at most 5 N/mm2.
• The out-of-roundness of bearings should be as small as possible and film
gates are preferred.
• Bearing plastics with PTFE are preferred especially for applications without
lubrication.
• Boundary lubrication is must better than running dry.
• Grease or oil can affect plastic bearings (swelling & ESC)
Dictaat Hfdst. 3 tekst