薄膜润滑

0.3
0v
0.2
10v
20v 30v 40v
0v
10 mm/s
0.1
0.0 0
0.3
0.2
200 400 600 800 1000 1200 1400 1600 1800 2000 2.5 mm/s
0.1
0.0 0
0.3
200 400 600 800 1000 1200 1400 1600 1800 2000 0.5 mm/s
100
h/nm
10
Pressure: 297 MPa
base oil
added with 0.05% UDP
added with 0.3% UDP
added with 0.5% UDP
1
0.1
1
10
100
v/mm/s
Effect of UDP concentration on film thickness
200 180 160 140 120 100
80 60 40 20
0 0
TiO2 Cr
Ti
Al
10
20
30
40
50
Film thickness (nm)
3.4 TFL under external electric field
h/n m
20
18
16
14
12
10
8
6
13604+5% oleic acid
4
2
13604+1% dodecanoic acid
0 0
5000
10000
U/mv
15000
Film thickness v.s. voltage
3.5 Film with nanoparticles (2)
0.20
PEG
0.15
PEG+0.5%UDP
0Βιβλιοθήκη Baidu10
0.05
0.00 0
PEG+0.1%UDP
PEG+0.3%UDP
1000 2000 3000 4000 5000 6000
t/s
Time effect of UDP concentration on friction force
Snow ball
3.3 Film thickness with substrates
Film thickness(nm)
100
10
1 0.1
EHL TFL
1
10
Speed (mm/s)
Al Cr Ti TiO2
100
Lubricant: 13604, Load: 4 N, Temperature: 25C
Running time: 1 min
40
Speed: 3.12 mm/s Running time: 40 min
20
a
0
-100
-50
0
50
100
Position (m)
Film in cross section of Hertz region Lubricant: Paraffin liquid, Load: Temperature: 30ºC, Ball: 23.5 mm
-50
0
50
Position /m
100
150
Film thickness in the central cross-section Lubricant: mineral oil with viscosity of 36 mPa.s at 20C Temperature: 25 C, Diameter of ball: 20 mm, Load: 6.05 N
– Israelachvili’s group (USA) – Granick’s group (USA)
Calculation in TFL – Tichy, Thompson, Robbins, Hu, Popov, et al.
2. Testing technology (1)
Schematic of NGY-2
Thin film lubrication and mixed lubrication in nano scale
LUO Jianbin
State Key Laboratory of Tribology Tsinghua University, Beijing, China
Contents
1. Introduction 2. Testing technology 3. Properties of thin film lubrication (TFL) 4. Failure of fluid films 5. Lubrication model & map 6. Contact ratio in nano-mixed lubrication 7. Conclusion
1. Introduction (3)
Experiment on Thin film lubrication (TFL) – Spikes’s group (UK) – Wen and Luo’s group (SKLT, TU, China) – Hartal’s group (Czechoslovakia)
3.1 Film thickness v.s. parameters
1000
Film thickness (nm)
100
10 1
Polyplycol oil 1, 47 mm2/s Polyplycol oil 2, 145 mm2/s Polyplycol oil 3, 329 mm2/s Polyplycol oil 4, 674 mm2/s Polyplycol oil 5, 1530 mm2/s
3.2 Effect of time
Film thickness (nm)
60 50 40 30 20 10
0 0
A B C
20
40
60
80
100
120
Time (min)
A: Decane+3% Palmitic, Load: 4 N, T=30C, v=0 mm/s B: Decane+3% Palmitic, Load: 4 N, T=30C, v=3.12 mm/s C: White oil, Load: 20 N, T=20 C, v= 54.5 mm/s
Main Qualifications:
Measure range: 0 ~ 500 nm Vertical resolution: 0.5 nm Horizontal resolution: 1 m Velocity: 0.2~1900 mm/s Friction force resolution: 0.1 mN Temperature range: ~ 120°C
What’s the relationship between such regime and EHL or Boundary lubrication?
1. Introduction (2)
1.3 Jost’s questions (Tribology 2000): ➢ What’s the definition of boundary lubrication?
(e) 30v,18N,0s (f) 30v,18N,200s (g)30v,38N,0s
(h)30v,38N,200s
(i) 40v,38N,0s
(j) 40v,38N,40s
Effect of electric voltage on TFL
3.5 Film with nanoparticles (1)
7. Mandril
Friction coefficient Effective viscosity (mPas)
0.30 0.25 0.20 0.15 0.10 0.05 0.00
0
Al
Cr
Tio2 Ti
50
100
150
sliding speed (mm/s)
Friction with different substrates Lubrication: paraffin liquid; Load: 2N
1.4 Granick’s questions (Science, 1991) ➢What determines the effective viscosity of such ultrathin film? ➢What makes the film change into solid state from liquid when it is enough thin? ➢Why dose the solid film can endue a continuous sliding？
1. Introduction (1)
1.1 What’s Thin film lubrication (TFL)?
HDL(1886)
EHL(1950s) ？ Boundary
Lurication(1921)
Dry slide (Coulomb,1785)
1.2 My questions: What’s the state of the region？ What’s its lubrication mechanism?
2. Testing technology (2)
Resolution of film thoickness /nm Resolution of film thoickness /nm
1.0
=700 nm
0.8
=600 nm
=450 nm
0.6
0.4
0.2
0.0
20
40
60
80
100 120 140 160 180
0.2
0.1
0.0 0
200 400 600 800 1000 1200 1400 1600 1800 2000
t/s
Friction coefficient v.s. velocity
(a) 30v,4N,0s (b) 30v,4N,200s (c)30v,8N,0s
(d)30v,8N,200s
Optical intensity
1.0
0.8
n=1.5
n=1.47
n=1.4
0.6
0.4
0.2
0.0
20
40
60
80
100 120 140 160 180
Optical intensity
(a) Different wavelengths
(b) Different refractive indexes
Resolution of film thickness v.s. optical interference intensity
膜厚 nm
-40-30-20-10 Y
0 10 μm
20
30
40
0
20 40
60 80 100
120 140 160 180 200 -30-20-入10口x 0—μ1—0m>20出3口0
Film thickness in contact region a-b-c-d
3. TFL properties
3.1 Film thickness v.s. influencing factors 3.2 Film thickness v.s. solid surface energy 3.3 Effect of running time on TFL 3.4 Effect of external electric field on TFL 3.5 Effect of nano-particles on TFL 3.6 TFL viscosity
10
100
1000
Speed (mm/s)
Film thickness v.s. viscosity and speed
Film thickness curve
Film thickness /nm
100 80 60 40 20 0 -150
-100
Static state v=4.7 mm/s v=10.1 mm/s v=12.4 mm/s
（a）White oil+0.5%UDP
（b）White oil
SEM photos of ball surface
Load: 4 N，Running time: 30 min
3.6 Effective viscosity of TFL (1)
Floating device for friction measurement 1. Carrier of strain gauge；2. Strain gauge； 3. Beam; 4. Plank；5. Steel ball；6. Oil cup;
Film thickness curve
Film thickness (nm)
80
60
Rolling speed: 3.12 mm/s
Running time: 40 min
40
Speed:18.6 mm/s Running time: 1 min
20
b
80
60
Rolling speed: 18.6 mm/s