薄膜润滑

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
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
– 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
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
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
-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
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
(e) 30v,18N,0s (f) 30v,18N,200s (g)30v,38N,0s
(h)30v38N,40s
Effect of electric voltage on TFL
3.5 Film with nanoparticles (1)
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?
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
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
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
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？
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
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)
3.4 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
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
200 180 160 140 120 100
80 60 40 20
0 0
TiO2 Cr
Ti
Al