1. R. Ahmed Heriot-Watt University United Kingdom
An Analysis of Micro-Plasto-Hydrodynamic Lubrication Using a Strip Drawing Rig
R. Ahmed
Heriot-Watt University
United Kingdom
M. P. F. Sutcliffe
Cambridge University
United Kingdom
Industrial Collaborator(s)
Corus / Avesta Sheffield, UK

2. STRUCTURE of PRESENTATION
Context of the Problem
Experimental Analysis
Mathematical Modelling
Results
Conclusions

3. CONTEXT OF THE PROBLEM - Lubrication Mechanisms
Lubrication Regime dictates the tribology and hence the functional requirements such as surface gloss.
Hydrodynamic oil entrainment at the inlet to the bite and expulsion of entrapped oil in isolated pits due to relative sliding (MPHL).
Reduced rolling speeds and high scrap rate plague productivity.

4. SEM OBSERVATIONS (Shot blasted Surface)
Lubricant Entrapment

5. SEM OBSERVATIONS (Micropits and grain Boundaries)

6. Schematic of inlet and MPHL Lubrication Mechanisms
Strip
Roll
Oil drawn out of pit due to MPHL action
Oil drawn at the inlet due to entrainment action
Sliding of roll
relative to strip

7. STRIP DRAWING RIG Indentation Ram Drawing Ram Shackle Die
Specimen Strip
Die Holder

8. Direction of sliding of workpiece
MPHL Model p 
Rigid tool
Lubricant
Pressure exerted by trapped lubricant
Normal Load
Direction of sliding of workpiece
of workpiece
Micro-plasto-hydrodynamic lubrication
Flow of lubricant
Schematic of micro-plasto-hydrodynamic lubrication.
Sliding
P*= Average pressure
Oil
AoLo Lo L 
Tool

9. AFM PLOT (pit geometry)
AFM measurement to reveal geometry of remnant pits
(1 = 10o ; 2 = 20o ; 3 = 7o ; 4 = 17o ; 5 = 25o)

10. OPTICAL COMPARISON (Rolling and Strip Drawing)
Cold Rolling

11. SCHEMATIC OF STRIP INDENTATIONS
Vickers indentations
Micro-Vickers indentations
Knoop indentations
Brinell indentations
25 mm
2 mm
45o

12. Pit Behaviour Through Bite During Strip Drawing

13. RESULTS
(a)Sliding distance (cm)
Area ratio and film thickness for pit angle of 35 degree, V-68 oil
(Ao=0.5; Lo=300m; *=0.7; u=16 m/s; B=0.0219; C=1.99E-06
(b)Sliding distance (cm)

14. CONCLUSIONS
Hydrostatic pressure build-up in the entrapped oil can significantly reduce sheet conformance.
A transition from hydrostatic to hydrodynamic conditions caused by sliding in the bite can assist elimination of individual pits. This may cause problems in sheet conformance in an area around the pits due to oil extrusion.
Pit angle, spacing and depth can have a significant effect on the MPHL and consequently on the evolution of surface.