Tribology Lab

1
Tribology Lab
ME 4053

• Objectives Characterize elastohydrodynamic (EHD)
  lubrication using an optical technique. The
  study involves
• Measurement of the lubricating film thickness as
  a function of
• rolling velocity
• normal load
• Comparison of the measured film thickness with a
  theoretical film thickness (from the Hamrock
  Dawson equation)
• Experimental Setup (DO NOT COPY THESE)

Light Source
2
Experimental Setup (contd)
Camera
Light Beam
side view
top view
Nd
glass disc
u
oil film
rc
Fringe pattern
h
W(load)
Nd rpm u rolling velocity h film thickness
Rolling velocity
Measured oil film thickness
, where
exp
? wavelength of light in air (600nm) N fringe
order n refractive index of oil (1.5) ??
phase shift constant (0.1)
3
Experimental Procedure obtain the following
table for W16N W30N
measured
computed from Nd, N
computed from HD equation
Theoretical Thickness, hp The Hamrock Dawson
Equation
p
R ball radius W dimensionless load
parameter U dimensionless speed parameter G
dimensionless material parameter
4
Results Presentation
Theoretical/Experimental Comparison
Practical note on load adjustment
Load 2 x (spring value - tare value)
(tare 3.2N)
Ex to get W16N, set spring value to 11.2N 16
2 x (11.2 - 3.2)
5
Reporting Requirements

• Notebook entry only
• Must have objective, setup, procedure, per usual.
  Be sure to have plot of results similar in
  format to what is shown on previous slide
• Provide conclusions. Be sure to address how well
  experimental results match theoretical and
  explain relationship between normal load,
  rolling velocity, and film thickness

6
Equation Parameters

• Rrb12.7 mm
• Rc63 mm
• hoil0.304 Pa-sec
• a25.4 E 9 m2/N
• E120 E 9 N/m2