1. ME 4053
Tribology Lab
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:
Light Source:
Camera
Monitor
Camera
Light
Source Nd
aperture
Loading
Mechanism
Semi-
reflective
Surface
Glass plate (connected
to motor)
Steel ball
Fiberoptic
Cable
condenser
Contact Area

2. Experimental Setup (cont’d)
Camera
top view:
side view:
Light
Beam 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. Theoretical Thickness, ht: The Hamrock & Dawson Equation
Experimental Procedure: obtain the following table for W=16N & W=30N
measured
computed from Nd, N
computed from
HD equation
Theoretical Thickness, ht: The Hamrock & Dawson Equation t
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 W=16N, set spring value to 11.2N
16 = 2 x ( )

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