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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
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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 Semi- reflective Surface Loading Mechanism Glass plate (connected to motor) Steel ball Fiberoptic Cable condenser Contact Area
Experimental Setup (cont’d) 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)
Experimental Procedure: obtain the following table for W=16N & W=30N computed from Nd, N computed from HD equation measured Theoretical Thickness, ht: The Hamrock & Dawson Equation t R: ball radius W*: dimensionless load parameter U*: dimensionless speed parameter G*: dimensionless material parameter
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 (11.2 - 3.2)
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