2nd semester 2012-2013 - 2nd and 3rd lecture - journal bearings and lubrication

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2nd and 3rd Lecture of Machine Elements 2

Ardi Noerpamoengkas, ST

Lubrications

Lubricants Classifications

Lubrications Functions

Forms of Lubrications

Types of Journal Bearings

Journal Bearings and Lubrication FormulationsFormulations

Lubrications Methods

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Liquid lubricants

Semi-liquid lubricants

Solid lubricants


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Lubrications Functions

Reducing wear

Reducing power losses

Carrying chips from metal erosion process

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Forms of Lubrications

Hydrodynamic lubrication

Hydrostatic lubrication

Elastohydrodynamic lubrication

Boundary lubrication

Solid-film lubrication

Types of Journal Bearings

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Journal Bearings and Lubrication Formulations Radial clearance (c)

Absolute viscosity (μ)

Kinematic viscosity (v)

Absolute viscosity at Test Temperature (Z)

Viscosity Index (%) Viscosity Index (%)

Frictional torque (Tf)

Load per projected area of journal (P)

Journal Bearings and Lubrication Formulations Bearing characteristic number (S’)

Heat lost (H)

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Journal Bearings and Lubrication Formulations Radial clearance (c)

c = rb – rj

rb = radius of bearing

rj = radius of journal

Look at Fig 8 3 Look at Fig 8.3.

Journal Bearings and Lubrication Formulations Absolute viscosity/dynamic viscosity (μ)

reyn (English Sys), poise (Metric Sys)

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Journal Bearings and Lubrication Formulations Kinematic viscosity (v)

v = kinematic viscosity (stokes)

absolute viscosity (poise) μ = absolute viscosity (poise)

ρ = mass density (kg/m3)

Journal Bearings and Lubrication Formulations Absolute viscosity at test temperature

(Z) in cp(Z) in cp

S = Saybolt Universal Seconds S = Saybolt Universal Seconds

ρt = Specific gravity at test temperature

ρt = Spesific grafity at 60 deg Fahrenheit

t = Test temperature (deg F)

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Journal Bearings and Lubrication Formulations Viscosity Index (%)

L = Visc. of standard 0% VI at 100 F

H = Visc of standard 100% VI at 100 F H = Visc. of standard 100% VI at 100 F

U = Visc. of unknown VI at 100 F

Look at Table 8.1.

Journal Bearings and Lubrication Formulations Frictional torque (Tf)

Tf = Frictional torque (lb.in) μ = Absolute viscosity (reyns) L L th f b i (i ) L = Length of bearing (in) r = Journal radius (in) n = journal speed (rpm) h = radial clearance (in)

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Journal Bearings and Lubrication Formulations Load per projected area of journal (P)

W = Journal load (lb)

r = Radius of journal (in) rj = Radius of journal (in)

L = Length of journal (in)


n‘ = relative speed between journal and bearing (rps)bearing (rps)

P = Load per projected area of journal (psi)

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n‘ = relative speed between journal and bearing (rps)bearing (rps)

P = Load per projected area of journal (psi)

Journal Bearings and Lubrication Formulations Viscosity-temperature chart for SAE

numbered oils (Fig 8 13 )numbered oils (Fig 8.13.)

Pressure variation around journal bearing (Fig 8.14.)

Minimum film thickness variable (Fig 8.15.)

Friction coefficient variable (Fig 8.16.)

Lubricant flow variable (Fig 8.17.)

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Journal Bearings and Lubrication Formulations Flow ratio (Fig 8.18)

Temperature rise variable (Fig 8.19.)

Journal Bearings and Lubrication Formulations Heat lost (H) in BTU/hr

C = heat transfer coefficient (BTU/(hr.ft2.F))

A = effective heat transfer area (ft2) A = effective heat transfer area (ft2)

tb = bearing housing temperature (deg F)

ta = ambient air temperature (deg F)

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Lubrications Methods

Wick-feed oiler

Drop-feed oiler

Ring-oiled

Splash-system oiled

Pump oiled / pressure fed systems

Literation References

Deutschmann. 1975. Machine Design, theory and practice Macmillantheory and practice. Macmillan Publishing Co., Inc.

Lansdown. Standard Handbook of Machine Design. McGraw-Hill

Budynas-Nisbett. Shigley’s Mechanical Engineering Design. McGraw-Hill

2nd semester 2012-2013 - 2nd and 3rd lecture - journal bearings and lubrication

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