University of Mumbai 2008-3rd Sem M.E Mechanical Engineering Tribology - - Question Paper

VMM

V ( <>** r ),x non- ^rr?T *y\l C 0'*^a4-¹    nt:5PK ^pi

al.l -/

-TV V90 'f'>y .    .

BB-8772

(4 Hours)    {Total Marks : 100

N,B.: (1)    Question No. 1 Is compudsory-

(2)    Attempt arty four questions out of remaining stx (questions.

(3)    Assume necessary data, if required, wfth proper justifications.

(4)    Figures to the right indicate fufi marks.

(5)    Use of standard databooks and certified charts is permissible.

1.    Write short notes on any four of foe foBowing

(a)    Viscosity and its measurement.

(b)    Generalised, three dimensional Reynold's equation, significance of each tern and applications of Reynold's equation.

(c)    Stick slip phenomenon.

(d)    Preloadihg of rolling contact bearings.

(el Ploughing theory of friction,

(f) Solid lubricants.

2.    (a) Define static and dynamic load capacities of a rotting contact bearing and explain

their sigmfice in the selection of bearings.

A single row b&M bearing has to be selected for a 46 inm shaft subjected to a ladiaS load 3 kN. and ia thrust load 2 kN at shaft speed of 600 RPM. Bearing is subjected to irtHd shock, inner race only rotates and the life required Is 12000 hrs. Select a suitable bearing.

A cylindrical roter bearing is subjected to4o#owing loading cycle repealed continuous.y.

(b)

Sr. No.	Radial load (kN)	Speed <RPH)	Running time secs.
1.	5	1200	6
2.	10	1500	3
a	12	700	4
4.	15	600	2

Find the expected hfe of tho bearing in hours and in miRtons of revolutions. il the dynamic capacity is 56 kN    _>    ,

Describe the kings btiry*s electrical analogy method for measurement of pressures developed in a hydrodynarnicafly ktiricated bearwig.

Design a hydrodynamicatty lubricated journal bearing to support a radial load ol 25 kN for a steam twtane shaft operating at 12000 RPM Show the thermal balance of the bearing and determine operating parameters tike oil temperature, viscosity, flow rate, coefficient of friction, friction power loss, maxaniun pressure etc. assuming it to be self contained baring.    *

Con. 5914*-8B-8772-07.     2

M\L(ltohir>I 21/0 Sr / in hrvtojfj' tltld*

4.    (a) Describe the constructional features and principle of operation of a hydrostatic thrust ft

bearing. Explain the use of compensators and their functions. State and compare different types of compensators used.

(b) Making suitable assumptions design-an externally pressurised thrust bearing to 12 support a thrust toad o*45JkN wfth shaft rotating at 360 RPM. The bearing is fed from a manifold pressure of 50 bar through a capitay coenpensator, fiim thickness is 140 microns, ofi viscosity 32 CP. density 0-86 and specific heat 1 /6 kJ/kg *C Calculate bearing inlet pressure, oil flow rate, friction powftr io*s. pump power and bearing stiffness. Afeo cafctrfato fie rise * temperature of oi from manifold temperature to the temperature ol oi at the outfit of the bearing.

5.    (a) Describe oil lift in hydrostatic bearing.    20 (b) The following data is given for a hydrostatic thrust bearing (hydrostatic thrust

bearing) :

0)	Shaft speed of hydrostatic thiust bearing	JB	1000 RPM
()	Supply pressure	s	6 MPA
(iii)	Film thickness	C	0-2 mm
(>v>	Specific heat of lubricant		1-75 kJkg,
(V)	Shaft diameter	-	500 mm
(Vi)	Recess diameter	s	250 mW
(vii)	Viscosity of lubricant		30 CP
fviii)	Specific gravity of tabricant	S	0-0

Calculate its foad capacity, flow requirements t mnrrVsec, frictional power loss, pumping power toss. h*l power loss and temperature rise. Assume the total power loss is conwrted into frictional loss.

6. (a) Discuss the various theonss of friction.    2P

(b) Define wear. Describe adhesive wear in brief.

7. (a) Write the merits and demerits of hydrostatic bearing.    20

(b) Discuss the rote played by additives in enhancing the properties of lubricants

Attachment: university-of-mumbai-2008-m-e-mechanical-engineering-51626-1.pdf

Earning:   Approval pending.