INDEPENDENT OF THE PRESSURE WHICH OF THE STATEMENTS GIVEN ABOVE ARE...

4. Independent of the pressure

Which of the statements given above are correct?

(a) 1, 2, 3 and 4

(b) 1 and 4 only

(c) 2, 3 and 4 only

(d) 2 and 3 only

μπ

2

2

DN

NL

DL

D

μπ

_×

π

₌

IES-36 Ans. (a) Viscous resistance (F) = T

×

Area =

60

t

IES-37. The bearing characteristic number in a hydrodynamic bearing depends on

(a) Length, width and load

(b) length, width and speed. [IES-1996]

(c) Viscosity, speed and load

(d) viscosity, speed and bearing pressure.

IES-37Ans. (d)

IES-38.

It is seen from the curve that there is a minimum value of the coefficient of

friction (μ) for a particular value of the Bearing Characteristic Number

denoted by α. What is this value of the Bearing Characteristic Number

called?

[IES-2004]

(a) McKee Number

(b) Reynolds Number

(c) Bearing Modulus

(d) Somerfield Number

IES-38Ans. (c)

IES-39. Assertion (A):

In equilibrium position, the journal inside a journal bearing

remains floating on the oil film.

[IES-1995]

Reason (R): In a journal bearing, the load on the bearing is perpendicular to the

axis of the journal.

(a) Both A and R are individually true and R is the correct explanation of A

(b) Both A and R are individually true but R is not the correct explanation of A

(c) A is true but R is false

(d) A is false but R is true

IES-39Ans. (b) Both A and R are true but R is not correct explanation for A.

IES-40.A full journal bearing having clearance to radius ratio of 1/100, using a

lubricant with

μ=28×10 Pa s

^-3

supports the shaft journal running at N = 2400

r.p.m. If bearing pressure is 1.4 MPa, the Somerfield number is [IES-2001]

(a)

8×10

^-3

(b)

8×10

^-5

(c)

0.48

(d)

0.48×10

μ

⎛ ⎞

IES-40Ans. (a)

=

⎜ ⎟

⎝ ⎠

N

s

r

s

p

c

IES-41.

A sliding contact bearing is operating under stable condition. The

pressure developed in oil film is p when the journal rotates at N r.p.m. The

dynamic viscosity of lubricant is μ and effective coefficient of friction

between bearing and journal of diameter D is f. Which one of the following

statements is correct for the bearing?

[IES-2001]

(a) f is directly proportional to μ and p

(b) f is directly proportional to μ and N

(c) f is inversely proportional to p and f)

(d) f is directly proportional to μ and inversely proportional to N

π

μ

^{⎛ ⎞}

=

⎜ ⎟

⎝ ⎠

+ →

IES-41Ans. (b) Petroff’s law

2

²

n

^s

r

0.002

f

k

P

c

IES-42. Which one of the following sets of parameters should be monitored for

determining safe operation of journal bearing?

[IES-2000]

(a) Oil pressure, bearing metal temperature and bearing vibration

(b) Bearing vibration, oil pressure and speed of shaft

Design of Bearings

S K Mondal’s

Chapter 4

(c) Bearing metal temperature and oil pressure

(d) Oil pressure and bearing vibration

IES-42Ans. (a)

IES-43. Consider the following pairs of types of bearings and applications: