## GATE ME solved Questions on Design of Rolling and Sliding contact Bearings(Machine Design)

**Question #1**

A self-aligning ball bearing has a basic dynamic load rating ( $C_{10}$ for $10^6$ revolutions) of 35 kN. If the equivalent radial load on the bearing is 45 kN, the expected life (in revolutions) is

(A) below 0.5

(B) 0.5 to 0.8

(C) 0.8 to 1.0

(D) above 1.0

**[GATE 2018 Set 1, 2 marks]**

**Answer: (A) **

expected life of ball bearing at load P is given by,

$L=\left (\frac{C}{P} \right )^3$

$L=\left (\frac{35}{45} \right )^3$

$L=0.47$ million revolutions …..(Answer)

**Question #2**

Which of the bearings given below SHOULD NOT be subjected to a thrust load?

(A) Deep groove ball bearing

(B) Angular contact ball bearing

(C) Cylindrical (straight) roller bearing

(D) Single row tapered roller bearing

**[GATE 2016 Set 3, 1 mark]**

**Question #3**

For ball bearings, the fatigue life L measured in number of revolutions and the radial load F are related by 𝐹𝐿^{1/3}=𝐾, where K is a constant. It withstands a radial load of 2 kN for a life of 540 million revolutions. The load (in kN) for a life of one million revolutions is ________

**[GATE 2015 Set 3, 2 marks**]

**Question #4**

Ball bearings are rated by a manufacturer for a life of 10^{6} revolutions. The catalogue rating of a particular bearing is 16 kN. If the design load is 2 kN, the life of the bearing will be P × 10^{6} revolutions, where P is equal to _______

**[GATE 2014 Set 4, 1 mark]**

**Question #5**

Two identical ball bearings P and Q are operating at loads 30 kN and 45 kN respectively. The ratio of the life of bearing P to the life of bearing Q is

(A) 81/16

(B) 27/8

(C) 9/4

(D) 3/2

**[GATE 2011, 2 marks]**

**Question #6**

A ball bearing operating at a load F has 8000 hours of life. The life of the bearing, in hours, when the load is doubled to 2F is ____

**[GATE 2007, 2 marks]**

**Question #7**

The life of a ball bearing at a load of 10 kN is 8000 hours.Its life in hours , if the load is increased to 20 kN, keeping all the conditions same, is

(A) 4000

(B) 2000

(C) 1000

(D) 500

**[GATE 2000, 2 marks]**

**Question #8**

A hydrodynamic journal bearing is subject to 2000 N load at a rotational speed of 2000 rpm. Both bearing bore diameter and length are 40 mm. If radial clearance is $2\mu m$ and bearing is lubricated with an oil having viscosity 0.03 Pa-s, the Sommerfeld number of the bearing is _______

**[GATE 2014 Set 1, 2 marks]**

**Question #9**

A journal bearing has a shaft diameter of 40 mm and a length of 40 mm. The shaft is rotating at 20 rad/s and the viscosity of the lubricant is 20 mPa-s. The clearance is 0.020mm. The loss of torque due to the viscosity of the lubricant is approximately.

(A) 0.040 Nm

(B) 0.252 Nm

(C) 0.400 Nm

(D) 0.652 Nm

**[GATE 2008, 2 marks]**

**Question #10**

A natural feed journal bearing of diameter 50 mm and length 50 mm operating at

20 revolution/s and carries a load of 2 kN. The viscosity of the lubricant is 20 mPa-s,

the radial clearance is 50 μm. The Sommerfield number for the bearing is

(A) 0.062

(B) 0.125

(C) 0.250

(D) 0.785

**[GATE 2007, 2 marks]**

**Question #11**

Which one of the following is a criterion in the design of hydrodynamic journal bearings?

(A) Sommerfeld number

(B) Rating life

(C) Specific dynamic capacity

(D) Rotation factor

**[GATE 2005, 1 mark]**

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