**Pune University Previous Question Papers Metal Working Tribology **

Time: 3 Hours] [Max. Marks :100

Instructions to the candidates:

** 1) **Answer one question from each Unit in Section -1 and Section – II.

** 2) **Answers to the two sections should be written in separate answer books.

** 3) **Figures to the right indicate full marks.

** 4) **Assume suitable data, if necessary.

SECTION – I Unit – I

Q1) a) What are the measurement systems of surface roughness. [6]

b) Define a tribo-system and how do you monitor its functions. [10]

OR

Q2) a) Explain the structure of a tribo-system. [6]

b) How do you characterize a surface. [10]

Unit – II

Q3) a) What are the sliding friction mechanisms? [8]

b) Derive a modified Bowden and Tabor friction equation. [10]

OR

Q4) a) Derive friction equation involving hard material. [8]

b) Explain ‘Pin-on-Disc’ method of friction measurement. [10]

Unit – III

Q5) a) Enumerate different types of wear. [6]

b) Derive wear equation for hard material over a soft material in sliding.

[10]

OR

Q6) a) Derive ‘Archard’ equation of wear. [10]

b) Discuss the parameters affecting wear and how do you prevent them.

SECTION – II

Unit – IV

Q7) a) Discuss different types of lubricant used in industries. [4]

b) What is meant by ‘Viscosity Index’ of lubricant. [4]

c) Describe some methods of applying lubrication to the system. [8]

OR

Q8) a) With figure explain in detail mode of lubrication. [12]

b) What are the properties required in lubricants? [4]

Unit – V

Q9) a) Derive the equation for hydrodynamic lubrication [12]

dp h – h\— = [——] dx h(all having usual symbols) b) Derive ‘Petroff’ equation involving concentric earing. [6]

OR

Q10)a) Derive an equation for circular step bearing under hydrostatic lubrication.

[10]

b) Find out leakage in litres/min through a shaft of 25mm9 which is running concentric to sleeve of 25.03 mm 9, 25mm length using water under pressure of 5 bar. [8]

Unit – VI

Q11)a) Derive an equation for two circular plates approaching each other involving squeeze film operation. [10]

b) Two circular plates of 125 mm 9 approaching each other with velocity of 12.5 cm/s in liquid of ^ = 0.035 Pas. Find out pressure, load and time for film thickness to come down from 0.25 mm to 0.005 mm. [6]

OR

Q12)a) Derive squeeze film equation for rectangular plate approaching a rigid surface. [10]

b) Write short notes on : [6]

i) Tyre-road tribology.

ii) Rail-wheel tribology.

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