advanced design of weldments_seme1_2006

7/27/2019 Advanced Design of Weldments_seme1_2006

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Ex/MME/6135/97/2006

MASTER OF MECHANICAL ENGG. EXAMINATION, 2006

( 1stSemester )

ADVANCED DESIGN OF WELDMENTS

Time : Three hours Full Marks : 100

(50 marks for each part)

Use a separate answer-script for each part.

PARTI

Answer question no. 1 and any two from the rest.

Assume relevant data, if needed and

underline them.

1. (a) Show with deduction that the volume of

material required for cast iron structure is 45 times

that required for mild steel structure of a cantilever of

rectangular section for equal loading capacity and

stiffness, if the working stresses for cast iron and mild

steal are 30 MN/m

2

and 90 MN/m

2

respectively andmodulus of elasticities of cast iron and mild steel are

ll05MN/m

2and 2l0

5MN/m

2respectively.

(b) An I section cantilever, 'd' mm deep and

'b' mm wide consist of two identical flanges of 20 mm

thickness and a web of 10 mm thickness (d-40) mm

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depth. What will be the optimum volume if the 20 mm

long cantilever is loaded with 300 KN at its free end?

Allowable deflection is 1 mm, allowable stress is90 MN/m

2and material is St-42 steel.

(c) A cantilever St-37 steel solid rod is subjected

to a load P at its free end. Find the size of the weld

which is provided by an all round fillet to fix the rod

with a vertical side g a structure to withstand the

load P. 6+8+6

2. Write short notes on:

(a) Requirements for arc welding power source.

Or

Selection of welding power source.

(b) Joint Design.

Or

Factors which affect the welding cost.

(c) Effects of Polarity on MAW process. 35

3. (a) State briefly two possible causes of hotcracking in carbon steel fusion welds and explain how

this effect may be avoided.

(b) State briefly the procedures to counteractcold cracking glow alloy high tensile steel 8+7

4. (a) For good welding, heat balance is necessary.

Explain.

(b) U joint preparation is superior to X jointpreparation.Comment. 27.5


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PARTII

Do not answer more than 50 marks.

5.(a) Draw a neat sketch of the indentor in

connection with directional hardness.

(b) Deduce the relation from fundamental

All notations carry usual meaning. 6+12 = 18

6. (a) What is friction welding ?

(b) Mention the advantages of friction welding

over other welding processes.

(c) What is the application potential of friction

welding ?

(d) What are the factors producing cracking ?

4+4+4+4=16

7.(a) Explain the concept of carbon equivalent.

(b) Cr-Mo steel has the following composition :

Calculate the preheating temperature.

(c) What do you mean by residual stress? Why

is it so important ? 5+6+5=16

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8. Write notes on ( anyfour): 44=16

(a) T I G welding

(b) Electroslag welding

(c) Importance of preheating temperature

(d) N D T

(e) Reversed polarity

(f) Distortion and shrinkage.

advanced design of weldments_seme1_2006

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