R05321803-mechanical-working-of-metals

Set No. 1

Code No: R05321803

III B.Tech Supplimentary Examinations, Aug/Sep 2008 MECHANICAL WORKING OF METALS (Metallurgy & Material Technology) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. (a) How Mohr’s circle is used to solve three dimensional stresses? Explain. (b) The principle strains of a point are given by ε1 =2×10−3 , ε1 =-3×10−3 , ε3 = -4×10−3 calculate the octahedral normal and shearing strains.

[8+8]

2. (a) Explain the strain hardening phenomenon. What is the effect of strain hardening on plastic deformation? Explain. (b) Stress analysis of a spacecraft structural member gives the state of stress as shown in figure 2b. If the part is made from aluminium alloy with σ0 =500Mpa, will it exhibit yielding? If not, what is the safety factor. [8+8]

Figure 2b 3. (a) Describe the following methods of analysis of metal forming processes. i. slab method ii. slipline field method. (b) Explain about dynamic recrystallization and dynamic recovery.

[10+6]

4. (a) Explain the various steps for the design of forging dies. (b) Write short notes on the following. i. Materials of die blocks ii. Machining allowance in forging.

[8+8]

5. (a) Explain theory of hot rolling. (b) Discuss the types of rolling mills with neat sketches.

[8+8]

6. (a) What is the rolling load if a steel sheet is to be hot rolled by 25% from a 1.4 inch thick slab using a 34 inch diameter roll? The slab is 30 inch wide. 1 of 2

Set No. 1

Code No: R05321803

Assume µ = 0.28. The plane-strain flow stress is 18 ksi at and 28 ksi at the exit from the roll gap due to the increasing velocity. (b) Explain the role of back tension in rolling.

[10+6]

7. (a) What properties are required for hydrostatic extrusion? Explain their advantages. (b) A steel rod of 10mm extruded with a tube of 7.5mm outer diameters and 5 mm internal diameters. Determine the extrusion ratio. [10+6] 8. (a) What are the locations which are prone to cracking in the deep drawing of circular blank into a cup? (b) What is the difference between redrawing and reverse drawing? (c) What is a bull block?

[6+6+4] ⋆⋆⋆⋆⋆

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Set No. 2

Code No: R05321803

III B.Tech Supplimentary Examinations, Aug/Sep 2008 MECHANICAL WORKING OF METALS (Metallurgy & Material Technology) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. What is the significance of Mohr’s circle. Draw the Mohr’s circle ( 3 Dimensions) for Uni-axial tension, Uni-axial compression, bi-axial tension, Tri-axial tension, Uni-axial tension, Plus bi-axial compression and Explain them in detail. [16] 2. (a) Mention the various factors that affect the plastic deformation of metals. Give examples. (b) Derive the expression True stress=Engineering stress(1+ Engineering strain).

[8+8]

3. (a) Discuss the various processes occuring during recovery stage of a cold worked metal. (b) Explain why the strength of a poly crystalline metal at room temperature decreases as its grain size increases. (c) Write a short notes on ‘Warm working’.

[7+5+4]

4. (a) Why should grain flow patterns in forging be studied? Explain. (b) What properties of metals contribute to good forgeability? Explain. (c) Describe the construction of a drop forging hammer.

[5+7+4]

5. (a) The strain hardening of an annealed metal is expressed by σ = 200,000 ε0.5 where stress is in psi. A 25mm diameter bar is drawn down to 20 mm and 15 mm in two steps using tapered cylindrical dies. Determine the plastic work per unit volume for each reduction. (b) What type of processes involved dynamically in hot working? Explain them. [8+8] 6. (a) Why all primary rolling operations are done hot? What type of furnaces used for reheating of steel? (b) Differentiate between hot and cold rolling.

[10+6]

7. (a) Compare and contrast between direct extrusion and indirect extrusion. (b) Critically discuss on the effects of temperature, deformation velocity and deformation on hot extrusion process. [8+8] 8. (a) What is die ringing? Explain the phenomenon of die ringing. (b) Show that strain rate of wire being pulled through a die can be expressed by ε˙ = (2 tana)/r(dx/dt). What is the maximum strain rate for a 0.4′′ diameter wire pulled at 1,500 ft/min through a 100 semi-angle die? [8+8] 1 of 2

Set No. 2

Code No: R05321803 ⋆⋆⋆⋆⋆

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Set No. 3

Code No: R05321803

III B.Tech Supplimentary Examinations, Aug/Sep 2008 MECHANICAL WORKING OF METALS (Metallurgy & Material Technology) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. (a) Find the principal stress and determine their orientation for the following situation. σx = 400 Mpa, σx = 50 Mpa, τxy =-60 Mpa. Also determine the maximum shear stress. (b) What do you mean by directional cosines? Explain with examples. What is their significance? (c) Explain the term ‘Invariant quantity’. (d) What are principal planes and principal stresses:

[8+4+2+2]

2. (a) Explain why the difference between engineering strain and true strain becomes larger as strain increases. (b) Draw the yield locus for maximum-shear stress criteria and von-mises criterion and comment about the plots. Why is the divergence between two criteria and explain the reasons. [6+10] 3. (a) What is recrystallization temperature? Is it possible to have hot working of metals at room temperature? How? Explain with suitable examples. (b) Explain the importance of heating in the recovery range, for some industrial applictions. (c) Give any two methods for lowering the recrystallization temperature of a given metal? Explain them. [7+5+4] 4. (a) What are the various basic forging operations? Explain about them. (b) Derive an equation for forging pressure in plane strain with columb friction. [8+8] 5. (a) Explain forward slip and the position of neutral point, in rolling operation. How they are mathematically derived? (b) What is the effect of rolling process variables on the process efficiency? [8+8] 6. (a) What is the rolling load if a steel sheet is to be hot rolled by 25% from a 1.4 inch thick slab using a 34 inch diameter roll? The slab is 30 inch wide. Assume µ = 0.28. The plane-strain flow stress is 18 ksi at and 28 ksi at the exit from the roll gap due to the increasing velocity. (b) Explain the role of back tension in rolling.

1 of 2

[10+6]

Set No. 3

Code No: R05321803

7. (a) Determine the extrusion ratio when a steel rod of diameter 12 mm is extruded into a tube of 8 mm outer diameter and 6 mm internal diameter. (b) Explain the different type of equipment used in extrusion processes with neat sketches. [8+8] 8. (a) Explain the effect of different factors on residual stresses developed in wire and rod drawing operation. (b) Explain the effect of die angle on the components of the total energy of deformation in wire drawing. [8+8] ⋆⋆⋆⋆⋆

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Set No. 4

Code No: R05321803

III B.Tech Supplimentary Examinations, Aug/Sep 2008 MECHANICAL WORKING OF METALS (Metallurgy & Material Technology) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. Consider cube as an element. Describe the stress of a point. Write all the stess components needed to define stress state at a point. Describe the sign convention used to define normal and shear stresses. [16] 2. (a) If the yield strength of a steel is 950 Mpa, determine whether yielding will have occured on the basis of both the Von-Mises and Tresca criteria. The stress state is given by   0 0 300  0 −400 0  M pa 300 0 −800 (Assume any necessary data). (b) Explain briefly about yield surface state von-Mises and Tresca criteria.[13+3] 3. (a) Describe the following methods of analysis of metal forming processes. i. slab method ii. slipline field method. (b) Explain about dynamic recrystallization and dynamic recovery.

[10+6]

4. (a) What is sledge hammer? With the help of a neat sketch, explain its working and give its application. (b) With the help of relevant sketches, explain the production of steel by forging process. [8+8] 5. (a) Explain theory of hot rolling. (b) Discuss the types of rolling mills with neat sketches.

[8+8]

6. (a) Explain the analysis of rolling load and rolling variables. (b) What are the problems and defects in rolled products?

[8+8]

7. (a) What is piercing method? How is it different from extrusion? (b) Explain the process of seamless pipe production. (c) What are the different types of tubing processes?

[6+6+4]

8. Write short notes: (a) The effect of die angle on the components of the total energy of deformation in wire drawing. 1 of 2

Set No. 4

Code No: R05321803

(b) Limit of drawability for a steady-state wire drawing. ⋆⋆⋆⋆⋆

2 of 2

[8+8]