Mechanical Working Of Metals Rr

Set No. 1

Code No: RR321802

III B.Tech II Semester Supplimentary Examinations, Aug/Sep 2007 MECHANICAL WORKING OF METALS (Metallurgy & Material Technology) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. (a) Determine the expressions for octahedral shear stresses and strains. What is their importance? (b) Explain the construction of Mohr’s circle in 2D state of stress.

[8+8]

2. Give equations for significant stress and significant strain. Show that flow curve equation can be applied to significant stress and significant strain under uniaxial conditions. [16] 3. Discuss the effect of the following on working range of an alloy : (a) strain rate (b) Strain induced precipitation (c) Phase transformation

[5+6+5]

4. Explain the following: (a) Role of flash in closed die forging (b) Forging defects (c) The strength of forged component versus casting 5. Explain the forces and geometrical relationships in rolling.

[5+5+6] [16]

6. Extrusion is a process involving three-dimensional compression. Explain why brittle materials can be worked by extrusion more successfully than by some other metal working methods.? [16] 7. With neat sketches and necessary equations explain and analyze tube drawing. [16] 8. Compare the force required to draw 25 mm X 6 mm Copper strip to 45% reduction of area with that required for an equal reduction on round bar of the same cross sectional area, using: (a) 120 included angle dies (b) 300 included angle dies, if µ = 0.07. redundant work may be neglected. [8+8] ⋆⋆⋆⋆⋆

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Set No. 2

Code No: RR321802

III B.Tech II Semester Supplimentary Examinations, Aug/Sep 2007 MECHANICAL WORKING OF METALS (Metallurgy & Material Technology) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. (a) Define stress and strain for a uniform cylindrical bar of length L experiencing an axial tensile load. Also derive a relationship between stress and applied load using the free body diagram [8] (b) A body is in equilibrium under the action of external forces, p1 , p2 . How do you approach to define stress at an arbitrary point ‘O’ Figure 1b [8+8]

Figure 1b 2. A tensile specimen with 12mm initial diameter and 50mm gage length reaches maximum load at 90 kN and fractures at 70kN. The minimum diameter at fracture is 10mm. Determine (a) Engg stress at max load

[3]

(b) True stress at max load (assume the gage length is 60 at UTS)

[3]

(c) True fracture stress

[3]

(d) True strain at fracture

[3]

(e) Engineering strain at fracture

[2]

(f) Gage length at fracture

[2+3+3+3+3+2]

3. Write short notes on the following (a) Establishment of principal directions for a known state of stress (b) Relation between θn and θs (c) Construction of Mohr’s Circle for 2D state of Stress 4. Explain the processes of cogging a billet? 1 of 2

[5+5+6] [16]

Set No. 2

Code No: RR321802 5. Discuss the forces acting on the strip during rolling?

[16]

6. An annealed copper strip, 228 mm wide and 25 mm thick, is rolled to a thickness of 200mm. The roll radius is 300 mm and rotates at 100 rpm. Calculate the [8+8=16] (a) roll force and (b) power required for rooing 7. With neat sketches and necessary equations explain and analyze tube drawing. [16] 8. Compare the force required to draw 25 mm X 6 mm Copper strip to 45% reduction of area with that required for an equal reduction on round bar of the same cross sectional area, using: (a) 120 included angle dies (b) 300 included angle dies, if µ = 0.07. redundant work may be neglected. [8+8] ⋆⋆⋆⋆⋆

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Set No. 3

Code No: RR321802

III B.Tech II Semester Supplimentary Examinations, Aug/Sep 2007 MECHANICAL WORKING OF METALS (Metallurgy & Material Technology) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. The state of stress is given by σx = 25p and σy = 5p plus shearing stresses τxy . On a plane 450 counterclockwise to the plane on which σx acts, the state of stress is 50MPa tension and 5MPa shear. Determine the values of σx , σy , τxy [16] 2. Draw flow curves for (a) Rigid ideal plastic material (b) Ideal plastic material (c) Ideal elastic material (d) Strain hardening material

[4 × 4 = 16]

3. (a) Differentiate between hot working & cold working. (b) Explain the mechanisms of recrystallization, recovery and their dependence of room temperature on amount of cold work. [8+8] 4. Explain the stresses in the forging of a plate of constant thickness under conditions of plane strain. [16] 5. What is the effect of co-efficient of friction and roll diameter on the draft in rolling? [16] 6. An annealed copper strip, 228 mm wide and 25 mm thick, is rolled to a thickness of 200mm. The roll radius is 300 mm and rotates at 100 rpm. Calculate the [8+8=16] (a) roll force and (b) power required for rooing 7. (a) An Aluminum alloy is hot extruded at 4000 C at 2 in/sec from 6 inch diameter to 2 inch diameter. The flow stress at this temperature is given by σ = 200 (ε)0.15 MPa. If the billet is 15 inches long and the extrusion is done through square dies without lubrication, Determine the force required for the operation. (b) With the necessary equations and sketches, describe and explain the extrusion process. [8+8] 8. (a) State appropriate reasons for the application of glass as the lubricant in many metal working operations. (b) What types of lubricants are used for high temperature extrusion of steel and Nickel based alloys? 1 of 2

Set No. 3

Code No: RR321802

(c) What is the purpose of using these lubricants in these processes? ⋆⋆⋆⋆⋆

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[6+5+5]

Set No. 4

Code No: RR321802

III B.Tech II Semester Supplimentary Examinations, Aug/Sep 2007 MECHANICAL WORKING OF METALS (Metallurgy & Material Technology) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. The state of stress is given by σx = 25p and σy = 5p plus shearing stresses τxy . On a plane 450 counterclockwise to the plane on which σx acts, the state of stress is 50MPa tension and 5MPa shear. Determine the values of σx , σy , τxy [16] 2. Give equations for significant stress and significant strain. Show that flow curve equation can be applied to significant stress and significant strain under uniaxial conditions. [16] 3. Write short notes on (a) Recrystallization (b) Recovery (c) Grain growth

[5+5+6]

4. (a) A 30 mm dia, 20 mm height, M.S round is to be forged to have an enlarged diameter. Step at one end with step length of 40 mm and dia 60 mm. Estimate the number of passes required for operating with horizontal forging machine. [10] (b) What Properties of metals contribute to good Forgeability? 5. Derive the equation for roll torque and power with neat diagram?

[6] [16]

6. Draw a neat sketch showing various forces acting during rolling and derive the relation for specific roll pressure. [16] 7. (a) Estimate the pressure required to extrude an Aluminum alloy curtain rail of I section 22.5 mm high with 8.5 mm wide flanges, all 4.5 mm thick from 38 mm diameter bar stock. (b) With neat sketches explain the classification of tube drawing processes. [9+7] 8. Circular Aluminum blanks with 25 mm diameter and 3 mm thickness are to be produced as the starting material for the tooth paste tube extrusion. The press has a capacity of 50 KN. The fracture strain and stress of the material are 2 and 80 N/mm2 . No shear is provided to the punch. Determine (a) the optimum clearance between the die and the punch (b) the maximum number of blanks which can be punched simultaneously per stroke and the (c) Power required if the punch speed is 60 cycles/min. 1 of 2

[5+5+6]

Set No. 4

Code No: RR321802 ⋆⋆⋆⋆⋆

2 of 2