Rr321802-mechanical-working-of-metals

Set No. 1

Code No: RR321802

III B.Tech II Semester 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) Distinguish between True and Engineering stresses and strains.

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(b) Explain principal planes, stresses ans axes. Show that σx + σy + σz = constant for any plane. [9] 2. Write short notes on the following: (a) Flow curve (b) Anelastic behaviour (c) Proportional loading.

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3. (a) The state of stress is given by σs =15k, σy =10k and a shearing stress, τ xy . On a plane at 300 counter clockwise to the plane on which σ x acts, the stress state is 40MPa tension and 5MPa shear. [8] Determine the values of σ x , σ y , τ xy and σ y ’ (b) Using the above data. Find out the principal normal stresses and max shear stress and their angular relationship with σ x and τ xy [8] 4. Explain the following terms with respect to forging of a plate in a plain strain condition. [4 × 4] (a) Colombs law of sliding friction (b) Von Mises yield criterion (c) Friction hill (d) Neutral surface. 5. (a) Explain the construction of rolling mill? (b) Give the classification of rolling mills? 6. Explain with neat sketches

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(a) Direct extrusion (b) Indirect Extrusion. 7. (a) Describe with neat sketches classification of extrusion processes (b) Derive an equation for ideal extrusion pressure. 8. (a) Distinguish between:

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Set No. 1

Code No: RR321802 i. Tube drawing and wire drawing ii. Direct extrusion and indirect extrusion (b) Explain the effect “tube sinking” ⋆⋆⋆⋆⋆

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Set No. 2

Code No: RR321802

III B.Tech II Semester 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. 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. (a) What are the basic assumptions made by Von-Mises’ in proposing yield criterion? Derive it. [8] (b) Stress analysis of a structural number gives the state of stress as shown in figure 2. If the part is made from an alloy with σo =400 MPa, will it exhibit yielding? If not what is the safety factor? [8]

Figure 2 3. (a) What are the effects of friction in metal forming processes?

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(b) Why is it necessary to have a lubricating system in plastic deformation processes and what are the various lubricating systems used in metal forming units. [10] 4. Discuss the various operations in open die forging

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5. Discuss the effect of strip tension on the distribution of roll pressure with neat diagram. [16] 6. Write short-notes on the following: (a) Torque and horse power in cold rolling (b) Strain rate effect 1 of 2

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Set No. 2

Code No: RR321802

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. [8] (b) With the necessary equations and sketches, describe and explain the extrusion process. [8] 8. (a) The following equation expresses the pressure for the extrusion of Aluminum bars : [8] p = σ o (0.47 + 1.2 ln R) exp [4µL/D] billets 8 inch in diameter and 16 inch long are extruded into 3/4 inch diameter bars. In order to increase the length of the product by 10 feet, would it be more economical in terms of pressure to increase the billet length or diameter? (Assume that µ = 0.10) (b) In the hot extrusion of Aluminum at 3500 C, σ o = 250 MPa for a 12 inch diameter billet, 36 inch long [4+4] i. What is the break through pressure needed to extrude a 3 inch diameter if µ = 0.10? ii. What is the required extrusion pressure at the end of stroke? ⋆⋆⋆⋆⋆

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Set No. 3

Code No: RR321802

III B.Tech II Semester 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) What are the different mechanism involved in elastic deformation? Is there is any volumetric change in the case of elastic deformation? If yes, what could be the reason. [10] (b) Describe strain at a point.

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2. (a) explain stages of annealing in detail (b) explain maximum shear stress theory.

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3. (a) Draw the planes on which τ1 , τ2 , τ3 act. You may consider σ1 , σ2 , σ3 as principal stresses. You may draw different figures for τ1 , τ2 , τ3 as shown in figure 3a. [8]

Figure 3a (b) What do you infer from the term τxy ? What does x & y represent what is the notation followed to assign and particular sign to the shear stresses. Show that τxy = τyx [8] 4. (a) Give the classification of forging processes (b) Explain the process, advantages and disadvantages of the following

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i. Open die forging ii. Closed die forging. 5. Derive the equation for roll torque and power with neat diagram?

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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

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Set No. 3

Code No: RR321802 (a) roll force and (b) power required for rooing.

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7. (a) Describe deformation in extrusion and explain possible defects and suitable remedies. [8] (b) Compare direct extrusion with indirect extrusion.

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8. (a) State appropriate reasons for the application of glass as the lubricant in many metal working operations. [6] (b) What types of lubricants are used for high temperature extrusion of steel and Nickel based alloys? [5] (c) What is the purpose of using these lubricants in these processes? ⋆⋆⋆⋆⋆

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Set No. 4

Code No: RR321802

III B.Tech II Semester 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. The stress state as shown in figure 1

Figure 1 (a) Find out principal stresses, max shear stresses and their orientation with the current axes. [10] (b) Draw the principal plane w.r.t. the current axes and denote the stress state. [6] 2. (a) Define ideal plastic solid and derive relationship between stress and strain for an ideal plastic solid. [8] (b) Derive Levy-Mises equations for an Ideal plastic solid.

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3. Explain the method of analyzing mechanical working mechanics by Uniform deformation energy method. [16] 4. A block of lead 30mmx30mmx150mm is pressed between flat dies to size 6.5mmx100mmx150mm. If the uniaxial flow stress is σ o =10MPa and µ = 0.25 determine the pressure distribution over the 100mm dimension and the total forging load. [16] 5. Explain the following terms with respect to rolling. (a) Rolling load

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(b) Roll separating force

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(c) Specific roll pressure

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(d) Angle of bite

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(e) Neutral point

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Set No. 4

Code No: RR321802

6. What are the basic assumptions made in developing a theoretical treatment of cold rolling and derive the relationship between normal pressure and horizontal compressive stress. [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. [9] (b) With neat sketches explain the classification of tube drawing processes. 8. (a) Write short notes on the following: i. ii. iii. iv.

Extrusion dies Extrusion constant Breakthrough pressure Extrusion ratio. ⋆⋆⋆⋆⋆

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