GTU BE/B.Tech 2019 Winter Question Papers || Gujarat Technological University
Subject Code: 2142106
GUJARAT TECHNOLOGICAL UNIVERSITY
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BE - SEMESTER- IV (New) EXAMINATION - WINTER 2019
Subject Name: Plastic Deformation of Metals
Time: 10:30 AM TO 01:00 PM
Instructions:
- Attempt all questions.
- Make suitable assumptions wherever necessary.
- Figures to the right indicate full marks.
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Q.1
- (a) Draw a labeled stress strain diagram for ductile and brittle material. Explain yield point phenomena with neat sketch. (03 Marks)
- (b) Differentiate Slip and Twinning as mechanism of Plastic deformation. (04 Marks)
- (c) Define the Terms: (i) Young’s Modulus (ii) Shear Modulus (iii) True Stress & True strain (iv) Engineering Stress and Engineering Strain v) Ultimate tensile stress vi) Proof stress vii) braking strength. (07 Marks)
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Q.2
- (a) Discuss the various techniques of observation of dislocation. (03 Marks)
- (b) Differentiate between plastic deformation by slip and twinning. (04 Marks)
- (c) Discuss the mechanism of Frank-Read source of dislocation multiplications. (07 Marks)
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OR
- (a) What is Schmid’s law? Derive the expression of critical resolved shear stress (03 Marks)
- (b) Write a formula stating relationship between Shear Modulus (G), Elastic Modulus(E), and Poisson’s ratio of materials (04 Marks)
- (c) What is Hall Petch relationship? Discuss the basis of strengthening of materials by grain —size reduction method. (07 Marks)
Q.3
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- (a) Define Dislocation? Differentiate Edge and Screw dislocation with neat sketch. (03 Marks)
- (b) OR What is Slip system? What is the use of Burger Circuit? (04 Marks)
- (c) Differentiate between the annealing twins and the deformation twins with neat schematics. (07 Marks)
Q.4
- (a) Differentiate the following with help of schematic representation (03 Marks)
- (I) Ductile fracture and Brittle fracture
- (II) Intergranular fracture and Trans granular fracture
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- (b) Enlist various strengthening mechanisms in metallic alloys. (04 Marks)
- (c) Differentiate the climb and the cross slip of dislocation with the help of the schematics. (07 Marks)
- (a) A Large plate is fabricated from a steel alloy that has a plain strain fracture toughness of 45 MPavm. If during service use, the plate is exposed to a tensile stress of 250 MPa, determine the minimum length of a surface crack that will lead to fracture (Assume f=1.0) (03 Marks)
- (b) OR Explain “Ductile-Brittle Transition Temperature” (DBTT) curve (04 Marks)
- (c) With a Neat Sketch, explain how dislocation line can end abruptly inside a crystal itself by forming a continuous loop? (07 Marks)
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- (a) Derive a Griffith’s equation for a propagation of cracks in brittle material and using equation calculate, of The half-length of cracks in a steel is 3µm. Taking E= 150GNm-2 , Estimate the brittle fracture strength at low temperature, if the surface energy is 1.5 Jm-2 (03 Marks)
Date: 07/12/2019
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Total Marks: 70
Q.5
- (a) What are the pre-requisite for an alloy to be age-hardenable? Explain giving suitable example. (03 Marks)
- (b) Compare recovery and recrystallisation in terms of (i) driving force (ii) mechanisms, and (iii) effects on mechanical properties (07 Marks)
OR
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- (a) Define Strain Hardening effect. State the effect of it on the mechanical properties of steels? (03 Marks)
- (b) What is creep? Draw a typical creep curve and discuss its different regions. (04 Marks)
- (c) Draw typical S-N Curve for an aluminium alloy and steel . Define the terms: (1) Endurance Limit (i1) Fatigue strength and (ii1) Fatigue life. (07 Marks)
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