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Courses » Defects in Crystalline Solids (Part-I)
Unit 5 - Week 4
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Week 4 Lecture 16:
History of Dislocations Lecture 17:
Volterra Model + Structure of Dislocations + Burger vectors Lecture 18:
Characteristics of Dislocations Lecture 19:
Mixed Dislocations + Dislocation Loops Lecture 20:
Elastic Continuum Model + Strain field for screw dislocations Quiz : Assignment 4 WEEK 4 - FEEDBACK - Defects in Crystalline Solids (Part-I) Assignment 4 Solution
Due on 2018-09-12, 23:59 IST.
1) 1 point
2) 1 point
3) 1 point
Assignment 4
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Which one is correct option?
A. Orowan and Polyani explained weakening of crystal B. Tempe give stress field theory
C. Volterra described elastic properties of materials
Only A Only A and B All A, B and C Only B and C No, the answer is incorrect.
Score: 0
Accepted Answers:
All A, B and C
What is the theoretical strength of steel (assuming no dislocation)?
8 GPa 80 GPa 8 MPa 80 MPa
No, the answer is incorrect.
Score: 0
Accepted Answers:
8 GPa
What is the approximate dislocation density of annealed metal/alloy?
1010-1012 μm-2 1010-1012 mm-2 1012-1014 cm-2 1012-1014 m-2 No, the answer is incorrect.
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4) 1 point
5) 1 point
6) 1 point
7) 1 point
Score: 0
Accepted Answers:
1012-1014 m-2
Which of he following are true regarding characteristics of dislocations?
A. Dislocation line must forma a loop or branch into other dislocation B. Line direction may change but burger vector remains constant C. Burger circuit is always conserved
D. Slip characteristics of burger vector remains constant
Only A, B and C Only A, B and D All A, B, C and D Only B and C No, the answer is incorrect.
Score: 0
Accepted Answers:
Only A, B and D
Dislocation can terminating by which of the following ways?
A. Ending at surface B. Branching
C. Start and finish combine together to form a loop D. Terminate at center of crystal
All A, B, C and D Only B and C Only A and B Only A, B and C No, the answer is incorrect.
Score: 0
Accepted Answers:
Only A, B and C
Elastic continuum model is used to understand:
A.Stress field B.Strain field
C.Energy stored in dislocation
Only A and B Only C All A, B and C Only B and C No, the answer is incorrect.
Score: 0
Accepted Answers:
All A, B and C
Which is true for shear strain in screw dislocation whose line direction is along Z direction ?
eyz = ezy = [(b.Cosθ)/(4Π.r2)]
eyz = ezy = [(b.Sinθ)/(4Π.r)]
eyz = ezy = [(b.Cosθ)/(4Π.r)]
Defects in Crystalline Solids (Part-I) - - Unit 5 -... https://onlinecourses.nptel.ac.in/noc18_mm11/u...
2 of 4 Wednesday 17 October 2018 12:42 AM
8) 1 point
9) 0 points
eyz = ezy = [b.Sinθ)/(4Π.r2)]
No, the answer is incorrect.
Score: 0
Accepted Answers:
eyz = ezy = [(b.Cosθ)/(4Π.r)]
Which is correct expression for shear stress in screw dislocation whose line direction is along Z direction?
σyz = σzy = [(G.b.Cosθ)/(2Π.r)]
σyz = σzy = [(G.b.Cosθ)/(2Π.r2)]
σyz = σzy = [(G.b.Sinθ)/(2Π.r2)]
σyz = σzy = [(G.b.Sinθ)/(2Π.r)]
No, the answer is incorrect.
Score: 0
Accepted Answers:
σyz = σzy = [(G.b.Cosθ)/(2Π.r)]
Plot shows strength of metal/alloys with changing dislocation density. What do region A, B and C in plot represent?
A. Dislocation free whiskers B. Annealed metal/alloy C. Work-hardened metal/alloy
A: Dislocation free whiskers, B: Annealed metal/alloy, C: Work-hardened metal/alloy A: Annealed metal/alloy, B: Dislocation free whiskers, C: Work-hardened metal/alloy A: Work-hardened metal/alloy, B: Annealed metal/alloy, C: Dislocation free whiskers A: Work-hardened metal/alloy, B: Dislocation free whiskers, C: Annealed metal/alloy No, the answer is incorrect.
Score: 0
Defects in Crystalline Solids (Part-I) - - Unit 5 -... https://onlinecourses.nptel.ac.in/noc18_mm11/u...
3 of 4 Wednesday 17 October 2018 12:42 AM
10) 1 point Accepted Answers:
A: Dislocation free whiskers, B: Annealed metal/alloy, C: Work-hardened metal/alloy Figure below shows shear stress against shear strain for LiF. Which of the following characteristics of the material changes along the direction of arrow?
Decreasing dislocation density Increasing density of point defect Increasing grain size
Decreasing crystallinity No, the answer is incorrect.
Score: 0
Accepted Answers:
Decreasing dislocation density
