Plastic Deformation of Single Crystal MCQ

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• What is the resolved shear stress, when dislocation density in metal is equal to 1012m-2? Given that shear stress needed in the absence of dislocation is 500MPa. Numerical constant is 0.3 and shear modulus is 80GPa, burger vector is 1 nm.
  ক

  500MPa

  খ

  550MPa

  গ

  600 MPa

  ঘ

  524 MPa
• Strain hardening due to ___________ process arises from short range force occurring over a distance of 5 to 10 atomic distance. This hardening can be overcome at finite temperatures with the help of thermal fluctuations, and therefore, it is temperature and strain-rate-dependent.
  ক

  dislocation cutting

  খ

  dislocation pile-up

  গ

  second phase particle

  ঘ

  alloying
• The formation of jogs in screw dislocations _________ its motion. Jogs in edge dislocations _________ its motion.
  ক

  restricts, do not restricts

  খ

  do not restricts, restricts

  গ

  restricts, restricts

  ঘ

  do not restrict, do not restrict
• Cross slip can occur in both the edge dislocation as well as in screw dislocation.
  ক

  True

  খ

  False
• The interaction of dislocation does not result in ______________
  ক

  jog

  খ

  kink

  গ

  dislocation threading

  ঘ

  slip
• The dislocation of low mobility that is produced by a dislocation reaction is called a ______ dislocation.
  ক

  sessile

  খ

  glissile

  গ

  screw

  ঘ

  edge
• A zinc crystal is strained to point A, unloaded, and then reloaded in the direction opposite to the original slip direction: What is the reason for the drop in shear stress when loaded in the opposite direction?
  ক

  Back stress

  খ

  Strain hardening

  গ

  Increase in the number of slip system

  ঘ

  Slip plane reorientation
• Which of the following is not a source of dislocation multiplication?
  ক

  Condensation of the vacancy

  খ

  Frank read mechanism

  গ

  Emission from high angle grain boundary

  ঘ

  Annealing
• Inhomogeneous deformation of crystal results in regions of different orientation called deformation bands. Deformation bands have been observed in both fcc and bcc metals, but not in hcp metals.
  ক

  True

  খ

  False
• Among the given metal, which has the highest stacking fault energy?
  ক

  Aluminum

  খ

  Copper

  গ

  Brass

  ঘ

  Stainless steel
• Metals with wide stacking faults (low SFE) strain-harden more rapidly, twin easily on annealing, and shows a different temperature dependence of flow stress than metals with narrow stacking faults.
  ক

  True

  খ

  False
• The _______ the stacking-fault energy, the higher the separation between the partial dislocations and the ________ the stacking fault.
  ক

  lower, wider

  খ

  higher, wider

  গ

  lower, narrow

  ঘ

  higher, narrow
• Which of the following represents the extrinsic stacking fault in the FCC Metal?
  ক

  ABCABCABC

  খ

  ABCBCABC

  গ

  ABCACBCABC

  ঘ

  ABABABABA
• The stacking fault in FCC will create a thin region of ___________ in stacking of the FCC.
  ক

  HCP

  খ

  BCC

  গ

  SC

  ঘ

  DC
• The stacking sequence of the atomic arrangement for HCP is ___________
  ক

  ABCABCABC

  খ

  ABABABABA

  গ

  AABBAABBAA

  ঘ

  AAAAAAAAA
• The stacking sequence of the atomic arrangement for FCC is ___________
  ক

  ABCABCABC

  খ

  ABABABABA

  গ

  AABBAABBAA

  ঘ

  AAAAAAAAA
• Which of the following is not matching correctly? Metal ————> Twin Plane ———> Twin Direction b) Silver ———-> (111) ————–> c) Copper ———-> (111) ————–> d) Zinc ————> (112) ————–>
  ক

  alpha iron ——> (112) ————–>

  খ

  111

  গ

  111

  ঘ

  111
• There are three metals given below. Metal A – Very few numbers of the slip systems Metal B – High critical resolved shear stress Metal C – High number of the slip system Which of the following is more susceptible for twining?
  ক

  Metal A

  খ

  Metal A and Metal B

  গ

  Metal A and Metal C

  ঘ

  Metal C
• Twinning is not associated with specific crystallographic direction; it only depends on the direction of mechanical force. There is no preferred orientation of twinning in crystal.
  ক

  True

  খ

  False
• Tin cry phenomena is associated with ______________
  ক

  twin

  খ

  slip

  গ

  annealing

  ঘ

  oxidation
• Which of the following is not a favorable condition for the formation of mechanical twins?
  ক

  The rapid rate of loading

  খ

  Low temperature

  গ

  BCC or HCP lattice

  ঘ

  Higher temperature
• In slip, the orientation of the crystal above and below the slip plane is _________ after deformation as before. While twinning results in ___________ orientation across the twin plane.
  ক

  same, different

  খ

  different, same

  গ

  same, same

  ঘ

  different, different
• Which two metal shows the significant strain hardening among Cu, Al, Mg, Zn?
  ক

  Cu, Al

  খ

  Mg, Zn

  গ

  Cu, Mg

  ঘ

  Al, Zn
• The ratio of the resolved shear stress to the axial stress is called the Schmid factor m.
  ক

  True

  খ

  False
• How the addition of impurity in pure metal affects the critical solved shear stress?
  ক

  Increases

  খ

  decreases

  গ

  Remains unaffected

  ঘ

  Cannot be predicted
• Slip begins when the shearing stress on the slip plane in the slip direction reaches a threshold value called the critical resolved shear stress.
  ক

  True

  খ

  False
• Find the shear strain in the material if the burger vector of dislocation is 0.1nm, average distance moved by dislocation is 1 micron, and dislocation density is 108 m-2?
  ক

  10

  খ

  108

  গ

  10-8

  ঘ

  10-10
• The unit of dislocation density is ___________
  ক

  m

  খ

  m2

  গ

  m-2

  ঘ

  m3
• The Peierls stress (stress required to move the dislocation) will be least in which type of crystal element?
  ক

  Covalent compound

  খ

  Metallic compound

  গ

  Ionic compound

  ঘ

  Intermetallic compound
• The force required to move a dislocation is known as ____________
  ক

  peierls-nabarro force

  খ

  hearing-nabarro force

  গ

  drag force

  ঘ

  frictional force