Question 1
A dissolution in which an extra portion of a plane of atoms or a half plane terminates within a crystal is called as ________
A. Edge dislocation
B. Mixed dislocation
C. Interfacial dislocation
D. Screw dislocation
View Answer
Answer: Option A
Explanation:
Edge dislocations are the linear crystalline defects that are formed due to the extra half plane of atoms in the lattice.
Question 2
Edge dislocation and skew dislocation are linear crystalline defects.
A. TRUE
B. FALSE
View Answer
Answer: Option A
Explanation:
Line defects are mainly dislocations which can be broadly classified into two distinct defects. These two dislocations are called edge dislocation and screw dislocation.
Question 3
In an edge dislocation, a helical path is traced around the dislocation line.
A. TRUE
B. FALSE
View Answer
Answer: Option B
Explanation:
A helical path is traced along the dislocation line in screw dislocation whereas in edge dislocation a new additional half plane of an atom is inserted and a screw like path is not traced by the dislocation.
Question 4
In which type of dislocation an extra plane is inserted inside the crystal?
A. Edge dislocation
B. Screw dislocation
C. Jog dislocation
D. Mixed dislocation
View Answer
Answer: Option A
Explanation:
The edge defect is simply pictured as an additional half plane of atoms in a lattice. The dislocations are termed a line defect because of the number of defective points created within the lattice along a line. Hence, an extra plane of atoms is added inside the crystal in this type of defect.
Question 5
In which type of dislocation planes are displaced relative to each other through shear?
A. Edge dislocation
B. Screw dislocation
C. Jog dislocation
D. Mixed dislocation
View Answer
Answer: Option B
Explanation:
In screw dislocation, planes are displaced relative to each other through shear. The trace of the atomic planes around the screw dislocation makes spiral or whorled path sort of resembling a screw and hence, it is named screw dislocation.
Question 6
Path of screw dislocation is in the form of _______
A. Circular
B. Cylindrical
C. Spiral or helical
D. Rectangular
View Answer
Answer: Option C
Explanation:
Ramp that is traced around dislocation line is spiral or helical that’s the reason it is called screw dislocation.
Question 7
The magnitude and direction of lattice distortion are expressed in terms of which vector?
A. Dislocation vector
B. Screw vector
C. Edge vector
D. Burger vector
View Answer
Answer: Option D
Explanation:
Burger vector is used to denote magnitude and direction. In physics, the Burgers vector, named after Dutch physicist Jan Burgers, is a vector, often denoted as b, that represents the magnitude and direction of the lattice distortion resulting from a dislocation in a crystal lattice.
Question 8
To determine yield strength of a material which of the following needn’t be affected?
A. Solute hardening
B. Precipitation hardening
C. Work hardening
D. Martensic transformation
View Answer
Answer: Option D
Explanation:
Burgers vector plays an important role in determining yield strength by affecting solute hardening, precipitation hardening and work hardening. Martensic transformation which refers to quenching from high temperature doesn’t play any role in the determination of yield strength.
Question 9
What are the dislocation in which the line direction and Burgers vector are neither perpendicular nor parallel?
A. Screw dislocation
B. Edge dislocation
C. Jog dislocation
D. Mixed dislocation
View Answer
Answer: Option D
Explanation:
Mixed dislocation are dislocation consisting of both screw and edge dislocation character where in screw dislocation the line direction and burger vector are parallel and for edge dislocation it is perpendicular. Therefore, the angle between line direction and Burgers vector is neither perpendicular nor parallel.
Question 10
What is the difference between the angle of Burgers vector and dislocation line in edge dislocation and screw dislocation?
A. -90 degrees
B. 0 degrees
C. 45 degrees
D. 90 degrees
View Answer
Answer: Option D
Explanation:
The angle between Burgers vector and dislocation line in edge dislocation is 90 degrees while the angle between burger vector and dislocation line for screw dislocation is 0 degree. To find the difference we have subtract 0 from 90, giving us 90 degrees as our final answer.
Question 11
What is the mechanism in which edge dislocation move out of the slip is called _______
A. Climb dislocation
B. Screw dislocation
C. Shear dislocation
D. Slip dislocation
View Answer
Answer: Option A
Explanation:
In this type of dislocation edge moves perpendicular over its slip plane.
Question 12
What is the relative orientation of dislocation lines for edge dislocation?
A. Parallel
B. Perpendicular
C. Circular
D. Both parallel and perpendicular
View Answer
Answer: Option B
Explanation:
For edge dislocation the nature of dislocation line is perpendicular.
Question 13
What type of direction will the burger vector of dislocation for a metallic material show?
A. Closed-packed crystallographic direction
B. Rounded-packed crystallographic direction
C. Open-packed crystallographic direction
D. Parallel-packed crystallographic direction
View Answer
Answer: Option A
Explanation:
For a metal being solid, its atoms are closely packed and also metals are crystalline in nature so the direction shown by the vector will be closed packed crystalline direction.
Question 14
Which of the following can be theoretical shear stress produced in metals? ( GPa stands for Giga pascal)
A. 10 GPa
B. 32 GPa
C. 2 GPa
D. 50 GPa
View Answer
Answer: Option A
Explanation:
The theoretical shear stress is in the range of 3 Gpa to 30 GPa. 10GPa is the only option which lies within that range while 32 GPa, 2 GPa and 50 GPa are beyond the range in which the theoretical shear stress can lie for pure metal.
Question 15
Which of the following dislocation can glide but not climb?
A. Screw dislocation
B. Edge dislocation
C. Jog dislocation
D. Mixed dislocation
View Answer
Answer: Option A
Explanation:
Screw dislocation can only glide in a crystal lattice along the helical path while edge dislocations can glide and climb as there is an extra plane of atom present.
Question 16
Which of the following is fields are not present for edge dislocation?
A. Tensile
B. Compressive
C. Shear stress
D. Strain
View Answer
Answer: Option D
Explanation:
In the edge dislocation, tensile, compressive and shear stress field are present due to an additional half plane of atom added because of which stresses are produced but no strain is produced because of an edge dislocation.
Question 17
Which of the following is fields are present for screw dislocation?
A. Tensile
B. Compressive
C. Shear stress
D. Strain
View Answer
Answer: Option C
Explanation:
As in screw dislocation a helical path is traced along a dislocation line, there is only presence of shear stress field and no compressive, tensile or strain field is produced. Shear stress field is produced due to the spiral aspect of this type of dislocation.
Question 18
Which of the following statement is false?
A. Burger vector is the right angle to edge dislocation
B. In screw defect the line defect is parallel to the displacement vector
C. Grain boundary defect is a type of line defect
D. Line defect occurs during the recrystallization process or during slip
View Answer
Answer: Option C
Explanation:
Grain boundary defect is a two-dimensional defect. Grain boundary is the interface between two grains and hence they stop the dislocations from moving freely. Therefore, they cause a two-dimensional defect to spread around the grain boundary.
Question 19
Which type of defect are line defects?
A. One-dimensional defect
B. Zero-dimensional defect
C. Two-dimensional defect
D. Three-dimensional defect
View Answer
Answer: Option A
Explanation:
Line defects are one dimensional defects as they extend in a singular direction in space. Line defects are present in solids whereas the whole row of atoms is arranged in anomalous order. Hence line defects are linear defects and one dimensional in nature.
Question 20
Which type of deformation occurs due to dislocation?
A. Slip plastic deformation
B. Elastic deformation
C. It does not show deformation
D. Slip elastic deformation
View Answer
Answer: Option A
Explanation:
Dislocation involves sliding of crystal blocks over one another along the definite crystallographic plane which results in a slip.
Question 21
Which technique is used to observe dislocation?
A. Positron annihilation technique
B. Thermal imaging
C. Thermal expansion measurements
D. Electron-microscope technique
View Answer
Answer: Option D
Explanation:
This type of microscope consists of a high magnification transmission electron micrograph in which dark lines represent dislocation.
Question 22
Which type of stress is involved in the motion of screw dislocation?
A. Tensile stress
B. Shear stress
C. Compressive stress
D. Does not involve stress
View Answer
Answer: Option B
Explanation:
If shear stress is increased in screw dislocation it results in a slip of one layer over other which ultimately leads to deformation.
Question 23
Which type(s) of dislocation are included in mixed dislocation?
A. Only Edge dislocation
B. Only shear dislocation
C. Only screw dislocation
D. Both edge and screw dislocation
View Answer
Answer: Option D
Explanation:
Mixed dislocation is a combination of screw and edge dislocation. It does not consist of only pure edge or pure screw dislocation.