13826065
Descripción
Test por Anton Permyakov, actualizado hace más de 1 año
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Creado por Anton Permyakov
hace alrededor de 6 años
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Pregunta 1
Pregunta
The dislocation can move by requiring [blank_start]........ bond[blank_end] to be broken at a time.
Respuesta
-
only one bond
-
multiple bonds
Pregunta 2
Pregunta
Positive and negative dislocations move in opposite directions to produce shear of the [blank_start]same[blank_end] sign.
Respuesta
-
same
-
different
Pregunta 3
Pregunta
Positive and negative dislocations (of same type, e.g., screw) attract each other, positives (or negatives) repel.
Respuesta
- True
- False
Pregunta 4
Pregunta
The slip plane is defined as ......
Respuesta
-
the plane on which the dislocation nucleates.
-
the plane on which the bond breaking occurs.
Pregunta 5
Pregunta
For an edge dislocation, the slip plane is defined as the plane which contains both the line direction an Burgers vector of the dislocation.
Respuesta
- True
- False
Pregunta 6
Pregunta
Dislocation motion can be conservative or non-conservative:
• Conservative motion [blank_start]involves no mass transport[blank_end] (i.e., diffusion)
• Non-conservative motion requires [blank_start]the addition/subtraction of atoms[blank_end] or [blank_start]vacancies to the extra half[blank_end] plane
Respuesta
-
involves no mass transport
-
the addition/subtraction of atoms
-
vacancies to the extra half
Pregunta 7
Pregunta
The force required to move the dislocation is known as .......?
Respuesta
-
dislocation force
-
glide force
-
strain force
Pregunta 8
Pregunta
Enter the symbols the Frank's rule formula (not given in the formula sheet by the way):
T = [blank_start]..............[blank_end]
Use * as a multiplication sign , alpha as a constant alpha, G as a shear modulus and b as a Burgers vector.
Respuesta
-
alpha*G*b^2
Pregunta 9
Pregunta
The Peierls stress is the stress to glide a dislocation through an otherwise perfect crystal.
Respuesta
- True
- False
Pregunta 10
Pregunta
What is the definition of the dislocation width?
Respuesta
-
The distance over which the disregistry is greater than one half of its maximum value.
-
The distance over which the size of the extra plane of atoms is greater than one half of its maximum value.
Pregunta 11
Pregunta
Why is the energy or stress is minimised by slip on the close packed planes in the close packed directions?
Respuesta
-
Because the atomic slip distance is a minimum.
-
Because atoms in the closed packed directions have least interaction potential.
Pregunta 12
Pregunta
Which type of dislocations is more mobile and hence has smaller Pierls Stress?
Respuesta
-
Edge dislocation
-
Screw dislocation
Pregunta 13
Pregunta
The energy or stress increases with a decrease in dislocation width.
Respuesta
- True
- False
Pregunta 14
Pregunta
In FCC metals, Peierls stress is a strong function of temperature while in BCC metals, Peierls is not a strong function of temperature.
Image:
Bcc (binary/octet-stream)
Respuesta
- True
- False
Pregunta 15
Pregunta
What can cause an increase in number of dislocations/ dislocation density?
Choose one or more than one of the answers.
Respuesta
-
Grain Boundaries
-
Interfaces between matrix and precipitates
-
Migrating grain boundaries
-
Homogenous nucleation of dislocations due to very high applied stresses
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