The dislocation can move by requiring only one bond multiple bonds( only one bond, multiple bonds ) to be broken at a time.
Positive and negative dislocations move in opposite directions to produce shear of the same different( same, different ) sign.
Positive and negative dislocations (of same type, e.g., screw) attract each other, positives (or negatives) repel.
The slip plane is defined as ......
the plane on which the dislocation nucleates.
the plane on which the bond breaking occurs.
For an edge dislocation, the slip plane is defined as the plane which contains both the line direction an Burgers vector of the dislocation.
Dislocation motion can be conservative or non-conservative: • Conservative motion ❌ (i.e., diffusion) • Non-conservative motion requires ❌ or ❌ plane
The force required to move the dislocation is known as .......?
dislocation force
glide force
strain force
Enter the symbols the Frank's rule formula (not given in the formula sheet by the way):
T = Use * as a multiplication sign , alpha as a constant alpha, G as a shear modulus and b as a Burgers vector.
The Peierls stress is the stress to glide a dislocation through an otherwise perfect crystal.
What is the definition of the dislocation width?
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.
Why is the energy or stress is minimised by slip on the close packed planes in the close packed directions?
Because the atomic slip distance is a minimum.
Because atoms in the closed packed directions have least interaction potential.
Which type of dislocations is more mobile and hence has smaller Pierls Stress?
Edge dislocation
Screw dislocation
The energy or stress increases with a decrease in dislocation width.
In FCC metals, Peierls stress is a strong function of temperature while in BCC metals, Peierls is not a strong function of temperature.
What can cause an increase in number of dislocations/ dislocation density? Choose one or more than one of the answers.
Grain Boundaries
Interfaces between matrix and precipitates
Migrating grain boundaries
Homogenous nucleation of dislocations due to very high applied stresses
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