Line Defect (Leaving Cert Engineering): Flashcards
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Line defects
Line defects
Structural imperfections along a line in crystal lattice
Dimensionality of line defects
Dimensionality of line defects
One-dimensional imperfections extending through material
Most common type of line defect
Most common type of line defect
Dislocation
Structure of a dislocation
Structure of a dislocation
Incomplete row of atoms within crystal structure
What makes dislocations mobile
What makes dislocations mobile
Shear stress (forces sliding material parts)
Where dislocations travel under stress
Where dislocations travel under stress
From interior towards surface
Stress concentration in dislocations
Stress concentration in dislocations
Incomplete row of atoms creates high stress areas
What happens when dislocation reaches surface
What happens when dislocation reaches surface
Forms starting point for a crack
Effect of dislocations on mechanical properties
Effect of dislocations on mechanical properties
Makes materials harder or more brittle
Why dislocations move easily through crystal
Why dislocations move easily through crystal
Less energy needed than deforming perfect crystal
What dislocation movement allows material to do
What dislocation movement allows material to do
Accommodate applied stress
Failure progression pathway in metals
Failure progression pathway in metals
Internal dislocation → surface crack → complete failure