Structural Imperfections

Classify the structural imperfections according to their length scale.

Describe the interstitial and substitutional impurity atoms by sketching a representative material structure where these point defects exist.

Describe the edge and screw dislocations by denoting them in a typical crystalline structure, and state the fundamental differences between these two.

The two different lattices with dislocations are given in the figure below. Identify the type of dislocation and plot the Burger's vector for each.

Give three examples for surface defects.

What could be an implication of a bulk defect in a glass plate with regard to its overall macroscopic tensile strength?

Concepts of Stress and Strain

$7.$ A steel bar is $100$ mm long, and has a $20$ mm by $10$ mm cross$-$section. Its Young's modulus $E$ is $207$ GPa $,$ and Poisson's ratio $v$ is $0\mathrm{.}26.$ It is subjected to following load combination: a tensile load of ${10}^{4}N$ on its $20mm10mm-$ face, a compressive load of ${10}^{5}N$ on its $100mm20mm-$face, and a tensile load of ${10}^{5}N$ on its $100mm10mm-$ face.

Determine:

a$)$ the change in volume of the bar,

b$)$ the new value of the compressive load so that there is no volume change.