Review for Test 2 Covering Chapters 4, 5 & 6 in Meyers and Chawla + Notes.

1. Generally know the classification of defects (i.e., 0,1,2 & 3-D) and be able to identify examples.

2. Know the differences between edge and screw dislocations.

3. There are several equations involving dislocations. The most important to know how to manipulate are:

The energy of a dislocation- U_r = Gb²/10 + {Gb²/(4p[1-n]}{1 – n cos²a)}{ln (r^-1/2) / (5 b)}

Where a = p/2 for an edge dislocation and a = 0 for a screw dislocation.

The energy of a dislocation is often approximated by U_r = Gb² / 2.

The force/unit length applied to a dislocation: F = t b.

The force of a dislocation due to the energy associated with a dislocation: F = Gb² / 2R.

Notice, the two above equations leads to the conclusion: t = Gb / 2R.

[The average dislocation radius can be approximated by: R = r^–1/2, where r is the dislocation density.]

4. Know how to decide whether or not a dislocation reaction can occur [ pp215-222 + notes].

5. Understand the principle behind the Frank-Read Source. [Note: F = T ds / R].

6. The stress on the lead dislocation due to pileup is: t* = n t and the length of pileup is: L = n Gb/ pt.

7. The principle of the Peierls-Nabarro stress is important – not necessarily the exact equation.

8. Know how to measure the grain size in a micrograph.

9. Know the difference between twinning and slip. (P. 266 and Figure 5.18).

10. The Hall-Petch equation is important! Why? You do not have to know who suggested which theory in trying to explain the Hall-Petch observations, but you should be familiar with some of the ideas behind the theories.

11. The Orowan equation [ Eq. 4.23] relates the global plastic strain to the individual dislocation motion and density. This eq. helps explain work-hardening. Study Figures 6.2, 6.3, 6.4 & 6.5.

12. Know how to calculate the stress of plastic deformation: Schmid Law. [ remember to review notes].

13. Know the relationship between yielding and the dislocation density [ Eq. 6.5].

14. You are not responsible for: 4.1.1, 4.1.2, 4.1.5, 5.1.3 (except know meaning of Fig. 5.6), 5.1.4,5.1.5, 5.1.6, 5.5, 6.2, 6.2.4, 6.3.1, 6.3.2,.6.3.3,.6.4,6.5.