Materials for engineering, 3rd Edition - (Malestrom)

Problems 221
1800
1720
1600
Liquid
1400
Temperature (°C)
1200
1000
β
α
δ
ε
800
γ
0 10 20 30 40 50 60 70 80 90 100
Weight % Ni
Fig. 7.2
7. Sketch portions of a linear polypropylene molecule that are (a) isotactic,
(b) syndiotactic and (c) atactic.
8. Compare the crystalline state in metals and polymers.
9. Compare the non-crystalline state as it applies to polymers and inorganic
glasses.
Chapter 2
1. The portion of the true stress–strain curve for a certain material may be
described empirically by the Hollomon relationship:
σ = Kε n
where n is known as the strain hardening coefficient.
In a tensile test on this material, find the value of the true plastic strain
at necking instability.
[Answer: n]
2. Find the maximum surface stress in an elastically loaded beam of width
10 mm and thickness 5 mm under a load of 2 kg in (a) three-point bending
with 100 mm between the outer knife edges (L) and (b) four-point bending
with 25 mm between the inner and outer knife-edges (d).
[Answers: (a) 120 MPa; (b) 10 MPa]