Industrial Engineering Chapter 3 Permissions Department Pearson Education Inc Upper Saddle River Using The Information Given

Chapter 3

Structure and Manufacturing

Properties of Metals

Questions

3.1 What is the difference between a unit cell and

a single crystal?

3.2 Explain why we should study the crystal struc-

formation about various properties can be in-

ferred. By relating structure to properties, one

3.3 What effects does recrystallization have on the

properties of metals?

As shown in Figs. 3.17 on p. 96 and 3.18 on

p. 97, strength and hardness are reduced, duc-

higher the ductility of the metal. Also, the slip

system and the number of active slip systems

for plastic deformation. See also Section 3.3.1

3.5 Explain what is meant by structure-sensitive

and structure-insensitive properties of metals.

structure-insensitive properties.

3.6 What is the relationship between nucleation

rate and the number of grains per unit volume

of a metal?

This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited

reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or

likewise. For information regarding permission(s), write to:

Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.

3.7 Explain the difference between recovery and re-

crystallization.

3.8 (a) Is it possible for two pieces of the same

metal to have different recrystallization temper-

atures? Explain. (b) Is it possible for recrys-

tallization to take place in some regions of a

workpiece before other regions do in the same

workpiece? Explain.

3.9 Describe why different crystal structures ex-

hibit different strengths and ductilities.

tility of a metal depends on how many of the

is the plane spacing), and the b/a ratio depends

on the slip system of the chemical structure.

(See also Section 3.3.1 starting on p. 87.)

become oriented nonrandomly in a workpiece

when it is deformed, because the slip direction

of a crystal tends to align along the general

deformation direction. Mechanical fibering is

caused by the alignment of impurities, inclu-

preferred orientation resulting from the recrys-

tallization process. Copper is an example of a

chanical fibering in a workpiece? Explain.

This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited

reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or

likewise. For information regarding permission(s), write to:

Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.

3.14 Explain why we may have to be concerned with

the orange-peel effect on metal surfaces.

Orange peel not only influences surface appear-

ance of parts, which may or may not be desir-

able, but also affects their surface characteris-

3.15 How can you tell the difference between two

parts made of the same metal, one shaped by

cold working and the other by hot working? Ex-

parts.

Some of the methods of distinguishing hot vs.

cold worked parts are:

(a) The surface finish of the cold-worked part

would be smoother than the hot-worked

(b) If hardness values could be taken on the

behavior.

(d) Metallographic examination of the parts

grain size increases.

Strength increases as more entanglements of

the strength will be lower. (See also Eq. (3.8)

on p. 92.)

3.17 What is the significance of some metals, such as

lead and tin, having recrystallization tempera-

tures at about room temperature?

formability. However, as the strain rate in-

creases, their strength at room temperature in-

creases because the metal has less time to re-

3.18 You are given a deck of playing cards held

together with a rubber band. Which of the

material-behavior phenomena described in this

chapter could you demonstrate with this setup?

What would be the effects of increasing the

number of rubber bands holding the cards to-

gether? Explain. (Hint: Inspect Figs. 3.5 and

The following demonstrations can be made with

Fig. 3.5a on p. 86.

(b) Surface roughness that develops along the

p. 99.

(e) Presence of a rubber band indicates elastic

behavior and recovery when unloaded.

This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited

reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or

likewise. For information regarding permission(s), write to:

Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.

3.19 Using the information given in Chapters 2 and

3, list and describe the conditions that induce

brittle fracture in an otherwise ductile piece of

metal.

tension components,

(d) radiation damage, and

for a (1) paper clip, (2) bicycle frame, (3) ra-

tions, the particular requirements that are sig-

(a) Yield stress, elastic modulus, corrosion re-

sistance.

3.21 Explain the advantages and limitations of cold,

These are explained briefly in Section 3.7 on

p. 98. Basically, cold working has the advan-

tages of refining the materials grain structure

while increasing mechanical properties such as

3.22 Explain why parts may crack when suddenly

subjected to extremes of temperature.

Thermal stresses result from temperature gra-

(See also Section 3.9.5 starting on p. 107 re-

3.23 From your own experience and observations,

(3) copper, (4) magnesium, and (5) gold.

There are numerous acceptable answers, includ-

ing:

3.24 List three applications that are not suitable for

This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited

reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or

likewise. For information regarding permission(s), write to:

Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.

(1) steel, (2) aluminum, (3) copper, (4) magne-

sium, and (5) gold.

car tire, portable computer case.

(b) aluminum: cutting tools, shafts, gears, fly-

3.25 Name products that would not have been devel-

oped to their advanced stages, as we find them

3.26 Inspect several metal products and components

and make an educated guess as to what mate-

3.27 List three engineering applications each for

(c) High thermal conductivity: cookware, car

radiators, precision instruments that resist

3.28 Two physical properties that have a major in-

fluence on the cracking of workpieces, tools, or

dies during thermal cycling are thermal conduc-

the stresses will be lower for a given tempera-

ture gradient. When thermal stresses reach a

traditional materials.

chasing an aluminum automobile?

This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited

reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or

likewise. For information regarding permission(s), write to:

Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.

3.31 Lead shot is popular among sportsmen for hunt-

ing, but birds commonly ingest the pellets

(along with gravel) to help digest food. What

substitute materials would you recommend for

lead, and why?

Obviously, the humanitarian concern is asso-

ciated with the waterfowl ingesting lead and,

therefore, perishing from lead poisoning; the

3.2 on p. 98, materials with a very high density

3.32 What are metallic glasses? Why is the word

“glass” used for these materials?

tation. Thus, none of the traditional metallic

characteristics are present, such as deformation

by slip, anisotropy, or grain effects. Because

this is very similar to the microstructure and

behavior of glass, hence the term.

3.33 Which of the materials described in this chap-

ter has the highest (a) density, (b) electri-

cal conductivity, (c) thermal conductivity, (d)

1050 MPa, and the highest cost (which varies

3.34 What is twinning? How does it differ from slip?

This is illustrated in Fig. 3.5 on p. 86. In twin-

3.35 Calculate the theoretical (a) shear strength and

(b) tensile strength for aluminum, plain-carbon

steel, and tungsten. Estimate the ratios of their

τ=G

2π

σ=E

10

2.1 on p. 32, and Gis calculated using Eq. (2.24)

on p. 49,

G=E

2(1 −ν)

Thus, the following table can be generated:

Mat- E G τ σ

3.36 A technician determines that the grain size of

a certain etched specimen is 6. Upon further

checking, it is found that the magnification used

was 150, instead of 100 as required by ASTM

standards. What is the correct grain size?

late from Table 3.1 on p. 93 or obtain the data

for a larger number of grain sizes, as well as the

grain diameter as a function of the ASTM No.

This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited

reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or

likewise. For information regarding permission(s), write to:

Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.

-3 1 0.7 1.00

-1 4 5.6 0.50

0 8 16 0.35

1 16 45 0.25

1.5= 0.0293mm

As can be seen from the table, this corresponds

As can be seen in Table 3.1 on p. 93, an ASTM

grain size of 9 has 185,000 grains/mm3. An or-

(50.5)(185,000)=9.34 million.

3.38 The natural frequency fof a cantilever beam is

given by the expression

where Eis the modulus of elasticity, Iis the

that any cross section will result in the same

trends, so students shouldn’t be discouraged

from considering, for example, circular cross

will decrease with increasing temperature (see

Fig. 2.9 on p. 41). Consider the ratio of initial

f2

0.56qE2I2g

w2L4

2

(W/L2)L4

2

L3

2

L2=L1(1 + α∆T)

Therefore, the frequency ratio is

This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited

reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or

likewise. For information regarding permission(s), write to:

Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.

3.3 on p. 106, the coefficient of thermal expan-

sion for steel is 14.5 µm/m◦C (average of the

extreme values given in the table), so that the

3.39 A strip of metal is reduced in thickness by cold

working from 25 mm to 15 mm. A similar strip

is reduced from 25 mm to 10 mm. Which one

of these strips will recrystallize at a lower tem-

perature? Why?

A review of Fig. 3.18 will indicate that, because

3.40 A 1-m long, simply-supported beam with a

round cross section is subjected to a load of 50

kg at its center. (a) If the shaft is made from

AISI 303 steel and has a diameter of 20 mm,

what is the deflection under the load? (b) For

shafts made from 2024-T4 aluminum, architec-

tural bronze, and 99.5% titanium, respectively,

what must the diameter of the shaft be for the

shaft to have the same deflection as in part (a)?

δ=P L3

48EI

δ=P L3

48EI =64P L3

48πEd4

Solving for d, we have

2024-T4 Al 79 25.2

Arch. bronze 110 23.2

If the grain size is 5, there are 2900 grains per

mm3of aluminum, and each grain has a volume

of 1/2900 = 3.45 ×10−4mm3. Recall that for

an fcc material there are four atoms per unit

cell, with a total volume of 16πR3/3, and that

the diagonal, a, of the unit cell is given by

This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited

reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or

likewise. For information regarding permission(s), write to:

Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.

0.25 nm or 0.25 ×10−6mm. The volume of an

aluminum atom is

or 6.54 ×10−20 mm3. Dividing the volume of

aluminum in the grain by the volume of an alu-

See Table 16.4.

16.4 on p. 971. Average values have been used

to obtain these plots.

600

800

1000

1200

Copper

Stainless steel Nickel

Tungsten

Titanium

Molybdenum

Steel

150

200

250

350

400

Elastic modulus (GPa)

Molybdenum

Nickel

Steel

3.43 The following data is obtained in tension tests

(µm) (MPa)

15 150

20 140

50 105

75 90

100 75

Does this material follow the Hall-Petch effect?

If so, what is the value of k?

This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited

reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or

likewise. For information regarding permission(s), write to:

Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.

160

100

120

140

0.05 0.3

The least-squares curve fit for a straight line is

Y= 35.22 + 458d−1/2

Material k α k/α

Plastics 0.4 72 0.00556

Wood 0.4 2. 0.20

Glasses 1.7 4.6 0.37

Lead 35. 29.4 1.19

Graphite 10. 7.86 1.27

Ceramics 17. 5.5 3.09

Iron 74. 11.5 6.43

Nickel 92 13.3 6.91

Gold 317. 19.3 16.4

Si 148. 7.63 19.3

Silver 429 19.3 22.2

Copper 393 16.5 23.8

Molybdenum 142 5.1 27.8

Tungsten 166. 4.5 36.9

This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited

reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or

likewise. For information regarding permission(s), write to:

Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.

This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited

reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or

likewise. For information regarding permission(s), write to:

Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.

This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited

reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or

likewise. For information regarding permission(s), write to:

Rights and Permissions Department, Pearson Education, Inc., Upper Saddle River, NJ 07458.