Chapter 2

MATERIALS AND PROCESSES

69

 

 

For specific information on material properties, consult the following: H. E. Boyer and T. L. Gall, ed. Metals Handbook. Vol. 1. American Society for Metals: Metals Park, Ohio, 1985.

2

U. S. Department of Defense. Metallic Materials and Elements for Aerospace Vehicles and Structures MIL-HDBK-5H, 1998.

R. Juran, ed. Modern Plastics Encyclopedia. McGraw-Hill: New York, 1988.

J. D. Lubahn and R. P. Felgar, Plasticity and Creep of Metals. Wiley: New York, 1961.

For information on failure of materials, consult the following: J. A. Collins, Failure of Materials in Mechanical Design. Wiley: New York, 1981.

N. E. Dowling, Mechanical Behavior of Materials. Prentice-Hall: Englewood Cliffs, N.J., 1992.

R. C. Juvinall, Stress, Strain and Strength. McGraw-Hill: New York, 1967.

For information on plastics and composites, consult the following: ASM, Engineered Materials Handbook: Composites. Vol. 1. American Society for Metals: Metals Park, Ohio, 1987.

ASM, Engineered Materials Handbook: Engineering Plastics. Vol. 2. American Society for Metals: Metals Park, Ohio, 1988.

Harper, ed. Handbook of Plastics, Elastomers and Composites. 2nd ed. McGraw-Hill: New York, 1990.

J. E. Hauck, “Long-Term Performance of Plastics.” Materials in Design Engineering, pp. 113-128, November, 1965.

M. M. Schwartz, Composite Materials Handbook. McGraw-Hill: New York, 1984.

For information on manufacturing processes, see:

R. W. Bolz, Production Processes: The Productivity Handbook. Industrial Press: New York, 1974.

J. A. Schey, Introduction to Manufacturing Processes. McGraw-Hill: New York, 1977.

 

 

 

2.13 PROBLEMS

Table P2-0

Topic/Problem Matrix

2-1 Figure P2-1 shows stress-strain curves for three failed tensile-test specimens. All are plotted on the same scale.

2.1 Material Properties

(a)

Characterize each material as brittle or ductile.

(b)

Which is the stiffest?

2-1, 2-2, 2-3, 2-4, 2-5, 2-6, 2-7,

2-8, 2-9, 2-10, 2-11, 2-12, 2-18,

(c)

Which has the highest ultimate strength?

2-19, 2-20, 2-21, 2-22, 2-23

(d)

Which has the largest modulus of resilience?

(e)

Which has the largest modulus of toughness?

2.4 Hardness

2-2 Determine an approximate ratio between the yield strength and ultimate strength for each 2-13, 2-14

material shown in Figure P2-1.

2.6 General Properties

2-3 Which of the steel alloys shown in Figure 2-19 would you choose to obtain 2-15, 2-16, 2-17, 2-24, 2-25,

2-26

(a)

Maximum strength

(b)

Maximum modulus of resilience

2.8 Selecting Materials

(c)

Maximum modulus of toughness

2-37, 2-38, 2-39, 2-40

(d)

Maximum stiffness

 

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Image 179

Image 180

Image 181

 

70

MACHINE DESIGN -

An Integrated Approach

 

 

 

2-4 Which of the aluminum alloys shown in Figure 2-21 would you choose to obtain Stress 

 

 

(a)

Maximum strength

 

2

(b)

Maximum modulus of resilience

 

(c)

Maximum modulus of toughness

 

 

(d)

Maximum stiffness

 

 

 

2-5 Which of the thermoplastic polymers shown in Figure 2-22 would you choose in order to obtain

 

 

 

 

 

(a)

Maximum strength

 

 

 

(b)

Maximum modulus of resilience

 

 

 

(c)

Maximum modulus of toughness

 

 

(d)

Maximum stiffness

 

 

 

Strain 

*2-6 A metal has a strength of 414 MPa at its elastic limit and the strain at that point is 0.002.

 

(a)

Assume the test specimen is 12.8-mm dia and has a 50-mm gage length. What is its

 

 

modulus of elasticity? What is the strain energy at the elastic limit? Can you define the

 

Stress 

type of metal based on the given data?

 

 

 

 

2-7 A metal has a strength of 41.2 kpsi (284 MPa) at its elastic limit and the strain at that

 

 

 

point is 0.004. Assume the test specimen is 0.505-in dia and has a 2-in gage length.

 

 

 

What is the strain energy at the elastic limit? Can you define the type of metal based on

 

 

 

the given data?

 

 

 

 

 

*

 

2-8 A metal has a strength of 134 MPa at its elastic limit and the strain at that point is 0.003.

 

 

 

 

What is its modulus of elasticity? Assume the test specimen is 12.8-mm dia and has a

 

 

 

50-mm gage length. What is its modulus of elasticity? What is the strain energy at the

 

 

 

elastic limit? Can you define the type of metal based on the given data?

 

 

 

*2-9 A metal has a strength of 100 kpsi (689 MPa) at its elastic limit and the strain at that

 

Strain 

point is 0.006. What is its modulus of elasticity? What is the strain energy at the elastic

 

 

(b)

limit? Assume the test specimen is 0.505-in dia and has a 2-in gage length. Can you

 

 

define the type of metal based on the given data?

Stress 

2-10 A material has a yield strength of 689 MPa at an offset of 0.6% strain. What is its

 

 

modulus of resilience?

 

 

 

 

2-11 A material has a yield strength of 60 kpsi (414 MPa) at an offset of 0.2% strain. What is

 

 

its modulus of resilience?

 

 

 

 

*2-12 A steel has a yield strength of 414 MPa, an ultimate tensile strength of 689 MPa, and an

 

 

elongation at fracture of 15%. What is its approximate modulus of toughness? What is

 

 

its approximate modulus of resilience?

 

 

 

2-13 The Brinell hardness of a steel specimen was measured to be 250 HB. What is the

 

 

material’s approximate tensile strength? What is its hardness on the Vickers scale? The Strain 

 

Rockwell scale?

(c)

*2-14 The Brinell hardness of a steel specimen was measured to be 340 HB. What is the material’s approximate tensile strength? What is its hardness on the Vickers scale? The F I G U R E P 2 - 1

Rockwell scale?

Stress-Strain Curves

2-15 What are the principal alloy elements of an AISI 4340 steel? How much carbon does it have? Is it hardenable? By what techniques?

 

*2-16 What are the principal alloy elements of an AISI 1095 steel? How much carbon does it have? Is it hardenable? By what techniques?

 

2-17 What are the principal alloy elements of an AISI 6180 steel? How much carbon does it

 

*

have? Is it hardenable? By what techniques?

Answers to these problems are

provided in Appendix D.

2-18 Which of the steels in Problems 2-15, 2-16, and 2-17 is the stiffest?

 

Image 182