1. A knowledge of what four aspects is critical to the successful application of a material in an engineering design?
2. What are some properties commonly associated with metallic materials?
3. What are some of the more common nonmetallic engineering materials?
4. What are some of the important physical properties of materials?
5. Why should caution be exercised when applying the results from any of the standard mechanical property tests? 6. What are the standard units used to report stress and strain
in the English system? In the metric or SI system? 7. What are static properties?
8. What is the most common static test related to mechanical properties?
9. Why might Young’s modulus or stiffness be an important material property?
10. What are some of the tensile test properties that are used to describe or define the elastic-to-plastic transition in a material?
11. Why is it important to specify the “offset” when providing yield strength data?
12. What are two tensile test properties that can be used to describe the ductility of a material?
13. Is a brittle material a weak material? What does “brittleness” mean?
14. What is the toughness of a material?
15. What is the difference between true stress and engineering stress? True strain and engineering strain?
16. What is strain hardening or work hardening? How might this phenomenon be measured or reported? How might it be used in manufacturing?
17. How might tensile test data be misleading for a “strain rate sensitive” material?
18. What are some of the different material characteristics or responses that have been associated with the term hardness? 19. What are the similarities and differences between the Brinell
and Rockwell hardness tests?
20. Why are there different Rockwell hardness scales?
21. When might a microhardness test be preferred over the more standard Brinell or Rockwell tests?
22. Why might the various types of hardness tests fail to agree with one another?
23. What is the relationship between penetration hardness and the ultimate tensile strength for steel?
24. Describe several types of dynamic loading.
25. Why should the results of standardized dynamic tests be applied with considerable caution?
26. What are the two most common types of bending impact tests? How are the specimens supported and loaded in each? 27. What aspects or features can significantly alter impact data? 28. What is “notch-sensitivity” and how might it be important in
the performance of a product?
29. What is the endurance limit? What occurs when stresses are above it? Below it?
30. Are the stresses applied during a fatigue test above or below the yield strength (as determined in a tensile test)?
31. What features may significantly alter the fatigue lifetime or fatigue behavior of a material?
32. What relationship can be used to estimate the endurance limit of a steel?
33. What material, design, or manufacturing features can contribute to the initiation of a fatigue crack?
34. What are fatigue striations and why do they form?
35. Why is it important for a designer or engineer to know a material’s properties at all possible temperatures of operation? 36. Why should one use caution when using steel at low temper-
ature?
37. How might we evaluate the long-term effect of elevated tem- perature on an engineering material?
38. What is a stress–rupture diagram, and how is one developed? 39. Why are terms such as machinability, formability, and
weldability considered to be poorly defined and therefore
quite nebulous?
40. What is the basic premise of the fracture mechanics approach to testing and design?
41. What three principal quantities does fracture mechanics attempt to relate?
42. What are the three most common thermal properties of a material, and what do they measure?
43. Describe an engineering application where the density of the selected material would be an important material consideration.
44. Why is it important that property testing be performed in a standardized and reproducible manner?
45. Why is it important to consider the orientation of a test specimen with respect to the overall piece of material?
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Problems
1. Select a product or component for which physical properties are more important than mechanical properties.
a. Describe the product or component and its function. b. What are the most important properties or characteristics? c. What are the secondary properties or characteristics that
would also be desirable?
2. Repeat Problem 1 for a product or component whose domi- nant required properties are of a static mechanical nature. 3. Repeat Problem 1 for a product or component whose domi-
nant requirements are dynamic mechanical properties.
4. One of the important considerations when selecting a mater- ial for an application is to determine the highest and lowest operating temperatures along with the companion properties that must be present at each extreme. The ductile-to-brittle transition temperature, discussed in Section 2.4, has been an important factor in a number of failures. An article that sum- marized the features of 56 catastrophic brittle fractures that made headline news between 1888 and 1956 noted that low temperatures were present in nearly every case. The water temperature at the time of the sinking of the Titanic was above
the freezing point for salt water but below the transition point for the steel used in construction of the hull of the ship. a. Which of the common engineering materials exhibits a duc-
tile-to-brittle transition?
b. For plain carbon and low-alloy steels, what is a typical value (or range of values) for the transition temperature? c. What type of material would you recommend for con-
struction of a small vessel to transport liquid nitrogen with- in a building or laboratory?
d. Figure 2-34 summarizes the results of impact testing per- formed on hull plate from the Titanic and similar materi- al produced for modern steel-hulled ships. Why should there be a difference between specimens cut longitudinal- ly (along the rolling direction) and transversely (across the rolling direction)? What advances in steel making have led to the significant improvement in low-temperature impact properties?
5. Several of the property tests described in this chapter produce results that are quite sensitive to the presence or absence of
notches or other flaws. The fracture mechanics approach to materials testing incorporates flaws into the tests and evaluates their performance.The review article mentioned in Problem 4 cites the key role of a flaw or defect in nearly all of the head- line-news fractures.
a. What are some of the various “flaws or defects” that might be present in a product? Consider flaws that might be pre- sent in the starting material, flaws that might be introduced during manufacture, and flaws that might occur due to ship- ping, handling, use, maintenance, or repair.
b. What particular properties might be most sensitive to flaws or defects?
c. Discuss the relationship of flaws to the various types of loading (tension vs. compression, torsion, shear).
d. Fracture mechanics considers both surface and interior flaws and assigns terms such as crack initiator, crack propagator, and crack arrestor. Briefly discuss why location and orien- tation may be as important as the physical size of a flaw.
Chapter 2
CASE STUDY
Separation of Mixed Materials
B
ecause of the amount of handling that occurs during material production, within warehouses, and during manufacturing operations, along with the handling of loading, unloading, and shipping, material mix-ups and mixed materials are not an uncommon occurrence. Mixed materials also occur when industrial scrap is collected or when discarded products are used as raw materials through recycling. Assume that you have equipment to perform each of the tests described in this chapter (as well as access to the full spectrum of household and department store items and even a small machine shop). For each of the following material combinations, determine a procedure that would permit separation of the mixed materials. Use standard data- source references to help identify distinguishable properties.1. Steel and aluminum cans that have been submitted for recycling
2. Stainless steel sheets of Type 430 ferritic stainless and Type 316 austenitic stainless.
3. 6061-T6 aluminum and AZ91 magnesium that have become mixed in a batch of machine shop scrap. 4. Transparent bottles of polyethylene and polypropylene
(both thermoplastic polymers) that have been collected for recycling.
5. Hot-rolled bars of AISI 1008 and 1040 steel. 6. Hot-rolled bars of AISI 1040 (plain-carbon) steel and