Designers have been interested for decades in the possibility of using

Question

(This passage was written in 1980)

Designers have been interested for decades in the possibility of using ceramics in heat engines such as turbines and diesels. However, it was not until recently that the two prerequisites were present: thermal-shock-resistant structural ceramics sufficiently developed to be considered as engineering materials, and, equally important, computer capability sufficiently developed to handle the complex job of detailing stresses with the high degree of refinement required in brittle materials design.

Ceramics based on silicon carbide and silicon nitride have a unique combination of properties that makes them very attractive to designers of vehicular engines, energy conversation systems, and industrial heat exchangers. In particular, they provide high strength at high temperatures, good thermal stress resistance, and excellent resistance to oxidation, corrosion, and erosion. This combination of properties can be used to increase the operating temperature or to reduce the heat lost to cooling in gas turbine, diesel, and Stirling engines and in industrial heat exchangers, thereby yielding more power per unit of fuel. The low density of these ceramics may provide engine components of lower weight and inertia, which would translate into improved performance for conventional automotive engines. Recent estimates indicate that  fuel savings of one-half billion barrels of oil per year, amounting to $17.5 billion at current prices,  might be realized if ceramics were used in highway vehicles and industrial heat exchangers. Moreover, the universal abundance and inherent low cost of the element’s silicon, carbon, and nitrogen contrast sharply with the increasingly short supply and increasingly high cost of critical metals—such as chromium, nickel, cobalt, and tungsten—that are used in high-temperature allows.

So far, I have made silicon carbide and silicon nitride ceramics sound like panaceas. If these materials have so many attractive properties, why are they not used operationally in today's engines, other energy conversion devices, and industrial heat exchangers? One answer is that ceramic materials are too brittle—but this alone is too simplistic an answer. All engineering design represents a trade-off in which (50) (we hope) the best compromise in the use of materials and design emerges. The practice in engineering design to date has been to take advantage of the fact that metals relieve local overstresses by local yielding, simplifying the design process. The trade-off is that metals soften or melt and must be cooled for high temperature use. Management of the cooling fluid adds design complexity and weight and drains power. Up to now, the compromises in design that have been required to use metals have had a net payoff. However, in either economic or actual physical terms, the end of this line of development is in sight. Further development of heat engines requires higher temperatures with reduced cooling and at acceptable costs. Thus, the materials—design trade-offs will soon favor ceramics.    1 
 1. The primary purpose of the passage is to

(A) pose a questions
(B) defend a decision
(C) criticize a proposal
(D) resolve a controversy
(E) discuss an alternative

2 
 2. It can be inferred from the passage that the author would most likely agree with which of the following generalizations about engineering design?

(A) When engineers attempt to simplify the design process, they frequently make trade-offs thar result in damage to the environment.
(B) When engineers choose materials for particular design purposes, they are usually influenced both by the physical properties of the materials and by the cost of using those materials.
(C) Once engineers have developed the computer capability to design a machine using a particular material, the adoption of that material for that machine will usually follow.
(D) In examining the design trade-offs that engineers have made, one can assume that an ideal use of materials has been achieved.
(E) Materials are not sufficiently developed to be considered as engineering materials until engineers have discovered how to take advantage of all the inherent physical properties of the materials.

3 
 3. According to the passage, which of the following is a property of metals that is an advantage when metals are used in engines?

(A) Low cost
(B) Low weight
(C) Local yielding
(D) Resistance to erosion
(E) Thermal—stress resistance

4 
 4. The author mentions “fuel savings of one-half billion barrels of oil per year, amounting to $17.5 billion at current prices” ( Highlighted ) most probably in order to

(A) support the argument that ceramics have a combination of properties that makes them very attractive
(B) criticize the suggestion that low-density materials should be used in conventional automotive engines
(C) defend the use of conventional automotive engines on the grounds that the use of ceramics will greatly increase the fuel consumption of such engines
(D) imply that improving the performance of conventional automotive engines is less important than saving fuel in other highway vehicles and in industrial heat exchangers
(E) suggest that current prices for oil are unusually high and that estimated fuel Savings might therefore decrease in the future

5 
 5. It can be inferred from the passage that one of the impediments to using ceramics in turbines and diesels in the past was

(A) an insufficient supply of the elements that compose silicon carbide and silicon nitride ceramics
(B) the inability of designers to detail stresses in a very precise manner
(C) the low density of silicon carbide and silicon nitride ceramics
(D) the high temperature at which turbines and diesels operate
(E) the design complexity that is required for reducing heat in engines

6 
 6. The statement that ceramics are too brittle to be used in engines is regarded by the author as an

(A) illogical assertion
(B) insufficiently complex explanation
(C) erroneous description of the current use of ceramics
(D) irrelevant analysis of the physical properties of ceramics
(E) appropriate response to a straightforward question

7 
 7. It can be inferred from the passage that, compared to engines that use metals, engines that use ceramics would require

(A) less cooling
(B) less refined stress analyses
(C) more fuel
(D) more protection from oxidation
(E) higher operating temperatures

8 
 8. The passage provides the answer to which of the following questions?

(A) What development in computer technology has enabled designers to do highly refined analyses of stresses?
(B) How were thermal-shock-resistant structural ceramics developed?
(C) How much fuel might be saved by using ceramics in highway vehicles and industrial exchangers?
(D) Why does further development of heat engines require higher temperatures?
(E) Why do silicon carbide and silicon nitride ceramics provide high strength at high temperatures?

odiodeserunt · Answer

Q1. Answer E
the passage talks about an existing idea " Designers have been interested for decades in the possibility of using ceramics in heat engines such as turbines and diesels. " and explore it further

miag · Answer

Hi, 
I would advise also looking into your reasoning for why you considered the other options to be incorrect to ensure you are rejecting them on solid grounds, this will further help solidify your understanding and help with RC as a whole.

Sajjad1994 · Answer

Passage Map and Summary

Paragraph 1:  The Emergence of Ceramics for Heat Engines
 Main Point:  Long-standing interest in ceramics for engines was only recently possible due to two key advancements.

Paragraph 2:  Advantages of Silicon Carbide & Silicon Nitride Ceramics
 Main Point:  These ceramics offer a unique and attractive set of properties for high-temperature applications.

Paragraph 3:  The Design Trade-Off & Future Outlook
 Main Point:  Despite advantages, ceramics aren't widely used yet due to brittleness, but the fundamental design trade-off is shifting in their favor.

Summary

The passage explains that while designers have long considered ceramics for heat engines, their practical use only became feasible with recent advances in thermal-shock-resistant materials and complex computer stress analysis. Ceramics like silicon carbide and silicon nitride are highly attractive due to their unique combination of properties-high-temperature strength, durability, low density, and the use of abundant elements-which can lead to more efficient, powerful, and fuel-saving engines. Although their brittleness has hindered widespread adoption, the passage argues that the engineering trade-off is shifting. Metals, while forgiving, require heavy, power-draining cooling systems. As the pursuit of higher engine temperatures with less cooling continues, the compromises necessary for using ceramics will soon become more advantageous than those required for metals.

Designers have been interested for decades in the possibility of using

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Designers have been interested for decades in the possibility of using

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