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Rede Temtica em Engenharia de Materiais

UFOP - CETEC - UEMG

_________________________________________________________________________Belo Horizonte, 28 de julho de 1997.

Exame de seleo para o ingresso no Mestrado em Engenharia de Materiais.Segundo semestre de 1997

Prova de Ingls

Instrues ao Candidato:

1. Leia o texto anexo e redija, em portugus, uma interpretao livre de cada um dos pargrafos presentes no originalem ingls.

2. O exame ter uma durao de 2h (duas horas).

Adapted from

Materials Courses for Student Engineers in the 1990s

by Lawrence H. Van Vlack

Journal of Materi als, january 1990

IntroductionIts well acknowledged that engineers of all disciplines encounter technical materials in their professional

activities. The products that they make, and the systems that they develop and monitor, involve parts and components that

utilize a wide variety of materials which possess the specific characteristcs and properties to meet the necessary demands.While mechanical, electrical and many other types of engineers normally do not develop the materials to be used, each of theseengineers work closely with materials engineers in the selection, processing and enhancement of the materials required for

their products and systems. Therefore, they must posses a basic understanding of the engineering materials. As their products

and systems become more sophisticated and the number and variety of materials increase, a renewed attention is warranted

with respect to the initial course in materials that is offered to engineers who will not be materials science and engineering

(MSE) majors.

In this article, the introductory course in materials is reexamined. Being a introductory materials course, it

assumes a background in general chemistry and physics. Typically, this is the only materials course in these engineering

curricula. It is usually located near the middle of the undergraduate curriculum, since it should precede design courses. This

sequence of basic science >materials>design requires that attention be given to the necessary coupling if the engineering

curricula are to be optimized.

The current trend has been toward emphasizing basic principles and applying these principles appropriately

to various materials.

BackgroundThere has been an evolutionary change in the nature of the materials courses taught to engineers. The shop

course of pre-World War Il days has completely disappeared. Commonly, it included metal casting and some metal shaping bydeformation and machining. The civil engineering version included concrete, plus selected properties of structural metals.

During that same period, what is now know as materials engineering focused separately on: extractive

metallurgy; the forming and firing of ceramics; and the chemical synthesis that is applicable to plastics. These courses started

with raw materials. The characteristics of the material product received by the technical consumer were basically dictated by

the primary process. The above categories were isolated, since, in general, the nature of the raw materials led to distinct

processing procedures for plastics, ceramics and metals.

Although the metallurgical engineer, the ceramic engineer, and the polymer chemist improved existing

products and develop new products from their raw materials, the concerted effort to tailor-make materials for specific usesrequired the combined effort of those making materials and those using them in technological applications. This approach has

been accelerated over the past few decades, and palces and emphasis on the materials instruction for all engineers.

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During the period just cited, metallurgists played a leading role in the classroom since metals were apredominant material for technological advances. Further, many metals were simpler and more readily understood than were

the commonly avaialable ceramics and plastics. This led to earlier process control and product improvements among many

metals. If there were a metallurgy department, a course in metallurgy could be required in the curriculum, particularly for

mechanical engineers. In the absence of a metallurgy department, the mechanical engineering department commonly included

a metallurgist as a faculty member.

Relatively few schools had ceramic engineering departments. Also, academic contacts between the

engineering units and those chemists focusing on plastics were commonly remote. Thus, as engineering uses on nonmetallicmaterials increased in the technical world, their inclusion into a materials course lagged. When included, those materials would

receive attention as an inserted chapter in an otherwise metallurgical text. Such additions had relatively low odds of being

covered within the time pressures of a course. Typically, these inserted topics were limited to the description of selected

processing equipment, or to the presentation of unrationalized data.

More recently, an effort has been made toward balancing the presentation of all types of materials. This

integration is a result of several factors. First, a materials science and engineering community has emerged as a federation of

the several materials disciplinesmetals, ceramics and polymers. Second, design engineers have demonstrated and increasing

willingness to consider substitute materials when these materials are shown to have the required characteristics. Third, unifying

principles that apply to more than one of the materials categories have been expanded. From this, younger staff members feel

freer to venture into the adjacent materials disciplines in both research and teaching. Fourth and finally, textbooks have

become available that develop the principles that control properties and service behavior.

The pattern for the 1990s is already emerging as a consequence of the above mentioned inputs. It involves a

greater attetion to basic science principles, to the structural response of various materials to these principles, and to propertyconsequences that result. Processing steps are an important adjunct, which may vary with the clientele of the course and the

sequel design courses. The next item lists some principles that apply to a variety of different materials, and should be part of

any introductory course in materials science.

Principles Pertinent to SolidsBasic principles apply to all types of materials since they are governed by the laws of natures. In some cases,

parallelisms between material categories are easy to envisage. Such examples include the crystallization of metals and the

crystallization of most oxide ceramics. Further, crystallinity may be expected in some of the polymeric materials such as the

high density polyethylene.Likewise, the age-old process of supercooling silicate liquids past their glass transition temperature to

produce silicate glasses is duplicated among the majority of the common polymers with resulting amorphous or vitreous

phases. Thus, it was also anticipated that very rapidly quenched metals could be glassy, and that they too would exhibit glass-

trasition temperatures. This has proved to be the case. A large number of other parallelisms between ceramics, polymers andmetals could be cited. Included would be examples such as diffusion, powder processing, notch sesitivity for fracturing,

radiation damage, vapor deposition, magnetic saturation in superconductors, and crystal imperfections to name a few.Of course, it is necessary to recognize that the response of various materials will not behave identically.

Aluminum silicate, with a more complex structure than aluminum oxide, crystallizes more slowly. Conversely, pure metals

crystallize so rapidly that it is nearly impossible to obtain them in vitreous form. For example, glassy iron for low-loss

magnetic applications must include solutes such as phosphorus, silicon or boron to slow crystallization to a practical quenching

rate. Any materials course that builds on the commonality of principles must also address the differences in the response of the

materials.

Therefore, the basic topics that should be included in an introductory materials course include: chemical

bonding, crystallinity, disorder, phase relationships, reaction rates, and microstructural development.