Definition

Section 5.3.9

Definition

Develop paragraphs by definition when you want to setworking generalizations that will help control the meaning and scope of important terms. Defining is an effective way of controlling the scope ofterms. In the following paragraph, an extended definition is used as part of the introduction to a research article. The intention here is both to establish the terms of the discourse and to establish the importanceof the subject. By exploring the meaning of the term bimetals, the writer creates ashared concept that focuses the discussion that follows. Note the use of other devices, such asfunctional description and enumeration.

Bimetallic Components
Bimetals are components made up of two separate metallic units, each occupying a distinctposition in the component.  Bimetal rods or wires (also called clad metal, duo- or dual-metal) aremade of dissimilar metals.  The rod core, a cylindrical body made of one metal, is surrounded bya concentric, cylindrical sleeve of another metal.  Some fibrous metals may also be regarded asbimetallic; for example, rods made by unidirectional solidification of some eutectic compositionscontain a metallic (or nonmetallic) compound of fibrous filaments embedded in an almost puremetallic matrix.  The structure of a present-day Nb-Sn superconducting core can be even morecomplex.  It is multimetallic--containing more than two dissimilar metals.  The two elements of abimetallic product are usually intimately interlocked, so that they function in unison.Bimetal rods or wire stems make it possible to combine properties of dissimilar metals.  Forexample:
      Aluminum-clad steel wire combines the strength of steel with the electrical          conductivity and corrosion resistivity of aluminum.
     
 Superconductor core clad with copper sleeve combines superconductivity at          cryogenic temperatures with assurance against failure when a local temporary rise          in resistance or temperature occurs.

Although the number of desired bimetallic combinations for practical use is virtually unlimited,manufacturing difficulties restrict the number of bimetallic combinations actually inuse.

--Based on B. Avitzur et al., "Criterion for the Prevention of Core Fracture duringExtrusion of Bimetal Rods," Journal of Engineering for Industry

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