31. P.F. Thomason, Ductile Fracture of Metals, Pergamon Press, Oxford, 1990
32. J.R. Rice and M.A. Johnson, Inelastic Behavior of Solids, M.F. Kanninen, Ed., McGraw-Hill, New
York, 1970, p 641
33. J. R. Rice, Fracture—An Advanced Treatise, H. Liebowitz, Ed., Academic Press, New York, 1968, p
191
Introduction to the Mechanical Behavior of Metals
Todd M. Osman, U.S. Steel Research; Joseph D. Rigney, General Electric Aircraft Engines

Selected References
Structure of Metals
• D.A. Porter and K.E. Easterling, Phase Transformations in Metals and Alloys, Van Nostrand Reinhold,
Birkshire, UK, 1987
• C.R. Barrett, W.D. Nix, and A.S. Tetelman, The Principles of Engineering Materials, Prentice-Hall,
Inc., Englewood Cliffs, New Jersey, 1973
• W. Hume-Rothery and G.V. Raynor, The Structure of Metals and Alloys, The Institute of Metals,
London, 1956
• D. Hull and D.J. Bacon, Introduction to Dislocations, Pergamon Press, London, 1984
• P.B. Hirsch, Ed., Defects, Vol 2, The Physics of Metals, Cambridge University Press, Cambridge, 1975
• U.F. Kocks, C.N. Tome, and H.-R. Wenk, Texture and Anisotropy, Cambridge University Press,
Cambridge, 1998
• D. Hull, An Introduction to Composite Materials, Cambridge University Press, 1975
Deformation of Metals and Strength of Metals
• M.A. Meyers and K.K. Chawla, Mechanical Metallurgy: Principles and Applications, Prentice Hall,
Inc., 1984
• J.M. Gere and S.P. Timoshenko, Mechanics of Materials, 2nd ed., PWS Publishers, 1984
• T.H. Courtney, Mechanical Behavior of Materials, McGraw-Hill, New York, 1990
• J.W. Martin, Micromechanisms in Particle Hardened Alloys, Cambridge University Press, 1980
• P.F. Thomason, Ductile Fracture of Metals, Pergamon Press, Oxford, 1990
• R.W.K. Honeycombe, The Plastic Deformation of Metals, 2nd ed., Edward Arnold, London, 1984
Special Conditions in Flow and Fracture
• J.F. Knott, Fundamentals of Fracture Mechanics, Butterworths, 1981

derived in structure and content from the article “Fundamental Structure-Property Relationships in Engineering
Materials,” in Materials Selection and Design, Volume 20 of ASM Handbook (Ref 2). In light of the
bewildering number of different engineering materials within each class, discussions were limited to a number
of general examples typifying the general features of the major classes of nonmetallic materials.
References cited in this section
1. N.E. Dowling, Mechanical Behavior of Materials: Engineering Methods for Deformation, Fracture,
and Fatigue, 2nd ed., Prentice Hall, 1999, p 23
2. T.H. Courtney, Materials Selection and Design, Vol 20, ASM Handbook, ASM International, 1997, p
336–356
Introduction to the Mechanical Behavior of Nonmetallic Materials
M.L. Weaver and M.E. Stevenson, The University of Alabama, Tuscaloosa

General Characteristics of Solid Materials
Engineering materials can be conveniently grouped into five broad classes: metals, ceramics and glasses,
intermetallic compounds, polymers, and composite materials. Metals, ceramics and glasses, polymers, and
composites represent the most widely utilized classes of engineering materials, whereas intermetallic
compounds (i.e., intermetallics), which are actually subcategories of metals and ceramics, are an emerging class
of monolithic materials. The general features of five major classes of materials are summarized in Fig. 1 and are
described in the following sections. Though this article deals with the properties of nonmetallic materials, a
brief discussion of the general characteristics of metallic materials is included where pertinent.

Fig. 1 General characteristics of major classes of engineering materials. Adapted from Ref 3
Metals
Metals represent the majority of the pure elements and form the basis for the majority of the structural
materials. The mechanical behavior of metals depends on a combination of microstructural and macrostructural
features, which ultimately depend upon bonding, chemical composition, and mode of manufacture. Metals are
held together by metallic bonds. Metallic bonds arise because on an atomic scale, the outer electron shells in
metals are less than half full. As a result, each atom donates its available outer shell (i.e., valence) electrons to
an electron cloud that is collectively shared by all of the atoms in the solid. This is referred to as metallic
bonding and is responsible for the high elastic moduli and the high thermal and electrical conductivity exhibited


Fig. 2 Schematic representation of ionically bonded NaCl. Note that this structure consists of Na
+
and Cl
-

ions sitting on interpenetrating fcc Bravais lattices.
Covalent bonding occurs in compounds containing electronegative elements. Covalent bonding involves the
sharing of valence electrons with specific neighboring atoms. This is schematically illustrated for methane
(CH
4
) in Fig. 3. For a covalent bond to occur between C and H, for example, each atom must contribute at least
one electron to the bond. These electrons are shared by both atoms, resulting in a strong directional bond
between atoms. The number of covalent bonds that form depends on the number of valence atoms that are
available in each atom. In methane, carbon has four valence electrons, while each hydrogen atom has only one.
Thus, each hydrogen atom can acquire one valence electron to fill its outer orbital shell. Similarly, each carbon
atom can accommodate four valence electrons to fill its outer shell. This type of bonding makes covalent solids
strong, brittle, and highly insulative because electrons are incapable of detaching themselves from their parent
and moving freely through the solid. Covalent solids also have lower CNs due to this localized electron sharing
resulting in lower densities. For example, diamond, which is an elemental covalent compound, has a CN of 4
(Fig. 4). Like ionic solids, covalent solids tend to exhibit very narrow composition ranges and exhibit little
tolerance for alloying additions. Examples of covalent molecules, elements, and compounds include H
2
O,
HNO
3
, H
2
, diamond, silicon, GaAs, and SiC.


strengths and elastic moduli, are often used in precipitate form to strengthen commercial alloys (e.g., Ni
3
Al in
Ni-base superalloys), and their low densities and high microstructural stability makes them attractive for use in
high-temperature structural applications such as turbine blades, exhaust nozzles, and automotive valves.
Examples of some typical intermetallic compounds are illustrated in Fig. 5. Of the more than 25,000 known
intermetallic compounds, recent emphasis has focused on the development of NiAl, FeAl, Ni
3
Al, TiAl, and
MoSi
2
base alloys for use as monolithic alloys in structural applications (Ref 4). As in the cases of ceramics and
glasses, the same bonds that impart intermetallics with high strengths render most of them with low ductility
and fracture toughness at ambient temperatures.

Fig. 5 Some simple intermetallic crystal structures