METAL PROPERTIES, CHAR, USES, AND CODES - OD1643 - LESSON 1/TASK 1
the damage has begun.
In short, a tough metal, such as a cold
chisel, is one that can withstand considerable stress, slowly or
suddenly applied, and that will deform before failure. Toughness has
been defined by some metallurgists as having the property of
absorbing considerable energy before fracture and, therefore,
involves both ductility and strength. Toughness is a measure of the
total energy-absorbing capacity of the material, including the energy
of both elastic and plastic deformation under a gradually applied
load.
Generally speaking, toughness applies to both strength and
Thus, a very easily deformed substance of low strength
would not be considered tough, nor would a material of high strength,
but with little plasticity, such as hardened tool steel.
The true
tough metal is one that will rapidly distribute within itself both
the stress and resulting strain caused by a rapidly applied load.
(8) Brittleness.
The term "brittleness" implies sudden failure.
It is the property of breaking without warning; that is, without
visible permanent deformation.
It is the reverse of toughness in
the sense that a brittle piece of metal has little resistance to
rupture after it reaches its elastic limit. Brittleness can also be
said to be the opposite of ductility, in the sense that it involves
rupture with very little deformation. In many cases, hard metals are
brittle; however, the terms should not be confused or used
synonymously.
(9) Corrosive Resistance. Corrosive resistance is the resistance
to eating away or wearing by the atmosphere, moisture, or other
agents, such as acid.
(10) Abrasion Resistance.
Abrasion resistance is the resistance to
wearing by friction.
(11) Fatigue. When metal is subject to frequent repetitions of a
stress, it will ultimately rupture and fail, even though the stress
may
not
be
sufficient
to
produce
permanent
deformation
if
continuously applied for a relatively brief time. Such a repetition
of stress may occur, for example, in the shank of a rock drill.
Alternation of stress will produce failure more rapidly than
repetition of stress.
Alternations of stress mean the alternate
tension and compression on any material.
The definition of fatigue
is the failure of metals and alloys that have been subjected to
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