METAL PROPERTIES, CHAR, USES, AND CODES - OD1643 - LESSON 1/TASK 1
substance known is tungsten-molybdenum; titanium and nickel follow in
order of strength of commercially pure metals.
Pure iron is much
weaker, but, when alloyed with the chemical element known as "carbon"
to make steel, it may then become stronger than any of the pure
metals except tungsten.
Strength and plasticity (discussed in
paragraph 2d(6) on page 6) are considered the two most important
properties that a metal can possess.
(a) Tensile Strength.
Tensile strength is the ability of a
metal to resist being pulled apart by opposing forces acting in a
straight line (figure 1, view A, on the following page).
It is
expressed as the number of pounds of force required to pull apart a
bar of material 1 inch wide and 1 inch thick.
The tensile test is
the one most often used to measure the strength of metals.
Pure
molybdenum has a high tensile strength and is very resistant to heat.
It is used principally as an alloying agent in steel to increase
strength, hardenability, and resistance to heat.
(b) Shear Strength.
Shear strength is the ability of a
material to resist being fractured by opposing forces acting in a
straight line but not in the same plane (figure 1, view B, on the
following page).
(c) Compressive Strength.
Compressive strength is the ability
of a material to withstand pressures acting on a given plane (figure
1, view C, on the following page).
(2) Elasticity.
Elasticity is the ability of material to return
to its original size, shape, and dimensions after being deformed
(figure 1, view D, on the following page).
Any material that is
subjected to an external load is distorted or strained. Elastically
stressed materials return to their original dimensions when the load
is released, provided that the load is not too great. Distortion or
deformation is in proportion to the amount of the load, up to a
certain point. If the load is too great, the material is permanently
deformed, and, when the load is further increased, the material will
break.
The property of regaining the original dimensions upon
removal of the external load is known as elasticity.
(a) The elastic
limit
is
the
point
at
which
permanent
deformation begins.
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