Chapter 5: Mechanical Properties of Metals Flashcards
Metals are known to be:
Malleable & Ductile
High density
High Melting Point
High Thermal Conductivity
High Electric Conductivity
how much force an
object can withstand without bending
or breaking (compression, tension, &
shear)
strength
refers to a material’s
response to tensile stress, or its
ability to be stretched, rolled or
extruded without breaking.
ductility
refers to a material’s
response to tensile stress, or its
ability to be stretched, rolled or
extruded without breaking.
ductility
refers to compressive stress, as in
flattening.
malleability
important properties of metals
ductility
malleability
toughness
fatigue resistance
hardness
represents an ideal
balance between strength and ductility.
The toughest metals are those that can
absorb the highest amounts of energy
before fracturing. In simple terms, the
toughest parts are the most difficult to
break
toughness
is a measure of a
part’s ability to undergo repeated,
cyclical stress without fracturing or
permanently deforming.
Fatigue resistance
A material’s power to
resist a permanent change in shape
when acted upon by an external force
hardness
Crystalline Structure of Metals
FCC (Face-centered cubic)
BCC (Body-centered cubic)
HCP (Hexagonal close packed)
mechanical properties of FCC
Low young modulus
Low yield strength
Low hardness
Good ductility and high ability for
forming.
mechanical properties of BCC
High yield strength
High young modulus
High hardness
High tensile strength
Limited ability to forming
mechanical properties of HCP
Brittle
Low yield strength
Inability to forming
The ___ of a material
reflects its response or deformation in
relation to an applied load or force.
mechanical behavior
Key mechanical design properties are
stiffness, strength, hardness, ductility,
and toughness
One of the most common mechanical
stress–strain tests is performed in
tension
It is conducted in a manner similar to the tensile
test, except that the force is compressive and the specimen contracts along
the direction of the stress. Same equation use in strain and stress as in
tension. Used when a material’s behavior under large and
permanent (i.e., plastic) strains is desired, as in manufacturing applications,
or when the material is brittle in tension.
is a variation of pure shear in which a
structural member is twisted in the manner of
torsional forces produce a rotational motion about
the longitudinal axis of one end of the member
relative to the other end.
torsion
is a function of the orientations of the
planes upon which the stresses are taken to act.
stress state
a more complex stress state is present that
consists of a tensile (or normal) stress 𝜎
′
that acts normal to
the p-p’ plane and, in addition, a ___ that acts
parallel to this plane; both of these stresses are represented
in the figure.
shear stress 𝝉’
is non-permanent,
which means that when the applied load is
released, the piece returns to its original
shape. As shown in the stress–strain plot
Upon release of the load, the line is
traversed in the opposite direction, back to
the origin.
elastic deformation
With increasing temperature,
the modulus of elasticity
___
decreases
defined as the
ratio of the lateral and
axial strains
Poisson’s ratio 𝝂
In most metals, G is about ___
0.4E
The stress necessary to
continue plastic deformation
in metals increases to a
maximum, point M and then
decreases to the eventual
fracture, point F. Unit Mpa
or psi
Tensile Strength (TS)
It is a measure of the
degree of plastic
deformation that has been
sustained at fracture.
Ability of metal to drawn out
into wire. Performance under tensile stresses
ductility
Knowledge of the ductility of materials is important for at
least two reasons.
1.) It indicates to a designer the degree to which a
structure will deform plastically before before fracture
2.) It specifies the degree of allowable deformation
during fabrication operations.
Metal that experiences
very little or no plastic
deformation upon fracture
brittle
Is the capacity of a material to
absorb energy when it is
deformed elastically
and then, upon unloading, to
have this energy recovered.
resilience
is the ability of a material to absorb energy and
plastically deform before fracturing
toughness
which is a measure of a material’s resistance to
localized plasti
hardness
Values normally range between
1.2 and 4.0
Selection of ___ will depend on a number of factors,
including economics, previous experience, the accuracy
with which mechanical forces and material properties
may be determined, and, most important, the
consequences of failure in terms of loss of life and/or
property damage.
N
showing linear elastic
deformation for loading
and unloading cycles.
Schematic
stress–strain diagram
