Guide to Mechanical Properties
- [Mechanical Properties of Common Materials] - [Materials Page] -
Coefficient
of Thermal Expansion (CTE)
How much a material shape will change for each degree of
temperature change.
Coefficient of Friction
Compressive
Strength
This number describes how much of a non-moving load a bar can
take before it is crushed. Units are normally
thousands of pounds per square inch. (103 psi) - Mega Pascals
(mPa). Higher numbers indicate stronger materials
which can withstand a heavier load before they break.
Density
This is defined as the weight of a material per unit volume.
Units - pounds per cubic inch (lb/cu in) grams/cubic
centimeter. Higher numbers indicate heavier materials. Note:
Density in lbs/cu in, and Specific Gravity are
conveniently related by the following ratio:
Dielectric
Strength
This is an electrical property and gives an indication of how
well the material acts as an electrical insulator. It
describes how much of an electrical voltage can be built up on
one side of the material before it is communicated to
the other side. Units - Volts per mil of thickness (volts/mil).
Higher numbers indicate materials which are better
insulators. C means that the material conducts electricity and
therefore has no dielectric strength.
Flexural Strength
This is also known as bending strength. It describes how much of
a non-moving load can be applied before a bar
yields or breaks. Units are normally thousands of pounds per
square inch. (103 psi) - Mega Pascals (mPa). Higher
numbers mean that material is stronger and can withstand a
heavier load.
Flexural Modulus
This is a number associated with the stiffness of materials. It
is used to calculate how far a bar will bend when a
bending load is applied to it. Units are normally millions of
pounds per square inch. (106 psi) - Giga Pascals (gPa).
Higher numbers for materials mean that they are more resistant to
deflection when equal thickness are being
compared.
Modulus of Elasticity
Poisson's
Ratio
The ratio of transverse strain to axial strain during axial load.
Rockwell
Hardness
This is a property of material which describes its
ability to be indented. The Rockwell method for measuring
hardness forces a steel point into the material and then measures
the penetration of the point. The different letters in
the Rockwell reading describe the shape of the point and the load
applied during the test. Units - Rockwell units
with the appropriate suffix letter. The letter and number cannot
be separated. Higher numbers with the same letter
indicate harder materials. Harder materials have more resistance
to penetration by another substance.
Tensile
Modulus
When a bar is pulled in tension, it has to get longer. The
tensile modulus is used to calculate how much longer it will
get when a certain load is applied to it. Units are normally
millions of pounds per square inch. (10 6 psi) - Giga
Pascals (gPa). Higher numbers indicate materials which will not
elongate as much as others when they are being
compared under equal tensile loading conditions.
Tensile
Strength
This number describes how large a non-moving load a bar can
withstand before it breaks due to elongation. Units
are normally thousands of pounds per square inch. (103 psi) -
Mega Pascals (mPa). Higher numbers indicate
materials which can withstand a stronger pull before breaking.
Thermal Coefficient of Expansion
This is a measurement of how much the length of a material will
change when the material is heated or cooled. The
value given is based on the inch as a unit. The number given
shows how much this inch of material will increase if
the temperature of the material is raised one degree Fahrenheit.
Units - inches per inch per degree Fahrenheit
(in/in/°F) - Meters/Meter/°C. Higher numbers mean that the
material will expand or lengthen more for each degree
rise in temperature. Smaller numbers indicate relative stability
to changes in temperature.
Thermal Conductivity
This property is known as the K factor. It is a measure of the
transfer of heat by conduction. It tells how much heat
is transferred from one side of a plate to the other side. It is
measured as BTUs (units of heat in the English system)
per hour per unit area (square feet) for a thickness of one inch
and a temperature difference of one degree
Fahrenheit between both sides of the plate. Units -
BTU/hr/sq/°F/inch. - Watt/(Meter Deg Kelven) W/MK. Higher
numbers mean that the material will absorb more energy before it
is broken by a moving weight.
Viscosity
A measure of the resistance of a liquid to flow.
Young's Modulus
Young's modulus describes the mechanical stiffness
properties and is expressed as the ratio of stress to strain. In
a piezoelectric material, mechanical stress produces an
electrical response which opposes the resultant strain. The value
of the Young's modulus depends on the direction of stress and
strain and the electrical conditions. The inverse of Young's
modulus, Y, is the elastic compliance, s.
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