Modulus of Toughness Modulus of toughness is a mechanical property of a material that indi-
cates the ability of the material to handle overloading before it fractures.Strength-to-Weight Ratio As the term implies, this is the ratio of the strength of the material
to its specific weight (weight of the material per unit volume). Based on the application,
engineers use either the yield or the ultimate strength of the material when determining the
strength-to-weight ratio of a material.Thermal Expansion The coefficient of linear expansion can be used to determine the change
in the length (per original length) of a material that would occur if the temperature of the mate-
rial were changed. This is an important material property to consider when designing products
and structures that are expected to experience a relatively large temperature swing during their
service lives.Thermal Conductivity Thermal conductivity is a property of material that shows how good the
material is in transferring thermal energy (heat) from a high-temperature region to a low-
temperature region within the material.Heat Capacity Some materials are better than others in storing thermal energy. The value of
heat capacity represents the amount of thermal energy required to raise the temperature of
1 kilogram mass of a material by 1C, or, using U.S. Customary Units, the amount of thermal
energy required to raise one pound mass of a material by 1F. Materials with large heat capac-
ity values are good at storing thermal energy.
Viscosity, vapor pressure, and bulk modulus of compressibility are additional fluid
properties that engineers consider in design.Viscosity The value of viscosity of a fluid represents a measure of how easily the given fluid
can flow. The higher the viscosity value is, the more resistance the fluid offers to flow. For
example, it would require less energy to transport water in a pipe than it would to transport
motor oil or glycerin.Vapor Pressure Under the same conditions, fluids with low vapor pressure values will not
evaporate as quickly as those with high values of vapor pressure. For example, if you were to leave
a pan of water and a pan of glycerin side by side in a room, the water will evaporate and leave
the pan long before you would notice any changes in the level of glycerin.Bulk Modulus of Compressibility A fluid bulk modulus represents how compressible the fluid
is. How easily can one reduce the volume of the fluid when the fluid pressure is increased? For
example, as we discussed in Chapter 10, it would take a pressure of 2.24 10
7
N/m
2
to reduce
1 m
3
volume of water by 1% or, said another way, to a final volume of 0.99 m
3
.
In this section, we explained the meaning and significance of some of the physical prop-
erties of materials. Tables 17.1 through 17.4 show some properties of the solid materials. In
the following sections, we will examine the application and chemical composition of some
common engineering materials.17.2 Electrical, Mechanical, and Thermophysical Properties of Materials 557
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