What is the importance of material properties?

Construction in civil engineering demands high strength, durability, and longevity. These targets can be achieved by better design and analysis, along with the correct choice of materials. Different materials have different properties and hence, they respond and performs differently under the various condition of external loadings. It is therefore a critical task of an engineer to select the right material based on the property that the material is supposed to function in real-time. When speaking about the property, there are different categories of material properties like chemical property, physical property, mechanical property, electrical property, magnetic property, thermal property, etc. These material properties form the basis of material selection in various applications.

These properties of materials are distinct for individuals and they differ greatly. Site estimation regarding soil strength, porosity, weather estimation like wind forces and frequency, frequency of seismic disturbances, and other environmental factors such as precipitation characteristics, extensively decides materials based on their properties.

Here, in this article, a brief introduction has been provided regarding the different material properties, which form the fundamental criteria in material selection.

Properties of materials

As discussed above, a material becomes eligible to be referred to as building material if it meets certain engineering properties which make it suitable to sustain engineering conditions like loads and deformations. When it comes to building materials, the primary materials used are metals. Metal such as structural steel is the first choice of engineers regarding structural applications.

SI units are primarily adopted in most civil engineering applications to specify the material property.

The material properties are classified as follows:

Physical properties

Physical properties of material include those properties that represent the physical state of the materials. These characteristics are distinct and are not constant. The properties tend to alter when subjected to external parameters like heat.

Mechanical properties

Mechanical properties refer to the property of materials that reacts due to the application of external loads. The mechanical property represents the ability of materials to resist deformation and the scope of its usability in engineering applications.

Chemical properties

The chemical property of a material is a distinct property that is visible when a material responds to a chemical reaction, like corrosion. The composition and identity of a substance are changed under a chemical reaction.

Electrical properties

It generally indicates the suitability of a material to act as a conductor. Free electrons decide the suitability of a material to act as good conductors of electricity.

Thermal properties

The thermal property of a material is associated with the thermal characteristics of a material. Characteristics such as thermal expansion, thermal conductivity, specific heat, melting points, etc. are all thermal properties.

Magnetic properties

The magnetic properties represent the responses induced in the atomic and subatomic levels of a material when they are placed under the influence of an applied magnetic field.

Some of these properties are discussed in detail in the subsequent sections.

Physical properties of materials

The important physical properties of materials are outlined below.

Density

The density of a material denotes the quantity of mass a substance holds under a given volume of the substance. Density in other words is the ratio between the mass of the substance and the volume of the substance.

Specific gravity

The specific gravity of a substance is also known as the relative density of a material. A material's relative density is the ratio between the density of that material and the density of a standard substance. Mostly the standard substance is chosen to be water.

Fire resistance

Fire resistance refers to the resistance property of materials to fire. Fire resistant properties are measured by determining the changes in shape and internal structures when a material is subject to fire. Generally, a material will provide higher fire resistance if it has high melting points.

Mechanical properties

Some of the important mechanical properties of materials are discussed below.

Strength

The strength of a material denotes the ability of a material to resist deformations under the action of external loadings. When a material is subjected to loads, it develops internal stresses which give rise to strain. The stresses are internal resistive forces induced in response to an external load that tries to deform it. For example, the tensile strength of a material is the strength characteristics of the material in response to tensile loadings. Strength characteristics such as tensile strength, compressive strength, elastic strength, yield strength, and yield point, etc. are experimentally determined and analyzed through the stress-strain diagram.

Ultimate strength

the ultimate strength of a material indicates the maximum value of load that a material can withstand after plastically deforming and before developing the first sign of necking. Beyond necking, the material fails by fracture. Ductile materials show ultimate strength characteristics, which are rather absent in brittle materials.

Hardness

The hardness property of metals signifies the ability of metals to withstand external load values until the first sign of crack appears. The hardness property of metals is determined by performing a hardness test. Brinell hardness test is one such example.

Thermal properties

The thermal properties are associated with temperature-related properties that include the behavior of atomic arrangements and induce lattice vibrations in materials. Some of the important thermal properties are outlined below.

Specific heat

Specific heat refers to the amount of heat a material can withstand or need to be supplied to raise the temperature of one gram of material by one degree Celsius. Water has high specific heat and hence it is used as a main working fluid in numerous cooling devices.

Thermal conductivity

Thermal conductivity indicates the ease with which a material can conduct heat. Heat conduction is primarily a function of free electron transfer, thermal agitation, and degree of lattice vibrations. The coefficient of thermal conductivity of a material plays a major role in the building wall systems in the construction field. Metals such as aluminum, copper, and steel have the highest thermal conductivity.

Thermal expansion

Thermal expansion is the property of a material that is characterized by the change in shape, volume, area, and density in response to a change in temperature. This property is decided by the coefficient of thermal expansion. The coefficient of thermal expansion forms an important parameter in designing steel structures such as bridges, trusses, stadiums, etc. as these structures are frequently subjected to variations in temperatures.

Context and Applications

This topic is widely taught in many undergraduate and postgraduate degree courses of:

• Bachelors in Technology (Mechanical Engineering)
• Bachelors in Technology (Civil Engineering)
• Masters in Technology (Materials Science and Engineering)

Practice Problems

Q1. Which of the following unit systems is majorly used in representing material properties?

1. SI units
2. CGS units
3. English units
4. None of these

Answer: Option a

Explanation: To represent material properties, the SI unit system is majorly used.

Q2. Which of the following is a mechanical property?

1. Boiling point
2. Elastic modulus
3. Boiling point and elastic modulus
4. Melting point

Answer: Option b

Explanation: Elastic modulus represents the mechanical property of a material. The elastic modulus represents the resistance provided by the material in response to axial deformation when an axial load acts on the material.

3. Which of the following materials has the highest thermal conductivity?

1. Aluminum
2. Thermoplastics
3. Thermosets
4. Copper

Answer: Option d

Explanation: Of all the materials, especially metals, copper has the highest thermal conductivity followed by aluminum.

Q4. How hardness of a material is estimated?

1. Using Brinell hardness test
2. Using stress-strain diagram
3. Both a and b
4. None of these

Answer: Option a

Explanation: Brinell hardness test is the method to determine the hardness of a material.

Q5. What is the ultimate strength of a material?

1. It is the stress value of a material where the behaves deform plastically.
2. It is the stress value where the material undergoes strain hardening.
3. It is the maximum stress value that a material can induce before it undergoes fractures.
4. None of these

Answer: Option c

Explanation: Ultimate tensile strength is the maximum stress value or the load that a material can withstand before fracture.