What is meant by properties?

A property of a material describes its characteristics and distinguishes it from the others. The material properties are described it in terms of its hardness, color, appearances, and so on. The material properties generally depend on the type of material, or whether it is a metal or an alloy. There are different kinds of material properties such as mechanical properties, thermal properties, physical properties, and chemical properties. Chemical properties describe the material in terms of a chemical change. The mechanical properties come into existence when the material is acted upon by an external load. Thermal properties are associated with the temperature of the material and specific heat.

Physical properties of a material

Density

It is the property of a system that signifies the amount of matter contained in the body. The ratio of the amount of mass contained in a body with the body's volume signifies density. Usually, the density of an alloy is more than that of a metal.

Specific gravity

The other name of specific gravity is relative density. When the ratio is considered between the density of a given material and water, that ratio results in the relative density of that material.

Corrosion resistance

Corrosion occurs when a material begins to lose electrons due to oxidation that is caused mainly by harsh environmental conditions. The ability of the material to hold its electrons from getting escaped is known as the resistance of the material to corrosion.

Color

The color of the material is due to the allowance of the material for the passage of a certain wavelength of light that falls on that material, absorbing the remaining wavelengths. Metal is characterized by its shiny appearance.

Melting points

It is the exact temperature point at which the phase of solid material changes to its liquid form.

Boiling point

It is the temperature at which the liquid phase turns into the vapor phase due to the phenomenon of boiling.

Mechanical properties

Tensile strength

When a material is under the influence of an axial load, the material deforms along the axis of application of the load. The material tries to resist the deformation by inducing internal stresses. That resistance to deformation is known as tensile strength, which exists due to tensile stresses. The SI unit of tensile stress is Pascals, Pa. It can be determined by performing a tensile test and plotting a stress-strain curve.

Hardness

A material can absorb several repeated applications of loads over its surface before the first indentation occurs. This resistance is called the hardness of material.

Brittleness

It is a material property generally exhibited by high carbon content materials. If material is brittle, it undergoes sudden fracture even before necking occurs, as indicated by the stress-strain curve. Cast iron is an example of a metal that exhibits brittleness.

Elasticity

The material property that permits the material to return to its original orientation after the release of load is called elasticity. The final state where a material exhibits these characteristics is the elastic limit. Up to this point, the stress is proportional to strain.

Plasticity

The material when undergoes a high degree of elongation or deformation without much increase in the stress values is known as yield, which can be seen in the yield point. The stress corresponding to yield point is the yield stress. The SI unit of yield stress is Pa. Just before the yield point the material gains the property of plasticity, that is, under this condition, the material does not return to its original orientation after the load has been released. Plastic is an excellent example of such material that exhibits this phenomenon.

Toughness

Toughness is the material property that defines the ability of the material to withstand high degrees of cyclic loadings without getting a fracture.

Ductility

This material property is shown by materials that have lower carbon compositions. Under this property, the material undergoes sufficient plastic deformations and undergoes necking before the occurrence of fracture. An example of a metal that exhibits ductility is stainless steel.

Brinell hardness test

Hardness is generally the number of indentations that the material undergoes under the action of loads. The idea behind hardness measurements is to measure the amount of indentation caused. If the indentation value is small, the material has a high degree of hardness. The process of experimentally determining the hardness is the Brinell hardness test. There are also other hardness measuring tests such as the Rockwell hardness test and Vickers hardness test.

A special carbide metal ball is used in the test. This ball is intentionally used to cause indentation on the required surface to be tested. The indentation depth is then finally measured by a Brinell microscope.

Context and Applications

This topic is significant in the professional exams for both undergraduate and graduate courses, especially for

• Bachelor in Technology (Automobile Engineering)
• Bachelor in Technology (Aerospace Engineering)

Practice Problems

1. Which of the following is a mechanical property of a material?

1. Density
2. Specific gravity
3. Tensile strength
4. Specific heat

Correct option- c

Explanation: Due to an externally applied load along the axis of the component, the component undergoes deformation and internal stresses are generated to resist that deformation. Tensile strength is the property of the material that resists axial deformation due to tensile forces.

2. Which of the following is a test to determine the hardness of the material?

1. Rockwell hardness test
2. Brinell hardness test
3. Vickers hardness test
4. All of the above

Correct option- d

Explanation: The hardness test is used to determine the property of hardness associated with the material. Rockwell hardness, Brinell hardness, and Vickers hardness tests are used to determine the hardness values of the material.

3. Plasticity is the property of a material to remain deformed even after the removal of external force. This given statement is true or false?

Correct answer: True

Explanation: As from the stress-strain curve, ductile materials loaded beyond the elastic limit exhibit plasticity. The remains plastically deformed even after the removal of forces.

4. Which of the following properties serves as a limit for the proportionality of stress and strain?

1. Plastic limit
2. Yield strength
3. Necking point
4. Elastic limit

Correct option- d

Explanation: The material exhibits the proportionality limit of stress and strain up to the elastic limit. After that, the material behaves non-linearly.

5. What is the SI unit of tensile stress?

1. Pascals, Pa
2. Newton, N
3. Pound square inch, Psi
4. None of the above

Correct option- a

Explanation: The SI units of tensile stress or any stress is pascals, Pa.

Related Concepts

• Thermoelectricity and thermoelectric property
• Resistivity
• Thermal properties of ductile materials
• Specific heat of gases
• Gases have two specific heats, while solids have only one specific heat.