What is Hardness, and how are materials selected?
Hardness is the property of a material by which the material resists penetration.
How are materials selected?
For any purpose or application, when selecting the right material or determining its condition, the following properties are considered.
- Physical Properties
- Chemical Properties
- Mechanical Properties
Physical Properties
Physical Properties is a properties that identify the outer structure or state of a material. These properties help determine in which environment a material can be used, such as in heat, cold, or humidity.
Main Physical Properties
- Density: Indicates how heavy the material is.
- Melting Point: The temperature at which the material melts.
- Electrical Conductivity: How well the material conducts electricity.
- Thermal Conductivity: How efficiently the material transfers heat.
- Color: It indicates the color of the material.
- Boiling and Melting Points
- Shape: Indicates what is the shape of the material.
Examples:
- Copper is a good conductor of electricity, so it is used in wiring.
- Aluminium is lightweight, making it suitable for the aerospace industry.
Chemical Properties
In chemical properties, we study how a material reacts or behaves when it comes in contact with other substances. Such as air, acid, rust, fire, or during oxidation. These properties describe the material’s tendency to undergo chemical changes or form new compounds.
Main Chemical Properties
- Corrosion Resistance
- Oxidation Resistance
- Acid/Alkali Resistance
Mechanical Properties
In mechanical properties, it tells how a material behaves under extra force or pressure. Means that how is the hardness, tensile strength, elasticity, ductility, or toughness of a material.
Use in Industry:
When making machine parts, tools, or structures, materials are selected based on their mechanical properties.
Main Mechanical Properties:
- Hardness → Ability to resist pressure or wear.
- Tensile Strength → The limit before the material breaks when pulled.
- Elasticity → Ability to return to its original shape after removing the force.
- Ductility → Ability to be drawn into wires.
- Toughness → Ability to withstand twisting or sudden impact.
Examples:
- Steel is hard and strong, so it is used in machine shafts and gears.
- Aluminium is light and somewhat flexible, so it is used in aircraft bodies.
