Some are commonly or mostly preferred mechanical properties of materials  are:

1. Stiffness

2. Elasticity

3. Plasticity

4. Ductility

5. Brittleness

6. Malleability

7. Toughness

8. Hardness

9. Creep

10. Fatigue

What are the mechanical properties of materials ?
Mechanical properties of materials

i) STIFFNESS: It is the ability of materials to resist deformations under the action of loads. That is a material should not change its shape when the load is applied.

1. Its unit is N/mm or kN/mm. It is load applied to produce per unit deflection. i.e., in order to produce deflection of 1mm, how much load should be applied i.e., in terms of Newtons.

2.  It is mostly considered in the design of springs.

Stiffness is given by the formula:

K = 𝐿𝑜𝑎𝑑(𝑊) / 𝐷𝑒𝑓𝑙𝑒𝑐𝑡𝑖𝑜𝑛 (𝛿)

(ii) ELASTICITY: It is a property by which a material changes its shape when load is applied and will regain its original shape when load is removed. So this the definition of Elasticity.

 For example when we apply load over rubber band, then its shape will change. The moment I removed load over this, the rubber band come back to its original position.Elasticity is measured by a term called as „Young's Modulus‟ or „Modulus of Elasticity‟

1. Its Unit is „N/mm2‟ (or) „kN/mm2‟ 

2. Young‟s modulus decides how much elastic the material is.

For example, if „Young‟s Modulus‟ or „Elastic Modulus‟ is very high, it means the material is very elastic. If the value of Elastic Modulus is less, it means that material will behave in a less elastic manner.

(iii) PLASTICITY: It is the property by which a material is not able to regain it‟s original shape when the load is removed.It means here in case of plasticity, the material will not regain it‟s original shape.For example, if I have a pen and load is applied on this. It will change its shape. On the removal of load, the pen will not regain its original shape.It is a permanent deformation. Materials used in machines are never allowed to behave in a plastic manner. See this is very important consideration like whatever the materials we are using for the machine design, that materials they should not operate in a region where the deformation would be plastic. i.e., they are not allowed to behave in a plastic manner. That means whatever the machines we are seeing in the machines, they are designed on the concept of elasticity. That is they should regain their original shape when the load is removed. They should not behave in a plastic manner.

(iv) DUCTILITY: It is a property by which materials can be drawn into wires. A very important property that if a material is having ductility it means it can be drawn into wires. Now whatever wires we are seeing like incase of electrical connections those wires the material with the help of material which they are made that material it is called as ductile material. So here I can say that

 Ductile materials have the ability to flow. To flow means when the load is applied the material will elongate. It will change its shape.

 Example: Copper wires used in electric cables.Aluminum which is soft material is also a ductile material.

(v) BRITTLENESS: It is ability of a material by which it can break or develop cracks when loaded. Brittle materials are those in which when we are applying load either they can break suddenly or cracks would be developing in that material.Example: Wood, Concrete, cast-iron (Contains more amount of carbon, the more amount of carbon we add, the more brittle it becomes)

 Brittle materials can break without any prior warning or they can develop cracks.

(vi) MALLEABILITY: It is the property by which materials are able to be beaten or converted into thin sheets. See whatever the sheets of metal which we are seeing that metal it has the property of malleability that is why it is conerted into sheets.Materials which are elastic are better in malleability

Examples: steel, copper, Aluminum, brass, bronze, Zinc

(vii) TOUGHNESS: It is the property by which a material is able to resist shocks or impact loading. Impact loading refers to load falling from a height.

(viii) HARDNESS: Hardness is the opposite of Toughness. It is the property of a material by which it can resist scratches, marks, or wear and tear. Hardness is the independent of the weight of a material. This property is mostly preferred while designing components which slide over one another.Brittle materials are more hard. It means brittle materials are able to resist scratches more. Like for example, Cast iron, Concrete, Glass, Diamond.

(ix) CREEP: It is the ability of materials to resist high or extremely high temperatures.So as from the definition I think it is very much clear that any material which is able to resist high amount of temperatures that material we will say that it is CREEP RESISTANT. And if the material changes its shape when the temperature is high then it would be called as the material is not able to resist the high temperature, then it would be LESS IN CREEP.Because of Creep, high amount of temperature stresses are developed. As we know when we have a metal when we heating that metal we know that it will expand. Because of that expansion there is some stress which is stored in the material. That stress would be called as temperature stress.

Examples: I.C. Engines (Internal Combustion Engines), Boilers, Steam-turbines, and Furnaces require creep resistant materials.