Explain Mechanical properties of materials ?

 Mechanical properties of materials

1. Elasticity

       When a body is subjected to a system of external forces, deformation of body take place. This deformation disappears at once the external forces are removed. 

This property of material by which a body regains its original shape and size after deformation when applied forces are removed is known as elasticity.

Example: Steel and rubber are some materials having good elasticity.

2. Plasticity

        Plasticity is the property of a material by which a body remains deformation due to applied load without rupture, even after the removal of applied load. Most materials become plastic under the application of heavy forces.

 Plasticity plays an important role in manufacturing process like forming, forging, swaging, coining, extrusion.

Example: clay and lead are same materials having good plastic.

3. Ductility

   Ductility is the property of a material  y which the material can be drawn out or elongated into thin wires without rupture by applying a tensile force.

 A ductile material should be strong and plastic in nature.

 Ductility of a material is usually measured by the percentage of elongation and percentage of reduction in area at fracture.

 This property is very important  in manufacturing processes like rolling, wire drawing.

Example: mild steel, copper, aluminium, zinc. gold and platinum.

4. Malleability

    Malleability is the property of a material by which the material can be flattened into thin sheets without cracking by hot or cold working processes.

 A malleable material possesses a high degree of plasticity and  can be hammered or rolled into any desired shape without rupture.

 This property is very important in manufacturing processes like forging, hot rolling, drop forging, wire drawing.

Example: Mild steel, copper, wrought iron  are some materials having high ductility.

5. Machinability

     Machinability is the property of a material by which the material can be easily machined by cutting tools in various machining operation.

 The machinability of different materials can be compared with the help of  machinability index.

The following are the advantages, if the material having good machinability:

• The rate of metal removal is high
• Long life of cutting tool
• Less power consumption
• good surface finish

Example: grey cast iron has excellent machinability.

6. Castability

Castability is the property of material by which the material can be easily cast into different size and shapes. castability of a material can be decided by considering the solidification rate, shrinkage during cooling gas porosity and hot strength.

7. Weldability

weldability is the property of a material by which the material can be be welded into a specific and suitable designed structure and to perform satisfactorily in the desired objective.

8. Strength

     Strength is a property of a material by which the material can withstand or resist the action of external force or load without breaking or yielding. strength of a material is dependent on the type of load acting on it. This property plays an important role in the designing of various structures and machine elements.

9. Stiffness (or) Rigidity

    Stiffness is the property of a material to resist elastic deformation or deflected due to the applied load. It is also know as rigidity. It is measured by the modulus of rigidity. A stiffer material undergoes smaller deformation when subjected to load. This property is very important in the design of beams, shaft and springs.

10. Toughness

      Toughness is the property of a material to resist the fracture by absorbing energy due to heavy shock loads or blow, without rupture. It is measured by the amount of energy that an unit volume of material can absorb before the point of point of actual failure takes place. This property is desirable in structural members and machine elements which are subjected to absorb shock and vibration.

Example: cast iron, mild steel and brass are some materials having high toughness.

11. Brittleness

         Brittleness is the property of a material by which the material will fail or fracture all of sudden without any significant deformation. The property is desirable in machine parts which may be subjected to sudden compressive loads.

Example: cast iron, concrete, glass and stone are some materials having high brittleness.

12. Hardness

         Hardness is the ability of a material to resist surface penetration, abrasion and scratching. it is usually expressed as a which is relative to the hardness of standard specimens. Hardness of a material is decreased by heating.

 It is an important property involved in the design of machine members such as gears, cams, chain sprockets, etc. Which are under constant rubbing action.

Example: Hard steel, cast iron, glass and diamond are the some materials having hardness.

13. Wear resistance

        Wear resistance is the property of a material to resist wear. Wear resistance can be increased by increasing the hardness of the working surface by case hardening process.

14. Fatigue strength

     The stress at which a material fails by fatigue is known as fatigue strength. Fatigue strength decreases when temperature increases. it is mainly affected by the type of loading and working natre of the material.

15. Endurance limit (or)  Fatigue limit

      Endurance limit (or)  fatigue limit is a maximum stress below which a load may be repeatedly applied at infinite of times without causing fatigue of material by fatigue. The limiting stress is most important while designing machine elements which are subjected to repeated or cyclic loading.

16. Creep

       Creep is the property of a material by which the material deformed  slowly and progressively under a constant load over a long period.

Mechanical creep: If the slow and progressive deformation of material is due to constant loading which is well below the elastic limit then the creep is called creep.

Temperature creep: If the slow and progressive deformation of material is due ti rise in temperature. Thermal expansion of material then the creep is called temperature creep. Creep is considered important in the following:

• The soft metals like tin, zinc, lead and their alloys used at room temperature.
• I.C engine components.
• Components of gas turbines, steam turbine and boilers working at high temperature.
• Components of rockets, missiles, etc.