MATERIALS |CLASSIFICATION OF MATERIALS |MECHANICAL PROPERTIES OF MATERIALS

 MATERIALS

Mild steel, tor steel, cast iron, brass, aluminium, copper, concrete, bricks, tiles, stone, timber, glass, etc. are some commonly used materials for engineering purposes. The important properties of materials are mechanical, thermal, magnetic, electrical, chemical, physical, etc. From this subject point of view, here we shall discuss only mechanical properties of materials. Before going into the details of these properties, it is necessary to understand the classification of materials.

CLASSIFICATION OF MATERIALS

The materials generally used for structural purposes, machine parts or electronic devices can be classified as (i) elastic, (ii) plastic, (iii) ductile and (iv) brittle.

(i) Elastic Material:- A material is said to be perfectly elastic when the deformation produced under the action of external loads vanishes completely on the removal of the load.

(ii) Plastic Material:- If a material does not regain its original size and shape on the removal of the load and get permanently deformed, it is called plastic material A perfectly plastic material is that in which the material shows a phenomenon of flow with comparatively less load. For example, clay and lead are the plastic materials.

(iii) Ductile Material:- If a material can undergo a considerable deformation without rupture or can be drawn into wires, it is called a ductile material. A ductile material has a large tensile strain upto the point of rupture. For example, mild steel (low carbon steel), copper, gold, platinum, silver etc. are the examples of ductile materials. A ductile material must be both strong and plastic. A ductile material gives prior warning before its failure.

(iv) Brittle Material:- If a material cannot undergo any deformation under the action of external loads and it fails by rupture, it is called a brittle material. A brittle material fails suddenly upon attaining its maximum load and has a small tensile strain upto the point of rupture. Cast iron, concrete, glass, stone, etc. are the examples of brittle materials.