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Saturday, March 19, 2011

Mechanical Properties of Engineering Materials Part 2.

One had started mechanical properties, for the start click here.The remaining are discussed here.

(1.) Ductility: The ability of a material to withstand bending or elongation without breaking. A material that has this characteristics is said to be ductile. This property is valuable in chains and ropes because they don't snap off or break due to elongation and bending during service.
(2.) Malleability:
This is the ability of a material to be hammered or rolled easily into thin sheets without rupturing. Malleability of a material increases with the increase in temperature.
(3.) Toughness: is the resistance of a material to rupture. This resistance to rupture is due to the force of attrac tion between each molecules which gives them the power to resist any force tending to tear them apart. Toughness of a material can be expressed as the energy absorbed per unit volume of the material participating in the absorption of energy. It's unit is Nm/m^3.
(4.) Brittleness: This is when a body breaks easily when subjected to shocks. Such a material is said to be brittle.
(5.) Hardness: is the resistance of a material to penetration. The hardness of engineering materials is generally carried out by pressing an indentor into the surface of the material through slowly applied load. The extent of the resulting impression caused by the indentor is then measured mechanically and optically. A large impression means that the material is soft while a small impression means that the material is hard.
(6.) Fatigue: When materials are subjected to flunctuating or repeating loads (or stresses), they tend to fail. This type of failure is different from that which they experience when subjected to steady loads. This type of failure is called FRACTURE. The phenomenon that leads to fracture is FATIQUE.
(7.) Creep: is the slow plastic deformation of metals under constant stress or when they are subjected to prolonged loading at high temperature. Creep can lead to fracture at static stresses which are much smaller than those which will break the material by loading quickly. Creep is specially taken care off in Internal Combustion enginer, boilers and turbines

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