The Nature of Elasticity. The elasticity of a metallic substance is a resistance of its atoms to separation or compression or rotation about one another, and thus is a fundamental property of the material. So elasticity is demonstrated as a function of atomic forces.
Yield Point. This is a point on the stress – stress curve at which the stress levels off or actually decreases while strain continues. The term is strictly applicable only to mild steels.
Ultimate Strength. The greatest load that the specimen has supported divided by the original cross-sectional area is called the ultimate tensile strength or the ultimate strength of the piece.
Ductility. It is the capacity of a metal to be permanently deformed in tension without breaking.
Toughness. It has been defined as the property of absorbing considerable energy before fracture. The toughness of a metal is indicated by the amount of slip, which may occur within the crystals without resulting in rupture of the metal.
Malleability. It is the property of a metal, which permits permanent deformation by compression without rupture.
Brittleness. It implies sudden failure. It is the property of breaking without warning, i.e. without visible permanent deformation.
Failure of metals and alloys under repeated or alternating stresses, too small to produce even a permanent deformation when applied statically, is called fatigue failure.
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