mechanical properties of materials

the important properties of material are

• physical properties: It includes luster,color,size,shape,density,elasticity,thermal conductivity and melting point.

• chemical properties: it includes chemical composition structure etc,.

• mechanical properties : The mechanical properties of the material are the properties which describe the behavior of the material under the action of external forces they usually relate to elastic and plastic behavior some mechanical properties are as follows :

  A. Strength: It is the ability of material to resist the externally applied force without breaking or yielding

  It is expressed as tensile strength a compression strength or shear strength.

  B.stiffness : It is the ability of the material to resist its original shape and size after the deformation under stress

  C.Elasticity: It is defined as the ability of the material to regain its original shape and size after deformation when the external forces are removed. All engineering metals are elastic but the degree of elasticity varies from metal to metal.Steel is perfectly elastic within elastic limit. This property is desirable for materials used in tools and machines.

  D. Plasticity : It is defined as the ability of of the material to retain deformation produced under the load on permanent basis. It is necessary for forgings, in stamping images on coins and ornamental work.

  E. Resilience : the ability of a material to absorb energy within its elastic limit without any permanent deformation is called Resilience It is measured by a quantity called modulus of resilience. It is essential for spring materia

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F. Toughness : It is defined as the ability of the material to absorb the energy before fracture has taken place

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It is the property of the material to resist fracture due to high impact loads like hammer blow

the toughness of a material decrease when it is heated. this property is desirable in parts subjected to shock and impact loads the toughness is measured by quantity called modulus of toughness. G.Ductility: Ductility is a measure of a metal's ability to withstand tensile stress—any force that pulls the two ends of an object away from each other.

H.Malleability:Malleability is a physical property of metals that defines the ability to be hammered, pressed or rolled into thin sheets without breaking.

I. Hardness

Hardness is defined as the ability of a metal to cut another metal. A harder metal can always cut or put impression to the softer metals by virtue of its hardness. It is a very important property of the metals and has a wide variety of meanings. It embraces many different properties such as resistance to wear, scratching, deformation and machinability etc.

J. Brittleness

Brittleness is the property of a material opposite to ductility. It is the property of breaking of a material with little permanent distortion. The materials having less than 5% elongation under loading behavior are said to be brittle materials. Brittle materials when subjected to tensile loads, snap off without giving any sensible elongation. Glass, cast iron, brass and ceramics are considered as brittle material.

K. Creep

When a metal part when is subjected to a high constant stress at high temperature for a longer period of time, it will undergo a slow and permanent deformation (in form of a crack which may further propagate further towards creep failure) called creep.

L. Formability

It is the property of metals which denotes the ease in its forming in to various shapes and sizes. The different factors that affect the formability are crystal structure of metal, grain size of metal hot and cold working, alloying element present in the parent metal. Metals with smal1 grain size are suitable for shallow forming while metal with size are suitable for heavy forming. Hot working increases formability. Low carbon steel possesses good formability.

M. Castability

Castability is defined as the property of metal, which indicates the ease with it can be casted into different shapes and sizes. Cast iron, aluminium and brass are possessing good castability.

N. Weldability

Weldability is defined as the property of a metal which indicates the two similar or dissimilar metals are joined by fusion with or without the application of pressure and with or without the use of filler metal (welding) efficiently. Metals having weldability in the descending order are iron, steel, cast steels and stainless steels.