What is Material and Engineering Materials ?

 

Material

A material is a substance or mixture of substances that constitutes an object. Materials can be pure or impure, living or non-living matter. Materials can be classified based on their physical and chemical properties, or on their geological origin or biological function. Materials science is the study of materials and their applications.

Raw materials can be processed in different ways to influence their properties, by purification, shaping or the introduction of other materials. New materials can be produced from raw materials by synthesis.

 

Engineering Materials

 

Any materials that are used as raw material for any sort of construction or manufacturing in an organized way of engineering application are known as Engineering Materials.

            For example, the Mobile or  the Refrigerator  we use,  are  manufactured  through controlled  engineering  processes. These gadgets make use of materials like Silica, glass, copper, aluminium, tin, etc. in their  fabrication. Civil  construction  works  like  building, bridges, dams,  roads, pavements are carried out with raw materials like steel, stone, chips, cement, clay, paint, bars, etc

Properties of Engineering Material:

 A quality that define a specific characteristic of a material is as a property. The properties of a material provide a  basis  for predicting its behavior under various conditions. They are the tools the engineer uses to solve his material problems .Some of the  most important properties of  engineering  material are:

1.Physical Properties:Size,Shape,density,porosity,structure.

2.Mechanical properties: Strength, elasticity, plasticity, stiffness,ductility, malleability, resilience, creep.

3.Chemical Properties: Corrosion, resistance, acidity, alkalinity, chemical, composition.

4.Thermal Properties:Specific heat,thermal expansion,conductivity.

5.Magnetic Properties: Conductivity,dielectric permittivity,dielectric strength.

6.Electrical Properties:Conductivity,dielectric permitivity, dielectric strength.

Important Properties of Engineering Material:

Most Properties of Engineering Materials must be evaluated entirely by experiment. Certain specific conditions are applied and the corresponding properties  are measured.Experiments for determining properties of engineering materials are usually called tests.Tests may provide properties for use in design or information on the quality of a material.The procedures are usually standardized because if identical procedures are always followed  the results of a number of test may be compared with some assurance.Much of the standardization is done by the national organization set up in each country to improved the use or materials in engineering constructions and also in industries.Some of these organizations are BSI(British Standard Institute),ASTM(American Society of Testing Materials),AASHO(American Association of State Highway Official),ACL(American Concert Institute).Each organization gives standard test methods of all kinds in addition to standard specifications for materials and standard definitions of terms.

The following are  the very important properties of engineering materials :

(1   Strength: It is the property of material that represents its ability  to resist internal forces or stresses. The three basic strengths of  a material, the type of force to which the materials is to be subject, must be known. As for example the compressive and tensile strength of structural steel are nearly equal. Whereas cast iron can take more compression and it is weak in tension.Similarly, concrete is very strong in compression but very week in tension.

(2   Elasticity: It is a property of a  material which allows it to return to its original shape and size after the load to which it is subjected is released.This is a very important property of engineering materials. The strain for a given of load during the unloading process is equal to the strain for the same value of load during the loading process. A limiting  value of load will be found at which the strain does completely disappear with the removal of the load.The value of stress corresponding to this load is called the Elastic Limit.

(3  Plasticity:  plasticity is the opposite property of elasticity. A perfectly plastic material does not return to its original shape and size when the load causing  deformation is remove.Lead is an example of plastic material.

(4  Malleability: This property permits  plastic deformation of a material when subjected to compression . materials that can be hammered into the thin sheets are malleable materials .

(5  Brittleness: The opposite property of  malleability is brittleness. Cast  iron is an  example of brittle material.

(6  Stiffness : The term stiffness designates the resistance of a materials to deformation in the elastic range .Stiffness of ductile material is measured by the modules of elasticity.

(7  Ductility: Ductility indicates the ability of a material to deform in the plastic without breaking. No accurate  measure of ductility exists.For comparative purposes. However, ductility is usually defined by the percentage elongation of a tensile specimen at fracture for a specified length.

(8   Toughness:This property matures the ability to absorb to release energy in the plastic range.

(9   Fatiguethe: Certain materials are very often subjected to repeated stress. The term    fatigue (fatigue strength) of a  materials is used to indicate its strength in resisting repeated stress.

(1    Hardness:The term hardness. When used as a technological property of materials .Is primarily associated with the surface .An appropriate definition of hardness is  the resistance of a material to permanent deformation of its surface. This deformation may be in the form of scratching  mechanical wear or cutting.

(1   Resilience:The resilience of a material is its ability to absorb energy in the elastic range.  It is measured by the energy per unit volume required to stress a material in tension form zero stress to the proportional limit.

(1   Creep:In many applications. Engineering materials are required to sustain steady loads for long periods of time R.C.C(reinforced cement concrete)beams,columns.etc. Under such conditions the material may continue to deform until its usefulness is serially impaired . Such time dependent deformations may be almost imperceptible but over the life time of a material or structure they can grow large and even result in final fracture without any increase  in load.

Selection of engineering  materials: selection   of materials for engineering applications depends first upon their properties in relation to intended use. The  engineer should be alert for new materials that may be developed but he should also keep his mind receptive to possible new ways of using existing materials.

The next important considerations are economy  and availability. Preference should always be given to the locally available materials. Sometimes, a material must be selected even though inferior properties. because the right material is not locally available or too expensive.