Diploma Strength of Materials N Scheme Study Materials Unit – 1
Strength Of Materials
Unit – 1
Chapter: 1.1: Engineering materials: Classification – definition of Mechanical properties – ferrous metals – cast iron – uses – advantages – types of cast iron – properties and applications – effect of impurities on cast iron. steel – classification – alloying elements – purpose of alloying – effect of alloying elements on steel – uses of steels – properties of mild steel – defects in steel – applications – properties of hard steel – market forms of steels – nonferrous metals – properties and uses.
Three Marks
Mechanical Properties ( three marks / 14 marks)
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Strength
- Strength is the mechanical property that enables a metal to resist deformation load.
- The strength of a material is its capacity to withstand destruction under the action of external loads.
- The stronger the materials the greater the load it can withstand.
2. Elasticity
- According to dictionary elasticity is the ability of an object or material to resume its normal shape after being stretched or compressed.
- When a material has a load applied to it, the load causes the material to deform.
- The elasticity of a material is its power of coming back to its original position after deformation when the stress or load is released.
- Heat-treated springs, rubber etc are good examples of elastic materials.
3. Plasticity
- The plasticity of a material is its ability to undergo some permanent deformation without rupture(brittle).
- Plastic deformation will take place only after the elastic range has been exceeded.
- Pieces of evidence of plastic action in structural materials are called yield, plastic flow and creep.
- Materials such as clay, lead etc are plastic at room temperature, and steel plastic when at bright red-heat.
4. Hardness
- The resistance of a material to force penetration or bending is hardness.
- The hardness is the ability of a material to resist scratching, abrasion, cutting or penetration.
- Hardness indicates the degree of hardness of a material that can be imparted particularly steel by the process of hardening.
- It determines the depth and distribution of hardness is introduce by the quenching process.
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Toughness
- It is the property of a material which enables it to withstand shock or impact.
- Toughness is the opposite condition of brittleness.
- The toughness is may be considering the combination of strength and plasticity.
- Manganese steel, wrought iron, mild steel etc are examples of toughness materials.
6. Brittleness
- The brittleness of a property of a material which enables it to withstand permanent deformation.
- Cast iron, glass are examples of brittle materials.
- They will break rather than bend under shock or impact.
- Generally, the brittle metals have high compressive strength but low in tensile strength.
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Stiffness
- It is a mechanical property.
- The stiffness is the resistance of a material to elastic deformation or deflection.
- In stiffness, a material which suffers light deformation under load has a high degree of stiffness.
- The stiffness of a structure is important in many engineering applications, so the modulus of elasticity is often one of the primary properties when selecting a material.
8. Ductility
- The ductility is a property of a material which enables it to be drawn out into a thin wire.
- Mild steel, copper, aluminium are the good examples of a ductile material.
9. Malleability
- The malleability is a property of a material which permits it to be hammered or rolled into sheets of other sizes and shapes.
- Aluminium, copper, tin, lead etc are examples of malleable metals.
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Impact Strength
- The impact strength is the ability of a metal to resist suddenly applied loads
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Fatigue
- The fatigue is the long effect of repeated straining action which causes the strain or break of the material.
- It is the term ‘fatigue’ use to describe the fatigue of material under repeatedly applied forces.
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Creep
- The creep is a slow and progressive deformation of a material with time at a constant force.
- The simplest type of creep deformation is viscous flow.
- Some metals are generally exhibiting creep at high temperature, whereas plastic, rubber, and similar amorphous material are very temperature sensitive to creep.
- The force for a specified rate of strain at constant temperature is called creep strength
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Resilience
- Resilience is the property of a material to absorb energy and to resist shock and impact loads
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Castability
- Castabilty is the property of metal by which it is easily formed into different complex shapes and sizes from its molten state
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Weldability
- Weldability is the property of a metal which easily joined by fusion with or without applying pressure
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Wear Resistance
- Wear resistance is the property of a metal which enables it to resist wear where there is relative motion between that metal and adjacent machine parts
- What is Ferrous metals?
- Ferrous metal are those which heva iron as their main constituent
- The commonly used ferrous metals are cast iron, wrought iron & alloy steels
- What is Cast Iron?
- Cast Iron is an alloy of Iron and Carbon
- Cast Iron usually contains 2.5 – 3.5 % carbon and varying amount of silicon,manganese, phosphorous and sulphur
- What are the applications of Cast Iron?
Cast Iron is used in
- Making pipes to carry fluid
- Making automotive parts
- Making pipes
- What is Steel?
Steel is an alloy of Iron and carbon contents upto 1.5% and other than carbon, sulphur, silicon, phosphorus, manganese is also present in steel
- What is the purpose of Alloying?
- The purpose of alloying is to increase hardness, toughness, strength, ductility, machinability & Weldability
- The purpose of alloying is to improve wear resistance, corrosion resistance, physical and electrical properties of the alloy
- What are the uses of alloy steels?
Alloy Steels are commonly used in forged products, Rolled products & sheet mill products
- What are the applications of aluminium?
Aluminium is used for power transmission in over head wires, cooking appliance, aircraft and automobile components
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