Mechanical Properties Of Engineering Materials
Some of the common mechanical Properties mostly preferred are as blow.
- Stiffness
- Elasticity
- Plasticity
- Ductility
- Brittleness
- Malleability
- Toughness
- Hardness
1. Stiffness
Stiffness is the ability of a material to resist deformation under the action of load. The ability of any given material to resist any deformation that material should not change its shape when the load is applied, and when we go on increasing the value of load the deformation should be very small. It should not increase with the increasing load.
Consider the 10N and deflection around 1mm if load 20N and deflection is 10mm, It should not like this. The deformation should be slow that is the meaning of stiffness. You go on increasing the load value but the deflection is less.
Its unit is N/mm or kN/mm
Stiffness is given by the formula:
Where k = stiffness
F = Load
δ = deflection
Stiffness is mostly consider in a spring.
2. Elasticity
It is the property by which a material change it's shaping when a load is applied and will regain it's original shape when the load is removed.
Consider I have a pen, when I applied load on that if I am pulling that pen then the shape will change and when I remove the load it will back to its an original shape that is meaning of elasticity.
Elasticity is measured by a term called 'young's modulus' or 'modulus of elasticity'.
Its unit is N/mm²
If Young's modulus is very high, it means the material is very elastic. If Young's modulus value is less it means that material will behave less elastic manner.
3. Plasticity
It is a property by which a material is not able to regain it's original shape when the load is removed.
Consider I have a pen if I applied load and pulling that pen then its shape will change and then I remove the load. It will not regain it's original shape means when the load was applied the shape has changed that change in shape will remain permanently. So we understand the plasticity is nothing but it is permanent deformation.
The material used in Machine is never allowed to behave in a plastic manner. it means whatever machine we are seeing the design on the concept of elasticity that is they should regain their original shape when the load is removed. They should not behave in a plastic manner.
4. Ductility
It is a property by which material can be drawn into wires.
If the material has in ductility in means it can be drawn into wires. Now wire-like in electrical connection those wire the material were made that material. It is called ductile material. Ductile material has the ability to flow when the load is applied. The material should be elongated. It will change its shape.
Copper wires used in electric cables, they have the ability to flow.
Consider a pen if pen made of ductile material I would be applying load. That will change its shape and the more amount of tensile I applied I pulled that material that will elongate and converted into wires. So again ductility is a very important property.
Aluminium which is a soft material is also a ductile material. We can use aluminium convert into the wire.
5. Brittleness.
It is the ability of a material by which it can break or develop cracks when loaded
Brittle material is those in which when we are applying load either they can break suddenly or cracks would be developing in that material.
Examples: wood, Concrete, Cast iron, etc..
Brittle material can break without any prior warning or they can develop cracks.
6. Malleability
It is the property by which material is able to be beaten or converted into thin sheets.
In case of malleability, the material has a property that they can be converted into thin sheets of metal which we can use of some of the application.
Material which is elastic is better in malleability.
Steel, copper, aluminium, brass, bronze, etc. are malleable material.
7. Toughness
It is the property by which a material is able to resist shocks or impact loading.
Impact loading refers to the load falling from a height.
So a material able to resist impact load means a load is falling from a height then that is called toughness and this property is very using in the design of spring.
Stiffness is required in the design of spring also toughness is also considered in the concept of design of spring.
8. Hardness
Hardness is the property of a material by which it can resist scratches, marks, or wear and tear.
Hardness is independent of the weight of the material.
We can not say that if a certain material is heavy it means it will be hard. If the material is light then hardness will be less. we can not say that, because hardness is independent in the weight of the material.
For example, Consider I have two pen, I went to decide their hardness, I would be scratching, I would be marking in an each pen and if able to mark very easily or I can able to scratch, for example, this red pen if I can scratch easily it means it is less hard or if blue pen scratching is difficult it means it harder. So hardness is regarding the scratches or wear and tear which is produced on the surface.
This property mostly preferred while designing components which slide over one another.
If we have two components, one which slides over the other then the surface contact is more and we require hard material because if material is soft then there sliding in place then there will be more wear and tear so in case of hardness we should be aware that the material is hard it means it should able to resist the scratches, wear and tear.
Brittle materials are harder.
For example cast iron, concrete, glass, diamond, etc..
9. Creep
Creep is the ability of a material to resist high or extremely high temperature.
Any material which is able to resist a high amount of temperature that material, we will say that it creeps resistance and if the material change it shapes when the temperature is high then it would be called as a lot able to resist the high temperature then it would be less in creep.
Because of creep high mount of temperature stresses are developed.
Creep results in temperature stresses. When we heating the metal it will expand because of the expanding their is more stresses which is stored in the material that stress would be called as temperature stress so creep is the property.
For example,
IC engine, Boiler, Steam turbine, furnace, etc. require creep resistance material.
Material should used in this machine, they should be not change it shape when the temperature is high.
10. Fatigue
Consider I have a pen if I am twisting the pen one another side and in opposition direction. I am change my direction, so suppose if this material is very thin then what will happen?, because of continuous twisting it will break, so here in fatigue failure.
It is property of a material to resist repeatable and fluctuating load.
It means if we have machine of element on which the load is repeatable that is cycle also in fluctuating, the load is constantly changing from minimum value to maximum value then material would be fatigue or it will be break.
IC engines are under fatigue. When it subjected in continuous a various in load and temperature that result in fatigue because of that failure which take place. It is called as fatigue failure.
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