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Some Mechanical Properties

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KCC INST. OF TECH. & MGMT Gr. Noida Presentation Theme :- M echanical P roperties of M aterials Pr@tik Rawat 2012 me batch 1
Page 1: Some Mechanical Properties


Presentation Theme :-

Mechanical Properties of MaterialsPr@tik Rawat 2012 me batch 1

Page 2: Some Mechanical Properties

Theme Outline

Engineering Materials Properties of Materials - Hardness,Toughness, Strength,

Malleability, Elasticity, Plasticity, Ductility

The Tensile Test: Stress-Strain Diagram Properties Obtained from a Tensile

Test True Stress and True Strain

Pr@tik Rawat 2012 me batch 2

Page 3: Some Mechanical Properties

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Metals Plastics


Stainless steel

Die & tool steel

Cast iron

Ferrous Non-ferrous











Engineering Materials

Page 4: Some Mechanical Properties

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Metals Plastics Composites

Reinforced plastics




Page 5: Some Mechanical Properties

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Properties of Materials

Mechanical Properties

Yield strength

Ultimate strength




Fatigue (cyclic load)

Creep (temp / time)

Physical & chemicalProperties

Thermal conductivity

Thermal expansion

Electrical conductivity

Magnetic properties



Melting point

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• The ability of a material to resist scratching, wear and tear and indentation.• Large hardness means: --resistance to plastic deformation or cracking in compression. --better wear properties.

e.g., 10mm sphere

apply known force (1 to 1000g)

measure size of indent after removing load

dDSmaller indents mean larger hardness.

increasing hardness

most plastics

brasses Al alloys

easy to machine steels file hard

cutting tools

nitrided steels diamond

Adapted from Fig. 6.18, Callister 6e. (Fig. 6.18 is adapted from G.F. Kinney, Engineering Properties and Applications of Plastics, p. 202, John Wiley and Sons, 1957.)

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Hardness is the property of material in which material opposes some acts such as rubbing, scratching, penetrating , marking.

The depth or size of the indentation is measured, and corresponds to a hardness number.

The softer the material, the larger and deeper the indentation (and lower hardness number).

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Page 8: Some Mechanical Properties

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Lower toughness: ceramics

Higher toughness: metals

Toughness is the ability to absorb energy up to fracture (energy per unit volume of material).

A “tough” material has strength and ductility.

Approximated by the area under the stress-straincurve.

Page 9: Some Mechanical Properties

• Energy to break a unit volume of material• Approximate by the area under the stress-strain curve.


smaller toughness- unreinforced polymers

Engineering tensile strain, ε

Engineering tensile stress, σ

smaller toughness (ceramics)

larger toughness (metals, PMCs)

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Page 10: Some Mechanical Properties

Malleability -> The ability of a material to be reshaped in all directions without cracking.

Strength -> The ability of a material to stand up to forces being applied without it bending , breaking, shattering or deforming in any way.

Elasticity -> The ability of material to absorb force and flex in all direction returning to its original position.

Plasticity -> The ability of material to be change in shape permanently.

Ductility -> It is a property of material by virtue of which materials can be drawn in wires. ( stretch without breaking or snapping)

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Page 11: Some Mechanical Properties

Stress-Strain Test


machinePr@tik Rawat 2012 me batch 11

Page 12: Some Mechanical Properties

Tensile Test

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(c)2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning™ is a trademark used herein under license.

• Localized deformation of a ductile material during a tensile test produces a necked region. • The image shows necked region in a fractured samplePr@tik Rawat 2012 me batch 14

Page 15: Some Mechanical Properties


Load - The force applied to a material during testing.

Strain gage or Extensometer - A device used for measuring change in length (strain).

Engineering stress - The applied load, or force, divided by the original cross-sectional area of the material.

Engineering strain - The amount that a material deforms per unit length in a tensile test.

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Page 16: Some Mechanical Properties

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Page 17: Some Mechanical Properties

Stress-Strain Diagram (cont) • Elastic Region (Point O–A) - The material will return to its original shape after the material is unloaded( like a rubber band). - The stress is linearly proportional to the strain in this region.

εEσ = : Stress(psi)E : Elastic modulus (Young’s Modulus) (psi) : Strain (in/in)


ε- Point B : Permanent Deformation Starts - a point where permanent deformation occurs. ( If it is passed, the material will no longer return to its original length.)


σE =or

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Page 18: Some Mechanical Properties

Yield Point (Point C & D )

Point C is called UYP . At this point there is an increase in strain even though there is no increase in stress (load)

A formation of creep from this point , makes the specimen plastic and the material begin to flow.

The value of stress corresponding to point C is called yield stress or yield strength.

The yield stress is defined as that unit stress which will cause an increase in length without an increase in load.

D is lower yield point

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Page 19: Some Mechanical Properties

• Tensile Strength (Point E) - The largest value of stress on the diagram is called Tensile Strength(TS) or Ultimate Tensile Strength (UTS) - It is the maximum stress which the material can support without breaking.• Fracture (Point F) - If the material is stretched beyond Point 3, the stress decreases as necking and non-uniform deformation occur. - Fracture will finally occur at Point 5.

Stress-Strain Diagram (cont)

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Stress-Strain Diagram (cont)

Strain Hardening is when a metal is strained beyond the yield point.

An increasing stress is required to produce additional plastic deformation and the metal apparently becomes stronger and more difficult to deform.

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Page 21: Some Mechanical Properties

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Typical stress-strain behavior for a metal showing elastic and plastic deformations, the proportional limit P and the yield strength σy, as determined using the 0.002 strain offset method (where there

is noticeable plastic deformation). P is the gradual elastic to plastic transition.

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THANKS !!!!! Pratik Rawat

Section - A

ME – 3rd year

R.No. - 094

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