Lecture 3- Properties of materials (3).pdf

properties

1. Properties of Materials
By
A.V.Phanse
Lecture 3

2. ✓Materials have different properties depending on what they are used for.
✓Some materials are hard, others are soft.
✓Various types of properties of materials are given below.
➢Physical Properties
➢Chemical Properties
➢Thermal Properties
➢Electrical Properties
➢Magnetic Properties
➢Mechanical Properties of Materials

3. Physical Properties of Materials
✓Physical properties of material are those which can be observed without change of
identity of material.
✓Physical properties of metals are density, color, size and shape, specific gravity of
material, porosity etc.
Electrical Properties of engineering materials
✓Electrical properties are their ability to conduct electrical current.
✓Various electrical properties are resistivity, Electrical conductivity, temperature coefficient
of resistance, dielectric strength and thermoelectricity.
Mechanical Properties
✓Mechanical properties of material help us to measure how materials behave under load.
✓In order to achieve optimal system performance, mechanical properties include density,
hardness and elasticity.
✓Mechanical properties of material reflect relationship between its response to and
deformation from an applied load or force.
✓Properties of materials that find out its behavior under applied forces are called
mechanical properties.

4. 1.Hardness
Hardness can be defined as resistance to deformation or indentation or resistance
to scratch.
Hardness can be measured using -
i.Indentation
ii.Scratch
iii.Rebound
➢Indentation hardness is of particular interest to engineers and is most
commonly used.
➢Indentation hardness can be measured by different methods.
➢Classified based on how it is measured.
➢Hardness can be categorized into three types
a)Rockwell Hardness
b)BrinellHardness
c)Vickers Hardness
Mechanical Properties

5. Rockwell Hardness
➢In this type of test, depth of indentation at a constant load is taken as the
measure of Hardness.
➢A minor load of 10 kg is first applied for good contact between the indenter and
the sample surface.
➢The major load is then applied and the depth of indentation is recorded on a
dial gage in terms of an arbitrary number.
➢The dial consists of 100 divisions, each division representing a penetration
depth of 0.002 mm.
Types of Indentors –
1.Ball 2. Diamond
Scales –
1. B-Scale 2. C-Scale

6. BrinellHardness
➢Indentation is done with 10 mm diameter steel ball.
➢A load of 3000 kg (500 kg for softer materials) is applied for 10 –30 s.
➢Diameter of the indentation is measured to obtain the hardness (Brinell
Hardness No.) from the relationship

7. Vickers Hardness
➢Vickers test uses a square-base diamond pyramid indenter having an angle of
136 degrees between the opposite faces. This angle approximates the ideal d/D
ratio (0.375) in Brinelltest (Fig. a)
➢The hardness, called DPH or VHN (Diamond pyramid hardness no. or Vickers
Hardness no.), is obtained by dividing the load (1 –120 kg) with the surface area
of the indentation.
➢The surface area is calculated from the diagonals length of the impression.

8. 2. Stress
The internal resisting force per unit area is called stress.
σ = P/A
Where, P = Applied load
A = Cross sectional area
3. Strain
The ratio of change in length to original length is called strain.
e = L/L = (L2–L1)/L1
Where,
L2= Final Length
L1= Initial Length
P
L1
L2

12. Stress-Strain curve for Mild Steel Specimen

17. Thank You…