Purpose

Many structural parts or machine parts are subjected to impact load. Therefore it is necessary to know the resistance of the materials to such impact loads. The purpose of this test is to find the resistance to impact or shock absorbing capacity of materials.


Object

1.   To understand the principle of impact test.

2. To determine the shock absorbing capacity of the materials using izod impact test.

3. Compare quality of different materials.


Reference

I.S 1598 – 196

I.S. 1751 – 1973


Apparatus

1.      Impact testing machine

2.    Standard specimen


Diagram


IZOD IMPACT MACHINE



Construction

  • Raise the pendulum hammer to the required height. Release it allowing free swing and observed the energy available in the hammer. Note the initial energy in observation table.
  • Raise the pendulum again to the same height as before and clamp it (warning : see that the hammer is clamped properly and nobody should touch the release mechanism of the hammer when the specimen is being fixed).
  • Fix the specimen on anvil properly.
  • See that nobody is standing in the swinging range of the hammer. Release the hammer by operator, release mechanism. The specimen breaks and the hammer wings to other side.
  • Conserved the energy reading on the scale after breaking the specimen. Note it as final energy in the observation table.
  • Repeat the procedure for different specimen and note the initial and final energy reading.
  • Calculate the shock absorbing capacity and note down in the table.



Observation

1.      Brass

Length = 72 cm

Breadth = 0.9 cm

Height = 0.9 cm


2.    Aluminium

Length = 72 cm

Breadth = 0.9 cm

Height = 0.9 cm


3.    Mild Steel

Length = 72 cm

Breadth = 0.9 cm

Height = 0.9 cm


Observation table


MATERIALS
INTIAL ENERGY kg. m OR (I)
FINAL ENERGY kg. m (I)
SHOCK ABSORB CAPACITY (I) INTIAL - FINAL
REMARK
ALUMINUM
17 kg. m
15.2 kg. m
1.8 kg. m
BREAK

2170 J
= 15.2 J
= 18 J

BRASS
17 kg. m
17.6 kg. m
0.6 kg. m
BREAK

170 J
= 17.6 J
= 6 J

MILD STEEL
17 kg. m
5.9 kg. m
11.1 kg. m
BREAK

170 J
= 5.9 J
= 111 J



Calculation

1.      Shock absorb capacity of the aluminium

= 170 J – 152 J

= 18 J


2.    Shock absorb capacity of the brass

= 170 J – 176 J

= 6 J


3.    Shock absorb capacity of the mild steel

= 170 J – 5.9 J

= 111 J


Result

Shock absorb capacity of the following standard specimen

1.      ALUMINIUM (BREAK) = 18 J

2.    BRASS (BREAK) = 6 J


3.    MILD STEEL (BREAK) = 111 J


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