IMPACT TESTING MACHINE

AIM OF THE EXPERIMENT: Determination of impact strength of a mild steel specimen.

APPARATUS REQUIRED:

1.Imact testing m/c

2. Centering gauge

3. Anvil

4. Spanner

5. Allen screw of the following sizes 2,3,4,5

DESCRIPTION OF THE MACHINE :

This m/c is used to determine the behaviour metal under impact loading conditions gives the prove of suspectibility of the brittle fracture and also determine the impact of iron ,steel ,cast iron,steel sections the fnuts and bolt materials .The m/c consists of following materials .

1. Base2. Stand(2 nos)3. Pendulum pipe4. Pendulum hammer5. Guard6. Latch7. Lock lever8. Release lever9. Dial10. Indicating pointer11. Pointer carrier12. Brake lever13. Supporting block for charpy &izod specimen14. Latching tube15. Izod release lever16. Bearing bracket17. Charpy setting gauge

In the machine, this specimen rests freely on two support . The notch at which the specimen breaks lies at the center of percussion of the striker . The impact straingth of the specimen is equal to the impact devided by the original cross sectional area of the specimen at the notch .The m/c dial is calibrated so as to indicate the energy absorbed for the specimen directly in kgm.

THEORY:The tensile test in which a gradual load is applied to the specimen is not satisfactory when it is desired to know the shock of imact resistance capacity of the material because of certain material may be quite safe under certain value of gradually applies load but may fall for earlier when the same is made to fallvfrom a certain height either once or a no. of times .

The loads that are suddenly applies to a structure are known as shock or impact load are

1.effect of these load is to produce stress waves.These waves prodused rapid builder of stresses and effect of resisting properties of materials . The property of a material associated with works required to cause ruoture is designated as toughness . The energy of effect is observed in many waves E.g elastic deformation of structure , plastic deformation ,hysteresis effect , frictional action and effect of impacts .

PROCEDURE :( for izod test )

1. F ix up the izod striker and the two buses of the hammer side plates to their respective positions.

2. Mount the latching tubes of izod test on the bearing bracket and the guards bymeans of the given fixing plates .

3. Loosen the clamping screw of this supports and insert the test specimen.4. Align the center line of the notch in the plane of support top , by using the setting gauge and the

claim the specimen by clamping screw .5. Touch the striker to the test specimen and adjust the indicating pointer to 16 kgm .6. Adjust the point carrier in such a way that it just touches the indicating pointer.7. Lift the pendulum by hand till it get latches in position.8. For releasing thependulum operate izod release lever and the further steps may be followed in

case of charpy test two of ten the energy observed by the test specimen.9. For removing the broken specimen hold the specimen by hand and remove the same after

loosening the clamping screw .

PROCEDURE : (FOR CHARPY TEST )

1.Fix of the charpy block and charpy striker in their respective position .

2.Place charpy test specimen on the supports .

3.Allign the center ofspecimen notch with respect to center of support by means of charpy setting gauge.

4.Touch the striker to the test specimen and adjust the indicating pointer to 30 kgm .

5. Adjust the pointer carrier in such a way that it just touches the indicating pointer .

6. Lift the pendulum by hand till it gets latched in position .

7.For releasing the pendulum operate lock lever and releasing lever successfully.

8. Allow the pendulum swing freely and break the specimen .

9. After rupture reduce the speed of pendulum by operating break lever.

10.Read the observe the energy directly on the dial as indicated by the indicating pointer.

11.Before proceeding for next test remove the broken pieces of the test pieces and bring the indicating pointer.

OBSERVATION :

Material of test pieces =

Type of notch =

Dimension of test piece =

Velocity of striking =

EVALUATION OF TEST :

The notch impact strength (1) is calculated as per the following formulae

I=K/Akg/c m2

Where I=impact strength in kg/cm2

K=impact energy absorved by the specimen during rupture in kgm

A=Area of cross section of specimen below the notch before test in cm2

TABULATION :

S.LNo.

Material Used Area below notch in cm2 Impact energy absorved(K)

Impact strength1=K/A

1 Aluminium 0.8 1a----------------------1b----------------------1c----------------------

1a----------------------1b----------------------1c----------------------

2 Copper 0.8 2a---------------------2b---------------------2c---------------------

2a---------------------2b----------------------2c----------------------

3 Brass 0.8 3a---------------------3b---------------------3c----------------------

3a---------------------3b---------------------3c----------------------

4 Mild steel 0.8 4a----------------------4b----------------------4c----------------------

4a----------------------4b----------------------4c----------------------

DISCUSSION:

We know the toughness is the property which signifies the amount of energy absorbed by a material at the time of fracture under impact loading the impact test has been found particularly valuable in revealing temper brittleness also it reveals the resistance to fracture to stress concentration from which cracks are liable to start and for a brittle material less energy is required to fracture the specimen than ductile material.

CONCLUSION :

The impact strength of the samples of mild steel, Cu, brass are ………………….