1. Summary
This test is aim to teach students how to do an impact test. The test should give the resistance of any particular notched metallic specimen
... [Show More] to fracture under particular type of blow. To do the experiment, the students will be used to measure the amount of energy is stored on a material during facture. The specimen used in the experiment which will include a notched metallic bar. The students will do the most common impact test for metallic materials which is called the Charpy. The experiment will require two types of Charpies. One type of the Charpies will be hot and the other type will be cold. It employs the pendulum principle.
During the test, you will see the swing of the pendulum. As a result, the small notched specimens will be broken during the flexure. The notch on the specimen must face away from the striking edge of the pendulum. . A notch shows imperfection in the system, and initiate failure at a location. The potential energy is found when the pendulum in the starting stationary position. When the pendulum is released, the energy will be converted to kinetic energy. To find the highest kinetic energy, it will at the highest point which is at the bottom of the swing.
The test will show students how brittle or ductile the two different types of specimens. The results of the test will show a clean cut through the cross section. The ductile failure will show elongated fibers. The test determines material toughness or its ability to resist impact loading. Results indicate differences in the condition of a metal.
2. Procedure
1. Measure and record the dimensions of the specimens.
2. Make sure the air compression valve is open and the power is connected. Turn on the equipment using the switch. These items are located on the back of the machine.
3. Verify the Charpy scale is set to 264 ft-lb. See the small LCD screen on the front.
4. Slide up the front glass door using the handle.
5. Using the metal tongs place the specimen in the slot with the notch facing away from the striking edge of the pendulum.
6. Make sure the specimen is centered in the cavity.
7. Slide down to close the front glass door using the handle.
8. Release latch by pressing start on the small LCD screen.
9. Record the energy of the impact.
10. Pull out the bottom metal drawer to pick-up the specimen.
11. Make observations after the specimen fails.
3. Laboratory Equipment
1. Tinius Olsen Impact Tester
2. Charpy Test Specimen
3. Micrometers
4. Tongs
4. Experiment Requirements
1. A report in tabular form the results of each test run giving the type test, the type metal, the energy to rupture, a brief description of the surface at the break, and a sketch showing the dimensions of the specimen.
2. On the analysis, page write a brief description of the principle of operation of the impact tester used in this experiment.
3. What physical property of a material is determined by means of an impact test?
4. Calculate the velocity of the pendulum hammer just prior to impact in the Charpy test.
5. What is the effective weight of the pendulum? 59.90 lb
6. Calculate the kinetic energy of the pendulum just after impact for the Charpy test.
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