Title: Untitled Document
Course: Materials of Engineering

MET 2200 CHARPY IMPACT STRENGTH EXPERIMENT
as a function of TESTING TEMPERATURE

INTRODUCTION:

Materials which would withstand a given stress level may fail as the result of those same stresses being applied instantaneously.  Impact loadings can result from many sources and it is important to know the reaction of common engineering alloys to the application of impact stresses since such loadings can result in catastrophic failures in equipment and pressure vessels.  Lowering ambient temperatures can also result in brittle failure of an alloy which might otherwise react in a ductile manner at higher temperatures.  Text reference pages 227-232.

OBJECTIVE:

It is the objective of this experiment to determine the impact strength of a spectrum of common engineering alloys and to correlate these results with the test temperature and hardness levels of these materials.

EQUIPMENT & MATERIALS:

Charpy impact test machine using available impact test specimens of the following engineering alloys:

1. AISI 1018 cold formed steel
2. AISI 1045 cold formed steel
3. AISI 4140 cold formed steel
4. AISI 303 stainless steel
5. CDA 360 free cutting brass
6. AA 6061-T6 aluminum alloy

PROCEDURE:

1. Mark each specimen number on both ends with a permanent ink marker.  Measure the dimensions and Rockwell hardness of the Charpy test samples to ensure consistency.  Hardness is to be measured on a surface of the specimens which is not in the impact zone of the tester and which will not cause the sample to be unevenly supported in the test machine.  Record the hardness value and hardness machine scale by specimen number.  Set up a raw data table to contain all experimental measurements.
2. Test specimens will be Charpy tested at ambient room temperature; melting ice temperature (0 degrees C); and dry ice temperature (-78 degrees C)
  1. Set the Charpy test machine dial indicator to zero (0).
  2. Load a test sample in the Charpy impact tester such that the “V” notch is positioned away from the direction from which the sample will be struck by the swinging pendulum of the tester.
  3. Raise and lock the test pendulum in the horizontal position.  Stand clear of the path of the pendulum and release the lock to allow the pendulum to strike the test sample.
  4. Record value of energy absorbed by the test specimen in foot-pounds from the Charpy test machine dial.  Also record the appearance of the fractured surface of the specimen with respect to the approximate proportion of brittle or ductile fracture appearance.
4. Repeat step 3a through 3d for each test sample in the test series.

DATA ANALYSIS

Discuss how all variations of experimental equipment, material, procedure, and data collection may have changed the results of the experiment and include reasons for these observations.  All collected raw data and data calculated from them are to be presented in tabular form.  Plot a graph of the available data using test temperature as the abscissa and the absorbed energy at failure as the ordinate of the graph.  Identify each data point with a letter that corresponds with the specimen material.  Determine the presence of any ductile to brittle transformation temperatures.  Raw data collected during the experiment is to be included as an appendix to the report.

Convert the Rockwell hardnesses to Brinell hardnesses and make an additional graph of the impact data using Brinell harness as the abscissa again identifying each data point with a letter that corresponds with the specimen material.  Use a French curve to form a smooth curve through the data on each graph.

DISCUSSION:

The following are required discussion points whi9ch must be supported by the data collected and the data analysis.  Discuss the impact resistance of the series of materials with respect to both test temperature and material hardness.  Discuss how the appearance of the fracture surface relates to the impact resistance of the specimens.  If there is a brittle to ductile transition for one or more of the alloys, discuss whether one should expect a similar temperature reaction in all alloys of that type and discuss its potential influence on uses for that alloy.  Explain any observed differences in performance between ferrous and non ferrous alloys.  Explain any observer differences within the ferrous family of alloys.  How do the results of this experiment compare with expected theoretical or with handbook results?

CONCLUSION:

What conclusion(s) can be drawn from this experiment on the series of engineering materials?