MFG 118: Introduction to Materials
Mr. David J. Stec
Lab Group B3
2/8/2006
Ashley Rake
Jeffrey Rodriguez
Mike Wilcosz
Objectives:
Creep test – The purpose of this experiment was to determine an elongation v. time graph for the given material.
Brinell hardness test – The purpose of this experiment was to determine the hardness of a sample piece of aluminum to make sure it met the given specifications.
Rockwell hardness test – The purpose of this experiment was to determine the hardness of a sample piece of tool steel and piece of aluminum using two different test methods.
Impact test – The purpose of this test was to determine the amount of energy (in Joules) required to break samples of aluminum and tool steel.
Procedure/Materials/Equipment:
Creep test –
Materials/Equipment: Creep test machine, test sample, weight set, stopwatch
Procedure: First, we started by mounting the test sample in the creep test machine. We then stacked 1.3kg of weight onto the machine, but did not apply it to the sample. Before the weight was applied, the dial indicator was set to zero. The moment the weight was released, we started the stopwatch. At twenty-second intervals, we recorded how far the test sample had stretched until it broke. We also recorded the time duration it took to break.
Rockwell hardness test –
Materials/Equipment: Steel sample, Aluminum sample, Rockwell testing machine, “C” and “B” type indenters
Procedure: First, we set up the machine for the type C test, making sure the proper indenter and weight were being used. We then loaded the Steel sample into the machine. We used the two needles on the machine to preload the test sample, as required. The weight was then applied until the indicator stopped moving. The weight was then released and a measurement was recorded. This was repeated three times for each sample metal. The test was repeated using the type B test in the aluminum sample.
Brinell hardness test –
Materials/Equipment: Aluminum sample, Brinell testing machine, Brinell measuring microscope
Procedure: First, we set up the machine, making sure the proper weight and indenter were being used. We then loaded the sample Aluminum into the machine. The weight was applied to the material for a length of time and then removed. The sample piece was taken out of the machine. The diameter of the indentation on the material was measured using the measuring microscope. The test was repeated three times.
Charpy Impact test –
Materials/Equipment: Steel sample, Aluminum sample, Charpy testing machine
Procedure: First, the pendulum on the machine was raised and locked into position. The sample piece was then loaded in the machine, with the cut centered as best we could by hand in the machine. The force indicator on the machine was then set to full force, all the way to the left. After making sure the area was clear, the pendulum was released. The measurement was then recorded from the indicator. The test was repeated using the other sample material.
Results and Discussion:
Creep test:
The first test we performed used 1.4kg of weight. After collecting the data, we found the weight was too heavy, and did not give us enough data points to plot an accurate graph. We repeated the test using 1.3kg of weight and got the following results:
Time (seconds) / Elongation (milimeters)0 / 3.4
20 / 3.97
40 / 4.21
60 / 4.38
80 / 4.59
100 / 4.97
120 / 5.89
140 / 8.11
160 / 15
To the slope of the line during the secondary creep we used the data points at 20 and 100 seconds.
(4.97-3.97) / (100-20) = 0.0125 millimeters per second
Rockwell hardness test –
The Rockwell type C test was performed three times on the sample tool steel that was provided. The sample piece was tested in three different places on the piece. Each test provided slightly different results. The first spot that was tested was a spot that has oxidized, or rusted. That test yielded a measurement of 19. The second spot we tested was a clean, un-oxidized spot that gave a measurement of 13.9. The third and final spot we tested was in the middle of a letter ‘G’ that was stamped into our piece. That test produced a measurement of 16.
A Rockwell type B test was performed three time son the sample aluminum that was provided. Similar to the steel piece, the test was performed three times in three different places on the sample. The first test was taken right in the middle of the sample and gave a result of 14.3. the second test was performed with the piece standing on end. This test gave a result of 24.3. The third test was taken near the corner of the piece and gave a result of 22.1.
The variance in the results is most likely from the different test points on the sample pieces. The process of machining, stamping, cutting, or any thing else could slightly alter the structure of the material where the operation was performed. The change in structure can affect how the material performs during the test.
Our calculations from Chapter 18 question 9 are as follows:
HRC =
40 =
60 =
Penetration = 120 μm
Brinell hardness test –
A Brinell hardness test was performed three times on the sample of aluminum provided. Each test was taken in a different spot on the sample. We also varied the length of time for each test. The results of the tests are shown in the table below:
Indentation Diameter / Hardness number2.55 / 96.3
2.56 / 96
2.58 / 95.9
Overall, the results from the Brinell test were consistent and did not vary much, despite our variances. Our results were also consistent with the specifications for 6061-T6 aluminum. According to the table that was provided, the Brinell hardness number should be 95. Also, according to the provided chart, our measurements from the Brinell test almost exactly match our measurements from the Rockwell test.
Our calculations from Chapter 18 question 8 are as follows:
BHN =
BHN =
BHN =
BNH =
BHN =
BHN =
BNH =
BHN = 500 kg/mm which is off by a decimal point because of the units.
Charpy Impact test –
The Charpy impact test was performed last on each of the samples. We, first, tested the aluminum sample and got a reading of 24. We then tested the steel sample and got a reading of 16.
After the tests were performed, we looked at each broken sample. When trying to piece them back together, the aluminum fit together at an angle. This seemed to indicate how much the sample had bent before breaking. The steel sample did not seem to bend at all after examining the broken pieces.
Possible variations in data could be from placement of the sample in the machine. Not centering the notch in each sample could have affected how the sample performed.