Skip to 0 minutes and 3 secondsThe experiment we are doing is an impact Charpy test, an experiment on steel samples at different temperatures. We want to look at the different impact energies of the same steel sample at different temperatures to see how the impact energy changes by cooling or heating up the sample. The Charpy tester has been around since the 1940s, mostly for analysis of metals. However, it's still widely used for different materials because it's relatively cheap and quick to test the samples. We use a rectangular sample, which has been notched in the centre, we place it between two anvils and we break it by swinging a pendulum.
Skip to 0 minutes and 46 secondsAnd by looking at how much this pendulum has moved after the impact, compared to the position of the pendulum before dropping it, we can calculate the energy absorbed by the sample. We will be analysing the samples at different temperatures. At 200 degrees, 100 degrees, room temperature, 0 degrees, -80 degrees, and -196 degrees. So we can start by testing the sample at room temperature. The sample is placed on top of the two anvils. We centre the sample - centre the notch - so it's perfectly opposite to the impact of the pendulum, close the door, and release the pendulum.
Skip to 1 minute and 38 secondsThe sample has been left at 100 degrees for about one hour to equilibrate to the temperature. And they're already placed inside with the notch facing away, so we can put it back in the machine.
Skip to 2 minutes and 8 secondsThe samples at 0 degrees has been left in a bath of ice for about one hour to equilibrate. So we use cold tongs to take the samples.
Skip to 2 minutes and 25 secondsThe sample at -80 has been left in the dry ice bath. Also, in this case, for about one hour.
Skip to 2 minutes and 41 secondsTo cool down the sample at -196, the sample is dipped into liquid nitrogen and left for about 10-20 seconds for the sample to equilibrate at the low temperature. And the same as for the other samples that has been cooled or heated, we need to transfer and break the sample quite quickly.
Charpy impact test: how would you write a procedure section?
This week, we have looked at the information that goes in a procedure section, the typical language conventions that this section should follow and the importance of a good experimental figure. Now let’s consider how we would apply this to describe a real engineering experiment.
In this video, we’ll revisit the Charpy impact experiment. As you watch the video, make a note of the information you would want to include in a procedure section.
- What information from the video would you be sure to include?
- Is there anything in the video that wouldn’t be relevant?
- What information do you think is missing?
- What figures might you want to include?
Share your thoughts with your fellow learners using the comments.