Smashing Beams for Science
Last month I graduated with my B.S. in mechanical engineering from the University of Florida and it is making me a bit nostalgic, thinking about all the cool engineering experiences I have had. It also reminds me of a time when I barely had any idea what you do in undergraduate engineering classes. Therefore I am motivated to share about the projects I got to work on for my own benefit of looking back, as well as giving people an idea of what undergraduate mechanical engineers actually do.
One of my favorite projects I got to work on was in Mechanics of Materials lab (affectionately known as MoM Lab by students). I got to smash stuff. Ok, well smash stuff and take important measurements.
Our final project for this lab was creating a beam that could absorb the most energy per unit of weight. This is also known as creating the lightest beam that can do the best at stopping a giant swinging hammer. Although not stipulated in the project description, cost was also a limiting a factor because we had to pay for all of the materials ourselves.
My partner and I decided we would go with a wood beam cut at specific angles with small metal strips on the front and back. We then designed the exact shape of the beam, carefully selected our type of wood, picked the specific beam, chose our type of glue, and picked a metal strip material and dimension to attach to the wooden beam.
We also got to have some lovely adventures at Lowe’s selecting the perfect pieces of wood. We probably looked like Goldielocks finding the beam that wasn’t too heavy, but also wasn't too small. We were working to at least meet the minimum energy absorbed qualifications for an A on this experiment, so this meant measuring the exact dimensions of each beam, as well as picking them up and making sure the density was around what we were looking for, all while in the store. This was a lot of choices to make and with only one chance for a test run, we needed to get the math right.
The metal strips were carefully cut on a band saw and chosen to sit on the smaller front of the beam where the hammer will first hit it, and a smaller sliver of aluminum was placed on the back center where the wood would cave outwards when hit. We used some heavy duty epoxy to attach the wood to the metal.
Something you quickly learn to deal with in an engineering degree is having a constant coating of super glue and epoxy on your hands. And subsequently loosing feeling in your fingertips. (No need to link me on articles that show this is not good for you. I know the sacrifices I have made.) Pro tip, nail polish remover acetone containers are great to get this off.
Our final design was a trapezoidal shape with a set angle for the removed triangles. We also did a bit of programming to create a program that recorded the required data.
Then we got to smash it.
Although the final result was success as far as energy absorbed (we got an A), the beam actually did something strange during the pendulum impact. Apparently, without us knowing, the center of the beam had some kind of wood rot or fungus inside of it, completely changing the way our beam splintered from what we had planned. This resulted in the beam actually flipping during the impact. You might be able to see it in the gif above. You definitely have to learn to expect the unexpected.
However, the amount of energy absorbed still hit the mark we needed. Then, I am not going to sugar coat it, we them wrote up a long lab report showing our final results. In engineering, the moments when you get to do some really cool hands on activities comes after hours of research, coding and math and is followed by many hours of data analysis and technical writing. It may not be as fun as smashing things, but you learn to love it. At least, I did.
Blog originally published at: http://www.erinwinick.com/blog/scientifically-smashing-beams
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