Warning: This post is simply about having a bit of fun with Abaqus.

I have a daughter and a son who, among other things, seem to enjoy mathematics and science. My wife and I are both engineers so we are happy to encourage this. One thing we like to do is search for cool things on and off the web that deal with math and science. Last week, while "studying" for her Geometry mid-term, my daughter found an interesting video of a 15-pendulum apparatus - it can be found through the following link http://www.youtube.com/watch?v=yVkdfJ9PkRQ. The relative lengths of the pendulums in the video were set up in such a way that their periods of oscillations bring various groups of pendulums in-and-out of phase with each other at different times which leads to some interesting patterns especially when looking at it from one end.

Now being a typical father I am always looking for ways to impress my kids and so I told my daughter that I could simulate her pendulum video in Abaqus. So while she got back to her Geometry I sat down and put together an Abaqus model of 15 pendulums. It is a fairly simple model using mass and connector elements along with gravity loading and the implicit dynamics procedure. The only tricky part was figuring out the correct relative lengths for each pendulum. Using a bit of thought and some simple equations I found a good set of lengths which reproduced the qualitative behavior seen in the video. The picture below is a perspective view of my 15 pendulum model. The attached animation shows the motion of the Abaqus pendulums looking down the x-axis - matching the view in the video. If you watch any single pendulum you will see it swings with a constant period and if you compare the video and the animation you will see a very satisfying agreement which impressed both my kids and me.

I have attached the input file (pednulum15_final.inp) in case you would like to try the simualtion yourself. It is interesting to view the animation from different perspectives.

In conclusion I had some fun with Abaqus and impressed my kids at the same time which goes into the books as a successful night.

That is the end of my post - I hope you enjoyed it.

In case you were wondering my daughter aced her Geometry mid-term.