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Exploding Dough And Fun With Carrots

Exploding Dough And Fun With Carrots

by Tony Abbey, FE Training

Welcome to my first blog for NAFEMS and an unusual title.

It has been a very busy two weeks travelling and teaching the NAFEMS “Introduction to FEA” class in the UK and Holland. As usual each class was very different - depending on the background of the client company and the individuals attending. Both classes were fun, I always enjoy meeting fellow engineers and talking about FEA and engineering. Two or three days working with a group gives a great opportunity to find out about everyone’s background, what aspects of analysis they are involved with and the engineering behind the products or process.

It is a privilege to have this opportunity and I have

been able to learn a great deal about a broad range of industrial sectors and their individual requirements and challenges. It has also given me a good insight into the changing nature of analysis over the years. And it certainly has changed. All the classes now have a wide span of engineers who are working with FEA; no longer a roomful of gurus who view FEA as an end in itself – there is a much broader, younger and questioning audience.
There is more discussion about aspects of idealization that we took for granted 20 years ago – why not just ‘pour’ elements into the CAD model and get on with the job. Good question, and I will revisit that in further blogs.

There is much more discussion about interface with CAD – can it be done effectively in a particular client’s environment, can we improve it? Again much scope for discussion in future blogs. There is also a very clear shift away from the traditional level of checking and manual verification, that is a concern and a reason for emphasizing this aspect on every course.

Anyway, back to the curious blog title. I like to give a lot of practical examples of structures and their behaviour during the class. One of those revolves around torsion in a shaft. A somewhat dry subject, with a curious pattern of shear flow running in a spiral manner around the shaft. That is difficult to picture, so I cheat and use an example from off the supermarket shelf. In my home city of Los Angeles the use of ready-made dough in tubes, for bagels and other goodies is very common. My wife uses these a lot and as an engineer I of course play with the things. They have a helical join along the tube – like a loo roll, and when twisted they shear along the join and fail. The resulting loud explosive pop is very satisfying and quite addictive – like bubble wrap. My wife has more loose dough than she needs as it is habit forming!

On many classes I get very blank stares and then have to explain the exploding dough tube. I do suggest a quick trip to the supermarket to try it out – of course you should buy any you pop! I am going to do a YouTube video one of these days just to prove I am not making it up. During this week’s class in Holland I explained all this. The next day I was delighted when one of the attendees came up with a tube of Dutch croissant dough in a tube! So we had a live class demonstration and it was very satisfying – not quite the same ‘bang’ as the US version, probably due to EU regulations!

I am tempted to take a tube into every class – but I am not sure what customs would say to my stash of explosive tubes…

What about the carrot? Again one of the classroom examples – a nice fresh carrot shows a similar type of torsional shear failure as a steel bar! I don’t carry carrots around either, but I was delighted when a young lady on the class produced her ‘experimental’ two halv

So, some homework folks … take your carrot, exploding dough and mix carefully!es of a carrot. Her boyfriend was a little bemused apparently – but what a great sport and it helped to make a fun class.

Until next time,



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