If a fat man sits on a plastic chair, will it break?

I do enjoy this blogging thing. Lots of you send me emails or comment in person that you enjoy reading my stuff… which is beyond gratifying! After a few years, though, I sometimes run out of something new to write. Luckily, I’ve just chiseled into a new vein of gold.

It’s never been my job to deeply understand the coding behind the engineering software I represent. I took exactly 1 masters level CFD course in the mid 90s. Yikes. I was pretty much done after struggling to write my own basic, ugly, hardly useful CFD solver. Pitiful.

My job is to look at a potential customer’s design challenge, relate that to some some sort of solution [hopefully, but not always, one I actually sell], and help to uncover the real business case that [hopefully] justifies the investment in said solution.

Most of the time, all of that information has to be packaged in such a way that the holder of the purse strings can understand. I guess that’s the other thing I’m pretty good at. Usually these people don’t (or shouldn’t) care about the deep details of the solution technology.

Most drivers can’t point out an alternator under the hood. Does that mean they aren’t qualified to make a car buying decision? Of course not. Explaining the high level benefits of CAE for non-experts has always been one of the guiding goals for my blog. Now that I’m digging more deeply into the rich world of structural analysis, I think it’s time for me to create a series of posts explaining the most common aspects of CAE in the simplest terms possible. I’ll try my best to come up with good “fat man” analogies.

When I first got into engineering simulation, I struggled to explain what I do for a living to civilians- er non-engineers. I’d be at a dinner party and someone would say, “Nice to meet you, what do you do?” To which I’d say, “I’m in engineering software.”

Now, I still recommend this approach at dinner parties…. because a deep discussion of FEA or CFD usually won’t create the desired social atmosphere. But, let’s say the person bites and wants to dig in, “Oh, what does that mean?” Don’t start talking about nodes, elements, boundary conditions, stress, and the like. Say something like this instead:

“Imagine you owned a company that makes plastic chairs. Maybe you want to use thinner plastic to cut costs and make more money. In our software, you could create a 3D virtual reality model of that chair, and simulate putting a big fat man on it. It’ll tell you if the chair will break or not… all before ever trying to build and test it in real life.”

image by zorilla



  1. That’s funny because I was thinking about the same thing – explaining to regular people what I do.  The “engineering software” line is a conversation killer – but that’s OK if you don’t feel like explaining to your aunt what CFD is.

    But I would do the chair line like this: “Suppose I put my fat ass into that chair…”

  2. Adam Green · ·

    Jeff – My chair just broke – I’m blaming you, Adam 

    1. Well, I’ve been using a burst-proof exercise ball for a chair over the last couple months. Recommend you give that a shot 🙂

  3. Funny…I’ve been asked, ‘What does your son do?” and been stumped for a good response.  I fumble around and never come with something that sounds like a real answer!  So, just plain “software engineer” ought to do it.  And hope there are no follow-up questions!


    1. Or you could just tell  ’em I sell Finite Element Analysis and Computational Fluid Dynamics software.  🙂

  4. Joe Galliera · ·

    People assume that I’m a software engineer who writes code, if I say I’m an engineer and I work for a software company.  I learned quickly like yourself, Jeff, to avoid this line of thinking completely.  I explain it now more like this:  I work with engineers and designers to make sure that the products that you use everyday will function properly, won’t break and in the end is the best design; all of this is done on a computer these days.  That’s what I do.
    Most times now I even cut out the whole part about engineers and designers, and just start it as: “I make sure that the products…”

  5. I love this topic. As a vehicle engineer, I like the cases close to daily life, not just in the industry area. for example, the analysis of how to cook rice better is much more interesting than avoid thermal issue in the engine compartment.
    from @brandon_loh:disqus 

    1. Yep, pretty amazing to think about how many products in our daily life have received this level of engineering thought.

  6. very interesting ! I also always wonder how to explain basics of FEA to non-specialists and it is quite hard… I will try the fat man analogy next time and tell you if it works or not 🙂 Just for the fun: do you actually made this plastic chair analysis ?

    1. Yes, always best to explain in the context of what civilians understand 😉

      No, I haven’t personally run this analysis… but I’m sure it’s been done.