Analyst or designer?

You will find many people ready to say that novices should not be allowed near FEA software. "It's too easy to make a big mistake goes the argument". It is always left unsaid that it is much more easy to screw up using good old fashioned hand calculations. You remember those don't you? How to reduce your fancy design to a plain cantilever beam! Ignore holes, and fillets and anything else inconveniently stuck on your free body diagram. Remember to check the text of those 1933 reference papers in Roark with their quaint uneven and unreadable graphs conveniently converted to number format.

So why the big downer on FEA from academics? Well it's true that FEA is rubbish in, rubbish out. However, being able to actually see the mesh, the applied loads, the stress plots, the displacements, a reasonably capable supervisor system should be able to spot any howlers; Theres the rub! Your boss usually didn't get there by being good at design: He doesn't know a Von Mises Stress plot from a hole in the wall. In fact Stress= Force/Area is the sum total of his engineering knowledge. This is something many managers (and engineers) freely admit. Somehow knowledge is not trendy. Who wants to be a geek? Hence if a boss needs an FEA system he will choose the most expensive one on the planet, with fully comprehensive user support so that he doesn't have to be exposed on his lack of knowledge.

Well I have gone down the whole route. I learned about discontinuity analysis before I uised FEA and I was thrilled when the results matched up. However, i also noticed that FEA pointed out a few things that I hadn't thought about. This is the true value of FEA. Over the years I have seen many FEA-averse engineers make complete howlers because they used over-simplified hand calculations instead of building a computer model and looking at the results. Hence, the philosophy I have is that everyone becomes a better designer by using FEA. Ignore the naysayers, most of whom couldn't design a box, and get out there and use it. No you don't need to know all about the maths behind it, and the little you do need to know I will tell you - in plain English.

Let me be clear. To me there is no distinction between analysis and design. Analysis is an integral part of design and it should be used at the start, in the middle and at the end of the design process. Either you can do design by analysis or you shouldn't be in the design department. If you are FEA-averse then go find another job: Carry around bits of paper from office to office, attend pointless meetings, write quality specs. and stay away from our design area, where the real work is done.

As a postscript to this, I once showed the engineering manager an ANSYS contour plot of yield fronts in two different annular seal designs. I pointed at the bad design and said that the yield zone (showing a plastic hinge) was in orange. For the other design, the better one, I said that the yield zone was in red. He immediately said - "but you said that the yield zone was orange". There is no moral to this tale except that we soon parted company. I felt if I was going to work for an idiot I might as well be self-employed.

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