5 ms·
My hot take is that, FEM is best used as unit testing of Machine Design, not a guide towards design that it’s often used as. The greatest mechanical engineer I
by sashank_1509 2y ago
My hot take is that, FEM is best used as unit testing of Machine Design, not a guide towards design that it’s often used as. The greatest mechanical engineer I know, once designed an entire mechanical wrist arm with five fingers, actuations, lots of parts and flexible finger tendon. He never used FEM at any part of his design. He instead did it in the old fashioned, design and fab a simple prototype, get a feel for it, use the tolerances you discovered in the next prototype and just keep iterating quickly. If I went to him and told him to model the flexor of his fingers in FEM, and then gave him a book to tell him how to correctly use the FEM software so that you got non “non-sensical” results I would have slowed him down if anything. Just build and you learn the tolerances, and the skill is in building many cheap prototypes to get the best idea of what the final expensive build will look like.
- eru 2y ago> The greatest mechanical engineer I know, [...] And with that you wrote the best reply to your own comment. Great programmers of the past wrote amazing systems just in assembly. But you needed to be a great programmer just to get anything done at all. Nowadays dunces like me can write reasonable software in high level languages with plenty of libraries. That's progress. Similar for mechanical engineering. (Doing prototypes etc might still be a good idea, of course. My argument is mainly that what works for the best engineers doesn't necessarily work for the masses.)
- navane 2y agoAlso, might work for a mechanical arm the size of an arm, but not for the size of the Eiffel tower.
- sashank_1509 2y agoEiffel Tower was built before FEM existed. In fact I doubt they even did FEM like calculations
- navane 2y agoI ment a mechanical arm the size of the eifel tower. You don't want to iterate physical products at that size.
- mitthrowaway2 2y agoThis is true, although it was notable as an early application of Euler-Bernoulli beam theory in structural engineering, which helped to prove the usefulness of that method.
- fluorinerocket 2y agoWould FEM be useful for that kind problem? It's more for figuring out if your structure will take the load, where stress concentrations are, what happens with thermal expansion. FEM won't do much for figuring out what the tolerance need to be on intricate mechanisms
- NathanaelRea 2y agoGarbage in garbage out. If you don't fully understand the model, then small parameter changes can create wildly different results. It's always good to go back to fundamentals and hand check a simplification to get a feel for how it should behave.
- antegamisou 2y agoGood luck designing crash resilient structures without simulating it on FEM based software though.
- tightbookkeeper 2y agoThey did this just fine until without such tools for the majority of innovation in the last century.
- antegamisou 2y agoExcept that everything's gotten abysmally complex. Vehicle crash test experiments are a good example of validating the FEM simulation (yes that's the correct order, not vice versa)
- tightbookkeeper 2y agoHow can you assert so confidently you know the cause and effect? Certainly computers allow more complexity, so there is interplay between what it enables and what’s driven by good engineering.
- drpossum 2y agoHaving worked on the design of safety structures with mechanical engineers for a few projects, it is far, far cheaper to do a simulation and iterate over designs and situations than do that in a lab or work it out by hand. The type of stuff you can do on paper without FEM tends to be significantly oversimplified. It doesn't replace things like actual tests, but it makes designing and understanding testing more efficient and more effective. It is also much easier to convince reviewers you've done your job correctly with them. I'd argue computer simulation has been an important component a majority of mechanical engineering innovation in the last century. If you asked a mechanical engineer to ignore those tools in their job they'd (rightly) throw a fit. We did "just fine" without cars for the majority of humanity, but motorized vehicles significantly changed how we do things and changed the reach of what we can do.
- angry_moose 2y agoTo be fair, FEM is not the right tool for mechanical linkage design (if anything, you'd use rigid body dynamics). FEM is the tool you'd use to tell when and where the mechanical linkage assembly will break.
- amelius 2y agoIf he were designing a bridge, however ...
- fastasucan 2y agoIts wrong to assume that everyone and every projects can use an iterative method with endless prototypes. Id you do I have a prototype bridge to sell you.