I was goofing off with some online bridge building games, and I got to thinking, is there any online service or software that would simulate loading of welded structures? For instance, I'd like to build a H-frame press (yeah I could reverse engineer one, but that's not the point). I was thinking that I could design the thing and then test it under various loading conditions and see where the stresses are and how much load it could take before yielding. I've got some great engineering books, but I simply don't have the time to really learn how do do all the calculations necessary for a proper analysis. I'm not wanting to make buildings or anything, but surely there is some software out there that could model simple steel welded structures. Or is this what FEA is all about? Anyone have any ideas??
You might find something online that would be fun to play with, but if you want to build something that you can trust to perform as expected, you need a real FEA program. Also, FEA programs are tools to help make the work easier, but the user still needs to understand what is important otherwise you end up with GIGO: garbage in = garbage out. I imagine FEA has come a long way since I played with Ansys in school, but I wouldn't wish it one anyone. Personally, I'd rather do the hand calcs for your project before doing FEA.
We had an '80s vintage FEA terminal in the lab at the auto frame plant. Doing the calculations on a full capacity part would take days time sharing on the company mainframe.
Even at that, it gave a color coded load diagram, but it did not have any way to recognise yield point, so it would show high loads and great deflections of members that would fail in real life.
It was a good tool in its day, state of the art at the time but I am sure they have come a long way since then.
Is anybody using a current technology FEA presently ?
This most practical text I have been exposed to is "Design of Welded Structures" by Omar Blodgett. Sold by Lincoln Electric at a modest cost. No Calculus, only straight forward Algebra.
It is not just a matter of selecting the proper structural members, the welds also have to be sized. Each individual weld joint must be analyzed for load carrying ability.
Yeah OBEWAN, that one is the most glaring hole in my library. Looks like I'll just have to make another cup of coffee and get the thinking cap back on... Thanks for the advice
You need to get that book Devo!
Also, in the Jame F. Lincoln foundation website, there's a link to the magazines (Welding Innovations) that had his (Omar Blodgett) column where he showed examples of how to calculate various components weld requirements & weld sizing and many more topics... So, go over to the Lincoln site and look for the James F. Lincoln Foundation link where you can find both, the listing of that book as well some other gems, and I believe those structural welding engineering magazines (Welding Innovations) are also there by way of an archives link but, I'm not 100% on that... Okay I found it and man is it in better shape since the last time I was there!!! Here's the link to JFLF Technical Papers:
http://www.jflf.org/papers/JFLF-Technical-Papers.aspxEnjoy the reading!!!
Respectfully,
Henry
It would be cool if they had something like that for a dummy...like me! Just for doing simple stuff like you said, a press. Got to build a specialty press and looking at what I have in the shop that is paid for and wondering how to make it happen and be strong enough. Guess I'll fall back on my "Farmers Fabrication Guide". Will probably need a 10k fork truck to move it but it won't break!!
In the case of a press frame, copy a Dake, Enerpack, or similar good quality product exactly. Deflection becomes an issue long before yield strength.
Stored energy from frame deflection is dangerous as it shoots parts like bullets when things finally let go. If the frame is rigid, they just drop free with no drama.
I have about 12 feet of 1" x 8" flat bar left over from another job, and a press seemed to be a good candidate to use up the material. It looks like the moment of inertia for C8 x 13.75 channel is 36.1 in^4, and for the flat bar it is 42.65, so deflection shouldn't be an issue.
Hey Devo,
All the FEA software out there rely on the person's knowledge on how to build the computer model, meshing and applying static/dynamic loads. As stated before, Garbage in = Gargbage out. If you don't have a working understanding of structural mechanics, you will probably get inaccurate answers.
Simple steel structures are not so simple. Connections are the critical points. It's easy to make the wrong assumption on how the model the connections. Modeling the welds are another story, but at least the software can tell you the stress being applied to the area of the welds. I use hand calcs or weld software created by the Canadian Welding Bureau (CWB) to analyze welds. The CWB software has some pretty high safety factors imbedded in the program.
FEA software is pretty daunting. Lots of stuff you have to know before starting. CAD software (Unigraphics) has a FEA-lite feature, but the answers seem to miss the mark. If you want a vague ballpark answer, then it might be okay.
My 2 cents....
Tyrone
Just placed my order for "Design of Weldments" and "Design of Welded Structures". From the James F. Lincoln foundation, the welded structures book is $22, from Amazon it is anywhere from $75 to $212.
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