Hi,
I'm trying to test if a part that I design is strong enough for what I need but I can't seem to do an FEA on it. I tried making it one single part and I got a message that the model is too unstable, so I activated the soft springs options, but nothing. It told me that the displacement was too big and didn't give me any result.
So I started again, this time make the model out of sepate parts and assembling them. I put in all the fixtures and forces, but now it gives me another error (picture). It suggested using the direct sparse solver, which gave me the "not stable" treatment again.
The main objective was to see if the model is strong enough and if the welding is.
Help would gravely be appreciated
1. I was under the impression that i'm doing a linear static study, at least that's what I selected when I chose new study. why do you say it's a non linear study ?
2. I didn't want to use shell, but SW won't let me put in a weld unless it's a shell. Doesn't work on solid bodies.
3. By taking the stresses away from the welds, you mean redesigning it so that the load doesn't stress the weld itself so much, right ? I'll try doing that. As for back-calculating, don't really know what you mean, so any additional info would really held me.
Thanks
you're using static, i think the results options thing threw shaun off, that is new for 2014. (it used to only be in nonlinear)
if you're new to sim, i'm guessing you're new to shells, i would start with some really simple shell cases to get a hang of it. and start simple. start either at the load or the fixture with a gravity load and get 2 parts connected to work before you work up to the bolted connections..etc.
what shaun's suggestion is to look at the general stresses in the assy with the parts bonded together (solids) and then use to estimate the welds necessary.
start a bit simpler
switch all the parts to solid elements (right mouse button click them)
make sure global bonded contact is enabled
remove your weld connectors
turn off soft springs
get it to run
then you can start looking at other stuff
I already did that and it worked. I know how to do that, but an important role in my design is the weld...
So,
I think i managed to get it right and from what plots it gave me, the design is fullproof. It's actually a bit overdesigned, but oh well.
From what I could tell, the problem was that I didn't contrain it enough, so I added a few more fixture (hope that i did that correctly). Also, I forgot to put in the contact sets.
I did all of that and the analysis ran without any error. What do you think ?
my suggestion is to look at displacement with the deformation scale at decent high number to see if it is bending/twisting the way you expect but the results look reasonable. this will help determine if you overconstrained it or not as well
Caihus,
I'm not skilled in using SolidWorks Simulation, but are you sure that the constraints you added actually make physical sense in the way your part is used or tested? If you don't get the boundary conditions (constraints and loads) correct, the simulation is useless.
Jerry S.
Jerry,
Before putting in those constraints, Solidworks used to tell me that there are not enough and so on (see above discussions). I started watching some tutorials on Simulation and applied some of the things shown in them.
There are 3 additional constraints that I added and I don't think they should interfere with the analysis. I applied a cilindrical constraint on the lower tube to stop it from sliding, one on the middle tube to stop it from going sideways and the last one to the upper part to stop it from rotating. When I put them, they actually make sense and I don't see how they could make the analysis null. I could be wrong though...
That's why I posted the update, to get opinions...
describe in more detail how it is "held" and how it is loaded and post your model using a pack and go zip and the advanced editor at the top right
Here is the model Jared.
Attachments
to interpret and comment on your setup, it might be good to create a drawing of how it gets used and how it gets loaded. or at least describe in as much detail as possible.
The rectangular part is inserted onto a rectangular tubing and tightened with the two bolts. In the lower tube, a rod is inserted and on that rod a weight will be placed. So basically, the rod will be pressed down and thus, the lower tube as well.
What is the goal of the analysis?
Without looking at your files, from your description and the picture, your model is probably over restrained.
Remember that fixtures fix things with respect to the environment. So your vertical tube will always stay vertical and it looks like your horizontal tube will stay horizontal.
Did you ever check displacements to make sure they are reasonable?
Going back to my original al suggestion. Start simple and make sure as you go things are working. This problem should only require a restraint at the bolted connection and something to act like the square tube. The lower tube should have a force on it.
I simplified the design a bit (don't think it should influence the results too much) and got some different results. The design is still good, but I didn't get such ridiculous numbers anymore.
What do you think ?
Caius,
That looks better than the previous constraints, but I still would not trust it.
It looks like you have fixed the top plate, which means you are not going to have any stress in it. It would be more realistic to leave the original shape and fix the top two plates. More realistic again would be to include the square tube that goes in the center and fix its ends.
It looks like you spread a downard force over the whole lower pipe. You would be better off to put a bearing stress on the lower half of the tube. Better again would be to include the rod and put your weight on the ends of the rod.
Assuming the load is purely vertical, you could cut your model down the center line and it should run about four times as fast. Assuming the load is perfectly centered, you could cut it into quarters and it should run about 16 times as fast.
Jerry S.
its getting there. add a deformed scale, taht will help you better visualize it
then you can add the next part.