Trying to solve a very complex system of equations containing 3 sets of equations. However it keeps appearing to get stuck at 46/47 processed. Not sure why this is happening, I have a very high powered PC since I have to run FEA with millions of elements. So an equation like this should be a breeze. Here is what the sheet looks like: https://imgur.com/a/r0JVOje Attached is the file if you want to dig around and try to get it to spit out the three values I need. Any help is GREATLY appreciated. Stresses.sm (37kb) downloaded 15 time(s).

EDIT: found an error, didn't change sigma.1h.1 to sigma.1. Problem still persists even after the change.

Edited by user 30 August 2022 05:39:38(UTC)  | Reason: Not specified

Thanks for the reply!

- thanks for catching that! I wrote the last part of the equation incorrectly, it should be everything multiplied by E.I instead of divided by.
- ahhh, I see the equations looked a lot more complicated than they were. I was able to get it to solve by setting one of the equations to a boolean equal and now it gives me the values I am looking for.

Thanks for your help solving this!

EDIT: Nevermind, error still persists. Cleaning out the old equations that were just trial got rid of the solution and it keeps saying the values are "undefined". Tried tossing it back into the solver with the corrected formatting, still won't solve it. Stresses.sm (33kb) downloaded 6 time(s). Here is the updated sheet.

So how do I get this to solve for the three values?

I should note, in Maxima debug, when trying to evaluate it Maxima returns "no data"

Edited by user 30 August 2022 22:50:24(UTC)  | Reason: Not specified

Thanks for the reply and attempting to solve this! The values are extremely low, I am expecting them to be around 50-200 MPa. Something must be wrong here, even when I change the wall thickness, the values barely change. The wall thickness is the major determinant (t.1, t.2) in these equations for stresses. I think it might be useful to drop the link to where the equations came from: https://ocw.mit.edu/courses/16-512-rocket-propulsion-fall-2005/357a8f245e0020bcfa43530ba6ed1283_lecture_9.pdf In there example they routinely got around 200 MPa but were using a thinner wall, when I tossed their thicknesses in, the values were still absurdly small.

Edited by moderator 31 August 2022 00:06:09(UTC)  | Reason: file link

Hi. From your source, the system is with equations (7), (10) and (13) and "From here, we either solve for σ2h, σ2c, σ1 (given geometry, Pg, Pl, Pq) or, for design, go the reverse route and decide on the geometry for assigned stresses."

I see equations (7) and (10) but for equation (13) I guess that there are something wrong there in the equations system to be solved.

Best regards.
Alvaro.