Aha! Thanks Victor. I missed the fact that I needed to specify the correct axis for the inertia. I never did get around to finishing the model. The model now seems to be doing what you'd expect.
Cheers
Hi Dave,
This model is really a very simple trial model just to explore if I can use this software for modelling rotational shafting systems with inertias and the like eg a motor with a reduction drive, a coupling and a large flywheel.
In this mode…
Victor
Thanks for that. I'm glad that it wasn't some obvious thing that I just missed!
I should be fine given that shaft rotation as you explain will be tolerated to a larger extent with a linear analysis. I should be able to do a separate an…
Victor
Thanks for that. I guess I should also be using ccx with nonlinear dynamic analysis because I will be using large deflections. Recently I got an unconstrained rotating link to rotate with a very light spring.
Tim
Greetings,
FYI - This last piece of info may help.
I made an error when I calculated the natural system frequency of the flywheel and shaft.
Its 2.8 Hz not 17.5 Hz. I mistakenly did not convert from Rad/sec to Hz. In actual fact for a 1.1m long 25…
Victor
Thanks for your help here. If you use the equations here (https://perso.univ-rennes1.fr/lalaonirina.rakotomanana-ravelonarivo/Stokey_chapter7.pdf) for a uniform shaft alone, you get about 700 Hz natural frequency (ignoring the flywheel) so I…
Hi Victor
Just a question related to the natural frequencies:
I have used both solid elements and beam elements for the shaft.
None of them seem to have any torsional modes? Does Mecway give torsional modes?
Tim
Thanks Victor
I did some more work and have answered some of my questions...
If we refer to the attached model and screenshots:
I make the torsional natural frequency of the shaft mass system to be 17.5 Hz (ignoring shaft mass and its own torsio…
Thanks for that. Just a question about applying torque to the shaft mass system. If I apply a short torque pulse of say 2. Milliseconds, I notice a high frequency sintorsion result in the shaft. Initially I thought it was the result of the natural f…
Greetings again
Thinking about the use of mecway for geared and belt drive shaft systems, is it possible to model rotational backlash with beam elements? I am thinking about when one has clearance between gear teeth or between coupling elements. I …
Hi Victor
Thanks for this. I think I now understand why I was fooled. If I remember correctly, I must have selected more than one node when I added the inertia.
Thank you also for pointing out what I found later about the constraint equations (s…
Greetings again
Finally got back to this. I used beam elements for the main chassis tubes and truss elements for the lower suspension arms. It has spring damper elements at 40 N/mm stiffness with 4 off 3000 N Loads in -Z direction above each corne…
I have a question about end releases on beam elements. Can these be done using ccx in this nonlinear 3D case? I need to use end releases on the end of each beam where they join the chassis. They will act as ball joints.
The manual section 10.9 talk…
Sergio,
thanks. The model isn't that good really - I found the hard points of a WRX online and then joined up the dots. The model is a proof of concept model to see what could be modeled.
I see what you mean about the results though.
I now have …
Thanks for this Victor. As always I appreciate the fast response.
Do you mean I can use beams+nonlinear with the CCX solver accessed by clicking within the Mecway GUI?
By the internal nonlinear is assume that u mean the nonlinear solver you have b…
Thanks Victor
I think I will try the first approach.
How would I apply a torsional spring at the inside diameter of the saw blade disk? Do you mean that I should use a beam connected to the disk by rigid links and rely on torsion of the beam?
Do y…
Hi Victor,
I must have missed this post "The convergence are currently ignored for output to CCX. You would need to specify that as custom step contents using CCX keywords. "
Do you mean that settings ticked in mecway for convergence are ignored wh…
VMH and Victor
Thankyou for that. I ended up using
*Static
0.1,100
instead of
*Static
0.1,1
because the solution quit early.
VMH's tip of ticking Displacement and work in convergence criteria also fixed the issue
Thanks all for you input. I a…
Thanks Victor,
I tried your suggestion exactly (*STATIC 0.1,1) and got what you see in the attachment. I also tried *STATIC 0.1,100 with the same result.
In Mecway, i specified 100 sec run time with 1 sec increments. Basically, the run finished v…
Hi
I think that I've just solved my own problem. The solution diverges just after yielding I think because of the low Tangent modulus (2 GPa). It is 1% of the Youngs Modulus (200 GPa). Assuming that the force I have applied to the end of the met…
VMH and others
RE STP file - before I sent the liml file, I right clicked on "Solution" on the tree and clicked clear. That removed all the solution data and left everything else.
I found CCX2.10_MT from https://github.com/ddfem/ccx_mingw64 (kwip…
I retried my model in the Liml file above in the last post using 100 time steps. It eventually froze the whole machine partway thru the process (about 10% I think). The solution seemed to be diverging and this froze all processes. I could not eve…