The long answer:
Some years ago I thought FreeCAD FEM should be able to have more solvers than CalculiX. The best way to do this was just to add another solver IMHO. Since the only solver I knew at that time was Z88, I choose Z88 for this. What I did was implementing the very basic functionality for Z88 and separeated all solver code. Thus for Z88 only constraind fixed, constraint force as well as only one material and so on are supported. Mainly all the stuff what we had in FEM when I came to FEM. Furthermore, result reading is only supported for displacements. Actually I do not know someone using Z88 solver in FreeCAD regulary. I also posted on Z88 forum but noone had any interest. For me it seams Z88 is not widely used outside Bayreuth university.
I understand. However, I am too new in FC to send sensible patches.
This is interesting because I heard about Z88 from companies. Especially the Z88 Arion V2 topology solver the presented on last years’ Hannover fair had an impact in companies.
I am an industry guy and to me it appears the opposite: Engineers know and use Z88 while they don’t use FC. For me it was the same since FC 0.16 was too unstable for industrial application. But now I am really amazed how stable FC is. But I am the first one from my colleagues investing time to learn FC. In my real life most people use Solidworks or AutoCAD and since they don’t know FC, they use these programs for the different simulation tools.
I do not know about companiees. It is just my feeling if I access the Z88 forum. There is just nearly no traffic at all. In conjunction on CalculiX mailing list are only rare posts as well, but one really get the feeling this software is used !
In the regard of FreeCAD, yes FreeCAD is geting better fast, really fast. The funny thing is at work I do use FreeCAD FEM from time to time but quite seldom. I mostly use FreeCAD for other stuff at work. I slided in FEM development some years ago and just never stoped sending PullRequest …
No way sir…
Running a FEM-analysis on FC is 10-times faster then using Z88.
Your Eigenfrequency problem: calculix gives very good results (compared to my test
problem: single beam fixed at one side).
About Z88 Arion: brillant idea from the developer, but the
result cant be used for CAD. You can try that by your own.
Design a model with FC, gmesh it in FC (1. order elements!), export mesh to Arion, run
optimization. You will get an stl wich you cant use for CAD.
Ever tried this?
Z88 as opensource software is not industrial standard. My opinion.
But I dont know there private policy.
according to https://en.wikipedia.org/wiki/Z88_FEM_software Z88 is specially for small and medium size companies… but there are also a few big names in the small list in wikipedia.
but i guess that that kind of companies use multiple solvers to compare the results.
Might be Prof. Rieg has some connections in the economy and gives direct support and thus they gone use his software. Thus we do not get noticed about this.
In the regard of debian. I do not belive people really use debian packages of z88 even if they gone install them These packages are over 5 years old, may be even older. In debian is still version 13 of z88os.
It seems you misunderstood me. To clarify, I opened this thread because in real life it is important to use at least 2 different solvers. Of course I tried out CalculiX with FC and it works fine. Nevertheless, using the same mesh in Z88 gives me other Eigenfrequencies than CalculiX and this is what I expected. Therefore it would be very valuable for real life application if FC would offer to perform simulation with different solvers.
It might be that Z88 is not bleeding edge or doesn’t have much user activity, but it seems that one can rely on its results. Therefore Z88 support should stay and it should be possible to use all analysis modes of Z88.
Concerning Z88 Aurion, I tried it of course already and that V1 of this solver did not have any output was kind of ridiculous. V2 offers now at least STL export. It is clear that this is not sufficient for integration with FC.
It seems to me that Z88 works together with companies and therefore they don’t offer that many possibilities. This would also explain the low activity on the Z88 forum because as employee you are normally not allowed to post in forums (on what project would you book this time etc.).
may be not. Two years ago on GSoC a new system for choosing the analysis type was introduced. The equation object. ATM this only works for ElmerSolver. If more analysis types should be used in Z88 I would recommend to use the Elmer Equation system. We would need to switch for Calculix too. I would take care of CalculiX if you decide to give it a try.
Hi Bernd,
I have no experience yet with Elmer, started to try it yesterday. However, I have now a fixed real life project where I will have to perform simulations and I will have to use Elmer.
I make now my first steps and when I am into it I want of course give something back. But since I am too new in FC FEM and need to learn first, I can currently only offer to test out things and give feedback.
As I wrote, it is important for real life projects to use at least 2 different solvers and I am amazed that FC offers this quite nicely. If for all 3 supported solvers, CalculiX, Z88 and Elmer FC would use the same equation system setup, it would be a big advantage to perform quickly multi-solver analyses.
I agree to to your comment.
To 80%. The missing 20% are:
Why do you compare solver versus solver (means: calculix versus Z88)
Why dont you calibrate your model at an existing analytical solution?
Can you give a screenshot of your problem. Freecad CAD file?
Thomas
I agree with Thomas. I don’t see why you would need 2 solvers just so you can check the validity of your solution. In my experience you are best off by making a simplified analysis first (either by hand or your favorite solver) and then refine where required.
That dates back some years when I worked at the university and we found out that Comsol gave other results that the simulation in Solidworks. The simulation guys checked that the mesh and geometry was the same. Since that I have this in mind. I don’t know how the different solvers calculate internally exactly and I don’t have the time at work to investigate this.
In reality we have a complex structure with many different holes (different diameters) in different “levels” of a block-like structure. Not trivial. I could run different solvers on a simple block without holes to “calibrate” them but I don’t know how the solvers work internally to judge if this “calibration” result can be transferred to complex meshes. I mean for my real geometry I already get different Eigenfrequencies with Z88 and CalculiX using the same mesh.
I’ll now try to run both solvers on a simple block and see how they behave. However, I don’t have the time to produce such a block and test if using the calculated Eigenfrequencies lead in maximal vibration amplitude for the produced part. And that is the point - I want to simulate as best as possible to modify the real block to shift the Eigenfrequencies to values above e.g. 300 Hz. Then I know there won’t be problems in reality. Thus if e.g. Z88 say the first Eigenfrequency is above 300 Hz while CalculiX says no, I better change the block geometry so that both solvers give me frequencies above 300 Hz. It is much quicker and much cheaper to run some more simulations than to produce the real part.
I must admit, that I don’t have that much expertise in simulations for real life so if you think I make a logical mistake please tell me that I can learn or correct myself.
I am an industry guy and cannot make screenshots of real bodies.
I see both points. I have to face them in daily business too.
May be all this depends on the part to analyses. I’m structural engineering guy. As long as I only calculate forces, there will be a possibility to make some simple calculations to get some result. The FEM should not be more than 20 … 30 % away, may be even less 5 … 10 %. This depends on the part. But I can imagine there is part geometry out there on which a calculation on paper is just not possible.
