Dear Creo simulate users.
I would like to simulate one structure touching another structure. Once the contact happens the rubber part is deformed at the same time that the shaft bends.
I would be interested not only in the stiffness of the structure but also the stress in the parts.
The main problem is that even using ½ of the model (and using mirror constrains) this type of simulation still would take several hours even with not much elemnts (ex.10000) – Maybe Simuklate simply does not use all CPUs in this case, I don´t know.
Thus a much more interesting approach is to run a 2D simulation. It is order of magnitude faster. Unfortunately I do not have too much experience in 2D. I tried it with another cases/assemblies and the result seems consistent. However I don´t see the right way to setup this model in 2D.
For example I tried 2D axisymmetric model (using ¼ of the model) but the result seems simply wrong. For example the shaft shows an odd distribution of stress and the bending of the shaft (displacement) does not match what I would get with the full 3D model (shaft only) using the same input force.
I would be glad if someone could give me good hint in how to have quick and reliable results for this case.
I´ll post the CAD model latter
Thank you in advance
R. Rabe
This thread is inactive and closed by the PTC Community Management Team. If you would like to provide a reply and re-open this thread, please notify the moderator and reference the thread. You may also use "Start a topic" button to ask a new question. Please be sure to include what version of the PTC product you are using so another community member knowledgeable about your version may be able to assist.
Thanks Patrick
I think your explanation made me understand why I was having some good results in one 2D axisymmetric problem but bad results in this one.
I had another model (with good results) that the rubber was being pressed against a plane (picture below) and in this case the load/displacement is indeed symmetric around the axis of symmetry. As you have pointed out this will not be the case in my current model with lateral load.
I did some tests and I found that in some cases the rubber property (when mixed with contact interface) was the main source of long computing time or simulation fail due to lack of convergence. In some cases a small changes in the rubber property solved the problem but it also changed its mechanical behavior enought that the results did not fit anymore the reference part.
By the way the rubber properties I got from colleagues using another FEM and real tested parts – so what I was trying to do was to “replicate” the model in Creo 2.0 to learn more about this capability. So far other FEM seems to be handing well this type of problem – but I have no idea how long takes a simulation. Besides their focus is to get the best result for a given part and not to design the part. This means that they may have solutions that will fit very well to a particular geometry but that does not need to be so robust that can work in any geometry.
Using infinite friction or frictionless contact were also factors that could made a simulation to finish or not (see that I´m not discussing if the result was ok or not – simply that the simulation finished). Sometimes instead of a material change refining the mesh helped. Even so even a small geometry change in the contact interface was enough to stop the simulation in the middle. And If I want to do run optimization I´ll probably have this issue again.
I had same model using enforced displacement but I did not noticed any substantial improvement. Maybe the solution is ready after 5h instead of 6h but in this case I was hoping to find something a lot quicker – that was my motivation to switch to 2D.
I tried to work with a slice of the 3D model and cyclic constrains – but again it may be valid only if the load/displacement are symmetric around the axis of symmetry (and thus I´ll be doing the wrong thing again – but now in 3D).
To see how “desperate” I´m looking for a way to speed up the simulation time I even played bit with the “mse_contact_tolerance_factor” in the config file. Sometimes I had a substantial reduction in simulation time and nearly the same result but in other models the result was simply rubbish. So it is a complex tool a dangerous way to go if you cannot “benchmark” the result or have sure that the result is reliable or not (analyzing convergence status for example?).
The search continues and thus any hint is welcome.
