topic Re: Excessive displacement in 3D Part & Assembly Design

Excessive displacement

rrakos — Wed, 02 May 2018 23:33:12 GMT

Hello,I have a simulation including a stationary body and a moving body. There is a contact between them. I often see the warning: "Excessive displacement at contact region". A software suggests smaller time step but I can not reduce it. The full moving process is described

Re: Excessive displacement

y于 — Thu, 25 May 2017 14:15:11 GMT

1.Refine the elements of the contact region and have a try,sometimes it's hard to converge for the solver when the elements are too large.

2.Before it contacts each other,you can give less steps,then you have more steps for the contact steps.

3.You can only define less than 100 steps with a non-linear anaysis.

Re: Excessive displacement

rrakos — Fri, 26 May 2017 15:00:00 GMT

OK,thanks, I understand. My main problem is the "max 100 time steps". I have a quite long moving process and I should divide the full process to small steps but the 100 step possibility is not enough for me...

Re: Excessive displacement

skunks — Fri, 26 May 2017 15:09:02 GMT

Roland,

i recommend: MSC MARC

creo simulate ist not possible in this case

regards

paul

Re: Excessive displacement

y于 — Sat, 27 May 2017 01:12:31 GMT

Creo can do this large deformation analysis(below),so I think your question in not a problem.

Re: Excessive displacement

skunks — Sat, 27 May 2017 06:41:17 GMT

Hi,

his problem is plasticity and contact and large deformation.

regards

paul

ps:

contact+large deformation: OK (example attached)

contact+plasticity: OK (example attached)

contact+plasticity+large deformation: not possible

Re: Excessive displacement

rrakos — Mon, 29 May 2017 06:57:35 GMT

My task is very similar to your 2. example (contact AND large deformation). But my model includes plasticity.

As far as I see, the main problem is that the time step has to be small because the parts are in contact continuosly. There is no a range during the motion process where the time step can be increased because the calculation will diverge in this range...

Second problem is that I has to calculate the backway of blue part. So my motion function (y in time):

I would like ot investigate the final state, after the springback. If the time step is large after the maximal y then the contact will not be correct. Finally, I should divide this full timerange to 100 steps and it seems to me that it is inpossible with correct time step size...

Re: Excessive displacement

mlindqvist — Mon, 29 May 2017 07:16:13 GMT

Paul wrote "contact+plasticity+large deformation: not possible"

Here's picture from a problem I ran a few years ago, with contact, plasticity and large deformation.

You are restricted to using solid elements, I recall having tried 2D, but that did't work at the time, so I did a one element thick 3D analysis instead. If I remember correctly I did this in Creo 2 or 3.

Re: Excessive displacement

skunks — Mon, 29 May 2017 07:42:42 GMT

Mats,

i mean 2d of course:

release: creo simulate 2.0 m080

regards

paul

Re: Excessive displacement

skunks — Mon, 29 May 2017 10:59:54 GMT

Roland,

example as 3D (without plasticity):

regards

paul

Re: Excessive displacement

skunks — Tue, 30 May 2017 05:23:43 GMT

OK,

example attached (contact, large deformation and plasticity).

Re: Excessive displacement

rrakos — Tue, 30 May 2017 13:55:31 GMT

OK, it is a perfect example. My testcase includes plus 2 additional problems:

- the motion (down) is more higher so the plastic deformation is more larger too

- it should be modeled the backway of rod (to see the backspring) so I need additional time step but the 100 is not enough

The simulation is ok with 4mm displacement but the 8mm...

Re: Excessive displacement

skunks — Wed, 31 May 2017 05:28:11 GMT

Hm,

i think it's a problem of force maybe:

better 2D-Analysis with MSC MARC

regards

paul

Re: Excessive displacement

skunks — Wed, 31 May 2017 09:49:41 GMT

a little example (very small):

Video Link : 7927

Re: Excessive displacement

rrakos — Wed, 31 May 2017 11:02:28 GMT

I checked your model...the first observation; the mesh element number is similar to mine but the calculation time is total different. In your case about 2 minitt. In my case is about more hours.... Altough I use single pass adaptive...instead of quick check

I control the motion by a displacement. (not with a force) As I mentioned, it should be investigate the backspring after maximal deflection. Therefore I can not control the end of rod as in your case. In this case the rod could not move free after maximal deflection.

My solution is unusual, I know but I control the support displacement. The support moves up 8mm and the end of rod is fixed as below:

As a result, the rod can springs back free after maximal deflection. The reason of this solution, I would not like to use force control at the end of rod because the convergence is very slow with this way...

The other difference is the material model. My model is defined by power law but your model is a simple bilinear. Can the calculation be more slower caused by the non linear plastic renge of material model?

Re: Excessive displacement

skunks — Wed, 31 May 2017 11:37:27 GMT

my last fea: nl_bending_little.zip

pic.1

pic.2

pic.3

pic.4

pic.5

pic.6

Re: Excessive displacement

rrakos — Thu, 01 Jun 2017 08:06:10 GMT

Hello Paul,

I dont understand what can cause the complexity of my model. See pls my result below:

After 6mm displacement, the contact lets loose the two parts....

I am using 100 time steps, total time is 1 s...I am not able to define smaller time step... Is this problem such complicated?

Re: Excessive displacement

skunks — Thu, 01 Jun 2017 08:25:33 GMT

Hello Roland,

you can test my start-part and/or start-assembly (attached).

worked for mechanica specially

regards

paul

Re: Excessive displacement

rrakos — Fri, 02 Jun 2017 11:16:48 GMT

By the way, do you use the "Quick check" method always?

Re: Excessive displacement

skunks — Sun, 04 Jun 2017 18:11:21 GMT

please, read my book

Pro/MECHANICA® verstehen lernen - für Pro/ENGINEER Wildfire® | Paul Kloninger | Springer