Learning Forum

[baezacaljo]

Hello dear all

i am looking for help

My name is Alberto, i am currently doing a project in transient structural, i am quite new in this topic. i found it quite interesting, but i do not find the solution of the next problem.

i have two spheres inside of a ''T'' tube, so when one moves in vertical direction (bigger sphere) the other one has moves as well. However, the spheres are not in contact. Hence, the motion of the minor sphere must be only when the bigger sphere touches.

I already set the system with fixed supports, also set the displacement, and the contact region between the spheres is frictionaless with bigger radius than the gap between the spheres.

Also, the minor sphere must be touching the some small triangles, in order to block the inlet of the tube.

However, when i am running the simulation with steps, one second for step (2 secs total), initial time step 0.05 s. Minimum time step 0.05s and maximum 0.1s stops after 30 percent around, and several messeges arises.

like,

Warnings

1 One or more MPC contact regions or remote boundary conditions may have conflicts with other applied boundary conditions or other contact or symmetry regions. This may reduce solution accuracy. Tip: You may graphically display FE Connections from the Solution Information Object for non-cyclic analysis. Refer to Troubleshooting in the Help System for more details.

2 Contact status has experienced an abrupt change. Check results carefully for possible contact separation.

3 The unconverged solution (identified as Substep 999999) is output for analysis debug purposes. Results at this time should not be used for any other purpose.

4 The solution failed to solve completely at all time points. Restart points are available to continue the analysis.

5 Although the solution failed to solve completely at all time points, partial results at some points have been able to be solved. Refer to Troubleshooting in the Help System for more details.

6 Large deformation effects are active which may have invalidated some of your applied supports such as displacement, cylindrical, frictionless, or compression only. Refer to Troubleshooting in the Help System for more details.

Errors

1 The solver engine was unable to converge on a solution for the nonlinear problem as constrained. Please see the Troubleshooting section of the Help System for more information.

I already read several post from you guys, but i can not solve the problem.

You can see this in the next image

Probalby the answer is too easy i am not able to see it. Sorry, and thank you in advance.

if you need more info plase let me know

[Kai]

Hi, the model was not able to converge. I recommend that you plot Newton Raphson residual force and check which areas are causing unconvergence issue. My guess is the frctionless contacts. You may reduce normal contact stiffness under contact settings if the issue is related to contact. Also, you time step size is too large for a nonlinear problem. I would use 0.001 even smaller as min time step size.nThanks,nKain