General Mechanical

General Mechanical

Convergence problem due to abrupt change in contact status

    • Rajneesh
      Subscriber

      Hi there!

      I am trying to solve a problem in which rotational velocities have been applied to three plates kept over one another. The bottommost plate rotates w.r.t. ground, plate above it rotates w.r.t. to this bottommost one and the topmost w.r.t. the middle one. The velocities change in a very short duration of 0.001 sec.

      Initially I solved the model for 12 steps where the last step ended for 4 sec and it worked as expected. Now I have to solve it for 60 sec, i.e., 180 steps but as soon as the solver reaches 18 sec (or 54th step) the solution fails with a number of warnings and errors. The first one among them is "Contact status has experienced an abrupt change. Check results carefully for possible contact separation." I have applied all the boundary conditions properly in order to prevent the rigid body motion. Even then it is happening each time.

      I have attached the snapshot of errors/warnings I get. Please help me correct it and get the complete solution.

    • Ashish Khemka
      Ansys Employee
      nnThe model may have a rigid body motion. Please see if the suggestion below helps.nnnRegards,nAshish Khemkan
    • Rajneesh
      Subscriber
      Hi Ashish,nI tried the steps mentioned in the suggestion. The solution proceeded further till 27.9995 sec (load step 84 or about 46%) but then again it failed with warnings and errors as can be seen in the snapshot below. I have turned on weak springs now and thus the warning 'Not enough constraints appear....' has gone away. But the warning that contact status has abruptly changed still appears at the same step as it was coming earlier. But now the solution proceeds further but with a warning for contact status change at each substep (as can be seen in the solver output) till the abovementioned time. After this step (84) it again fails.nPlease help to resolve this.nnnThanks & Regards,nRajneeshn
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