Non Convergence Error 941 of non linear Static analysis

Junhyeong Kang
Junhyeong Kang Altair Community Member
edited December 2023 in Community Q&A

Hey all, im doing non linear static analysis of a 1/6 Stator Model for Press fit effect. i gave constraints of 0 for DOF2(Y-direction) on 0 Degree and 60 Degree faces. and gave a pressure of 0.25 magnetitude(units are mm, N, MPa, s.) on outer of stator of every elements face(length of squar is 0.25mm*0.25mm and its totally 10MPa Effect.). and got a error message bellow

 A fatal error has occurred during computations:
  
  *** ERROR # 941 ***
  NON-CONVERGENT NONLINEAR ITERATIONS FOR SUBCASE 1
  
  Suggestions:
  
  ANALYSIS COMPLETED.
  
  *** SOME ERRORS WERE REPORTED DURING THE RUN,
  *** PLEASE VERIFY RESULTS AS THEY MAY BE INVALID.
  ...
  
 *** PROGRAM STOPPED: FATAL ERROR(s) ENCOUNTERED

 

i already referred the troubleshooting for optistruct non linear convergence problem. in Tutorials, How To, Troubleshooting - Troubleshooting for OptiStruct Nonlinear Convergence Issues (altair.com)

for my case there is no contact because i have only one Geometry. my suspect is because my geometry is not fully constrainted. Average Displacement are quite large. according to description this value should be very small. but im not sure which direction i should give constraints.  i already tried simulations with more constraints but i got same convergence error. can you guys help me. or have some ideas?  i attached my .fem, .out, 

Subcase         1  Load step: 1.0000E-03
--------------------------------------------------------------------------------
               Nonlinear Err. Measures   Gap and Contact Element Status MaxEquiv
 Iter Avg. U    EUI      EPI      EWI    Open Closed Stick Slip Frozen  PlasStrn
--------------------------------------------------------------------------------
  1  3.85E+03 9.90E+01 5.40E-14 5.40E-14     0     0     0     0     0  0.00E+00
  2  7.71E+03 4.95E+01 2.72E-14 1.36E-14     0     0     0     0     0  0.00E+00
  3  1.16E+04 3.30E+01 2.12E-14 7.06E-15     0     0     0     0     0  0.00E+00
  4  1.54E+04 2.47E+01 1.70E-14 4.24E-15     0     0     0     0     0  0.00E+00
  5  1.93E+04 1.98E+01 1.44E-14 2.87E-15     0     0     0     0     0  0.00E+00
  6  2.31E+04 1.65E+01 1.57E-14 2.62E-15     0     0     0     0     0  0.00E+00
  7  2.70E+04 1.41E+01 1.41E-14 2.02E-15     0     0     0     0     0  0.00E+00
  8  3.08E+04 1.24E+01 1.31E-14 1.64E-15     0     0     0     0     0  0.00E+00
  9  3.47E+04 1.10E+01 1.23E-14 1.36E-15     0     0     0     0     0  0.00E+00
 10  3.85E+04 9.90E+00 1.15E-14 1.15E-15     0     0     0     0     0  0.00E+00
  No convergence after   10 iterations
  Expert: Continue iterations
 11  4.24E+04 9.00E+00 1.50E-14 1.36E-15     0     0     0     0     0  0.00E+00
 12  4.63E+04 8.25E+00 1.41E-14 1.17E-15     0     0     0     0     0  0.00E+00
 13  5.01E+04 7.62E+00 1.32E-14 1.02E-15     0     0     0     0     0  0.00E+00
 14  5.40E+04 7.07E+00 1.27E-14 9.06E-16     0     0     0     0     0  0.00E+00
 15  5.78E+04 6.60E+00 1.22E-14 8.16E-16     0     0     0     0     0  0.00E+00

Answers

  • loistf
    loistf Altair Community Member
    edited December 2023
    you can run a normal modes analysis to check if there are rigid body modes
  • Junhyeong Kang
    Junhyeong Kang Altair Community Member
    edited December 2023
    loistf said:

    you can run a normal modes analysis to check if there are rigid body modes

    Hey, i already tried a normal modes analysis. which sign i can see and predict its rigid body modes?image